2009 CALIFORNIA ALMOND OBJECTIVE MEASUREMENT REPORT
JUNE 30, 2009 - 12:00 p.m. PDT
USDA/NASS California Almond
Objective Measurement Report
2009 CALIFORNIA ALMOND FORECAST DOWN
California's 2009 almond production is forecast at 1.35 billion meat pounds, down 7 percent from May's subjective forecast and 17 percent below last year's crop. The forecast is based on 710 thousand bearing acres. Production for the Nonpareil variety is forecast at 450 million meat pounds, 26 percent below last year's deliveries. The Nonpareil variety represents 36 percent of California's total almond production.
After a difficult spring, the 2009 almond crop is generally in good condition,although it looks to be about 2 weeks behind. Bloom progressed slowly due to wet conditions, and wet weather hampered pollination. Cool temperatures did extend the almond bloom in parts of the Sacramento Valley. Freezing temperatures in March caused damage to some almond orchards. Mites were present on almonds across the state; however, control measures combined with some spring rains resulted in little damage to the crop. Irrigation water availability is a concern but has had minimal impact on the 2009 crop.
The average nut set per tree is 5,589, down 25 percent from 2008. The Nonpareil average nut set of 5,136 is down 27 percent from last year's set. The average kernel weight for all varieties sampled was 1.58 grams, 10 percent above last year. A total 98.5 percent of all nuts sized were sound.
Tuesday, June 30, 2009
Objective Almond Crop Forecast...
Monday, June 29, 2009
Hull Split Part 2: Hull Rot of Almond
The basis of this article was contributed by Brent Holtz, PhD, UCCE Madera County
As almond trees approach harvest, at about mid hull split, clusters of dry leaves begin to appear scattered through the tree canopy. Individual spurs, small shoots or entire small branches may collapse due to hull rot infections (Photo 1). The loss of fruiting wood, especially in the lower parts of the tree, can negatively affect yield for years to come. Nonpareil is usually the most severely affected cultivar though Sonora and Kapareil can also sustain extensive damage. Hull rot is caused by either of two fungi, Monilinia fructicola or Rhizopus stolonifer. Monilinia fructicola is best known as one of the brown rot fungi and R. stolonifer is often called the bread mold fungus, and will turn bread left out black and moldy.
In the southern San Joaquin Valley I believe that Rhizopus is the primary pathogen responsible for hull rot while Monilinia may be more important in the Sacramento Valley. These two organisms are very different but can cause similar disease symptoms on almond. As the name implies, a lesion or dryish rotted area develops on the hull, and dense masses of Rhizopus spores produce a powdery dark gray to black growth between the hull and the shell (Photo 2). Monilinia spores are buff-colored and can be seen on inner and outer hull surfaces. The nut meat is not damaged, but a toxin produced in the infected hull moves from the hull into the neighboring leaves and shoots causing death of these tissues.
Neither Monilinia nor Rhizopus are able to invade the healthy outer hull surface. Only after hull split begins can spores gain access to the inside of the hull and initiate infections. Once hull split starts, trees are at risk of becoming infected. One or both pathogens may be present in an orchard, but Monilinia hull rot is less common in southern San Joaquin Valley orchards than in other almond growing regions of the state.
Leaves may become infected near infected nuts and sometime the hole spur or shoot can die as well. Clusters of dead leaves can become visible in the summer scattered among healthy green foliage (Photo 3). Spur and leaf die-back are attributed to fumaric acid which is produced by the pathogens and transported to the leaves and shoots. The black vascular tissues in the dead spurs and wood can be traced back to a pedicel or infected fruit (Photo 4). The nut kernel is not harmed but the death of the fruiting wood reduces bloom and yield in subsequent years (Photo 5). Sometimes infected fruit does not fall during mechanical harvest and must be removed by hand poling and can also provide overwintering sites for navel orangeworm (NOW).
Cultural practices play a crucial role in determining the severity of hull rot in an orchard. Vigorous, heavily-cropped, well-watered and fertilized orchards suffer the most damage. I have often referred to hull rot as the “good growers disease” since the disease is often worse in well maintained orchards. Beth Teviotdale calls hull rot the “gout of almond diseases–too much food and drink is bad for almonds just like it is bad for us.” The reasons for this are not clear. The association with heavy crops might be simply a matter of numbers: more infected fruit means more toxin produced which results in more leaf and shoot death.
Research by Drs. Beth Teviotdale, David Goldhammer, and Mario Viveros have shown that
hull rot can be reduced by inflicting mild water stress on trees during early hull split. In experiments in Kern County, hull rot incidence was lessened by half or more when half the normal amount of water was delivered to trees for two weeks during early hull split. Eliminating irrigation during the two weeks preceding harvest reduced hull rot by 400-500%, but completely denying trees water for two weeks may be dangerous and less drastic irrigation reductions may also reduce disease and stress trees less. In their research they irrigated almond trees at 70, 85, and 100% of potential evapotranspiration (Etc). There were two types of deficit irrigation: sustained and regulated. The sustained irrigation was just reduced irrigation the whole season while the regulated started the year at normal irrigation but then drastically reduced irrigations (50% Etc) during the period preceding and during hull split. For Kern county those dates included 50% Etc from 1-15 July (85% season Etc reduction) or 1 June- 31 July (70% season Etc reduction). The regulated deficit irrigations were much more effective at reducing hull rot than the sustained deficit irrigations.
The University of California tested several approaches to reduce water use under different irrigation strategies and soil types. In a large cooperative trial lead by Dr. Ken Shackel in Pomology at UC Davis and farm advisors, we used midday stem water potentials to monitor deficit irrigation in almond in order to reduce hull rot without severely stressing trees. We use a pressure bomb to monitor midday stem water potentials (SWP) through the season in order to keep fully irrigated trees between stem water potentials of -7 to -9 bars. Then during hull split we tried to irrigate less in order to achieve stem water potentials between -14 to -18 bars. The higher the negative number, the more water stress. Figure 1 shows a graph of our 2002 data where the grower standard is our RDI reduced deficient irrigation treatment (-14 to -18 bars) while the control consists of fully irrigated trees (-7 to -9 bars). Hull rot in the fully irrigated treatment averaged 44.4 strikes per trees while the RDI treatment averaged only 17.7 in 2002. In 2003 hull rot in the fully irrigated treatment averaged 17.7 strikes per trees while the RDI treatment averaged only 2.0 (figure 2). In both years the differences were significant.
Experiments in Stanislaus County demonstrated that hull rot severity increases with increasing amounts of nitrogen. Nitrogen should not be applied in excess of that needed for tree health and productivity. The nitrogen content of the irrigation water should be included in calculations of required added fertilizer.
As almond trees approach harvest, at about mid hull split, clusters of dry leaves begin to appear scattered through the tree canopy. Individual spurs, small shoots or entire small branches may collapse due to hull rot infections (Photo 1). The loss of fruiting wood, especially in the lower parts of the tree, can negatively affect yield for years to come. Nonpareil is usually the most severely affected cultivar though Sonora and Kapareil can also sustain extensive damage. Hull rot is caused by either of two fungi, Monilinia fructicola or Rhizopus stolonifer. Monilinia fructicola is best known as one of the brown rot fungi and R. stolonifer is often called the bread mold fungus, and will turn bread left out black and moldy.
Photograph 1: Hullrot of almond caused by Rhizopus stolonifer.
In the southern San Joaquin Valley I believe that Rhizopus is the primary pathogen responsible for hull rot while Monilinia may be more important in the Sacramento Valley. These two organisms are very different but can cause similar disease symptoms on almond. As the name implies, a lesion or dryish rotted area develops on the hull, and dense masses of Rhizopus spores produce a powdery dark gray to black growth between the hull and the shell (Photo 2). Monilinia spores are buff-colored and can be seen on inner and outer hull surfaces. The nut meat is not damaged, but a toxin produced in the infected hull moves from the hull into the neighboring leaves and shoots causing death of these tissues.
Neither Monilinia nor Rhizopus are able to invade the healthy outer hull surface. Only after hull split begins can spores gain access to the inside of the hull and initiate infections. Once hull split starts, trees are at risk of becoming infected. One or both pathogens may be present in an orchard, but Monilinia hull rot is less common in southern San Joaquin Valley orchards than in other almond growing regions of the state.
Photograph 2: Close up of fruiting bodies associated with Hull Rot of almond caused by Rhizopus stolonifer.
Leaves may become infected near infected nuts and sometime the hole spur or shoot can die as well. Clusters of dead leaves can become visible in the summer scattered among healthy green foliage (Photo 3). Spur and leaf die-back are attributed to fumaric acid which is produced by the pathogens and transported to the leaves and shoots. The black vascular tissues in the dead spurs and wood can be traced back to a pedicel or infected fruit (Photo 4). The nut kernel is not harmed but the death of the fruiting wood reduces bloom and yield in subsequent years (Photo 5). Sometimes infected fruit does not fall during mechanical harvest and must be removed by hand poling and can also provide overwintering sites for navel orangeworm (NOW).
Photograph 3: Spur dieback from hull rot of almond.
Photograph 4: Darkened vascular tissue from the translocation of hull rot toxins.The movement of these toxins is what kills the fruit wood.
Photograph 5: Dead branches of the lower canopy associated with hull rot damage.
Cultural practices play a crucial role in determining the severity of hull rot in an orchard. Vigorous, heavily-cropped, well-watered and fertilized orchards suffer the most damage. I have often referred to hull rot as the “good growers disease” since the disease is often worse in well maintained orchards. Beth Teviotdale calls hull rot the “gout of almond diseases–too much food and drink is bad for almonds just like it is bad for us.” The reasons for this are not clear. The association with heavy crops might be simply a matter of numbers: more infected fruit means more toxin produced which results in more leaf and shoot death.
Research by Drs. Beth Teviotdale, David Goldhammer, and Mario Viveros have shown that
hull rot can be reduced by inflicting mild water stress on trees during early hull split. In experiments in Kern County, hull rot incidence was lessened by half or more when half the normal amount of water was delivered to trees for two weeks during early hull split. Eliminating irrigation during the two weeks preceding harvest reduced hull rot by 400-500%, but completely denying trees water for two weeks may be dangerous and less drastic irrigation reductions may also reduce disease and stress trees less. In their research they irrigated almond trees at 70, 85, and 100% of potential evapotranspiration (Etc). There were two types of deficit irrigation: sustained and regulated. The sustained irrigation was just reduced irrigation the whole season while the regulated started the year at normal irrigation but then drastically reduced irrigations (50% Etc) during the period preceding and during hull split. For Kern county those dates included 50% Etc from 1-15 July (85% season Etc reduction) or 1 June- 31 July (70% season Etc reduction). The regulated deficit irrigations were much more effective at reducing hull rot than the sustained deficit irrigations.
The University of California tested several approaches to reduce water use under different irrigation strategies and soil types. In a large cooperative trial lead by Dr. Ken Shackel in Pomology at UC Davis and farm advisors, we used midday stem water potentials to monitor deficit irrigation in almond in order to reduce hull rot without severely stressing trees. We use a pressure bomb to monitor midday stem water potentials (SWP) through the season in order to keep fully irrigated trees between stem water potentials of -7 to -9 bars. Then during hull split we tried to irrigate less in order to achieve stem water potentials between -14 to -18 bars. The higher the negative number, the more water stress. Figure 1 shows a graph of our 2002 data where the grower standard is our RDI reduced deficient irrigation treatment (-14 to -18 bars) while the control consists of fully irrigated trees (-7 to -9 bars). Hull rot in the fully irrigated treatment averaged 44.4 strikes per trees while the RDI treatment averaged only 17.7 in 2002. In 2003 hull rot in the fully irrigated treatment averaged 17.7 strikes per trees while the RDI treatment averaged only 2.0 (figure 2). In both years the differences were significant.
Figure 1: Strikes per tree of Rhizopus, a hull rot pathogen of almond, in relation to two irrigation treatments.
Figure 2: Pressure chamber readings for irrigation regimes for reductions of hull rot in almond.
By using the pressure bomb to monitor tree stem water potentials we are imposing enough stress to reduce hull rot and not over stress the trees so that they are susceptible to mite damage or defoliation. Soils can vary greatly throughout the state and irrigation management can be very difficult. For instance, in some orchard experiments we could withhold water and reach -14 bars in just a few days while in other orchards with deep, well-drained soils it might take as long as 20-30 days to achieve -14 bars in stress. This is why irrigation management using mid day stem water potentials and a pressure bomb is in my belief the only real management strategy for hull rot control. Other benefits of hull split stress are more uniform nut maturity and earlier harvest which will have a significant impact on Navel Orange Worm (NOW) control and damage.Experiments in Stanislaus County demonstrated that hull rot severity increases with increasing amounts of nitrogen. Nitrogen should not be applied in excess of that needed for tree health and productivity. The nitrogen content of the irrigation water should be included in calculations of required added fertilizer.
Saturday, June 27, 2009
Hull Split is Approaching...
Hull split is approaching the the central San Joaquin Valley. In Kern COunty, hullsplit of almonds has been observed on the edges of blocks and tops of the trees, and will progress rapidly from this point forward. Hullsplit is a traditional time of making an application of insecticide to reduce navel orange worm damage and late season mite pressures. Blanks, or unpollinated or aborted fruit, will split first before the rest of the crop.
So, as a grower, what do we need to keep in mind during hull split?
1. Insect pest management, which includes Navel Orange Worm and Spider Mites.
2. Water Management to reduce the incidence of hull rot.
We will cover point 1 today, and the disease hull rot later this week.
1. Insect Pest Management practices for Hull split.
Spider Mites: A miticide will be necessary if a pyrethroid was used within the orchard. Pyrethroids target both spider mites and predator mite populations. Once the predator mites are reduced, the faster reproducing problematic spider mites can flare up, causing tree defoliation. It is essential to include a miticide tank mixed if spraying a pyrethroid. If not using a pyrethroid, scouting the trees can give you an idea if you need to include a miticide. Scouting for mites is simple, should be done in the morning when it is cool, and can give a good idea about the ratio of predator mites to spider mites in your orchard. Please refer to the University of California Integrated Pest Management page for information on how to scout for mites: UC IPM Scouting for Spider Mites.
There are several miticides to choose from at hull split. The most commonly used include Acramite, Envidor, Fujimite, Kanemite, Oil, Omite and Zeal. Each of these products can be effective, depending upon populations of spider mites present. The products need to be used before webspinning occurs. Webs that are spun within the leaves will repel the miticide, and will render it ineffective.
Navel Orange Worm:
Navel Orange Worm moths has been observed laying eggs on traps around the state, indicating that the next generation is about to begin. During this flight, eggs are laid on the suture and surface of the nut, and inside of a split-hull. The spray should be timed for the beginning of hull split if laid eggs are found on the egg traps. If eggs are not found on the traps at hull split, attempt to time the spray for the initiation of egg laying following hull split. Be aware that once hull split occurs, egg laying on traps will decrease. If you are not seeing eggs on traps, use degree-day information and apply a treatment at 1200 degree-days from spring biofix.
At hullsplit, a knockdown insecticide targeting navel orangeworm will reduce populations of adults, hatched larvae (worms), and eggs. Any in season use of a broad spectrum insecticide (AZINPHOSMETHYL(Guthion), CHLOROPYRIFOS (Lorsban), PHOSMET (Imidan), and ESFENVALERATE (Asana)) during this period or previously in the season to control navel orangeworm (or other insects) could possibly flare up spider mites, and thus a miticide should be included in the tank mix.
Use of softer, target specific chemicals (METHOXYFENOZIDE (Intrepid), SPINETORAM (Delegate), or SPINOSAD (Entrust or Success) will target navel orangeworm, and reduce the need for a miticide application. These insecticides are target specific, break down quickly in the environment, and lesser impacts on non-target organisms.
This season, it appears that the second twig borer flight will coincide with the flight of the navel orangeworm. This is good news as both pests will be targeted with a single spray!
More information on navel orangeworm and peach twig borer can be found at UC IPM Overview of Pests and Disease for Almonds
A link for Day Degree Hours from various locations around California from throughout the season can be found at Trece Field Reporter.
Let me know if you have any questions!
So, as a grower, what do we need to keep in mind during hull split?
1. Insect pest management, which includes Navel Orange Worm and Spider Mites.
2. Water Management to reduce the incidence of hull rot.
We will cover point 1 today, and the disease hull rot later this week.
1. Insect Pest Management practices for Hull split.
Spider Mites: A miticide will be necessary if a pyrethroid was used within the orchard. Pyrethroids target both spider mites and predator mite populations. Once the predator mites are reduced, the faster reproducing problematic spider mites can flare up, causing tree defoliation. It is essential to include a miticide tank mixed if spraying a pyrethroid. If not using a pyrethroid, scouting the trees can give you an idea if you need to include a miticide. Scouting for mites is simple, should be done in the morning when it is cool, and can give a good idea about the ratio of predator mites to spider mites in your orchard. Please refer to the University of California Integrated Pest Management page for information on how to scout for mites: UC IPM Scouting for Spider Mites.
There are several miticides to choose from at hull split. The most commonly used include Acramite, Envidor, Fujimite, Kanemite, Oil, Omite and Zeal. Each of these products can be effective, depending upon populations of spider mites present. The products need to be used before webspinning occurs. Webs that are spun within the leaves will repel the miticide, and will render it ineffective.
Navel Orange Worm:
Navel Orange Worm moths has been observed laying eggs on traps around the state, indicating that the next generation is about to begin. During this flight, eggs are laid on the suture and surface of the nut, and inside of a split-hull. The spray should be timed for the beginning of hull split if laid eggs are found on the egg traps. If eggs are not found on the traps at hull split, attempt to time the spray for the initiation of egg laying following hull split. Be aware that once hull split occurs, egg laying on traps will decrease. If you are not seeing eggs on traps, use degree-day information and apply a treatment at 1200 degree-days from spring biofix.
At hullsplit, a knockdown insecticide targeting navel orangeworm will reduce populations of adults, hatched larvae (worms), and eggs. Any in season use of a broad spectrum insecticide (AZINPHOSMETHYL(Guthion), CHLOROPYRIFOS (Lorsban), PHOSMET (Imidan), and ESFENVALERATE (Asana)) during this period or previously in the season to control navel orangeworm (or other insects) could possibly flare up spider mites, and thus a miticide should be included in the tank mix.
Use of softer, target specific chemicals (METHOXYFENOZIDE (Intrepid), SPINETORAM (Delegate), or SPINOSAD (Entrust or Success) will target navel orangeworm, and reduce the need for a miticide application. These insecticides are target specific, break down quickly in the environment, and lesser impacts on non-target organisms.
This season, it appears that the second twig borer flight will coincide with the flight of the navel orangeworm. This is good news as both pests will be targeted with a single spray!
More information on navel orangeworm and peach twig borer can be found at UC IPM Overview of Pests and Disease for Almonds
A link for Day Degree Hours from various locations around California from throughout the season can be found at Trece Field Reporter.
Let me know if you have any questions!
Monday, June 22, 2009
The Seasonal Patterns of Almond Production
When reviewing previous posts of this blog, I realized that not much information has been provided about the general biology of the almond tree. To cover this area, I decided to focus on the seasonal cycle of almond trees.
In general, the season progresses in the following pattern: Dormant,Delayed Dormant, Bloom, Post-Bloom, Fruit Development, Harvest, and Post Harvest. Each period will be broken down and discussed.
Dormant:
As the temperatures from the late fall continue to drop, the tree enters a period of rest that lasts through December/Early January. At this time, the tree has dropped all of its leaves naturally or through an application of zinc, and is maintaining a low level of water use and starch consumption. This "low" flow of starch through the tree is needed as the catabolic breakdown of starch to sugar prevents the sap from freezing. This is, of course, only if the tree was able to develop enough starch reserves in the previous fall. In the rare occasion of low starch reserves, cold damage can occur leading to canopy and scaffold loss.
Picture 1: A dormant spur.
The cold temperatures that the tree is exposed to at this time helps with the development of the fruit buds. The tree requires a certain amount of moisture and chilling hours to come out of dormancy. Once the chilling hour requirement has been met, bud grown will begin with warmer temperatures. Chill hours are dependent upon the variety,but almonds generally need between 500 and 600 chill hours. In general, chill hours are the number of hours between the temperatures of 32-45 degrees Fahrenheit. Winter hours above 60 degrees are subtracted from the totals.
Delayed Dormant:
In late January/early February the tree begins to push a flush of fine feeder roots. These roots provide moisture and nutrients for the future development of leaf and fruit bud. Roots will generally only grow where there is soil moisture, so it remains important that efforts are made to ensure a full soil-water profile if inadequate winter rains have fell. The soil-water profile will be discussed in a later blog about irrigation management.
Picture 2: The delayed dormant period is initiated upon the observance of swelled fruit buds.
Picture 3: The delayed dormant period is concluded upon the appearance of green tipped buds.
Delayed dormancy is described as the period of fruit bud swell (Picture 2) until the green tip (picture 3). During this period, preparations for bloom occur which include insect and disease management, orchard floor management, and completion of orchard sanitation. Please see the UC Integrated Pest Management (IPM) page on Dormant season practices at http://ucipm.ucdavis.edu/PMG/C003/m003dcwhydormant.html.
Bloom:
Flower buds begin expanding ahead of leaf and shoot buds around Mid-February to Mid-March. Flower buds are formed on at least one year old growth and can be found on the terminal bud of spur or shoot, as well as the lateral buds of a one year old shoot. The timing of the bloom is dependent upon the variety which is related to the amount of chilling hours received. In years of low chilling hours, the bloom period lasts longer and is more sporadic leading to poor pollination. Later blooming varieties are generally more affected by insufficient winter chilling. Keep in mind that even though more chilling hours are needed for later blooming varieties, they are less susceptible to crop damage from early season frost events.
Bloom occurs in a series of flowering stages which are as follows: green tip (Picture 3), pink bud (Picture 4), popcorn stage(Picture 5), full bloom (Picture 6), petal fall (Picture 7), and post-petal fall. Almonds, which are self-incompatible, need to be cross-pollinated with a compatible variety. Insects move the pollen from tree to tree - with honey bees being the insect of choice and efficiency in commercial orchards. Therefore, during bloom, at least two compatible varieties must be in bloom simultaneously for a successful pollination event to occur. To ensure a successful pollination, many growers plant a pollinator that blooms slightly before and slightly after the variety of choice, nonpareil.
During the bloom period, the new leaves emerge from the vegetative buds and the production of carbohydrates occurs through the process of photosynthesis. At this point, growth is no longer dependent upon the reserves of the tree produces from the following year.
Picture 4: Pink bud stage of blossom development.
Picture 5: Popcorn Stage of blossom development.
Picture 6: Full bloom of an almond blossom.
Picture 7: Petal fall period of an almond blossom.
The bloom period contains several important periods of pest and disease management which can be found at http://ucipm.ucdavis.edu/PMG/C003/m003bcwhybloom.html. Poor pest management practices during this period can lead to a substantial crop loss, loss of fruiting wood, and fungal problems that may persist for several years. Of major concern include the blossom diseases of brown rot, scab, anthracnose, and jacket rot, the insect peach twig borer (Picture 8 and 9) and completion of sanitation practices for navel orange worm.
Picture 8: Peach twig borer larvae on an almond blossom.
Picture 9: Damage to a young almond shoot by the peach twig borer.
Fruit Development:
After bloom, a period of rapid vegetative and fruit growth occurs. Hull and shell growth and development continues until May. During this period, the potential size of the fruit is established. Fruit size is dependent upon the vigor of the tree and the number of fruit on each spur - the more fruit on a spur, the smaller the average nut size. Some fruit may fall from the tree through a natural thinning process. This is often called "June Drop," which often occurs in May.
During April, the produced photosynthate is directed toward both shoot and fruit growth. These processes compete with each other for nutrients and water, and thus can be reduced by nutrient deficiencies and/or water stress. In late April, the fruit reaches full size, the inner shell begins to harden, and the outer shell remains soft. In some cultivars, growth stress at this time can disrupt the nut and shell development leading to kernal loss or reduced quality.
In May, the embryo begins to enlarge. This process takes considerable time and will last until June. The embryo is surrounded by a clear and watery embryo sac, called a nucellus. The nucellus is often referred to as jelly. At the tip of the nucellus, a small translucent tissue is present - this is the endosperm. Within a few weeks, the white embryo will appear and will eventually filling the entire shell. Moisture stress or disease may interfere with this process leading to an aborted or shriveled kernal.
By June, kernal fill is complete, and weigh accumulation begins. Since weight is reliant upon the amount of carbohydrates within the kernal, good water management is needed to maintain the highest level of photosynthetic productivity. Water stress during this period can lead to low quality and reduced nut kernal weight. Hardening of the shell is completed in late June/early July.
Fruit maturation is signaled by the occurrence of hull split. Hull split is defined as the separation of the nut along the suture line and the separation of the hull from the shell. There are 4 different periods of hull split, in which the hull goes from a slight abscission along the suture to a point in which the hull is completely separate from the shell. At the same time of hull split, an abscission layer is forming at the base of the hull and spur. This layer will allow for the nut to fall from the tree when the tree is shaken. Hull split requires careful moisture management. Too little water and the abscission layer will not form properly, leading to a large amount of stick tights. Too much water can lead to an over vigorous tree that delays the formation of the abscission layer. Also too much water can lead to over-succulent hulls which are then susceptible to hull rot - a disease caused by fungi that invades the hull tissue.
Hull split does not always occur evenly and may take up to 3-4 weeks. This period of the almond is susceptible to many pests including the insect navel orange worm - which lays its eggs along the suture. The egg then hatches, and the larvae crawls into the shell, eating the kernal (Picture 10), and spreading the fungus Aspergillus flavus, which produces the mycotoxin Aflatoxin - a major regulatory concern. A section on Navel Orange Worm control will be covered in a later blog.
Picture 10: Damage to an almond kernal by the insect navel orange worm.
Harvest:
Harvest should begin on the almond tree when 95-100% of the hulls have split. This period varies from year to year, but usually begins in mid-August. The almond trees are shaken and the nuts fall to the ground. Once on the ground, the hulls will dry if conditions are favorable. An early harvest can reduce the incidence of damage caused by navel orange worm, but can increase the incidence of ant damage. Therefore it is important to employ proper season long pest management practices.
Almond harvest mainly performed by machines. With the exception of young trees, almond trees are mechanically shook (Picture 11), the nuts wind-rowed, and mechanically harvested (picked-up) (Picture 12) by a series of machines. The use of machines has reduced the reliance upon labor and has increased the efficiency of almond production.
Picture 11: An almond shaker removing the nuts from and almond tree.
Picture 12: An almond harvester picking the nuts up off of the ground.
Post-Harvest:
While the fruit are maturing on the tree during the summer, the tree is also developing buds for the next years crop.Shoot bud initiation occurs in April-May, and enters into a period of dormancy from June-Mid August. After harvest, the buds in the leaf axils begin to differentiate into flower buds, while others remain as vegetative buds. During this period of bud differentiation, a severe stress such as a water stressed caused defoliation, can cause the developing buds to push out. This can negatively affect the next years crop. Once into October, however, these buds enter a period of dormancy and will not push until the required chilling hours are met.
In the fall, the tree begins to store the sugar produced through photosynthesis as starch to be used for next year's spring growth flush. The tree also reduces its total moisture content and begins to synthesize the needed proteins for the dormant period.
For more information regarding season long pest management practices for almonds, please see http://ucipm.ucdavis.edu/PMG/selectnewpest.almonds.html.
References used for blog:
Almond Production Manual. 1996. University of California: Agricultural and Natural Resources. Publication 3364.
Integrated Pest Management for Almonds, 2nd Edition. 2002. Statewide Integrated Pest Management Project. University of California: Agricultural and Natural Resources. Publication 3308.
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In general, the season progresses in the following pattern: Dormant,Delayed Dormant, Bloom, Post-Bloom, Fruit Development, Harvest, and Post Harvest. Each period will be broken down and discussed.
Dormant:
As the temperatures from the late fall continue to drop, the tree enters a period of rest that lasts through December/Early January. At this time, the tree has dropped all of its leaves naturally or through an application of zinc, and is maintaining a low level of water use and starch consumption. This "low" flow of starch through the tree is needed as the catabolic breakdown of starch to sugar prevents the sap from freezing. This is, of course, only if the tree was able to develop enough starch reserves in the previous fall. In the rare occasion of low starch reserves, cold damage can occur leading to canopy and scaffold loss.
Picture 1: A dormant spur.
The cold temperatures that the tree is exposed to at this time helps with the development of the fruit buds. The tree requires a certain amount of moisture and chilling hours to come out of dormancy. Once the chilling hour requirement has been met, bud grown will begin with warmer temperatures. Chill hours are dependent upon the variety,but almonds generally need between 500 and 600 chill hours. In general, chill hours are the number of hours between the temperatures of 32-45 degrees Fahrenheit. Winter hours above 60 degrees are subtracted from the totals.
Delayed Dormant:
In late January/early February the tree begins to push a flush of fine feeder roots. These roots provide moisture and nutrients for the future development of leaf and fruit bud. Roots will generally only grow where there is soil moisture, so it remains important that efforts are made to ensure a full soil-water profile if inadequate winter rains have fell. The soil-water profile will be discussed in a later blog about irrigation management.
Picture 2: The delayed dormant period is initiated upon the observance of swelled fruit buds.
Picture 3: The delayed dormant period is concluded upon the appearance of green tipped buds.
Delayed dormancy is described as the period of fruit bud swell (Picture 2) until the green tip (picture 3). During this period, preparations for bloom occur which include insect and disease management, orchard floor management, and completion of orchard sanitation. Please see the UC Integrated Pest Management (IPM) page on Dormant season practices at http://ucipm.ucdavis.edu/PMG/C003/m003dcwhydormant.html.
Bloom:
Flower buds begin expanding ahead of leaf and shoot buds around Mid-February to Mid-March. Flower buds are formed on at least one year old growth and can be found on the terminal bud of spur or shoot, as well as the lateral buds of a one year old shoot. The timing of the bloom is dependent upon the variety which is related to the amount of chilling hours received. In years of low chilling hours, the bloom period lasts longer and is more sporadic leading to poor pollination. Later blooming varieties are generally more affected by insufficient winter chilling. Keep in mind that even though more chilling hours are needed for later blooming varieties, they are less susceptible to crop damage from early season frost events.
Bloom occurs in a series of flowering stages which are as follows: green tip (Picture 3), pink bud (Picture 4), popcorn stage(Picture 5), full bloom (Picture 6), petal fall (Picture 7), and post-petal fall. Almonds, which are self-incompatible, need to be cross-pollinated with a compatible variety. Insects move the pollen from tree to tree - with honey bees being the insect of choice and efficiency in commercial orchards. Therefore, during bloom, at least two compatible varieties must be in bloom simultaneously for a successful pollination event to occur. To ensure a successful pollination, many growers plant a pollinator that blooms slightly before and slightly after the variety of choice, nonpareil.
During the bloom period, the new leaves emerge from the vegetative buds and the production of carbohydrates occurs through the process of photosynthesis. At this point, growth is no longer dependent upon the reserves of the tree produces from the following year.
Picture 4: Pink bud stage of blossom development.
Picture 5: Popcorn Stage of blossom development.
Picture 6: Full bloom of an almond blossom.
Picture 7: Petal fall period of an almond blossom.
The bloom period contains several important periods of pest and disease management which can be found at http://ucipm.ucdavis.edu/PMG/C003/m003bcwhybloom.html. Poor pest management practices during this period can lead to a substantial crop loss, loss of fruiting wood, and fungal problems that may persist for several years. Of major concern include the blossom diseases of brown rot, scab, anthracnose, and jacket rot, the insect peach twig borer (Picture 8 and 9) and completion of sanitation practices for navel orange worm.
Picture 8: Peach twig borer larvae on an almond blossom.
Picture 9: Damage to a young almond shoot by the peach twig borer.
Fruit Development:
After bloom, a period of rapid vegetative and fruit growth occurs. Hull and shell growth and development continues until May. During this period, the potential size of the fruit is established. Fruit size is dependent upon the vigor of the tree and the number of fruit on each spur - the more fruit on a spur, the smaller the average nut size. Some fruit may fall from the tree through a natural thinning process. This is often called "June Drop," which often occurs in May.
During April, the produced photosynthate is directed toward both shoot and fruit growth. These processes compete with each other for nutrients and water, and thus can be reduced by nutrient deficiencies and/or water stress. In late April, the fruit reaches full size, the inner shell begins to harden, and the outer shell remains soft. In some cultivars, growth stress at this time can disrupt the nut and shell development leading to kernal loss or reduced quality.
In May, the embryo begins to enlarge. This process takes considerable time and will last until June. The embryo is surrounded by a clear and watery embryo sac, called a nucellus. The nucellus is often referred to as jelly. At the tip of the nucellus, a small translucent tissue is present - this is the endosperm. Within a few weeks, the white embryo will appear and will eventually filling the entire shell. Moisture stress or disease may interfere with this process leading to an aborted or shriveled kernal.
By June, kernal fill is complete, and weigh accumulation begins. Since weight is reliant upon the amount of carbohydrates within the kernal, good water management is needed to maintain the highest level of photosynthetic productivity. Water stress during this period can lead to low quality and reduced nut kernal weight. Hardening of the shell is completed in late June/early July.
Fruit maturation is signaled by the occurrence of hull split. Hull split is defined as the separation of the nut along the suture line and the separation of the hull from the shell. There are 4 different periods of hull split, in which the hull goes from a slight abscission along the suture to a point in which the hull is completely separate from the shell. At the same time of hull split, an abscission layer is forming at the base of the hull and spur. This layer will allow for the nut to fall from the tree when the tree is shaken. Hull split requires careful moisture management. Too little water and the abscission layer will not form properly, leading to a large amount of stick tights. Too much water can lead to an over vigorous tree that delays the formation of the abscission layer. Also too much water can lead to over-succulent hulls which are then susceptible to hull rot - a disease caused by fungi that invades the hull tissue.
Hull split does not always occur evenly and may take up to 3-4 weeks. This period of the almond is susceptible to many pests including the insect navel orange worm - which lays its eggs along the suture. The egg then hatches, and the larvae crawls into the shell, eating the kernal (Picture 10), and spreading the fungus Aspergillus flavus, which produces the mycotoxin Aflatoxin - a major regulatory concern. A section on Navel Orange Worm control will be covered in a later blog.
Picture 10: Damage to an almond kernal by the insect navel orange worm.
Harvest:
Harvest should begin on the almond tree when 95-100% of the hulls have split. This period varies from year to year, but usually begins in mid-August. The almond trees are shaken and the nuts fall to the ground. Once on the ground, the hulls will dry if conditions are favorable. An early harvest can reduce the incidence of damage caused by navel orange worm, but can increase the incidence of ant damage. Therefore it is important to employ proper season long pest management practices.
Almond harvest mainly performed by machines. With the exception of young trees, almond trees are mechanically shook (Picture 11), the nuts wind-rowed, and mechanically harvested (picked-up) (Picture 12) by a series of machines. The use of machines has reduced the reliance upon labor and has increased the efficiency of almond production.
Picture 11: An almond shaker removing the nuts from and almond tree.
Picture 12: An almond harvester picking the nuts up off of the ground.
Post-Harvest:
While the fruit are maturing on the tree during the summer, the tree is also developing buds for the next years crop.Shoot bud initiation occurs in April-May, and enters into a period of dormancy from June-Mid August. After harvest, the buds in the leaf axils begin to differentiate into flower buds, while others remain as vegetative buds. During this period of bud differentiation, a severe stress such as a water stressed caused defoliation, can cause the developing buds to push out. This can negatively affect the next years crop. Once into October, however, these buds enter a period of dormancy and will not push until the required chilling hours are met.
In the fall, the tree begins to store the sugar produced through photosynthesis as starch to be used for next year's spring growth flush. The tree also reduces its total moisture content and begins to synthesize the needed proteins for the dormant period.
For more information regarding season long pest management practices for almonds, please see http://ucipm.ucdavis.edu/PMG/selectnewpest.almonds.html.
References used for blog:
Almond Production Manual. 1996. University of California: Agricultural and Natural Resources. Publication 3364.
Integrated Pest Management for Almonds, 2nd Edition. 2002. Statewide Integrated Pest Management Project. University of California: Agricultural and Natural Resources. Publication 3308.
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Monday, June 15, 2009
Foamy Canker in Almond
This is one of the most visually moving diseases found in almond. Once upon the location of the problem, not only is the disease obvious by looking at the trees, but the air is also filled with a fermented-like smell reminding one a bar when entering for happy hour.
Overall Orchard Information:
The orchard I was called out to visit was described as a complete loss to foamy canker. To me this came as a bit of a surprise as foamy canker typically comes later in the season. By time I have arrived, the grower was in the process of removing the orchard. The entire orchard was exhibiting symptoms of foamy canker (Picture 1), poor growth and dieing trees.
Photo 1: Overview of the almond variety Fritz with foamy canker
The orchard was a Nonpareil-Fritz-Monterrey on Lovell planted on clay/clay loam soil. The trees were in their 4th Leaf trees with average growth. Nut set of the trees was decent, but not great. Speaking with the grower, he mentioned that the orchard has a high water table, found at about 7 feet with subbing up to 4-5 feet. Quality of the water was unknown. The site is also high in boron within its soil, and has a history of verticillium wilt (old tomato and melon ground). Overall, the discussion yielded that there were many issues from the start with the orchard - over 30% of the Fritz variety planted in the first year did not survive and needed to be replanted.
Irrigation of the trees tends to be minimal due to the high water table. The grower does not irrigate often - only 8 inches last year through double line drip. Nitrogen usage is minimum, but tree vigor is high due to being the first generation orchard on old row crop ground.
Observed Symptoms:
Foamy canker was found on both Nonpareil and Fritz varieties (Picture 2), but not Monterrey. All varieties had extensive cracks up and down the trunk (Picture 3). Removal of bark from around trunk cracks indicated necrotic tissues (Picture 4). Removal of scaffolds indicated verticillium wilt infections - all scaffolds on trees surveyed had vascular discoloration. The grower told me about the progression of symptoms before seeing foamy canker. They are as follows: 2nd year, the trees exuded a clear gum, followed by amber gumming in the 3rd leaf. This year, over 80% of the fritz, 20% of the nonpareil have foamy canker. No clear evidence of any insect borer was found in the crotch of the trees.
Picture 2: Close up of the almond variety Fritz with the disease foamy canker.
Picture 3: Close up of cankers found on the trunk of almond trees associated with the disease foamy canker.
Picture 4: Bark removal from around the cracks of foamy canker affected almond trees yields a large canker that extends from the crotch to near the graft union.
A walk through the orchard after the visit with the grower yielded a "dead spot." About a 4 acre area of trees with interesting symptomology. The Nonpareils were completely dead, the Fritz all had foamy canker, and the Monterrey all were alive but were struggling. Viewing the excavated trees, the root systems looked equally developed, but the root systems by the Monterrey/Lovell looked slightly larger than the Fritz/Lovell or Nonpareil/Lovell (pictures 4-6). I assuming this is due to how vigorous Monterrey grows.
Picture 4: Overview of a row of the almond variety Fritz with foamy canker symptoms.
Picture 5: Overview of a row of the almond variety Nonpareil with foamy canker symptoms.
Picture 6: Overview of a row of the almond variety Monterrey with foamy canker symptoms.
Previous research on foamy canker has been limited. It typically affects the Carmel variety within the first four years of orchard life. Symptoms usually appear in the summer after a hot weather spell in which a reddish gum flows from cankers found on the trunk and the crotch of the tree. Symptoms are most pronounced when a white froth forms from the cankers, emitting an alcohol like smell. Cankers are irregularly shaped, and tend not to reactivate the following year. Foamy canker is often associated with previous diseases or problems.
The foam associated with the disease is due to the occurrence of the fermentative bacteria found within the vascular system known as Zymomonas. Koch's postulates were performed on Zymomonas, but causality was not defined. It is clear that this bacteria causes a buildup of gasses and fluids that erupt when the pressure is great enough to break through the surface of the bark. This is known as alcoholic flux (Picture 7). The formation of the anaerobic situation that happens within the vascular tissue of the tree is unclear, as well as what factors that predispose the tree to disease.
Picture 7: White froth/foam associated with the almond tree disease of Foamy Canker.
The appearance of the cracks on the bark and large canker found upon bark removal suggests that the disease is found throughout the tree. Further bark removal reveals a layer of white, macerated tissue found near the cambial layer (Picture 8). Observations of the scaffold area revealed a weak structure with excessive gumming (Picture 9). Trees can gum excessively when a large area is damaged, so this was not too much of an oddity. Could the excessive gumming, however, within the scaffold triggered the the anaeorbic conditions for the expression of the disease? As far as the bark cracking, I would guess that it is most likely from the previous year's infection.
Picture 8: The layer of white macerated tissue found near the cambial layer of an almond tree affected with foamy canker.
Picture 9: Excessive gumming from wind damage found within the crotch of the almond tree.
As one can see, there is much to be learned about foamy canker of almond. Not knowing the epidemiology of the disease, there are no direct recommendations that can be made for the grower. In this case, recommendations to the grower for future plantings were to maintain healthy trees and remove diseased trees when they become apparent.
EDITORS NOTE: For larger pictures please refer to http://www.flickr.com/dadoll
Overall Orchard Information:
The orchard I was called out to visit was described as a complete loss to foamy canker. To me this came as a bit of a surprise as foamy canker typically comes later in the season. By time I have arrived, the grower was in the process of removing the orchard. The entire orchard was exhibiting symptoms of foamy canker (Picture 1), poor growth and dieing trees.
Photo 1: Overview of the almond variety Fritz with foamy canker
The orchard was a Nonpareil-Fritz-Monterrey on Lovell planted on clay/clay loam soil. The trees were in their 4th Leaf trees with average growth. Nut set of the trees was decent, but not great. Speaking with the grower, he mentioned that the orchard has a high water table, found at about 7 feet with subbing up to 4-5 feet. Quality of the water was unknown. The site is also high in boron within its soil, and has a history of verticillium wilt (old tomato and melon ground). Overall, the discussion yielded that there were many issues from the start with the orchard - over 30% of the Fritz variety planted in the first year did not survive and needed to be replanted.
Irrigation of the trees tends to be minimal due to the high water table. The grower does not irrigate often - only 8 inches last year through double line drip. Nitrogen usage is minimum, but tree vigor is high due to being the first generation orchard on old row crop ground.
Observed Symptoms:
Foamy canker was found on both Nonpareil and Fritz varieties (Picture 2), but not Monterrey. All varieties had extensive cracks up and down the trunk (Picture 3). Removal of bark from around trunk cracks indicated necrotic tissues (Picture 4). Removal of scaffolds indicated verticillium wilt infections - all scaffolds on trees surveyed had vascular discoloration. The grower told me about the progression of symptoms before seeing foamy canker. They are as follows: 2nd year, the trees exuded a clear gum, followed by amber gumming in the 3rd leaf. This year, over 80% of the fritz, 20% of the nonpareil have foamy canker. No clear evidence of any insect borer was found in the crotch of the trees.
Picture 2: Close up of the almond variety Fritz with the disease foamy canker.
Picture 3: Close up of cankers found on the trunk of almond trees associated with the disease foamy canker.
Picture 4: Bark removal from around the cracks of foamy canker affected almond trees yields a large canker that extends from the crotch to near the graft union.
A walk through the orchard after the visit with the grower yielded a "dead spot." About a 4 acre area of trees with interesting symptomology. The Nonpareils were completely dead, the Fritz all had foamy canker, and the Monterrey all were alive but were struggling. Viewing the excavated trees, the root systems looked equally developed, but the root systems by the Monterrey/Lovell looked slightly larger than the Fritz/Lovell or Nonpareil/Lovell (pictures 4-6). I assuming this is due to how vigorous Monterrey grows.
Picture 4: Overview of a row of the almond variety Fritz with foamy canker symptoms.
Picture 5: Overview of a row of the almond variety Nonpareil with foamy canker symptoms.
Picture 6: Overview of a row of the almond variety Monterrey with foamy canker symptoms.
Previous research on foamy canker has been limited. It typically affects the Carmel variety within the first four years of orchard life. Symptoms usually appear in the summer after a hot weather spell in which a reddish gum flows from cankers found on the trunk and the crotch of the tree. Symptoms are most pronounced when a white froth forms from the cankers, emitting an alcohol like smell. Cankers are irregularly shaped, and tend not to reactivate the following year. Foamy canker is often associated with previous diseases or problems.
The foam associated with the disease is due to the occurrence of the fermentative bacteria found within the vascular system known as Zymomonas. Koch's postulates were performed on Zymomonas, but causality was not defined. It is clear that this bacteria causes a buildup of gasses and fluids that erupt when the pressure is great enough to break through the surface of the bark. This is known as alcoholic flux (Picture 7). The formation of the anaerobic situation that happens within the vascular tissue of the tree is unclear, as well as what factors that predispose the tree to disease.
Picture 7: White froth/foam associated with the almond tree disease of Foamy Canker.
The appearance of the cracks on the bark and large canker found upon bark removal suggests that the disease is found throughout the tree. Further bark removal reveals a layer of white, macerated tissue found near the cambial layer (Picture 8). Observations of the scaffold area revealed a weak structure with excessive gumming (Picture 9). Trees can gum excessively when a large area is damaged, so this was not too much of an oddity. Could the excessive gumming, however, within the scaffold triggered the the anaeorbic conditions for the expression of the disease? As far as the bark cracking, I would guess that it is most likely from the previous year's infection.
Picture 8: The layer of white macerated tissue found near the cambial layer of an almond tree affected with foamy canker.
Picture 9: Excessive gumming from wind damage found within the crotch of the almond tree.
As one can see, there is much to be learned about foamy canker of almond. Not knowing the epidemiology of the disease, there are no direct recommendations that can be made for the grower. In this case, recommendations to the grower for future plantings were to maintain healthy trees and remove diseased trees when they become apparent.
EDITORS NOTE: For larger pictures please refer to http://www.flickr.com/dadoll
Monday, June 8, 2009
Herbicide drift damage to a Butte/Padre almond orchard by 2,4-D
May is the time of the year for the herbicide injury to almonds. High winds, fast growing weeds, and too many orchard tasks to complete in a day are the typical causes of herbicide drift. Herbicide drift can be prevented by following a few simple principles:
1). Avoid windy days when applying herbicides,
2). Apply the correct herbicide that targets the correct weed,
3). and apply the herbicide at the proper rate.
A field call in mid-May by a grower yielded a case of typical 2,4-D injury to almond. The 2nd leaf orchard was 50% Butte and 50% Padre on nemaguard rootstock. The orchard was situated in sandy soil with microsprinklers used for irrigation. The grower reported multiple trees showing dieback of new growth. He was uncertain of the cause and thought verticillium wilt may be affecting his orchard. Picture 1 shows the overall symptoms of an affected almond tree.
Picture 1: Overall tree symptoms caused by 2,4-D herbicide drift. Note tip dieback and odd growth.
Overall, the distribution of the symptoms were found throughout a large percentage of the block. Many trees where showing a "shepherd's crook" of the new growth indicating either a wilt disease or herbicide/salt issue. Picture 2 shows the severity of the symptoms on the new growth of the almond tree.
Picture 2: Branch tip dieback due to 2,4-D herbicide drift.
Leaves at the tip of the crook were crispy, indicating a fast wilt. Shoots with contorted growth were found throughout the canopy. Pictures 3 and 4 are of these symptoms.
Picture 3: Branch damage from 2,4-D herbicide drift. Branch is showing the "shepherd's crook" symptom, typical of vascular wilt pathogens or salt/chemical damage.
Picture 4: Contorted growth of new growth caused by exposure to 2,4-D herbicide.
With the exception of the contorted growth, symtpoms expressed by the affected trees could be one of four possibilities which include verticillium wilt, nitrogen burn, peach twig borer (insect damage), or herbicide injury. Verticillium wilt is characterized by vascular staining and can be checked by cutting into the tissue of the affected branches. Peach twig borer is caused by an insect and tends to affect new growth, but typically does not cause crispy leaves. I was unsure about the possibility of nitrogen burn, but the grower was open with information relevant to his recent applications of nitrogen. He applied roughly 1.5 ounces per tree of straight nitrogen, which is an amount that would not cause burn on 2nd leaf trees. Knowing this, only one option remains - the cause which I suspected due to the contorted growth of the branches.
The herbicide used within the orchard was 2,4-D. When asked about application procedures, the grower said he hand gunned on the herbicide and applied it at the high end of the label rate. While hand-gunning of herbicide provides the ability to spot treat areas, it typically leads to over application of herbicides within the treated area. Furthermore, even though 2,4-D works well on most weeds, it has the ability to translocate within plants if it is somehow taken up by the plant. I suspected that this was the case with these trees.
I noted within the orchard that the damage to the trees looked related to a high weed kill around the base of the tree. Closer inspection of the tree trunks within these areas revealed several cracks in the bark at the ground level - probably cracks caused by the tree moving in the breeze. Inspection of the leaves of these trees also indicated damage caused by herbicide drift. It is unsure of whether or not the herbicide entered the tree through the trunk or the leaves, but it was clear that a sufficient amount of herbicide had the opportunity to enter the tree.
I advised the grower to be more careful with his subsequent herbicide applications. In mentioning the principles above, I placed emphasis on the proper application rate and avoiding windy days.
1). Avoid windy days when applying herbicides,
2). Apply the correct herbicide that targets the correct weed,
3). and apply the herbicide at the proper rate.
A field call in mid-May by a grower yielded a case of typical 2,4-D injury to almond. The 2nd leaf orchard was 50% Butte and 50% Padre on nemaguard rootstock. The orchard was situated in sandy soil with microsprinklers used for irrigation. The grower reported multiple trees showing dieback of new growth. He was uncertain of the cause and thought verticillium wilt may be affecting his orchard. Picture 1 shows the overall symptoms of an affected almond tree.
Picture 1: Overall tree symptoms caused by 2,4-D herbicide drift. Note tip dieback and odd growth.
Overall, the distribution of the symptoms were found throughout a large percentage of the block. Many trees where showing a "shepherd's crook" of the new growth indicating either a wilt disease or herbicide/salt issue. Picture 2 shows the severity of the symptoms on the new growth of the almond tree.
Picture 2: Branch tip dieback due to 2,4-D herbicide drift.
Leaves at the tip of the crook were crispy, indicating a fast wilt. Shoots with contorted growth were found throughout the canopy. Pictures 3 and 4 are of these symptoms.
Picture 3: Branch damage from 2,4-D herbicide drift. Branch is showing the "shepherd's crook" symptom, typical of vascular wilt pathogens or salt/chemical damage.
Picture 4: Contorted growth of new growth caused by exposure to 2,4-D herbicide.
With the exception of the contorted growth, symtpoms expressed by the affected trees could be one of four possibilities which include verticillium wilt, nitrogen burn, peach twig borer (insect damage), or herbicide injury. Verticillium wilt is characterized by vascular staining and can be checked by cutting into the tissue of the affected branches. Peach twig borer is caused by an insect and tends to affect new growth, but typically does not cause crispy leaves. I was unsure about the possibility of nitrogen burn, but the grower was open with information relevant to his recent applications of nitrogen. He applied roughly 1.5 ounces per tree of straight nitrogen, which is an amount that would not cause burn on 2nd leaf trees. Knowing this, only one option remains - the cause which I suspected due to the contorted growth of the branches.
The herbicide used within the orchard was 2,4-D. When asked about application procedures, the grower said he hand gunned on the herbicide and applied it at the high end of the label rate. While hand-gunning of herbicide provides the ability to spot treat areas, it typically leads to over application of herbicides within the treated area. Furthermore, even though 2,4-D works well on most weeds, it has the ability to translocate within plants if it is somehow taken up by the plant. I suspected that this was the case with these trees.
I noted within the orchard that the damage to the trees looked related to a high weed kill around the base of the tree. Closer inspection of the tree trunks within these areas revealed several cracks in the bark at the ground level - probably cracks caused by the tree moving in the breeze. Inspection of the leaves of these trees also indicated damage caused by herbicide drift. It is unsure of whether or not the herbicide entered the tree through the trunk or the leaves, but it was clear that a sufficient amount of herbicide had the opportunity to enter the tree.
I advised the grower to be more careful with his subsequent herbicide applications. In mentioning the principles above, I placed emphasis on the proper application rate and avoiding windy days.
Thursday, June 4, 2009
Zinc Deficiency in Almond
A farm call in early April yielded a problem that proved to be difficult to diagnose due to complicating factors.
The orchard was three years old with three varieties planted on nemaguard rootstock: 50% Nonpareil, and two pollinators Monterrey (25%) and Avalon (25%). The soil was loamy sand to sand, very coarse, and a hardpan was present. Tree sites were backhoed before planting to remove the hardpan within the tree site. The previous cropping cycle was almond, but methyl bromide was used to fumigate the soil to kill nematodes, soil pathogens, and weeds. Irrigation is by moveable sprinklers.
Initial Observations:
Overall the orchard has variable growth overall. Some trees are large, some trees are smaller. Branches in the top of the tree have sparse growth. This growth, however, seems to be limited to one variety - the nonpareil. The symptoms are therefore found in every other row. Photo 1 shows the symptoms of sparse growth in the upper trees of one row.
Photo 1: Overview of the orchard showing symptoms. Note that the symptoms are more severe on one row of trees.
Up-Close Observations:
Sparse tree growth has tufts f leaves that are "bootstrapped." Leaves are deformed are have not completely formed physiologically. Photos 2 shows a symptomatic tree and photo 3 shows a close up of effected leaves.
Photo 2: An individual tree showing symptoms of poor leaf growth and development.
Photo 3: An isolated branch showing "bootstrapped" leaves.
Possible causes:
Glyphosate (Herbicide) damage (Round-up)
Dormant applications of chloropyrifos (insecticide) (Lorsban)
Zinc Deficiency
Diagnosing:
The applications of chloropyrifos, a broad spectrum insecticide, can sometimes lead to similar growth responses in almond when applied in the delayed dormant stage. Questioning of the grower yielded that no chloropyrifos was used within the orchard - in fact, he doesn't use chloropyrifos in any of his orchards. Good - one down, two to go.
Questions about the use of glyphosate were also asked to the grower. He stated that no glyphosate was used within the orchard. The pest control advisor (PCA) also seconded the fact by saying that no glyphosate was ordered by the grower. This eliminates direct application by the grower, but not by issues of herbicide drift or accidental exposure by having remnants of the herbicide left in a spray tank.
Drift concerns were brought up. The grower agreed that drift was possible, but said that no glyphosate was used in the orchard to the south (an organic block), and very little was used in the orchard to the north. Prevailing winds are from North to South, but storms will have winds blow from South to North.
The question for me was why one variety is only showing the symptoms. Calling upon other experienced colleagues, they indicated that different varieties have different timing of "pushing" the buds in the spring. During this period, a variety may have tissues that are softer or harder than another variety. If glyphosate was drifted into the orchard, the nonpareil could have been more sensitive to the chemical, showing more severe symptoms.
Zinc deficiency causes a similar growth response. In fact, when showing pictures to my colleagues, the diagnoses was either zinc deficiency or glyphosate injury. Zinc deficiency often causes tufting and/or rosetting of the leaves in NEW growth. Since most metal cations are not moveable within the plant, old growth usually appears healthy when new growth appears deficient. This is why iron chlorosis always shows up on the new growth first. The grower mentioned that zinc foliar sprays were applied during the postharvest period. Being zinc deficient was a concern since they are on sandy soils. He mentioned that a spring zinc foliar spray was being scheduled and should remedy the situation if that was the problem.
So..down to two possibilities: Glyphosate and zinc deficiency. Only time will differentiate which is the correct problem/diagnosis. A check back in two weeks would reveal the condition of new growth. If it was glyphosate damage, the new growth will still show signs of glyphosate injury (bootstrapping of leaves, compacted growth, etc.). If it was zinc deficiency, and the grower does apply a zinc foliar spray, the new growth should appear closer to normal.
Three weeks later I went back to check the site. New growth was still rossetted/tufted, but the symptoms were not as severe as before and the leaves were fully developed. I was informed that a zinc foliar spray was made about two weeks prior to the visit. This strongly suggests that zinc deficiency was responsible for the symptoms. If it was glyphosate, the new growth would still have been showing severe symptoms of "bootstrapped" leaves.
Solution/Prevention of zinc deficiency:
Correction for zinc deficiency is as follows: 10 pounds of basic zinc sulfate applied in at least 100 gallons of water per acre. Two applications should be made, two weeks apart. If rain occurs proximal to the application, shot holing of the leaves may occur from the reactivation of the zinc remaing on the surface whose chelated "safening" molecule has degraded.
The orchard was three years old with three varieties planted on nemaguard rootstock: 50% Nonpareil, and two pollinators Monterrey (25%) and Avalon (25%). The soil was loamy sand to sand, very coarse, and a hardpan was present. Tree sites were backhoed before planting to remove the hardpan within the tree site. The previous cropping cycle was almond, but methyl bromide was used to fumigate the soil to kill nematodes, soil pathogens, and weeds. Irrigation is by moveable sprinklers.
Initial Observations:
Overall the orchard has variable growth overall. Some trees are large, some trees are smaller. Branches in the top of the tree have sparse growth. This growth, however, seems to be limited to one variety - the nonpareil. The symptoms are therefore found in every other row. Photo 1 shows the symptoms of sparse growth in the upper trees of one row.
Photo 1: Overview of the orchard showing symptoms. Note that the symptoms are more severe on one row of trees.
Up-Close Observations:
Sparse tree growth has tufts f leaves that are "bootstrapped." Leaves are deformed are have not completely formed physiologically. Photos 2 shows a symptomatic tree and photo 3 shows a close up of effected leaves.
Photo 2: An individual tree showing symptoms of poor leaf growth and development.
Photo 3: An isolated branch showing "bootstrapped" leaves.
Possible causes:
Glyphosate (Herbicide) damage (Round-up)
Dormant applications of chloropyrifos (insecticide) (Lorsban)
Zinc Deficiency
Diagnosing:
The applications of chloropyrifos, a broad spectrum insecticide, can sometimes lead to similar growth responses in almond when applied in the delayed dormant stage. Questioning of the grower yielded that no chloropyrifos was used within the orchard - in fact, he doesn't use chloropyrifos in any of his orchards. Good - one down, two to go.
Questions about the use of glyphosate were also asked to the grower. He stated that no glyphosate was used within the orchard. The pest control advisor (PCA) also seconded the fact by saying that no glyphosate was ordered by the grower. This eliminates direct application by the grower, but not by issues of herbicide drift or accidental exposure by having remnants of the herbicide left in a spray tank.
Drift concerns were brought up. The grower agreed that drift was possible, but said that no glyphosate was used in the orchard to the south (an organic block), and very little was used in the orchard to the north. Prevailing winds are from North to South, but storms will have winds blow from South to North.
The question for me was why one variety is only showing the symptoms. Calling upon other experienced colleagues, they indicated that different varieties have different timing of "pushing" the buds in the spring. During this period, a variety may have tissues that are softer or harder than another variety. If glyphosate was drifted into the orchard, the nonpareil could have been more sensitive to the chemical, showing more severe symptoms.
Zinc deficiency causes a similar growth response. In fact, when showing pictures to my colleagues, the diagnoses was either zinc deficiency or glyphosate injury. Zinc deficiency often causes tufting and/or rosetting of the leaves in NEW growth. Since most metal cations are not moveable within the plant, old growth usually appears healthy when new growth appears deficient. This is why iron chlorosis always shows up on the new growth first. The grower mentioned that zinc foliar sprays were applied during the postharvest period. Being zinc deficient was a concern since they are on sandy soils. He mentioned that a spring zinc foliar spray was being scheduled and should remedy the situation if that was the problem.
So..down to two possibilities: Glyphosate and zinc deficiency. Only time will differentiate which is the correct problem/diagnosis. A check back in two weeks would reveal the condition of new growth. If it was glyphosate damage, the new growth will still show signs of glyphosate injury (bootstrapping of leaves, compacted growth, etc.). If it was zinc deficiency, and the grower does apply a zinc foliar spray, the new growth should appear closer to normal.
Three weeks later I went back to check the site. New growth was still rossetted/tufted, but the symptoms were not as severe as before and the leaves were fully developed. I was informed that a zinc foliar spray was made about two weeks prior to the visit. This strongly suggests that zinc deficiency was responsible for the symptoms. If it was glyphosate, the new growth would still have been showing severe symptoms of "bootstrapped" leaves.
Solution/Prevention of zinc deficiency:
Correction for zinc deficiency is as follows: 10 pounds of basic zinc sulfate applied in at least 100 gallons of water per acre. Two applications should be made, two weeks apart. If rain occurs proximal to the application, shot holing of the leaves may occur from the reactivation of the zinc remaing on the surface whose chelated "safening" molecule has degraded.
Wednesday, June 3, 2009
Ceratocystis of Almond
Ceratocystis or “mallet wound canker” has been found on almond throughout California for almost 50 years. This fungal canker, caused by Ceratocystis fimbriata, can develop on areas of the trunk or branches that have been damaged by tractors, hedgers, and harvesting equipment. Pruning wounds are also susceptible. Cultivars that are most susceptible include Nonpareil, Mission, and Ne Plus Ultra.
Picture 1: Scaffold loss due to girdling of branch by Ceratocystis fimbriata.
Ceratocystis cankers appear as either water soaked or dry cankers. Amber-colored gum is found at the canker margins. Infected tissue turns brown and the area eventually becomes sunken. Unlike Phytophthora infections, Ceratocystis remains active during the summer months in which rapid canker growth can occur. Cankers can girdle limbs, scaffolds, and tree trunks. Limbs 4-6 inches in diameter have been observed to be girdled in 3-4 years, while smaller branches are killed more quickly.
Picture 2: Gumming by the almond tree in response to infection by Ceratocystis.
Picture 3: Close up of almond tree scaffold infected with Ceratocystis.
Several species of sap-feeding beetles and fruit flies spread Ceratocystis. These insects feed on the fungus, ingesting and coming into bodily contact with the spores. The spores are then transported to other trees and deposited on the bark by the insects. Rains and sprinkler irrigations can wash the spores into fresh pruning wounds or other injuries. Once the fungus infects the cambium, it will begin to invade the healthy bark and xylem tissues of the tree. Dark stains may permeate into the heartwood of the tree, but rarely is the fungus found in these tissues.
Ceratocystis cankers can be avoided by preventing shaker damage on trunks and scaffolds. Irrigation should also be reduced or avoided during the 2-3 weeks before harvest, as available water increases the susceptibility of the bark to bruising and insect vector activity. If the bark is injured, shave the damaged portions to promote callus formation. Avoid pruning before any rainy weather. Following bark injury, trees are susceptible to Ceratocystis infections for 8-14 days.
Established cankers can be surgically removed. Remove infected bark and 1/4 - 1/2 inch of the woody tissue underneath the bark. The cut should extend one inch beyond the canker margin. Limbs that have been killed by the enlarging canker should be removed by cutting six inches below the canker margin. Branch removal and surgery should occur during December-February when the pathogen and vector insects are less active. Attempts to remove cankers may be unsuccessful, in which case the fungus may continue to grow. Affected trees should be rechecked the following year, and the surgical process repeated if survival of the canker has occurred. Dressing of pruning or surgical wounds made during the winter is not needed as most vectors are inactive at this time.
Orchards severely infested by Ceratocystis have typically been damaged repeatedly by harvesters. Proper equipment usage in order to prevent tree injury will reduce the incidence of the disease.
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