Almond Tree Blow-Over Problems

Written by Bill Krueger, UCCE Glenn County

Periodically fall winter or spring storms with associated high winds and saturated soil conditions result in high tree losses. As an example, a March 1995 a storm brought 6 inches of rain and wind gusts up to 100 mph to the Sacramento Valley and resulted in an estimated loss of 15,000 acres of almonds worth $210 million. More recently a storm in January of 2008 with wind gusts in up to 70 mph resulted in tree losses of greater than 30% in some orchards.

When trees fall over their failure can usually be classified as windthrows or wood decay related. Windthrow is when trees with sound healthy roots are uprooted as a result of strong winds and wet soil conditions. Wood decay related failures are the result of infection from wood decay fungi, which consume the lignin in the cell walls of the heartwood. Eventually these trees fall, often in wind storms. Wood decay fungi are secondary pathogens and are not capable of penetrating intact plant membranes and must rely on some type of injury to gain access.

Survey work conducted by Joe Connell, Butte County Farm Advisor and Jerry Uyemoto, USDA Plant Pathologist following the March 1995 storm revealed the following. Generally, as trees aged tree losses increased. Windthrow was an important factor in young orchards (Fig.1). As orchards matured wood decay became more dominant. Wood decay accounted for approximately 90 % of the tree loss in mature orchards. Of 394 downed trees evaluated: 77% had wood decay and 81% had crown gall. Crown galls function as sites of entry for wood decay fungi.
Generally almonds on Marianna 2624 suffered lower losses than peach rooted trees. The exceptions included orchards in flooded areas with softened soil and unpruned orchards with dense canopies. Generally plum rooted orchards had less crown gall and wood decay.

Suggestions For Reducing Tree Losses From Blow Over Windthrow:
1. Orient strong roots in the direction of prevailing winds.
2. Avoid planting on high berms perpendicular to prevailing winds.
3. Pay attention to the orientation of irrigation wetting patterns particularly with regard to prevailing winds to ensure root distribution which favors anchorage.
4. Planting depth. On well-drained soil, it may be possible to plant plum rooted trees deeper than they were in the nursery. In addition to reducing the number of root suckers this may also provide for better anchorage.
5. Prune to even up variety related tree height differences. Taller trees will catch more wind and are at greater risk.
6. Avoid heading trees to high. Developing tops on high-headed trees will have greater leverage and are at greater risk.
7. Defoliate with zinc sulfate and or prune prior to fall and winter storms to reduce wind resistance.

Suggestions For Reducing Tree Losses From Wood Decay
1.Prevent crown gall. Buy trees from a nursery with a good crown gall prevention program. Treat new trees to prior to planting to prevent infection. Avoid spreading crown gall by injuring crowns and roots and mechanically transferring the disease through practices such as discing, mowing or cutting suckers.
2.Avoid practices which may injure trunks or roots and create an opening for wood decay fungi.

Environmental Impact Report on Ground Water Quality

Recently, The Watershed Coalition Newsletter Produced by the Central Valley Regional Water Board produced a newsletter dealing with the upcoming groundwater regulations.

The newsletter highlights the program options that the board is considering in the coming regulations to help protect groundwater. Options 3,4, and 5 will require a farm management plan in regards to application of irrigation water. These plans include just about every aspect of soil, nutrient, and water management/protection. Option 4 will require the use of all pesticides and fertilizers to be reported and justified.

I encourage you all to read the letter and provide input to your local water quality coalition.

Sampling for Plant Parasitic Nematodes

Many growers are facing the question of replanting orchard blocks. This aspect of orchard maintenance is critical and essential in maintaining an orchard business. Outside of the general tree removal, soil and ground preparation, there are 3 key biological replant problems that must be taken in consideration when replanting. These include plant parasitic nematodes, aggressive soil pathogens and pests, and replant disease of almond. This blog will focus on the first mentioned aspect of replant problems: nematode sampling and nematode control.

In almond production, there are three main parasitic nematodes that are of concern - Ring, Rootknot, and Lesion. Depending upon your soil type, planted rootstock, and previous cropping history, the populations of these nematodes can vary within the soil. It is important to keep in mind that plant parasitic nematode populations are directly related to tree production - in other words, the higher the number present, the more tree damage to expect. A previous blog describes the affect of nematodes on tree growth.

Orchard Sampling to Determine Nematode Populations.
To determine nematode populations, soil samples collected from the root zone area of a tree should be sent off to a laboratory for processing. In collecting samples, the following procedure should be used:
1. By using a soil map, identify soil texture changes within the orchard block,
2. Time the sampling to occur after the year of cover cropping or fallow period - if one occurred,
3. Attempt to sample from different soil textures and areas of previous tree performance. A good sampling strategy for a 40 acre block can be seen in figure 1. Please note the sampling in different soil textures and random samples throughout the field,
4. Use a soil tube and sample the 4"-16" depth of the profile - this is the area of most active root growth,
5. Place the soil in a PLASTIC bag, label with location, and place in a refrigerator until sent to a diagnostic lab. It is important to keep the soil out of the direct sunlight and extreme temperatures,
6. A minimum of 4 sample for a 20 acre block, 6 sample for a 40 acre block (Keep adding 2 more samples for every additional twenty acres) should be taken to give an accurate idea of the populations present.
Figure 1: Proper spacing for nematode sampling within a 40 acre block. Note the inclusion of different soil textures and areas of the field.

Interpreting the results.
Once the results are received back from the labs, the first question to answer is if nematodes are present or absent. If the populations are not detected, fumigation for nematodes may not need to occur. If they are detected, the population density will be used to determine which method of fumigation to use. It is important to note how the results are reported - the amount per liter of soil, per 250 mL of soil, etc. In order to use the following guidelines, please convert all results to nematodes per liter of soil.

Nematode Reduction for Orchard Sites.
Medium to Low Population Density (10-100 Nematodes per 1 Liter of Soil):
With a medium to low population density, many cultural practices can be used to help reduce nematode populations. These include an aggressive weed control program for 1-2 years before the orchard is removed, and taking a year off to cover crop with True Sudan. The principle behind these pratcices is to remove any nematode hosts (weed control) and plant a crop that nematodes feed on in order to "starve them out." These methods will only serve to reduce the population, not eradicate.

In the new block, choose rootstocks that have genetic resistance to the nematodes found. A list of rootstock performance in nematode-infested soils can be found in Dr. Michael McKenry's report in the 2008 Proceedings of the Almond Board of California.

If fumigation is possible, plan to treat a 6-8' row strip with Telon-II at 33 gallons per treated acre.

High Population Densities (>100 Nematodes per 1 Liter of Soil):
Plant to follow the same cultural and rootstock methods as outlined above. The only change is that fumigation is strongly encouraged, and a broadcast application of Telone-II at 33 gallons per treated acre should be used.

These practices will help reduce nematode populations and the corresponding damage to young almond trees.

Dealing with rain at harvest

A rain at harvest can be expensive - damage to the crop reduces the quality and premiums received from the huller, increase harvest costs reduce profit, and the use of forced air driers are costly. With rain imminent, it is important to keep in mind that practices should be employed to speed the drying of crop, whether it is in the tree or on the ground. The following guidelines may provide some help during a rain event during harvest.

If rain is forecasted, do not shake trees as almonds will dry more quickly when hanging on the tree due to increased air circulation.

If nuts are already on the ground, blow them away from trees but not into windrows or piles. Doing this will help prevent the nuts from sticking in the mud within the tree row strip. Once the nuts are stuck in the mud, it is difficult to move them away from the trees.

Once the rain event has completed, rake the almonds frequently, turning them until they are thoroughly dry.

If they are already windrowed, run them through a pickup machine and let the nuts fall out of the back. This will help turn the windrow nuts, increasing air contact, and will help remove wet debris from the pile.

A table developed by Larry Reinhart (North State Hulling Company) is provided below to serve as a further guide - especially if showers or high humidity persists.

Table 1: Prescribed actions for almond harvest involving a rain event.


Information sourced from Chapter 35 of the Almond Production Manual:
Connell, J.H., G.S. Sibbett, J.M. Labavitch, and M.W. Freeman. 1996. Chapter 35: Preparing for Harvest. Almond Production Manual. University of California, Division of Agriculture and Natural Resources. Publication 3364. Oakland, CA.

Post-harvest Boron Applications Can Increase Almond Yields

Written by Roger Duncan, UC Farm Advisor, Stanislaus

Boron deficiency is very common in orchards and vineyards planted on the eastern side of our county. This nutrient is essential in pollen tube growth and fertilization of the flowers. Moderate boron deficiency does not produce recognizable foliar symptoms but trees do not set their full potential of fruit.

Boron tends to accumulate in almond hulls and thus hull samples provide a better indication of boron status than do leaf samples. Harvest is an easy time to sample hulls. If samples are collected much earlier than harvest, a false reading may be obtained because boron may continue to accumulate in the hulls as long as they remain green on the tree.

The current boron guidelines for hulls are as follows:
80 ppm or lower = deficient
80-150 ppm = adequate
Over 200 ppm = may be toxic

Soil applications are the best way to correct a deficiency. Be very careful when applying boron—a little boron fertilizer goes a long way and will last for a few years. Soil applied boron fertilizers should be broadcast, not banded. Research has shown that even orchards with up to 120 ppm benefit from a post-harvest foliar application of boron. In University of California trials in Stanislaus and other counties, postharvest boron sprays often increased nut set and yield 20-30% the following year compared to non-treated trees.

Timing: The goal of the foliar application is to get the boron into the flower buds (actually pollen tube mother cells) that are developing for the next year. Therefore, timing of application is very important. During the growing season (March through July), large quantities of boron go into the developing hulls. If foliar boron is applied at this time, most of the boron will go into the hulls and is wasted. We want to target the period when the trees are funneling boron into next year’s developing flower buds. This occurs in late summer through early fall. Therefore optimal timing of foliar boron application is from well after hull split until the leaves become inactive in the fall (late October). Applications at bud swell work also, but not as well as postharvest.

Rate: The best results have been obtained with 1-2 lb. of Solubor® or a similar product (20% B) per 100 gallons of water. More than two pounds per 100 gallons often reduces the effectiveness or even results in lower fruit set than untreated areas. It appears that rate (amount of boron per 100 gallons), not amount of boron per acre, is important. In other words, you still put 5-10 lb. of a 20% B product in your 500 gallon spray rig whether you plan to spray 50 gallons, 100 gallons or 200 gallons of solution per acre.

Almond Articles from News Media

Came across the following articles this week in relation to almond production:

Almond Board of California's E-Outlook, which highlights the growth of almond shipments over the past 5 years. Topics also include the announcement of the 2009 almond conference, article about the summer farm advisor interns, a report on EPA's new fumigant application, and announcements/reports from upcoming/past events.

Minturn Huller has been making all types of media news, with numerous postings on blogs, in regards to its installment of solar panels. This is great exposure for the industry as outsiders can see that the industry is responding to the environment. A blog article can be found at Greentech Media Blog.

Financial news regarding the exportation of almonds to India - it appears that India is expected to become the #2 importer of California Almonds within 2 years.

Enjoy!