Tree Fruit and Nut Sprayer Calibration 101

Tree Fruit and Nut Sprayer Calibration 101

More rain - should I spray?

Rain is forecasted for the coming week. Many growers are wondering "Should I apply another fungicide?"

Foliar diseases of concern at this time of year are scab, shothole, and anthracnose. Conditions of leaf wetness and mild conditions favor growth of these fungi, which can infect and kill leaves, nuts, spurs, and shoots.

Currently, the forecast calls for 2-3 days of rain. If it rains all three days, there would be ample time for these fungi to infect your trees. Post-rain event weather conditions should also be considered when making this decision. If the weather looks to be warm and breezy, a spray might not be necessary as the conditions will dry out the trees. Some level of disease may occur, but the rate of secondary spread would be reduced to improper environmental conditions. A rain event following 4-5 days later, however, would increase the disease pressure within the orchard.

Since spring rain events tend to be one to two days in length, broad spectrum fungicides are a viable alternative for orchard applications. Applications of Captan, Captevate, Maneb, and/or Ziram can provide a cheaper treatment option than some of the other fungicides. These products provide moderate to good control of scab, shothole, and anthracnose and reduce the chance of resistance formation. For more information of treatment options and fungicide efficacy, please see the Fungicide Efficacy and Timing Charts for Almond.

Nitrogen Content in a Gallon of UAN-32

I have been emailed a few questions in regards to calculating the amount of nitrogen in a gallon of Urea Ammonium Nitrate (UN-32 or UAN-32). Since UN-32 is widely used to fertilize/fertigate almonds, it is necessary to know how much is being applied per application.

1 gallon of UN-32 weighs 11.02 pounds. 32% of the weight is nitrogen - hence the "32." This roughly equals 3.4 pounds of nitrogen per gallon, or 55 ounces.

So, following the guidelines suggested by Brent Holtz (UCCE San Joaquin),when fertigating 2nd leaf trees with UN-32, at 110 trees/acre, no more than 4 gallons should be used in a single application.

I hope this helps.

Drift Management to Avoid Herbicide Damage

Written by Kurt Hembree (UCCE Fresno County)

Reducing spray drift is necessary to prevent crop injury, both within the field being treated and off-site. Environmental conditions (air temperature inversions, wind velocity, etc.), applicator awareness, type of spray equipment, nozzle selection, spray boom operating pressure, water volume discharge, and other factors affect the degree of drift that may occur during any application. While spray shields do not guarantee drift will not occur, they can greatly minimize the risk of drift, especially in open fields or where young vineyard and orchard plantings are being treated.

The following steps should be taken to minimize the risk of drift from ground sprayer equipment:
1. Don’t spray when it’s windy: Do not spray in winds above 6 - 10 mph.

2. Be cautious on calm days: Do not spray under dead calm conditions in early morning, evening, or the night. Calm conditions are often associated with temperature inversions which can result in long-distance spray drift (1 mile or more). Burning brush on calm days can give an indication on the presence of temperature inversions (refer to local regulations on restrictions for obtaining a burning permit).

3. Check the buffer zones: Refer to the product label to determine adequate buffer zones outside of the field treated. Do not spray if the wind is blowing towards a nearby sensitive crop, garden, waterway, or other sensitive area.

4. Use a shield: Consider equipping your sprayer with a protective shield. A number of designs are available that can reduce drift between 35 and 75%. Avoid spraying trunk-to-trunk with unshielded spray booms.

5. Use a spray drift retardant: Spray drift retardants are available that can be added to many products to help reduce off-target drift.

6. Check the formulation: Use amine formulations of 2,4-D when possible. Use special care when using ester or other volatile herbicides. Avoid spraying these products on or immediately before hot days.

7. Sprayer type: Sprayers designed to apply herbicides at low volumes (<10 gpa), such as controlled droplet applicators, produce extremely fine droplets which can drift long distances. Advances in sprayer technology allow for certain postemergence herbicides (like glyphosate) to be applied through low volume, shielded equipment or in low doses based on weed populations present at the time of treatment.

8. Watch the nozzle pressure: Avoid nozzle pressures above 45 psi for conventional flat fan tips. Excessive pressure can create fine droplets that are prone to drift. Use a minimum of 10 gal/acre, unless otherwise specified on the label.

9. Nozzle height: Operate nozzles at their lowest recommended height. For 80° tips, this is 18”, and for 110° tips, this is 12”. Orienting nozzles forward also allows for further height reductions.

10. Nozzle selection: Special nozzles are available by various manufacturers, that create coarse, low-drift sprays. These nozzles can reduce drift by 50 to 95%.

Fertilizing one-year old trees - be careful!

Written by Brent Holtz, Ph.D., UCCE San Joaquin County

Nitrogen is the most important element we can apply to our tree fruit crops. Almond growth and productivity depend on the availability and uptake of nitrogen. Most fertilizer recommendations are based on making nitrogen available to our trees so that a nitrogen shortage does not limit tree growth or productivity.

Young almond trees don’t require as much nitrogen as older trees. I like Wilbur Reil’s rule of “one ounce of actual nitrogen per year of age of tree”. That rate can be applied several times per season, but never more than that at any one application. Thus, a first leaf (first year in your orchard) almond tree should not receive more than one ounce of actual nitrogen per any application. A five year old almond tree should not receive more than 5 ounces of actual nitrogen per one single application. The University of California only recommends one ounce of actual nitrogen per one year old tree over the course of the season, but I have been told by many growers and PCAs that this rate is not enough for the growth they desire. So, if you want to put out five ounces of actual nitrogen per one year old tree, do so in five applications and not all at once!

I have seen many trees burned by nitrogen, especially if liquid fertilizers like UN-32 (urea ammonium nitrate 32 %) or CAN 17 (a clear solution of calcium nitrate and ammonium nitrate) are used in single applications. These liquid fertilizers are very effective and easy to use but it doesn’t take much to burn young trees. I do not recommend using these liquid fertilizers on first leaf trees–I prefer to see triple 15-15-15 (15% Nitrogen - 15% Phosphorous – 15 % Potassium) fertilizers used on first leaf trees. I like to see these granular fertilizers placed at least 18 inches from the trunk. With micro-sprinkler and drip irrigation systems liquid nitrogen fertilizers can be used very efficiently and easily by growers. But be careful, I know several farm managers that will not allow more than 10 gallons of UN-32 per acre per application on mature almond trees. UN-32 contains 3.54 pounds of actual nitrogen per gallon, if you put out 10 gallons of UN-32 per acre you added 35.4 lbs of nitrogen per acre. If you have 120 trees per acre and do the math you come up with 4.72 ounces of actual nitrogen per tree–almost 5 ounces! I recommend not applying higher rates than this per application. I have seen nitrogen burn occur more often during hot summer temperatures when trees have elevated transpiration rates and obviously faster nitrogen uptake rates than what would have occurred at a cooler time of the year.

Orchard tasks to help prevent frost damage

A light frost event is predicted for Tuesday and Wednesday night. Last year, an unexpected frost event caused a lot of damage to almonds throughout the San Joaquin Valley. Today's entry will focus on frost protection.

Types of frost. There are two major types of frost events that occur throughout California. An advection frost occurs when a cold front moves into the region, displacing the warm air. These events are rare and will have temperatures dropping below freezing even though the it may windy. They are very difficult to protect against due to the rapid displacement of heat from the orchard. Radiation frosts are more common. They are characterized by clear skies, calm winds, and temperature inversions. These frost events occur due to the gradual loss of heat from the orchard.

Almond Susceptibility to Frost.
Generally speaking, the further the tree advances out of dormancy, the more sensitive to frost it becomes. A dormant tree is very tolerant to cold temperatures, while small nutlets are very sensitive to frost damage. At this point of the growing season - petal fall to early nutlet development - temperatures below 26F will cause significant to total loss of the almond crop, while temperatures above 28F will cause minimal damage to the crop. The small difference of 2F makes the difference, and is why frost prevention strategies can be used to reduce crop loss.

Frost damage prevention.
Assuming that the orchard has already been planted (Further information regarding site selection for frost prevention can be found in the UC Almond Production Manual), Growers can manage their soil moisture and ground cover to help reduce frost damage from a radiation frost event. Moisture within the soil retains heat. This heat is then radiated up into the trees during a cold night. Dry or cultivated soil usually holds less moisture due to loss by evaporation, thus making the orchard more susceptible to frost. Ground cover pulls this moisture from the soil AND prevents the heat from rising to the boundary layer of the almond tree. Therefore, ground covers should be mowed to a low level to reduce the chance of frost on a cold night. Irrigating the surface soil should be done in anticipation of a frost event. Re-wet as needed.

Active frost protection can be utilized by introducing air movement or heat. At one time heaters were widely used to prevent frosts. Most heaters have been banned due to pollution concerns by the CA air resource board. Check with your local ARB for an updated list. Wind machines and Helicopters have also been employed to bring heat into the orchard. Commonly used in citrus orchards, wind movement introduces warm air - usually from the inversion layer - into the orchard.

The use of microsprinklers and solid-set sprinklers typically provide the best, affordable form of frost protection. Upon the orchard temperature dropping, sprinkler irrigation systems should be turned on to wet the soil surface. This wetting prevents the soil surface from dropping below 32F, and provides radiant heat for the orchard. In some cases, applications of water by solid set sprinklers have provided temperatures that were 4F to 5F six feet above the ground. Within microsprinklers,enough water must be used to provide adequate and consistent wetting of the soil surface. For most microspinkler systems, the exception be low volume sytems, this means to just turn them on.

Make sure to check your irrigation pumps to ensure that they will start up when needed. No one wants to be caught out working a pump at 3:00 AM when the temperatures are below freezing.

Also keep in mind that the actual temperature may be colder in the orchard than predicted - sometimes up to 2-3F difference. Therefore, frost protection measures should be utilized when temperatures drop to 30F.

More information regarding frost protection can be found in the UC Almond Production Manual.

University of California Cooperative Extension 2010 Pomology/Almond Internships

Position Vacancy Announcement

Pomology—Almond Internship Program
University of California Cooperative Extension and Almond Board of California are pleased to offer an exciting internship opportunity. Prefer graduate or undergraduate students and recent alumni in the agricultural and biological sciences.

This paid internship offers the successful candidate(s) an opportunity to learn about and assist with cutting edge research and education programs in tree crop production, sustainable agriculture, integrated pest management, soil and water sciences, and other disciplines. The intern will also participate in educational and outreach efforts to educate farmers, pest control professionals, and the general public regarding scientific findings and improve methodologies of crop production and environmental protection. Working closely with experienced Cooperative Extension Farm Advisors, the intern will learn about the latest in agricultural practices and technologies pertaining to almonds and other tree crops.

Positions: Internship with University of California Cooperative Extension
• Six-Month Internship: Program Representative II title. Full time, six-month position, $2,889, plus some benefits. Extension of internship will be considered, dependent upon qualifications and availability of funding.
Graduate, undergraduate student, or recent alumni, in the agricultural or biological sciences is preferred. .

• Three to Four Month Summer Internship: Student Assistant II title. $12-$16/hour, dependent upon qualifications. Some benefits available. Full or Part time, for 3-4 months. Graduate, undergraduate student, or recent alumni in the agricultural or biological sciences is preferred.

Where: The candidate will be placed in one or more of several UCCE counties where almond and nut crops are important, located in Central Valley of California.

Qualifications: Strong science background and communication skills, good work habits, zeal for learning, some agricultural experience, ability to work with others.

When: Highly Flexible. Program Representative – schedule to be determined by employer and selected candidate. Student Assistant(s) mid-April through September 2010.

Application Deadline: March 19, 2010. Decision of selected candidates will be in mid-April 2010.

SEE WEBSITE FOR MORE INFORMATION AND APPLICATION.

More rain may warrant another fungicide application

Rain is predicted for today (Tuesday), tomorrow (Wednesday), Friday, and Saturday. If it has been over 10 days since your last fungicide application, it might be a wise move to make another application during the next break in the weather. Pick a fungicide that targets shot-hole, jacket rot, anthracnose, and scab. This could either be a strobilurin (FRAC 11, Pristine= FRAC 7/11), a DMI/Broad Spectrum tank mix (FRAC 3 plus 2,M3,M4,M5), or a broad spectrum (FRAC M3,M4,M5) - depending on what was sprayed earlier this season and your budget. Try to avoid back-to-back applications of fungicides within the same FRAC group to reduce resistance formation.

Fungicides and Bee Health

I have had a lot of questions/concerns regarding bee health and bloom fungicides sprays. Even though bloom is nearing its end, I thought I would try and answer a few questions I have received - and finally had some time to research and formulate an answer to these questions.

Do fungicides applied during bloom affect bee health?
The short answer is "We don't know." Research has shown that fungicides that are applied around or at bloom do adhere to the pollen, and are brought back to the hive during the process of pollination. The fungicides then inhibit the growth of different fungi within the bee hive, decreasing the the microbial diversity of the bee's food source. As of the Almond Board of California 2009 Research Proceedings, it is unknown whether or not the fungi affected benefit or harm the overall health of the hive.

Which Fungicides are transported back to the hive?
Researchers at the Carl Hayden Bee Research Center in Tuscon AZ found five commonly used fungicides in the bee bread (food source) of hives placed in almond orchards. These fungicides include Chlorothalonil, Cyprodinil, Fenbuconazole, Iprodione, Boscalid, and Pyraclostrobin. The amounts of fungicide appear to vary by orchard and timing of application - BUT - this data was only based on hives placed in three orchards with two or three samplings- for now. Also, it is not known which fungicides target which fungi, if they negatively affect bee health directly, and if they have a negative impact on the entire hive by reducing the quality of the food source. The research group headed by Dr. DeGrandi-Hoffman will be looking into these questions through this year.

What about Pristine (Pyraclostrobin-Boscalid) applications?
Essentially, we don't know exactly how this fungicide affects fungal growth in the hive. In vitro studies from Dr. DeGrandi-Hoffman's lab indicates that the low rates of Pyraclostrobin-Boscalid that are comparable to the concentrations applied in the field resulted in the reduced growth of all 12 fungi the group isolated from the bee bread. It varied from slight to complete growth inhibition. Future research will hopefully determine if the concentrations found in the hive are able to decrease fungal growth and if the reduction of fungal growth negatively affects bee health.

How should we adjust our spraying to prevent harm to our hives?
Again, I am unsure. My best guess would be to talk with your beekeeper regarding a fungicide spray program, make fungicide applications when the bees are not active, apply the fungicides only by ensuring the spray tank is clean, and apply when pollen shedding is low (usually in the evening). For the most part, fungicides are required, especially this year, to maintain a profitable harvest - but so are bees. I hope future research will help guide our fungicide application practices to reduce unwanted damage to bees during pollination.

An article published on March 7th, 2009 in "The Western Farm Press" discussing previous/similar/more research findings by the Carl Hayden Research Center can be found here.

Information sourced from G. DeGrandi-Hoffman. 2009. "Determining the effects of fungicide contamination on nectar and pollen on honey bee colony health." Almond Board of California Research Proceedings. Technical Report.