David Doll4 CommentsJune 22, 2018Diseases

Alkaline treatments have been shown to reduce hull rot

Recent research has found that alkalizing treatments applied at hull split are able to reduce the severity of hull rot caused by Rhizopus stolonifer. Over the past two years, work by Dr. Jim Adaskaveg and colleagues out of UC Riverside has repeatedly shown that several products reduce hull rot incidence. These products included dipotassium phosphate (applied as the product diKaP) applied at 48 ozs/acre, calcium hydroxide applied at 320 ozs/acre, and Cinetis applied at 24 fl. ozs/acre. A single application of each of these products made at 5% hullsplit was shown to be as effective as several fungicide combinations and reduced hull rot strikes by over 75% in comparison to the untreated control. Multiple applications, with one made at early suture split (traditional first navel orangeworm (NOW) timings), did not seem to reduce strikes further. The cause of the reduction in strikes is unknown. It doesnt appear to have a fungicidal effect on the fungus as often the fungus is present within the hulls. The current thought is that these products neutralize the fumaric acid that is produced by this fungus (this is the acid responsible for limb death).  It could also be due to an increase in tolerance to the toxin from the foliar product. Work is ongoing. With these products, timing is key. Apply around 5-10% hull-split. Since these products may be tank mixed with NOW products as well as other fungicides, confirm compatibility by running a jar test. If struggling in managing hull rot, consider trying these products on a selected blocks to see if they provide any reduction in observed damage. Just remember to leave an area untreated in order to determine treatment effectiveness.  Finally, keep in mind that the use of these type of products for hull-rot enters the “grey world” of registration.  Follow appropriate

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David Doll5 CommentsJuly 1, 2016Insects

Airblast v/s Electrostatic Rigs: Is there a Difference?

Hull-split sprays have began across the southern valley. These sprays are made to protect the crop from the infestation by Navel Orangeworm (NOW). During this time, it is common to receive questions regarding spray coverage. A common question received is about the comparison of electrostatic versus air-blast sprayers. A spray trial was conducted at the Nickels Soil Lab near Arbuckle, CA to compare the coverage and NOW control of an axial fan/air-blast and electrostatic spray rig.  Sprays were applied between 9:30 – 11:45 PM, when temperatures were below 75oF and relative humidity above 65%, to minimize evaporation and maximize spray coverage.  The replicated trial consisted of three treatments: Axial fan, air-blast sprayer (John Bean Spraying Co., 500 gallon tank, 36” fan, PTO driven; 143 gpa, 1.75 MPH, 170 psi system pressure) Air-shear, air-blast sprayer with electrostatic droplet charging (Progressive Ag, Model 2250, PTO driven; 50 gpa; 3.3 MPH and 30 psi system pressure). Air-shear, air-blast sprayer without electrostatic droplet charging (Progressive Ag, Model 2250, PTO driven; 50 gpa; 3.3 MPH and 30 psi system pressure). Eighth leaf ‘Fritz’ trees were sprayed with Delegate WG insecticide at hull-split timing. Applications included a molybdenum tracer to help determine spray deposition. Results: The spray coverage and NOW control results from the study (1 Day After Treatment) can be found in the table and summarized into four points. Sprayer Treatment Hull Mo Deposition – Upper canopy (15-20 ft) % NOW survival Upper Canopy (15-20 ft) Hull Mo deposition – Lower Canopy (5-7’) % NOW survival Lower Canopy (5-7’) Standard Axial-Fan/Airblast Sprayer 0.06 a 1.64% a 0.09 a 0.19% a Electrostatic Sprayer with electrostatic charge 0.05 a 3.20% b 0.18 1.01% b Electrostatic Sprayer w/o electrostatic 0.07 a — 0.15 b – Different letters indicate different statistical groupings at p<0.05. -Results pooled with those from

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Franz Niederholzer4 CommentsJuly 17, 2015Insects

Good Spray Coverage: Watch the Air

Written by: Franz Niederholzer, UCCE Farm Advisor, Colusa and Sutter/Yuba Counties and Luke Milliron, UCCE Horticulture Intern Good spray coverage is vital to effective pest control.  Nowhere is this truer than for NOW control at hull split.  Excessive sprayer speed kills spray coverage, especially in the tree tops.  But is there a simple way to figure out how fast to drive a sprayer to deliver good coverage in the tree tops while getting across the orchard in a timely manner?  Yes, watch the air.  Since airblast sprayers use forced air from the sprayer fan to carry pesticides throughout the tree, if the air from the sprayer fan(s) reaches the top of the canopy, the pesticide spray should get there, too. The following is a simple way to evaluate sprayer air movement in the canopy tops at different ground speeds.  Free hanging surveyors tape makes a great air movement indicator.  Tie 12-24” of surveyors tape to the top of a length of PVC pipe threaded through the branches in the middle of the tree row into the tree tops.  [Another option is to use a pruning tower to get up in the tree tops and tie several lengths of tape onto the highest shoots.]  Fill the sprayer half full of water, turn on the pump, close the spray booms, and run the sprayer down the row at a set speed with the fan on at operating tractor RPMs.  Have someone record a video of the movement of the tape(s) in the tree tops with a smart phone or iPad.  Review the video after the spray moves past the pole.  Did the tape move at all?  If no, then the sprayer air didn’t reach the tape, and neither will pesticide.  The sprayer needs to drive slower, or you need a sprayer with a larger

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David Doll4 CommentsJune 26, 2014Insects

Speed Doesn’t Kill Part 3: Economics

There has been a lot of research focusing on spray rig speed and spray coverage. Work by Jack Dibble back in the 70s-90s indicated that the best coverage is achieved at 1.5 MPH, and was the basis of the compromised recommendation of 2.0 MPH. This work has since been repeated by Dr. Joel Siegel (along with several collaborators) and Dr. Ken Giles and colleagues at Arbuckle, CA, and has indicated that at higher speeds, control of navel orangeworm (NOW) is lost in the upper canopy of the tree (>15′ high). This, interestingly enough, is where the majority of the crop is located. A few articles have been posted on this in the past (Speed Doesn’t Kill, Speed Doesn’t Kill, part 2).

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David Doll2 CommentsJuly 18, 2013Insects

Speed Doesn’t Kill (Part Two)

Ken Giles and colleagues have been reworking some of the old research on spray rigs, coverage, and insect control. Their most recent project reviewed ground speeds on insecticide coverage, but with a new twist – they incorporated spray efficacy (NOW control) into the control. In their most recent study – reported in the 2011-2012 Annual Research Report of the Almond board of California – they showed that coverage did not differ between two rig speeds, but survival of navel orange-worm (NOW) eggs decreased when Altacor was applied at the slower speed. The study was conducted at Nickels Soil laboratory near Arbuckle, CA. Sprays were made at either 1.8 mph or 2.4 mph using Altacor insecticide, R-11 non-ionic surfactant, and micro-nutrient tracers for disposition analysis. Applications were made with 100 gallons/acre. This volume was chosen because previous studies has shown it to the most effective volume in reducing insect infestation/damage. Disposition was measured using steel cylinders which had some resemblance of almonds within the trees. Leaf punches were also taken to measure disposition on leaves. After spraying, nuts were collected from the upper and lower canopy and NOW eggs were placed to determine efficacy of the pesticide application. Nuts were collected 1 DAT and 14 DAT. Spray deposition was not affected by tree location (upper v/s lower) and speed. Secondly, there were no difference between NOW survival in the nuts collected 1 day after treatment among the tree locations and speed. 14 days after treatment, however, significant differences in NOW survivability were found in the upper canopy of the tree – the slower rig speed reduced egg viability by 95.75% compared to 87.12% reduction at the faster speed. In other words, NOW eggs were 3 times more likely to survive in the upper canopy when the pesticide was applied at the

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Franz Niederholzer1 CommentJune 12, 2012Insects

Getting the Best Spray Coverage from a Hull Split Spray

Franz Niederholzer, UC Farm Advisor, Colusa/Sutter/Yuba Counties   Hull split is not far off. Where needed, an effective hull split spray can be the difference between good and bad (costly) reject numbers. Spray timing and pesticide selection are important parts of a good worm (and mite) control at hull split, but so is spray coverage. A bad spray job can waste time and money. In recent research conducted by Dr. Ken Giles (UC Davis Dept of Ag and Biol Engineering) and funded by the Almond Board of CA, hull split spray coverage and navel orange worm control was less in the tops of mature almond trees compared with that in the lower canopy. Here are a few things to consider when setting up your sprayer(s) for hull split spraying that should help improve spray coverage in the tree tops. Airblast sprayers are air carrier sprayers. The pesticide droplets go where the air from the sprayer’s fan goes. Increasing the spray volume per acre will not change coverage in the parts of the canopy – usually the tops – where sprayer air doesn’t reach. How can a grower make sure that good spray coverage is being obtained throughout the tree? Usually this means driving slow, giving the air from the sprayer fan time to reach the tree tops. How slow? Slow enough to give good coverage in the tops of the trees. In 2011, Dr. Giles and his team found that 2.0 MPH compared to 2.5 MPH sprayer speed significantly improved navel orange worm control at hull split. Slower was better. Not sure what speed to drive in your orchard(s) with your sprayer(s) for the best spray coverage? Check ground speed and spray coverage in the orchard just before hull split. Here are some examples of how to do this: Watch the

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David Doll0 commentsJuly 26, 2010Insects

Pyrethroid v/s Reduced Risk product usage for Hullsplit/May Spray

A few people have inquired about the differences between spray product choices for worm control during Hull Split and/or “May” Spray. I thought I would highlight some of the thoughts that the UC has developed over the years regarding this decision. Some of this may be redundant, but hopefully some new points will be brought to the table. Which product is best?Determining which product is the best treatment option for your orchard depends on budget, pest pressure, timing, and familiarity. Pyrethroid products are effective in knocking down adult moths and killing larvae that come in contact with the product. Persistence of the product within the field is not as long as the reduced risk products (about 2-5 days less), but they are useful for later hullsplit applications – around 2-5% for optimal timing. The downside with pyrethroids is the assumed mite flare up, knock down of orchard beneficial insects, and water run-off issues. A miticide should be tank mixed with the hull-split application if applying a pyrethroid. “Reduced risk” products (i.e. Entrust, Success, Delegate, Intrepid, Belt, etc.) target the eggs and larvae of the moths. They do not knock down adult populations as well as pyrethroids, but control developing larvae more effectively and selectively. These products tend to persist within the orchard a little longer, providing longer control and thus can be applied earlier than pyrethroid products (when blanks split). They have a minimal effect on beneficials, allowing the natural predators to help control mite populations, usually preventing a mite flare up, thus not requiring the tank mixing of a miticide.  These products are very effective but resistance to the mode of action may occur – so chemical class rotation is important if products are sprayed more than once per season. Water impacts appear to be minimal. Currently, a pyrethroid treatment is cheaper

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David Doll1 CommentJune 27, 2009Insects

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

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