David Doll2 CommentsJanuary 29, 2022Diseases

Bloom Sprays: Spray Rig Strategy

Spraying trees during bloom and in the early spring is different than spraying in the summer. This is due to the reduced canopy which allows easier movement of the droplets. Rig speed, therefore, can be increased to help cover the orchard more quickly. Speeds from 3-3.5 mph (4.5-5.5 km/hr) are more common during this period. This contrasts with hull-split sprays which are typically done between 2.0-2.5 mph (3.2-4 km/hr). Many operations have considered every-other-row spray applications during bloom. Although not ideal, this strategy works reasonably well in lower density, small canopied, or young orchards. As the trees increase in size, however, the amount of wood within the canopy increases. This reduces the distribution of spray droplets through the tree, reducing protection on the unsprayed side. Spray rig speed must be moderate (~2.75-3.00 mph) and volume should be high (80-110 gpa, 750-1000 liters/ha) if using this strategy to improve canopy penetration by the droplet. I use this strategy for younger blocks when rain risk is high but uncertain– a spray is made to “side A”, with a follow-up spray made 7 days later to “side B.”  I typically follow up these two “half sprays” with a full spray using a different fungicide chemistry 7 days after the completion of the “B-side.” I only use this strategy for years 3 and 4 (up to 40% canopy coverage). In densely planted orchards, rig speed should be reduced (Figure 1). Increased tree density increases the amount of wood that blocks the distribution of droplets. To compensate, slower speeds must be utilized to improve air displacement and droplet movement. This would also be needed in orchards that have tall trees and have a lot of vertical wood growth. Every-other-row spraying should not be considered in these orchards due to the lack of coverage on the

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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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David Doll2 CommentsJune 22, 2010Insects

Speed doesn’t kill: Slow down your spray rigs!

As we prepare for hull-split, I thought I would take a minute to discuss spray rig speeds. It is easy to hurry with the hustle of applying a hull-split spray on a large number of acres, but attention should be payed to the ground speed in which chemicals are applied. The University of California recommends applying your sprays at a ground speed of 2.0 MPH to ensure adequate height coverage and canopy penetration of the spray. This recommendation has been based on numerous studies using ground rigs at varying speeds applying a water spray to water sensitive paper placed within the trees canopy. Figure 1 shows data from a recent trial conducted by Joel Siegel (USDA-ARS) conducted in pistachio. Figure 1: Spray coverage of a ground rig applying a water spray to water sensitive cards at 3 different ground speeds. Spray coverage for almond trees is based on the height and density of the tree. For the most part, if the height of the tree is under 10 feet, adequate spray coverage can be attained at almost any reasonable speed. For taller orchards, however, this is not true. As shown in figure 1, the difference of a 1/2 mph (2.0 mph v/s 2.5 mph) can reduce the coverage by 30% for trees 18′ or higher. Traveling at 3.25 MPH, less than 2% coverage was achieved at a height of 20 feet. This reduction makes the pesticide applied lose its efficacy due to low concentration and basically renders the application useless. It also increases the chance of resistance formation, loss of crop due to disease/insect damage, and tractor/rig damage. Many people say that their rigs are better than the ones used in the study and therefore they can go faster. I would doubt that statement unless they can clearly demonstrate it

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