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 higher rig speed. The results can be found below in the table. Please note that the data is presented as percentage of survival.

Rig Speed Deposition – Lower Canopy Deposition – Upper Canopy NOW Survival 14 DAT – Lower Canopy NOW Survival 14 DAT – Upper Canopy
1.8 MPH 9.2% 5.3% 3.73% 4.13%
2.4 MPH 9.1% 6.7% 4.25% 12.88%

This data suggests that slower rig speed increases the pesticide concentration deposited in the upper canopy, thus increasing the persistence of the product and corresponding NOW control. Another reason why speed doesn’t kill when it comes to NOW management.

Please see these entries for more information: Speed Doesn’t Kill, and Getting the Best Spray Coverage from a hull Split Spray.

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