Stop and Spray the Roses – More Efficiently!

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About Jason Deveau (Spray_Guy)

Dr. Jason Deveau (@spray_guy) has been the OMAFRA Application Technology Specialist since '08. He researches and teaches methods to improve the safe, effective and efficient application of agricultural sprays in specialty crops, field crops and controlled environments. He is the co-administrator of Sprayers101, co-author of the Airblast101 Textbook, a slow cyclist and a slower runner.

See all posts by Jason Deveau (Spray_Guy).

Article co-written with Jennifer Llewellyn, former OMAFRA Nursery Crops Specialist.

Spraying roses.
We always admire the photos of sprayers in tulips produced by the Netherlands. Rose protection in Ontario is equally beautiful.

Nursery growers apply pesticides to a diverse range of plant species. In a perfect world, sprayer operators would adjust their sprayer set-up to match each crop, but this is rarely done because of time constraints and a lack of guidance. Adjustments in product rate and spray distribution should reflect the plant size, row spacing and developmental stage of the crop and pest. Any such adjustments should be performed using a reference point for coverage and a strong history of efficacy.

To demonstrate the value of sprayer optimization, we marked out three, 65m x 6.5m blocks in a field of roses. One block was an untreated control. One block was the grower’s traditional set up of hollow cones (D4D45) on 50 cm centres at 300 psi and 3.0 mph (841 L/ha). The third block was the experimental condition where we used an optimized set up of hollow cones (D3D45) on 50 cm centres at 150 psi and 3.0 mph (388 L/ha). We validated this condition using an iterative process to dial in the coverage indicated by water-sensitive paper.

Setting up water-sensitive papers in the rose blocks.
Setting up water-sensitive papers in the rose blocks.
Rule-of-thumb fungicide coverage on water-sensitive paper.
Rule-of-thumb fungicide coverage on water-sensitive paper.

One application of Folpet + Nova was made on Sep 19, 2011. Roses were photographed before and after the treatment. The photographs were digitized and the amount of powdery mildew appearing on the upper surfaces was determined as a percent of the total visible leaf area. Six replications were randomly selected from each block.

Visual record of randomly selected roses prior to treatment.
Visual record of randomly selected roses prior to treatment (September 9).
Visual record of randomly selected roses following treatment.
Visual record of randomly selected roses immediately following treatment (September 20).

There was no significant difference in the amount of mildew presented in the two sprayed blocks one day after the application (September 20). Eight days after application (September 27), there appeared to be better control in the optimized sprayer set up condition versus the grower’s standard set up. The large standard error bars in the grower’s condition made this statistically insignificant. It is unclear why the untreated block presented with the least visual mildew at this point. This preliminary work demonstrates the value of customized application settings and their potential to conserve pesticide, water, and fuel without compromising pesticide efficacy.

Results of optimizing sprayer set up on the visual occurrence of powdery mildew on rose leaves.
Results of optimizing sprayer set up on the visual occurrence of powdery mildew on rose leaves. Bars represent standard error of the mean. Unclear why control block presented less mildew on Sept 27.

The Ontario Farm Innovation Program and the grower co-operator are gratefully acknowledged for making this research possible.