Stop and spray the roses – more efficiently!

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

Spraying roses.

Spraying roses.

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. Adjustments in product rate and spray distribution should reflect the plant size, row spacing and developmental stage of the crop and pest. It should NEVER be done without a reference point for coverage and a strong history of efficacy – you can read more about monitoring coverage and sprayer adjustments here. Sprayer operators often do not have the tools to determine the optimal sprayer set-up. This experiment demonstrated the value of customized application settings and their potential to conserve pesticide, water, and fuel – without compromising pesticide efficacy.

Setting up water-sensitive papers in the rose blocks.

Setting up water-sensitive papers in the rose blocks.

Three 65m x 6.5m blocks were marked out in a field of roses in September, 2011. An untreated control, the grower’s traditional set up of hollow cones (D4D45) on 50 cm centres at 300 psi and 3.0 mph (841 L/ha), and an optimized set up of hollow cones (D3D45) on 50 cm centres at 150 psi and 3.0 mph (388 L/ha) (determined through trial and error using water-sensitive paper as a coverage indicator).

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 leaf area. All reps were randomly selected.

Visual record of randomly selected roses prior to treatment.

Visual record of randomly selected roses prior to treatment.

Visual record of randomly selected roses following treatment.

Visual record of randomly selected roses eight days after treatment.

There was no statistically significant difference in visible damage between the grower’s typical application set-up and the customized set-up. It was unclear why the control presented with less mildew eight days after application. The focal point here is that efficacy was maintained with optimized settings.

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.

 

Nursery applicators should consider customizing sprayer settings for each crop using water sensitive paper to indicate suitable coverage. Adjusting application settings can.

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

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