FEBRUARY 2013
CELEBRATING 133 YEARS AS CANADA’S PREMIER HORTICULTURAL PUBLICATION
VOLUME 63 NUMBER 02
CROP PROTECTION
The drive for more precision in crop spraying KAREN DAVIDSON Like most farmers, Shane Ardiel considers himself a lifelong learner. Last year’s April frosts destroyed his apple crop, a first-time experience in his 29 years of farming. He still sprayed at least half of his Clarksburg, Ontario orchard to keep pests under control. It was a real-time experiment, because he doesn’t know what to expect this year. “I’m worried about brown marmorated stink bug,” says Ardiel. “I don’t know what products are available and what the timing will be to get the larvae.” 2013 will be a learning curve with not only a new invasive pest species, but questions spilling over from last year’s minimal spraying and pruning regime. That’s where crop scout Lindsay Pink shares some early observations from Ardiel and other clients with Georgian Bay Fruit Growers’ Inc. “This year, we’ll need to get on top of apple scab,” she warns. “For growers who didn’t spray last year, there will be a clean break from crop protection products and that will help reduce chances of resistance. However, we had quite an education about apple maggot. We never had a problem with this pest but without spraying last year, we were flabbergasted at the injury. There will be a lot more insect pressure this year.” As theory goes, a reduction in
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An airblast sprayer course has spurred Shane Ardiel to modify spraying practices on his apple farm. With steely concentration, he’s up to the precision task on his 95 acres of apple orchards at Clarksburg, Ontario. Photos by Glenn Lowson. insecticides should mean that more beneficial mites take over. But Pink says that more than a year will be required for this equilibrium to take place. “The situation did not selfcorrect as quickly as we thought it would,” she says. “This year’s education will be stressing control of apple maggot and codling moth.” For Ardiel who does all the tank mixing and spraying on his 95 acres, an entirely new question arises: How to adjust crop spraying for his 45 acres of semi-dwarf orchards and the 50 acres of spindle-type plantings now in vogue. That’s where Jason Deveau, OMAFRA’s application technology specialist, offers fresh thinking. “Many pesticide labels instruct applicators to use an appropriate amount of water and to spray to the point of run-off, ” says Deveau. “But are pesticide labels everything they could be?” Deveau points to 30 years of research demonstrating that not all trees have the same spray
requirements. The rule of thumb for classic, standard trees was to use 400 U.S. gallons of water per acre. When dwarf varieties were planted, growers made a pro rata
“
I’m a lot more cognizant of what we’re spraying and spray patterns. Proper speed and proper nozzles are a big part of it.” ~ Shane Ardiel reduction in spray volume. For example, if trees were half the volume of a standard tree, then it was assumed that half the volume of spray mix was required to achieve the same coverage. The model became known as Tree Row Volume.
The question is whether that’s a correct assumption. In Deveau’s experience, the operator’s perceptions of coverage and sprayer setups vary widely between canopies and equipment. He’s also concerned about inter-orchard variability due to growth stage, rootstock varieties, tree shapes, density plantings and pruning practices. Growers could easily be over-spraying or under-spraying pesticides because they are not adjusting for these variables. Even within orchards, the same crop could have different canopy volumes. A study in New Zealand showed a difference in product required between bud break and harvest. In another U.K. study, spraying at a fixed rate across orchards at different growth stages resulted in a six-fold variation in pesticide deposits. Recognizing that new plantings don’t require as much spray as mature plantings, growers are already modifying carrier volumes and/or dosage rates.
Unwittingly, growers may be overspraying. Or they could be underspraying which reduces coverage and may encourage insect resistance. These practices are in a no man’s land which may foil the best intentions of integrated pest management (IPM). With all these changes in orchard technology, workshops such as Airblast Sprayers 101 have become popular. Developed by Deveau and CropLife Canada, the course has migrated to British Columbia where pesticide specialist Madeline Waring has teamed with a local sprayer manufacturer and tailored the workshop to grape and tree fruit growers in the Okanagan Valley. Blueberry growers, also requesting a tune-up, are now doing trial runs with water on water-sensitive paper hung in the crop rows to gauge pesticide distribution. New nozzle types, calibration methods and adjustments for air flow are all part of the course. CONTINUED ON PAGE 3