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Project Leader(s): Margaret Tuttle McGrath,
Plant Pathologist, Dept. of Plant Pathology, Riverhead
Andrew Landers, Pesticide Application Technology
Specialist, Dept. Agricultural & Biological Engineering, Ithaca
Cooperator(s): Dale D. Moyer, Vegetable/Potato
Specialist, CCE Suffolk County
Type of grant: Pheromones;
biorationals; microbials; conventional pesticides
Project location(s): Suffolk County
Abstract: The goals of this project were
to identify equipment that maximizes spray coverage on the underside of leaves
of cucurbits and to determine if powdery mildew can be controlled effectively
with nonsystemic fungicides when coverage is maximized. Conventional nozzles
and sprayers deliver little spray material to the underside of leaves. Thus
systemic fungicides are currently essential for controlling powdery mildew in
cucurbits. Fungicide resistance is a major concern because systemic fungicides
are at-risk for resistance development due to their single-site mode of action
and because the powdery mildew fungus has demonstrated high potential for developing
resistance. Organic growers would also benefit from identification of a means
to improve spray deposition as there are no systemic fungicides approved for
organic production. The contact fungicide Bravo was applied using an air assist
sprayer and using two novel nozzles (twin jet and air induction) and three traditional
nozzles (flat fan, hollow cone, and cone jet) on a conventional boom. Parallel
experiments were conducted on muskmelon and on pumpkin because these cucurbit
crops have different canopies.
Neither the air assist boom nor the novel nozzles
improved control achieved with Bravo applied with conventional nozzles on a
hydraulic boom. Control was improved on the lower leaf surface only when systemic
fungicides were also used. This study has demonstrated that it is challenging
to improve spray coverage on the lower surface of muskmelon and pumpkin leaves
by changing spray equipment. This may be due to their large size. However, results
from one year of research cannot be considered conclusive. Considering the potential
great benefit of improved spray coverage on cucurbit crops, additional research
on novel nozzles and air assist application technologies is warranted. Perhaps
these nozzles will be more effective used at different pressure or gallonage.
If coverage can be improved sufficiently, growers will be able to reduce the
quantity of pesticides used because they will not need to apply systemic fungicides
as much as they now need to. Implementing the necessary changes to achieve better
spray coverage will not be very costly if the novel nozzle types for a conventional
boom can provide better coverage than traditional nozzle types. On the other
hand, perhaps it will only be possible to achieve better coverage with novel
spray application technologies on crops with smaller leaves, such as tomato.
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