Articles
Improving management of Stemphylium leaf blight of onion
Article number
1398_9
Pages
65 – 72
Language
English
Abstract
Stemphylium leaf blight (SLB), caused by the fungal pathogen Stemphylium vesicarium, is an important foliar disease of onions in Ontario, Canada.
The pathogen infects the leaves and symptoms start as tan water-soaked lesions that progress to leaf dieback that can defoliate the plant.
This can reduce bulb storage because the uptake of sprout inhibitor requires 5-7 green leaves for adequate absorption.
Crop loss also occurs from reduced bulb size.
Fungicide insensitivity in the pathogen is also a concern.
From 2019 to 2021, field trials have demonstrated that commonly used fungicides such as Luna Tranquility (fluopyram plus pyrimethanil) and Aprovia Top (solatenol plus difenoconazole) show no disease suppression.
In 2021 and 2020 respectively, Miravis Duo (pydiflumetofen plus difenoconazole) and seed treatment penflufen did suppress disease.
Current spray forecasting models trigger too many sprays.
In 2021, a field trial was conducted to evaluate various spray timing models to reduce spray applications.
Treatments were a calendar spray (7-10 days), two TOMcast model variations, and the BSPcast model, using a rotation of the fungicides Miravis Duo and Dithane (mancozeb). BSPcast was developed for SLB on pear.
The calendar spray schedule and TOMcast 15 reduced disease severity compared to the nontreated check with no penflufen on the seed: 33.3, 33.5 and 43%, respectively.
Three and four sprays were triggered by TOMcast 25 and 15, respectively, and there were six sprays in the BSPcast and calendar spray programs.
There was no difference in yield among treatments.
This demonstrates that the models triggered more fungicide sprays than needed.
An improved disease forecasting program is being developed by analyzing the minimal and optimal leaf wetness and temperature durations for infection in controlled environmental studies.
The objective is to improve current forecasting models and eliminate unnecessary fungicide sprays.
The pathogen infects the leaves and symptoms start as tan water-soaked lesions that progress to leaf dieback that can defoliate the plant.
This can reduce bulb storage because the uptake of sprout inhibitor requires 5-7 green leaves for adequate absorption.
Crop loss also occurs from reduced bulb size.
Fungicide insensitivity in the pathogen is also a concern.
From 2019 to 2021, field trials have demonstrated that commonly used fungicides such as Luna Tranquility (fluopyram plus pyrimethanil) and Aprovia Top (solatenol plus difenoconazole) show no disease suppression.
In 2021 and 2020 respectively, Miravis Duo (pydiflumetofen plus difenoconazole) and seed treatment penflufen did suppress disease.
Current spray forecasting models trigger too many sprays.
In 2021, a field trial was conducted to evaluate various spray timing models to reduce spray applications.
Treatments were a calendar spray (7-10 days), two TOMcast model variations, and the BSPcast model, using a rotation of the fungicides Miravis Duo and Dithane (mancozeb). BSPcast was developed for SLB on pear.
The calendar spray schedule and TOMcast 15 reduced disease severity compared to the nontreated check with no penflufen on the seed: 33.3, 33.5 and 43%, respectively.
Three and four sprays were triggered by TOMcast 25 and 15, respectively, and there were six sprays in the BSPcast and calendar spray programs.
There was no difference in yield among treatments.
This demonstrates that the models triggered more fungicide sprays than needed.
An improved disease forecasting program is being developed by analyzing the minimal and optimal leaf wetness and temperature durations for infection in controlled environmental studies.
The objective is to improve current forecasting models and eliminate unnecessary fungicide sprays.
Publication
Authors
M. Kooy, B.D. Gossen, M.R. McDonald
Keywords
insensitivity, disease suppression, forecasting, leaf wetness, temperature
Groups involved
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