There is a higher risk for aster yellows infection this year. Leafhopper infection rates are higher than they have been in the past 10 years and higher even than in 2012, the last time aster yellows was a major concern. That said, aster yellows remains only a possible risk at this point, as this year’s agronomic and climatic conditions differ from the wetter, colder conditions of 2012.
Growers and agronomists should sweep for leafhoppers if they are concerned. Leafhoppers prefer cereals over canola, so sweeping wheat is a better place to start. Leafhoppers also love brome grass and other ditch weeds; if canola is being infected, it is likely via leafhoppers moving in from ditches. To access information on potential testing of samples for aster yellows, email AAFC Field Crop Entomologist Tyler Wist.
If aster yellows symptoms occur, they are likely to appear by early August. Little can be done to tackle the disease as infection likely occurs early in the crop year, and there are no control options available once plants are infected. While at least one insecticide is registered for control of aster leafhoppers, a positive return on investment is not yet possible to predict. When thresholds are developed from ongoing research, they will likely include the number of aster leafhoppers, percentage of population infected, and amount of time spent feeding on canola. (Podcast: Aster yellows phytoplasma)
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