Soybean School: Scouting key to aphid spray decision

Will 2019 be a soybean aphid year?

With a short, late-developing crop that lacks a dense canopy, growers will have to be on the look out for the minuscule, light green, pear-shaped pests, says Ontario Ministry of Agriculture, Food and Rural Affairs entomologist Tracey Baute.

With smaller plants, it doesn’t take as many aphids to cause plant injury and yield loss. That means when growers see aphid counts approaching the 250 aphid per plant threshold, they need to consider spraying an insecticide. It will be a tougher decision this year as many growers wrestle with input costs and whether it’s worth investing in a crop that may not reach yield expectations. Baute does note, however, that such a short crop with a long way to go to harvest will require protection if aphids are near threshold.

Heavy infestations of soybean aphids may cause plant stunting, premature defoliation, reduced seed numbers and lower seed weight that can lead to yield losses as high as 50 to 70 percent.

Scouting the crop is the best way to make an effective spray decision. On this episode of RealAgriculture’s Soybean School, Baute shares how she uses her phone and the Aphid Advisor app to scout for soybean aphids. The app uses aphid and natural enemy numbers, as well as expected population growth rates, to indicate whether aphid populations will stay below action thresholds or if an insecticide application may be needed.

If growers need to spray there are lots of options. When choosing insecticides, Baute says it is important to read labels: some products cannot be applied during flowering; and when using a pyrethoid insecticide, it’s best to avoid spraying during the heat of the day.

Click here for more Soybean School episodes.

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