A nice late July rain is a great way to kick off soybean grain fill. It also helps control pests like spider mites before they can set up shop in the maturing crop.
On this episode of the RealAgriculture Soybean School, we visit with PRIDE Seeds market agronomist Matt Chapple at the company’s education centre at Pain Court, Ont. It’s mid August and spider mites are still active in soybean plots that have endured dry growing conditions throughout 2022.
Chapple notes that spider mites are often seen on the edges of fields around winter wheat harvest, but after “a nice one or two inches of rain” the pest is sufficiently suppressed to prevent them from moving into soybean fields. But for many areas of Ontario, those rain events have been hard to find in 2022. The pests didn’t wash away — they continued to cycle and reproduce and then moved into soybean fields.
The microscopic insects are about the size of a grain of sand. When they do show up, Chapple says the crop tends to turn a reddish or bronze colour and die off. Typically, a hand lens is required to identify the tiny insects, which congregate on the underside of the leaf. Scouting lower in the canopy is advised to identify the pests as early as possible before they can negatively impact the plant. According to OMAFRA field crop guidelines, control is required if growers find four or more mites per leaf or one severely damaged leaf per plant prior to pod fill.
Chapple says spot spraying or spraying the perimeter of the field can also help control the pest. He also adds there are several strategies that growers can pursue earlier in the season to keep spider mites at bay. He recommends leaving grass or a foraging area for the mites along the field edge. When field edges are nicely manicured and grass is mowed down, the pests often get moving and head for the nearby soybean field.
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