Canola School: Nighttime is the right time to spray cutworms

(Kara Oosterhuis/RealAgriculture)

When’s the best time to control cutworms in canola?  For growers wanting to take out the pest it’s best to put away the sun glasses and reach for the night vision goggles.

On this episode of the RealAgriculture Canola School, BASF agronomist Leighton Blashko walks a field of canola near Sherwood Park, Alta., and tells host Kara Oosterhuis why it’s best to spray cutworm insecticide at night.

Blashko says the sunshine-shy pests typically emerge from their underground home during the night so starting a foliar insecticide application at dusk is good timing. He notes that many of the insecticide products available are contact in nature. There are, however, some products that deliver residual control, which does provide some flexibility for daytime application.

Another factor that favours nighttime application is the impact of high daytime temperatures. Blashko points out that the synthetic pyrethroid class of insecticides becomes less effective when sprayed at higher temperatures — in the 25 to 28 degrees Celsius range — “so again, that’s another good reason to spray during the night.”

In the video, Blashko looks at the impact the pest can have on a canola crop, how to identify the pest in-field and shares thresholds for making spraying decisions. (Story continues after the video.)

When scouting for cutworms in canola, a patchy crop is a telltale sign. Walking through the field, growers will notice missing plants and they may also spot blue and purple colouring on the edge of leaves and notice some plants that are falling over. In some cases, the cutworm can be found at the base of the plant. “Typically, cutworms would be feeding at the root. They’ll chew the plants off, mow them off near the base of where the stem goes into the soil or just below the soil surface,” adds Blashko.

Cutworm impact can vary depending on the species and crop. When it comes to managing the pest, growers need to determine cutworm pressure in the field and decide whether the population exceeds recommended thresholds. In the video, Blashko notes that growers should consider an insecticide application when anywhere from one to four cutworm larva are found within 30 centimetres or one foot of row. Growers can also consider patch spraying if the pests are located mainly in specific areas of the field.

Tap here for more Canola School episodes.

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