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Flea Beetles Still Active in Canola (06/20/19)

Feeding injury from Phyllotreta flea beetles is still being reported in spring-planted canola fields located in northeast and north central areas of ND.

Feeding injury from Phyllotreta flea beetles is still being reported in spring-planted canola fields located in northeast and north central areas of ND. Due to the severe damage caused by flea beetles, some fields were sprayed three times for control or even replanted. The cool, wet weather was not favorable for the insecticide seed treatments registered against flea beetles. Canola seed sat in the cold, wet ground and did not effectively absorb the systemic insecticide since the plant was not actively growing. Flea beetles are strong flyers and can find the newly emerged canola fields, the most susceptible stage to feeding injury. Once the crop reaches the 4-6 true leaf stage, it can usually outgrow the flea beetle feeding damage. The good news is that we are near the end of adult longevity for flea beetles. They typically start to die off in mid- to late June. As they age, their appetites also decline. Currently, there is no forecasting model that predicts outbreaks of Phyllotreta flea beetles in the spring and their potential for damage to the canola crop.

Some growers have noted that canola planted with a cover crop or inter-seeded with a grain crop had less feeding damage this year. Past research comparing no-till to conventional tilled fields found lower population densities of flea beetles in the no-till fields, probably due to the cooler microenvironment, which is less preferred by flea beetles.

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Janet J. Knodel

Extension Entomologist

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