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Alfalfa Weevil Degree Day Update (05/23/19)

The current map indicates that no egg hatch is occurring in ND, similar to last’s week map.

The current map indicates that no egg hatch is occurring in ND, similar to last’s week map. But, most of the state has accumulated enough degree days (200) for adults to emerge. Due to the recent cool temperatures, we are still running about -50 to -140 degree-days behind the 5-year average for alfalfa weevil development!

Adult alfalfa weevils are only ¼ inch long, brown with a distinctive dark brown stripe running down the center of the back. Antennae are elbowed, clubbed and the snout is blunt. A 15-inch sweep net is useful for finding adults and larvae in alfalfa fields.

Scouting should begin immediately after egg hatch, and fields should be scouted weekly up through the first cutting. Egg hatch occurs at 300 accumulated degree-days. So, we are getting closer. More on scouting and thresholds in next issue.

For more information, see the NDSU Extension publication Integrated Pest Management of Alfalfa Weevil in North Dakota E1676

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Janet J. Knodel

Extension Entomologist

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