Crop & Pest Report

Accessibility


| Share

Alfalfa Weevil Update (06/14/18)

Based on the degree day accumulations (see map below) for alfalfa weevils in North Dakota, we are pass the period when adults and larvae cause significant feeding injury on alfalfa.

 Alfalfa Weevil Update

Based on the degree day accumulations (see map below) for alfalfa weevils in North Dakota, we are pass the period when adults and larvae cause significant feeding injury on alfalfa. Although adult weevils will feed on the foliage causing defoliation, larval feeding causes most of the defoliation. This is good news for alfalfa growers since cutting has started in many areas. There were a few field reports of severe defoliation caused by alfalfa weevil from Makoti-Ryder in north central area (T.J. Prochaska, NCREC) and Beach in southwest (Ryan Buetow, DREC). However, these alfalfa fields were cut early for hay and they avoided any insecticide treatments while preventing economic damage from alfalfa weevils. For alfalfa grown for hay, the most cost-efficient management is to cut the alfalfa early before feeding damage occurs. This also preserves our parasitic wasps that attack alfalfa weevils reducing populations naturally.

The degree-day model for alfalfa weevil use a base development temperature of 48F. Egg hatch begins at 300 accumulated DD and larval development occurs from 371 to 595 accumulated DD. Peak feeding occurs from 504 - 595 accumulated DD when larvae are in the 3rd to 4th instar. To assess the DD model, go to the NDSU’s NDAWN website and Applications – Insect DD. Then, click on the Map tab and select 48 F for your base temperature and Degree Days (DD) for your type.

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

knodel.8

knodel.9

Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

USDA logo

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.