Did Insect Pests Freeze With Recent Low Temperatures?

Last week’s articles were concerning the eye-popping numbers of black cutworm and armyworm moths being captured by pheromone trap cooperators and weevil damage being reported in southern Indiana alfalfa fields. Did the low temperatures (≤28°F) of April 15/16 freeze-out these pest insects? The short answer, probably not.

The black cutworm and armyworm’s most vulnerable stage for freezing, the neonate (newly hatched) larvae, were likely nestled within the soil or under plants (e.g., chickweed, cereal rye, etc.) in which they were feeding. Temperatures in these micro-environments are much warmer, especially with the radiant heat from the ground. Besides, it would take more than just a few hours of freezing temperatures to cause mortality. For alfalfa weevil, they early instar larvae are able to withstand temperatures as low as -2°F, much lower than those reached in any of the past couple nights. Though the top of the alfalfa may look terrible, the weevil larvae will move to areas within the plant to commence feeding. Happy Scouting!

 

Alfalfa may look ugly from the freeze, the weevils are just fine

Alfalfa may look ugly from the freeze, the weevils are just fine.

Share This Article
It is the policy of the Purdue University that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue is an Affirmative Action Institution. This material may be available in alternative formats. 1-888-EXT-INFO Disclaimer: Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current directions of the manufacturer.
Pest&Crop newsletter - Department of Entomology Purdue University 901 W. State St. West Lafayette, IN 47907

© 2021 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by Pest&Crop newsletter

If you have trouble accessing this page because of a disability, please contact Pest&Crop newsletter at luck@purdue.edu.