True Armyworm

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Just about every year, we will get reports of True Armyworm, Pseudaletia unipuncta, damage somewhere in the state.  Some years, like in 2001 or 2007, we can have severe outbreaks across a wide region.  In most years, there will be isolated cases but even those can be significant to the farm affected.  Crops most affected are grasses including field corn, grass hay and pasture crops.   It is important for farmers and consultants to be monitoring fields starting in mid-June.  At a high enough population, armyworms can create a lot of damage very quickly.  One comment I got from a farmer in 2007 went something like this, "We looked one day and saw a little damage, but when we looked a couple days later many of the plants were totally stripped!"  

If you detect a problem, try to assess the severity of the damage as well as the age/size and population of the larvae.  Spraying with an insecticide is expensive and may not be necessary (or too late).  The best time to look for the larvae is very early in the morning or just before dark.  Armyworm larvae tend to stay near the soil surface during the day when it is hot and feed at night.  For more information refer to the links and factsheets below:

Outbreaks of Armyworm in 2012

Insecticide Control Options from the VT Agency of Agriculture

Armyworm - Here We Go Again in 2007

Recovery of Field Corn, Haycrops, and Pasture Following Armyworm Damage


If you detect armyworm in your field crops or forages or have any questions contact  Jeff Carter, Dan Hudson, Heather Darby or Sid Bosworth.  

If you have armyworm damage, please email me and give me your name, phone number, crop(s) affected, acres, and extent of damage.  Sid.Bosworth@uvm.edu

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This site is maintained by Sid.Bosworth@uvm.edu, Plant & Soil Science Department, University of Vermont.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. University of Vermont Extension, Burlington, Vermont.University of Vermont Extension and U.S. Department of Agriculture, cooperating, offer education and employment to everyone without regard to race, color, national origin, sex, religion, age, disability, political beliefs, or marital or familial status

Last modified June 15 2012 05:25 AM