ASF Blog

Animal Science and Forages > ASF Blog > Posts > It is Time to Look for Fall Armyworms in Pastures and Hayfields

using sweepnet.jpgThis week cattlemen and extension agents  reported finding damaging populations of fall armyworm in hayfields in 4 counties: Pike, Calhoun, Etowah, and Marshall.  It is best to control fall armyworm caterpillars before they have molted into the last and largest size.  The caterpillar consumes about 80% of the food it will eat during the few days it is in this last feeding stage.  Then it burrows into the ground, and transforms itself into a moth and the life cycle starts all over again.  It takes about 30 summer days for a female fall armyworm to develop from an egg to the point where she is ready to lay an egg of her own.  That is why early on, it seems that the reports of fall armyworm damage come in in batches about a month apart, corresponding to a new generation of caterpillars molting into that last feeding stage.  Later in the season, the generations overlap, moths are laying eggs almost every day, and all sizes of fall armyworm caterpillars can be found in a given field.

A sweep net is a good way to find fall armyworms when they are small.  Sweep nets cost about $30-40 and you may eventually decide to buy one.  If you want to try one first, most county offices of the Alabama Cooperative Extension System have a sweep net that you can borrow to look for fall armyworm caterpillars.  Animal Science and Forages Regional Extension agents also have sweep nets you can borrow.  A few cattlemen in almost every county have sweep nets, too.  This video shows how to use a sweep net.  If you find armyworms with a sweep net, follow up by checking to see how many caterpillars are present per square foot.  If you find more than 2 caterpillars per square foot it is probably time to apply an insecticide, cut the hay, or graze the affected forage.

You can find helpful information related to Fall Armyworm underneath the “Fall Armyworm” section of the Forage Insect Pest Management Page on  Bookmark this link for resources on how to look for and control Fall Armyworm in pastures and hayfields.
Check out the latest map showing where damaging populations of fall armyworms have been found in Alabama pastures and hayfields.  Please let me know if you find them so we can keep updating the map.   
Stay informed of the latest Alabama forage crop information by liking the Alabama Forage Focus page on Facebook, or by subscribing to the Alabama IPM Newsletter by visiting
Kathy Flanders



There are no comments for this post.