We’re getting calls at our Diagnostic Center along with several of our Master Gardeners reporting armyworms in their yards. So, let’s talk about armyworms and what/if anything you should do about them.

Not exactly sure how the armyworm got its name, but it’s likely because you don’t typically see a single armyworm, you see a little “army” of these worms and sometimes that can be a little intimidating. Plus, when they get done with your yard, it can be quite a site to see several thousand armyworms crossing the street to dine on someone else’s yard, looking like a little army of caterpillars.

The adult form of the armyworm is a moth, and these moths have traveled here from the Gulf Coast of Texas or possibly even Mexico to join us here in Oklahoma. Upon their arrival, the females lay their eggs and there can be up to around 1000 eggs laid per moth. When these eggs hatch, the emerging caterpillars begin to eat as is true with most, if not all caterpillars. On the plus side, this feeding period only lasts about 2 to 3 weeks. At the end of this period, they dig down into the soil to pupate. A couple of weeks later they emerge as an adult moth and the life cycle begins again. This 5-to-6-week process can repeat itself multiple times up until October or even November when it starts to get cold.

With each female able to deposit 1000 eggs, you can see how their population can increase dramatically over pretty short periods of time. As the caterpillars are eating, they can do some damage to your lawns. They’ll eat most anything but seem to have a preference for fescue.

If you see damage to your turf, but don’t see any armyworms, there is a simple test you can do. Just add about an ounce of dish detergent to a gallon of water and pour that solution onto about a square yard of turf.

This mixture will serve as an irritant to the armyworms and cause them to become active trying to get away from the irritant. If you only see a few, you probably don’t need to do anything. However, if you see a lot, you might want to consider treatment. I say consider because yes, the armyworms can do damage to your turf, but the grass will grow back.

If you are not one who can take these minor setbacks in stride, bacillus thuringiensis (aka bT) is a good, organic pesticide to use on caterpillars. One of the good things about bT is that it is only effective on caterpillars, so there won’t be any collateral damage to other insects in your landscape. But again, oftentimes treatment is not necessary because your turf will grow back. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Frank Peairs, Colorado State University, Bugwood.org