On August 1st of this year, I warned homeowners in the Tulsa area through a blog to be on the lookout for Armyworms in their lawn, as the conditions this year with all the rain and lush growth are very similar to the last big invasion about 14 years ago. It appears that we could be in for at least some damage in areas, if not all over Tulsa and Northeast Oklahoma. Today (August 24th) I saw one lawn in south Tulsa devastated by Armyworms, and other lawns in the area had small worms down in the thatch. Then later in the day, as I was watering my blueberry patch out in the country, I looked down and saw Armyworms in my Bermudagrass. How dare they!
The Fall Armyworm is the larva stage of a small gray moth, which migrates up from Mexico and Texas during the summer. Remember learning about complete metamorphosis in Science class years ago? Well, it starts when the female moth flies in and lays up to 2000 eggs in grass, shrubs, fences, tree, etc. at night, with hatching occurring a few days later into tiny larvae. They are very small and hidden down in the thatch layers of the turf. You won’t see them unless you get down on your hands and knees and look carefully into the turf. They are pretty harmless at this point as they are so small. But over a week or so, as they eat more and more grass foliage, they become much larger, over an inch long; mainly green, with brown stripes down the side. About 80% of the damage caused by Armyworms occurs during the final two days of their feeding, before they burrow into the ground to change to the pupa stage. Then a weak or so later, the pupa hatches into, you guessed it, the adult moth, and the process starts all over again. Several generations occur from August up until frost in late October or November.
These devastating insect pests can destroy turf almost overnight, as they typically invade the lawns as an army marching over the turf. In 2000 with the last big invasion, I remember actually seeing the lawns move as thousands of caterpillars moved across the turf eating grass blades down to the dirt. You could actually hear the chomping of the insects eating the turf, at least I could back then when my hearing was better. So the key to controlling Armyworms is to treat them with an insecticide when they are smaller and before they do damage to the turf.
Fescue turf is the main concern, because if they eat Fescue down to the dirt, it will probably just die, especially when it is hot. We never recommend scalping Fescue, and an Armyworm invasion is like a super scalp job. If your Fescue dies, then you’ll be re-seeding your lawn this fall, which is much more expensive than an insecticide treatment (same cost as your regular lawn treatment). They also love to feed on Bermudagrass, and can take it down to the stems and dirt. However, Bermudagrass is pretty tough, and it will recover in most cases with good irrigation and fertilization. Your lawn will look awful though for several weeks before it recovers. If you have a Zoysiagrass lawn, you’re in luck, as typically they won’t touch it.
There are several common liquid insecticides that control Armyworm larvae, but that needs to happen soon before they get much larger. Scout your lawn, and if you see them, we recommend contacting LawnAmerica promptly, or just treat it yourself. It’s actually a fairly easy treatment for the homeowner if they can buy a hose end sprayer and drench the lawn with the insecticide. Sevin and Permethrin are two common products you’ll find, but just read the label to make sure Armyworms are on it. Granular insecticides are OK, but don’t work as well as a liquid drench for Armyworm control. If we experience a major invasion of Armyworms in Tulsa, we’ll be hard pressed to be able to treat everyone who calls that day. We’ll be ready and do the best we can. But they can explode almost overnight, so I would recommend scouting your lawn and treating when they are small. It will be first come—first served when people call or contact us on our website, so I’d get with us sooner than later.