Gardening is always interesting. I just lost my Chinese cabbage to cabbage loopers. Why, I wasn’t paying attention, and they got out of hand. I usually keep a better eye on my plants, but with the heat…need I say more? And we’ve been getting a lot of calls to our Diagnostic Center about armyworms, so let’s talk about some of these insects.

First of all, why do we call them worms? Probably for the same reason we call blue flowers purple (this has always been a pet peeve of mine). But anyway, when we talk about armyworms, cabbage worms, and web worms etc., technically they are not worms, but are larvae/caterpillars of some type of flying insect.

Armyworms are the larval form of a moth. These moths have travelled here from Mexico or the Gulf Coast of Texas (thanks Texas). Upon their arrival, the females lay their eggs.

Each female can lay up to 1000 eggs each. When these eggs hatch, they being to eat, which is true of most caterpillars. Fortunately, these periods of armyworm larval gorging only last about 2 to 3 weeks. Once they have eaten their fill, they dig down into the soil to pupate. A couple of weeks later, the adult moths emerge and begin the cycle again. With this life cycle taking only 5 to 6 weeks, there can be multiple generations up until October or possibly November. The cold brings this story to a close for the year.

If we do a little math, you can imagine how their populations can increase dramatically over time with one mama giving birth to 1000 eggs. If we assume there is a 50-50 split between males and females, that means there are 500 potential mama armyworms about to deposit 1000 eggs on nearby trees. If we figure 500 female times 1000 eggs, that 500,000 baby moths. Repeat that a few more generations and you can see the potential issue.

One of the challenges with this potential armyworm invasion is that they like to dine on our lawns. They will eat most anything but seem to prefer fescue lawns.

Typically, we begin to notice some damage on our turf before we see any armyworms. If this is your situation, you can mix up a solution of one gallon of water and an ounce of dish detergent and pour this on about a square yard of the area in question.

This solution will act as an irritant and cause the armyworms to try to get away from it. At this point you should see some armyworm activity. Depending on the quantity you find, you have a decision to make.

Yes, this feeding frenzy can damage your lawn, but in most cases the turf will grow back, especially if they are feeding on Bermuda. If you are not able to take this setback in stride, bacillus thuringiensis is a good organic pesticide to take care of this issue. Bacillus thuringiensis or bT, is an organic pesticide that specifically targets caterpillars so, other insects in the area won’t be affected by your use of bT. And bT loses its effectiveness pretty quickly, so there won’t be any long term impact to other insects.

Bacillus thuringiensis is one of our better treatments for most any caterpillar that is becoming a problem. This would include not only the armyworms but also cabbage loopers and fall webworms. You may have noticed webbing in branches around town. This is the fall webworm.

Here in Oklahoma, we have two different varieties of fall webworm, one is black or brown, and there is an orange variety as well. The first ones begin to hatch in late April and May and mature into moths in late June. We typically get 2 to 3 generations a year and it is a similar trajectory as the armyworm in that each mama lays about 500 eggs so with each generation, we get more and more fall webworms.

Fall webworms are interesting in that when they feel threatened, they begin to move in unison, rocking their webs on the ends of branches back and forth. We assume this is a defensive strategy that makes them look more ominous.

Fall webworms seem to prefer hickory, pecan, and black walnut trees but they have been documented on at least 88 different types of trees in the United States. One good thing about these insects is that while they can defoliate a tree making it look pretty terrible, the trees seem to bounce back in the spring. One would think that all that leaf loss would be fatal to the tree, but in reality, the trees have probably stored up all the energy they need for the winter and are going to be losing their leaves in a few weeks anyway, so in most cases, no harm-no foul.

Once again, bT works well on these insects, but it’s often hard for us to spray up in those tall trees. This would be the time to call an arborist if you are not inclined to live and let live.

If you can reach the area where the webs are, you can also just rip open the web to make it easier for birds to access what are apparently delicious caterpillars. One of my favorite ways of dealing with fall webworms came from a fellow Master Gardener who told me she like to stick a broom into the web and just wind it up like making cotton candy. She then walks the broom over to the trash can and pushes the web off the broom and into the trash. While I am not sure this as a long-term strategy, it does sound satisfying on a variety of levels.

Either way, while these caterpillars (worms) can cause some trouble, it’s not usually long-term damage. So, if you can stand it, we can just leave them alone and let the cooler weather take care of the problem. There is cooler weather approaching… right? See you in the garden!

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: Jason Sharman, Vitalitree, Bugwood.org