Fall Armyworms & Bermudagrass Stem Maggots

Announcer: Farm and Family is a production of the Mississippi State University Extension Service.

Amy Myers: Today we're talking about fall armyworms and bermudagrass stem maggots. Hello, I'm Amy Myers and welcome to Farm and Family. Today we're speaking with Dr. Blake Layton, Mississippi State University Extension entomologist. Blake, fall armyworms and bermudagrass stem maggots can be serious pests in Mississippi hayfields. The July through summer months are when they're most damaging, but are there any other times of the year when we should be on the lookout?

Blake Layton: I mean, those are the main months. We can see fall armyworms and the stem maggots began appearing in June, but it's really in July and August and on into September that we end up doing most of our spraying. I would caution that as we get way into the fall, sometimes when people are planting small grains in the fall, if we've had a bad fall armyworm year, even those can be at risk.

Amy Myers: What should we know about fall armyworms?

Blake Layton: The main thing to know about fall armyworm is it's a very sporadic pest, so that means we never really know how bad they're going to be any given year. And some years I've known years when growers in South Mississippi where I grew up got by without spraying any, and other years I've seen those same growers price the same fields six or eight times a year just to make their hay. So that's why it's important, do a little preliminary planning and be prepared and know what to do, know how to identify these things, and be ready to treat them.

Amy Myers: Okay, and what do the fall armyworms look like? How do we know we have them?

Blake Layton: So the caterpillars, when they're fully mature, about an inch and a half in length, they may vary anywhere from tan colored to green to black, depending on time of year, population levels, that type of thing. You really know you have them when you start seeing your grass disappear. Good hay producers learn to identify some earlier signs, there are little window panes that appear in the leaves, the leaf blades, when those first little caterpillars began to feed. And that real way you have to do it is to get down on your hands and knees and part the grass and look for the little quarter inch to half inch long caterpillars there, and that's the ideal time to treat these things before they cause much damage.

Amy Myers: So talk to me about bermudagrass stem maggots.

Blake Layton: Amy, this is a new pest. This only showed up in the state in 2012, so we still have a lot of growers that are learning how to identify this pest. And that's tricky because it's a tiny little fly, cattlemen are familiar with horn flies, these little flies are about the size of horn flies, except they have yellow abdomens, hard to spot though. The little maggot that does the damage feeds inside the grass stem, so we don't see them.

So the main sign you have to watch for is the death of that four to six inches of the end of a chute. We're having cattlemen and hay producers that don't realize what's going on with their field, and they say it just stops growing. Because if you get enough of these, they just kill those chutes and they don't grow, and they'll kill the side chute when it sprouts out, and they can just stop a field from growing. So it's a subtle pest, but one you really have to watch for. Watching for those dead chutes, they'll be about four to six inches of length, and when you see numbers of those, that's when you know you've got a bermuda stem maggot problem.

Amy Myers: So you're not really looking for the pest itself, you're looking for the damage, because you can't really see the pest itself.

Blake Layton: It's more important to look for the damage, yes, at low levels. And what we recommend for people is if you have 15 to 20% of your field that's damaged, this cutting, then that lets you know, hey, I need to spray in this next cutting for bermudagrass stem maggot.

Amy Myers: What should we do to be proactive so we don't have to deal with this?

Blake Layton: Well, unfortunately we may have to deal with it every year or some years. So the proactive thing is to know when to get out there and scout those fields, kind of like we just described. You got to get out of your truck, you've got to get out in the field, look at it, assess it, do I have much damage from stem maggot, do I see those dead chute tips? Part that grass, kind of fluff it up, and then look on the dirt to see if you see any fall armyworms. A lot of times they'll fall off and curl up, sometimes they'll be crawling around, so that scouting is really key.

And another caution I always like to give is to have your equipment ready to go, because these things can eat so much grass so fast, that if you find them on day one and it takes you two more days to get your equipment ready to spray, they may have destroyed the field in that time.

Amy Myers: To be proactive is just scouting, and to treat there's a spray that you get?

Blake Layton: We do have several effective sprays, they're fairly easy to control, and we have a publication that lists those insecticides that work well for fall armyworm, as well as for bermudagrass stem maggot.

Amy Myers: And to find those, we just go into our internet or Google search engine and type in, for edge pests, Mississippi State Extension, correct?

Blake Layton: That's right.

Amy Myers: Today we've been speaking with Dr. Blake. Layton, entomologist. I'm Amy Myers, and this has been Farm and Family, have a great day.

Announcer: Farm and Family is a production of the Mississippi State University Extension Service.