In Arkansas, more insects attack corn roots than roots of any other crop. Along with this fact, Arkansas Extension entomologist Glenn Studebaker presented a checklist of corn pests at a recent corn production meeting in Yell County. Among the pests and his comments:
Wireworms: “These can cause a lot of damage if there are enough in the field. The bad thing about wireworms is if you've had them last year, you'll have some again this year. They have a long life cycle and can make it through winter easily because they move through the soil profile. They're more a problem in fields that have been fallow with lots of grass growing for a while.”
Seedcorn maggot: “This pest is very common. They lay their eggs in recently plowed ground in the spring. As soon as it warms up a little, these insects can come out and can cause some problems.”
Fire ants: Typically, fire ants are more trouble in no-till fields. “To deal with them, one of the things you can do is a little conventional tillage. That's helps some.”
Lorsban also works well on fire ants. Put it out in a band. “In Louisiana, where they have a lot of fire ants, that's what is recommended. It doesn't necessarily kill them but keeps them away from the plants long enough to get some growth on the crop.”
Once the crop is well-established, fire ants are actually beneficial. “They'll eat corn borer eggs and other things that can cause trouble. You find these ants on the edges of fields mostly. Early in the season, they can come into the first few rows and pull seed out of the furrows for feed.”
Southern corn rootworm: “Seed companies are working on a rootworm protected type of corn — much like Bt. It's doubtful it will be available in Arkansas.”
Several years ago, Studebaker asked if he could test the new corn in Arkansas.
“The companies weren't very excited about pushing it in the South. That's because there are three species of rootworm in corn. Predominantly, we have southern corn rootworm. Unfortunately, this new gene they've got bred into their corn isn't as effective against southern corn rootworm. That's a shame because it's very effective against northern corn rootworm, which we don't have here.”
White grub: “This is another common pest in the state. I had a lot of calls on this grub in many crops in 2005. I even had a call on grubs in cotton — that was the first time I'd seen grubs feeding on cotton roots.
There are two predominant species of grubs in Arkansas. The true white grub has a two-year life cycle. The other is the white grub with a one-year life cycle that turns into the June beetles.
“All grubs like to feed on grass roots. They'll feed on corn and cause significant damage. You can deal with them with insecticides and seed treatments.
Chinch bugs: “This is troublesome early-season insect. It's very tiny, not even a quarter-inch long.”
Sometimes the damage they cause is a bit deceptive. A couple years ago in Keiser, Ark., “someone thought we had some drift problems occurring. I walked out in the field and started looking and found the base of plant stems were covered with chinch bugs, feeding away.”
As far as control, “there are many insecticides that work well — pyrethroids, Furadan. The problem is getting the insecticides to the chinch bugs at the bottom of plants or in the soil. Proper application is a huge factor in controlling this pest.”
Stink bugs: Stink bugs can sometimes feed on corn stems. “More than likely, what you'll see is when the leaves open up as the corn grows there's a series of oblong holes. That's stink bug damage. Some of the seed treatments — Gaucho, Cruiser — do help control this pest.”
Grasshoppers: If it's a dry year, there can be grasshopper problems in corn. “They can be especially problematic early in the season. They aren't too difficult to control but you need to watch for them.”
Budworms: “In corn, budworms are any worms that get into the whorl. Actually, we should probably call them ‘whorl feeders.’ These include fall armyworms and corn earworms. A lot of time corn can grow out of the early season damage these cause.”
Corn borer: There are two species of corn borers in Arkansas: European and southwestern. “Around West Memphis and Marianna there are a lot of southwestern corn borers. Southwestern is probably the most damaging and predominant species in the state. They'll get inside stems and girdle it. That weakens it and increases chances for lodging.”
To avoid borer damage, it can be a big benefit to plant early.
“One of the main controls for borers is Bt corn. That technology does a great job. Since we can't plant more than 50 percent of the corn in Bt varieties, I suggest producers plant the conventional varieties in the early window. Then, as the window closes, switch to Bt varieties.”