Armyworms are one of those pests who may never have heard about. If you've ever seen them in your field once, it's one you'll never forget. They only hit selected fields that drew them there in most cases, but then they hit, they are like an army, marching across a field and literally destroying vegetation at warp speed.
Purdue University Extension entomologist Christian Krupke says you can't wait to scout for this one. You need to scout today. If they are at the right stage of growth, they suddenly ravage a field overnight.
States to the south have been sounding the alarm. Krupke says while armyworm capture hasn't been as high in Indiana, it has been relatively high in specific fields.
Fields at highest risk are ones where there is still dense grass cover, such as wheat, grass hay or grass cover crop. If you no-tilled corn into annual rye, scout now, he insists.
Krupke says hatched larvae move from dying vegetation once it's sprayed to emerged corn. The damage is unique, showing a ragged appearance. Damage extends from the leaf margin down the leaf rib. If the population is high enough, most of the plant can be destroyed.
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Krupke and John Obermeyer, another entomologist, says that Bt corn isn't immune. This pest can do significant damage before the Bt gene reduces their feeding. Also, seed-applied insecticides will not control armyworm.
The solution in this case is scouting and following guidelines in the Purdue University Corn & Soybean pocket Field Guide or its companion iPad app to know when to spray.
The challenge is scouting soon enough and often enough to catch it while there is still time to spray and salvage the crop.
Put it this way – armyworm is not a heavy-hitter in terms of fields affected in any-one-season, but if it hits your field, it's easily a knock-out punch unless you're on top of it and combat it with treatment quickly.