Like many of the state’s grass farmers, Mississippi deer hunters hoping to produce rich food plots are dealing with a spotty outbreak of armyworms that has hit some areas pretty hard while leaving others alone.

The worst hit seems to be in the Northeast, but reports of small outbreaks have come from as far south as Natchez and as east as Meridian.

“In North Mississippi, we had a moderate swarm during August 2016, which we assumed would lead to a very active September,” said John Gruchy, the private lands coordinator for the Mississippi Department of Wildlife, Fisheries and Parks. “So far I have not seen another large swarm, but some of that could depend on crop maturity in response to the drought we are experiencing in some parts of the state.

“The swarm in 2015 was much more devastating to millets and other crops in the context of dove fields and duck holes. This year's swarm appears to have been bad on clovers and some millets. I have also seen them get young hardwood trees. They tend to be most devastating to early-planted wheat, millets, and pasture grasses (Bermuda grass, etc.).”

Gruchy said dealing with armyworms is difficult once they have established. The swarm of moths lay eggs, which then produce the worms.

“In terms of cultural control, the best thing you can do is wait to plant your fall food plots until later in September or even October,” he said.

Armyworms are the larval form of the fall armyworm moth that is native to Central and South America, and arrive in the United States riding strong southerly breezes.

“In general, bad years can result from air currents favorable to migration,” Gruchy said. “They tend to thrive in hot dry weather.”

While some areas of Mississippi have had rain, many others have not in the late summer and the first week of fall. The problem with the worms is that once you spot them, there is a very short window to react before the damage is done.

“It is true that large swarms can devour entire fields in a short order,” Gruchy said. “The speed at which they cause damage is dependent on the size of the swarms. Also, the worms are not easily detected until they are in the larger stages of development, thus a very fast moving infestation may appear to be even faster.

“Fall armyworms must be treated with insecticides as soon as they are spotted. It is advisable to scout plots regularly during August and September to avoid crop loss. We tend to recommend Karate or Mustang insecticides if the landowner has a restricted use permit, and Sevin or Malithion if they do not.”

Gruchy said it is not a good idea to treat land without first seeing the worms. 

“I would never recommend treating armyworms until they are known to be present,” he said. “Insecticides are great tools, but they are not to be abused.”

Gruchy suggested land managers should visit the Mississippi State University Extension website at https://extension.msstate.edu/sites/default/files/publications/publications/P2717.pdf for more information.