Monday, September 20, 2021

Worms gone wild! Be on the lookout for armyworms

• By Scott Stewart •

net full of armyworms
A sweep net full of fall armyworms — photo courtesy Jake Mallard

The fall armyworm outbreak of 2021 is going to be one to remember. My colleague, Dr. Gus Lorenz in Arkansas, called it “epic.”

We knew something was different this year when another colleague in Texas, Dr. David Kerns, gave us a warning over a month ago. So what’s different?

First, the fall armyworm flight is several weeks early. Second, larval infestations have been unusually high. And third, for whatever reason, control with pyrethroid insecticides has been unusually poor (ranging from sometimes acceptable to a complete failure).

So far, West Tennessee appears worst affected, but this will probably change as the armyworms continue their “march.” It almost goes without saying that bermudagrass pastures are at high risk.

It’s not every field, but some double-cropped soybean fields are heavily infested, and it’s even worse where volunteer wheat or other grasses were present that attracted the moths. Even bermudagrass lawns are being infested, and homeowners and landscapers need to be especially alert on newly sodded or seeded lawns (fall armyworms really love the tender new growth). What little sorghum that is out there, including sorghum sudangrass, is also at risk.

So what’s the game plan?

In pastures, refer to the 2021 Insect Control Recommendations at https://extension.tennessee.edu/publications/Documents/PB1768.pdf (pages 61-62) for insecticide recommendations, but avoid using the pyrethroid insecticide like Baythroid XL, Mustang Max and Warrior.

The alternatives will be more expensive, but you may make up the differences in making fewer applications in the long run.

Similar advice in soybeans. Avoid using pyrethroid insecticides, and if you do use them, tank mix with a minimum of 0.5 pound of acephate and check back within two to three days to make sure it worked.

A more trustworthy suggestion is to use products containing chlorantraniliprole (e.g., Besiege, Prevathon Vantacor, Elevest), or Intrepid, Intrepid Edge or Blackhawk. For the most part, you should be able to use the lower end of the recommended label rates.

For sorghum, follow the recommendation at https://guide.utcrops.com/sorghum/, but again, avoid products containing only a pyrethroid insecticide.

Options are more limited for homeowners trying to control armyworms in their lawns, refer to the following article from Mississippi State University, http://extension.msstate.edu/publications/control-insect-pests-and-around-the-home-lawn.

Dr. Scott Stewart is University of Tennessee Extension entomologist and West Tennessee Research and Education Center director. He may be reached at sdstewart@utk.edu

Related Articles

Soybean South E-News

Sign-Up

Connect with Soybean South