Saturday, December 4, 2021

Watch out for stink bugs and kudzu bugs

• By Sandy Steckel and Scott Stewart •

green stink bug
Adult green stink bug — photo courtesy University of Tennessee

Many soybeans in Tennessee have entered the reproductive stages, and this is a critical time for scouting insects. This is especially true for fields in the later development stages with seed forming in pods as they are very attractive to several species of stink bugs, which are seed feeders.

Green stink bugs

The most common insect pest in our soybeans are green stink bugs. We can also have brown stink bugs, brown marmorated stink bugs and a few other less common species.

The best way to determine what insects are present in your beans is with a sweep net. Just a reminder, adult and immature stink bugs both count toward the treatment threshold of 9 per 25 sweeps in R1-R6 soybeans.

The University of Tennessee recommends doing four sets of 25 sweeps in representative parts of the field, not just edges or middles. We know getting to the middles of most narrow-row fields is not always practical, but do the best you can.

Most pyrethroid insecticides work well on green stink bugs. However, be mindful if you have a fair number of brown stink bugs (20% – 30%). In this case, bifenthrin or acephate will do better at controlling both green and brown stink bugs.

Kudzu bugs on the rise

kudzu bugs
Photo courtesy Auburn University

Populations of kudzu bugs are also increasing in some areas. Adults and egg clusters are not difficult to find in soybean locally.

Do not trigger an application on adults, only nymphs. Treatment is warranted if you average 1 nymph per sweep (or 25 nymphs per 25 sweeps).

Products with the active ingredient bifenthrin are hard to beat at 5-6 oz/acre, but most pyrethroid insecticides generally provide good control with the exception of cyfluthrin (e.g., Baythroid XL and Tombstone).

Sandy Steckel is Extension assistant, and Dr. Scott Stewart is IPM Extension specialist. Both are with the University of Tennessee.

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