The kudzu bug has become a major economic pest of Alabama soybeans in certain fields throughout the state in recent weeks.

Populations as high as 50 or more adult bugs per plant were observed in early June. Some of these fields now have 200 or more immature bugs per plant (late June). Calls are being received from growers and field men in recent days from all over the state.

Kudzu bugs are most highly attracted to early planted (April and early-May) soybeans. Beans planted later, for example following wheat harvest, are much less attractive.

The primary questions asked are when should soybeans be treated and what insecticide should be applied.

The second part of the question is the easiest to answer. Most pyrethroid insecticides do a good job of controlling Kudzu bugs.

Working thresholds have been previously established by entomologists in Georgia, North Carolina and South Carolina. For pre-flower vegetative beans a treatment threshold of five adults per plant is suggested.

After flowering, a threshold of one immature per sweep, with a sweep net, is recommended.

As an alternative to sweep-net sampling, visual inspections of insect density lower in the canopy will suffice. 

If immature kudzu bugs are easily and repeatedly found on the leaf petioles and/or main stems, treatment is likely warranted. However, these threshold guides may be modified slightly based on the number of egg masses that are continuing to hatch.