Corn earworm larvae have been found well in excess of economic thresholds in several counties throughout Virginia the past two weeks. In Prince George, we sampled a field with 50+ larvae per 15 sweeps (see below photo). There are a few key things to remember for managing corn earworm in soybeans.
- It pays to scout. Use the economic threshold.
For corn earworm in soybeans, we have what’s called a “dynamic threshold”. The benefit of using a dynamic threshold is that it shifts with commodity prices, production practices, and the cost of control and you can be certain that you will get economic return on a spray under current conditions. You can find the calculator here. At an estimated soybean price of $10/bu, and $15 cost of control using a sweep net to sample 15 inch soybean rows you get an economic threhsold of 2.2 larvae per 15 sweeps.
We have expanded our corn earworm moth monitoring in 2025. While these traps do not indicate the need to spray alone, they can guide your scouting efforts and help make decisions. The monitoring tool is updated in real time and can be found here. - Select the right insecticide
Pyrethroids alone will have limited efficacy for corn earworm, particularly for large larvae. Our most recent efficacy data can be found in the figure below. These numbers are total number of corn earworm larvae per 15 sweeps at 2 days post application. If targeting stink bugs as well as corn earworm a product containing both a pyrethroid and a diamide (I.e. Besiege or Elevest) would be a good option. If you are also reaching defoliation thresholds (15% during reproductive stages) and have mostly soybean loopers, Besiege has offered limited control for soybean loopers in recent years. Intrepid Edge or Steward are good options to manage both corn earworm and soybean loopers.
As always, please contact me if you have any questions or concerns. Tim Bryant (btim2@vt.edu).