This time of the year many soybean producers tend to be on cruise control, however we don’t want to coast to the finish line just yet. We still have several potential pests we need to manage to prevent them from robbing yield. Many folks overlook stink bugs as a potential pest that can cause serious damage in soybean fields even though they may be one of the most important pests to manage when it comes to pod feeders. Scouting for stink bugs should be a part of any good IPM strategy for soybeans, especially in the southern half of the state.
There are two species of stink bugs that damage soybeans in Illinois. The most common is the green stink bug. The adult green stink bug is approximately ½-inch in length and is light green and shield shaped with fully developed wings. Nymphs or immature stink bugs are a combination of black green and yellow and have nonfunctioning wings. Both adults and nymphs have piercing sucking mouthparts for removing plant fluids. The stink bug overwinters as an adult, surviving under leaf debris outside of cropping areas. Stink bugs can have between one and three generations per year, with peak populations occurring in August and September. Stink bugs feed on pods, causing developing seeds to be shriveled, deformed, smaller and even aborted.
Adult Stink Bug Immature “Nymph” Stink Bug
Soybeans are able to withstand some insect feeding pressure during the vegetative state; usually around 35% defoliation before a treatment becomes necessary. Once the soybean plants begin to set pods, it becomes important to protect the leaf tissue from damage to maximize yields. Economic thresholds for leaf feeding decrease to 15% during R3. Not only will most insects you find in soybean fields damage leaf tissue, they will also feed on the pods causing injury to the pods or causing them to drop off the plant. An insecticide treatment would be warranted when the level of infestation reaches one adult bug or large nymph per foot of row during pod fill.
Using an insecticide with two modes of action like Endigo® ZC is crucial for getting those hard-to-control insects, and for resistance management. The insecticide needs to be able to deliver a fast knockdown and have good residual. For best results on sucking insects like stink bug, the insecticide needs to be “locally systemic” and move down into the leaf tissue to control insects under the canopy. Systemic insecticides will give the best results.
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Wade Meteer has been a sales representative for Syngenta since 2014, handling both Syngenta seed and crop protection products. He has been a Certified Crop Adviser since 2006 and spent 9 years as an agronomist focusing on nutrient management prior to his role with Syngenta. Wade can be contacted at wade.meteer@Syngenta.com or @meteer81 on Twitter.