We have recently captured a large number of green stink bug adults in our black light traps. While there are no established thresholds or recommendations based on trap catches for stink bugs, this does alert us to the fact that adult activity is elevated and that green stink bugs may be moving into crops.
In Delaware, we have three species of stink bugs; green, brown, and the invasive brown marmorated stink bug that we monitor using black light traps. All three species of stink bugs are considered polyphagous, meaning they feed on many different crops. In general, we think of them as being “seed” feeders because they use their piercing-sucking mouthparts to feed on developing seeds, pods, and fruit. Stink bugs are very good at locating preferred food sources and move throughout the landscape, keying in on host plants that are in the optimum plant growth stage (i.e. plants in reproductive growth stages). Early in the growing season, tree fruit, early planted sweet corn, and plants in natural areas that are producing seeds and fruit are most attractive to stink bugs.
However, stink bugs have also been known to occasionally feed on corn seedlings, causing the plants to tiller as seen in the photo below.
Brown stink bug feeding injury
Stink bug injury on corn seedlings is more common in states to our south and usually is not something that we need to manage. But with the high number of green stink bugs captured recently, and many fields with corn in growth stages vulnerable to injury (V1-V6), keep an eye out for green stink bugs moving into seedling corn fields.
Curious about how active adult stink bugs are in your neck of the woods? Click on the link below to view our Insect Trap Catch webpage and then click on the link to the stink bug trap catch page where we post trap catch results: http://extension.udel.edu/ag/insect-management/insect-trapping-program/
If you want to compare current stink bug trap catches to previous years, click on the “historical interactive graph” link at the top of the page and then select a trapping location and stink bug species. Once you have selected a trapping location and stink bug species, historical trap catch results will be visually displayed as an interactive graph. Clicking on the years will disable them and you can click and drag to zoom.
Recent research from North Carolina suggests that to sample seedling corn for stink bugs, sample at least 100 plants randomly throughout the field. Stink bugs usually are more concentrated on field edges so concentrate scouting efforts there first. If you find high levels of stink bugs on the field edge, make sure you are also sampling the field interiors.
Two new thresholds have been developed based on the sampling method, partial and entire plant. The partial plant method is based on only sampling a portion of the plant and recording the number of stink bugs per 100 plants. The entire plant sample is based on the percent of infested plants, visually searching the entire plant for stink bugs.
The partial plant threshold that were recently developed in North Carolina for stink bugs is as follows for field corn V1-V6 only sampling the stalk below the lowest green leaf:
- 6 stink bugs per 100 plants or fewer, do not treat.
- 13 or more stink bugs per 100 plants, treat.
- If the number of stink bugs per 100 plants is between 6 and 13, treat if you have 9 or more bugs per 100 plants.
If you sample the entire plant, the threshold that is being recommended in North Carolina is as follows for field corn V1-V6:
- <6% of the plants infested, do not treat.
- >11% of the plants infested, treat.
- If the % of the plants infested falls between 6-11%, treat if 8% or more of the plants are infested.
It should be noted that this threshold was recently published and has not been evaluated in Delaware.
Here is a link for more information on how to use the new stink bug threshold that was developed in North Carolina: https://entomology.ces.ncsu.edu/2018/04/new-stink-bug-thresholds-in-corn/