Stink Bug Damage to Vegetative Corn Plants
Figure 1. Stunted corn plants in Union County that were damaged by brown stink bugs. (Photo by Anna Hodgson, Penn State Extension)
When most corn plant are growing quickly this time of year, scouting can reveal aberrant plants that stick out like sore thumbs. In the last week, we have received a handful of calls about corn plants that are stunted and yellowed, some are tillered, whereas others have twisted leaves, but all have one or more rows of holes across the leaves (Figure 1). The holes can be round or elongate, but are ringed by a halo of yellow, chlorotic tissue (Figure 2). This damage was caused by stink bugs feeding on the growing point of young corn plants. The lines of holes resulted from feeding on leaves while they were still wrapped tight. Stink bugs inject saliva while they feed and this saliva and the physical damage from inserting their mouthparts into young plants appear to combine to cause the stunting and chlorotic tissue. In Pennsylvania, I have seen this damage caused by two stink bug species. About a decade ago, this damage was usually attributed to brown marmorated stink bug, which had recently emerged as a concern, but this year the damage seems to have been caused by the native brown stink bug (Figure 3), which can feed on a wide variety of crop species. Brown stink bugs are not a common pest of corn but can be problematic in corn fields established in high residue, including planting green. In my experience, it appears to be more common following leguminous cover crops, like hairy vetch or crimson clover, but it can also occur following cereal rye.
If you find the damage, it is likely too late to do anything other than make a note to scout earlier next year. If you find stink bugs hiding in whorls, they are unlikely to be still causing meaningful damage, which occurred earlier when plants were young. Avoiding this damage can be challenging, particularly if farmers are committed to high residue. Insecticidal seed coatings do not appear to have much activity on stink bugs and insecticide sprays would need to be properly timed with stink bug activity, so regular scouting is key, but the culprits can still be difficult to spot. This is a tough type of damage to avoid and the best advice I can provide is to scout closely and do all you can to plant when condition are optimal so plants grow through their vulnerable period as quickly as possible.
Figure 2. Damage to corn plants from brown stink bugs. Notice the lines of chlorotic holes in the leaves in the foreground, and stunted plants in the background. (Photo by Anna Hodgson, Penn State Extension)
Figure 3. Brown stink bug, which has damaged some corn fields this year. (Photo by David Cappaert, Bugwood.org)
