We are receiving phone calls from growers, consultants, and county agents about the huge surge of stink bugs coming into heading wheat fields. In most cases, it is predominantly rice stink bug but in a few cases and even in fields with rice stink bug there are also brown stink bugs.
These stink bugs appear to be across the entire wheat acreage of the state and are showing up as the wheat begins heading. The threshold in Arkansas has always been one per head, however, it is interesting to note that Angus Catchot, extension entomologist for Mississippi State University, quoted a threshold of 1 stink bug per 5-10 heads which is 10-20% infestation (see www.mississippi-crops.com). While lower than Arkansas, that’s still a lot of stink bugs. Also, it must be noted that wheat prices are very high…either way, it’s safe to say that it takes a lot of stink bugs to cause damage in wheat.
The susceptible stages of wheat to stink bug are the milk and soft dough stage. Prior to and later (hard dough) stages are safe from damage by stink bugs. More importantly, these infestations in wheat may lead to stink bug issues in other crops. Therefore, you should: 1) Scout seedling corn very closely for stink bugs. Stink bugs can be very damaging to seedling corn. Severe damage has been observed in corn in recent years. Corn should be scouted very closely due to the high levels of stink bugs currently present in fields. 2) Since stink bug populations appear to be building rapidly, scout rice closely when it begins to head. With reduced rice acreage that means more stink bugs looking for rice when the time comes….
Important Observations About These Stink Bugs For Scouting Stink Bugs
Numbers of stink bugs are much higher on the edges of the field. In our observations stink bug numbers can be high at the edge of the field, yet when you get into the field 50-100 feet, the numbers fall off drastically – most of the time 75% or more. So, while you may be at threshold on the edges you may be well below threshold on the majority of the field. If you think an insecticide application is warranted, strip treating the edges may be the best choice. Only good scouting will determine that.
Many of you may be applying a fungicide right now and want to just “stick in some pyrethroid.” Be sure to think about the cost effectiveness of that application to help make the right decision. Others may be considering “spraying now to kill them before they get to my rice or corn.” This is not a good IPM approach as it’s not effective, nor recommended to “spray now” for what may or may not happen in the future.
Stink bug Mobility.
Stink bug, especially rice stink bug, is an extremely mobile insect. We have often seen cases where fields of wheat that had large stink bug numbers one day had virtually none just 2-3 days later, even though no insecticide was applied to the field. Point being, if you decide to treat, before the application goes out, you might want to check and make sure the stink bugs are still there. We don’t understand what makes stink bugs pick up and move “en masse” but know that it does happen.
If treatment is warranted, make sure that the pyrethroid of choice is one that is labeled for use in wheat.