Stink Bugs Picking Up in Soybeans
With the exception of the last three years, stink bugs have always Mississippiâ€™s number one insect pest of soybean. There are many species of stink bugs in MS soybeans but the three predominate species are Southern Green, Green, and Brown stink bugs. While we have certainly reached treatable levels of stink bugs in soybeans in many fields over the last three years, we have not dealt with extremely high numbers of southern green stink bugs since 2009. The reason is the 2 very cold winters following the 2009 season. Southern green stink bugs are very sensitive to cold weather and numbers were beat back to near nothing. Now we are coming off of two relatively mild winters in a row and are seeing a resurgence in this species.
Southern greens are no more damaging or harder to control than green stink bugs but can reach much higher numbers. Prior to 2010 it was no problem to put southern green test out and easily find numbers of 50 or more per 25 sweeps in producer fields. I have been in quite a few fields recently where I am again finding nearly exclusively southern green stink bugs. I do believe with the very late crop we have this year we will be dealing with high numbers of stink bugs on substantial acres across the state. In fact this week I received quite a few calls where numbers are exceeding threshold, especially next to corn.
In 2008-09 we also reached treatable levels of another species of stink bug called the Redbanded stink bug. This species gained a lot of attention a few years ago because of its aggressive feeding behavior on soybeans but apparently is very similar to the southern green stink bug with its tolerance to cold weather. Numbers of this species crashed to nearly zero after the 2009 season also. This year it has begun to make its way back north in MS and has already reached treatable levels in a few south MS fields.
Stink Bug Thresholds in MS are 9 per 25 sweeps for all species except Redbanded stink bugs. Redbanded stink bug threshold is 6 per 25 sweeps. Currently we have no products that will offer more than 4-6 days residual on stink bugs. This means we may have to make multiple applications later in the season when early beans begin to dry down and stink bugs begin to move. I have already heard of this happening this year where threshold numbers were treated and controlled then high moisture corn was cut nearby and numbers went back above, and stayed above threshold 5-7 days later. There has been a lot of great research by our Mid-South Entomology Working Group over the years to validate stink bug thresholds in soybeans. I have a lot of confidence in them so there is no reason to â€œcheatâ€ them down.
What to use?
Southern Green, Green, Redshouldered: Pyrethroids, Orthene, or several premixed products.
Brown Stink Bugs: Orthene needs to be in tank.
Redbanded Stink Bugs: Highest rates of pyrethroids, pyrethroid + acephate combinations, Premixes such as Endigo or Leverage 360.
Sampling Stink Bugs: A few years ago we did a sampling study on stink bugs in soybeans. We found that significantly more stink bugs were found early in the morning verses mid-day or evening in the same fields. This is likely due to the fact that stink bugs move down in the canopy as temperatures rise in the day. Keep this in mind and sample deeper in the canopy later in the day.
Efficacy Trials on Southern Green Stink Bugs: Click to Enlarge
Stink Bug Identification: Click to Enlarge
1.) Green Stink Bug Adult, 2.) Green Stink Bug Nymph, 3.) Brown Stink Bug Adult, 4.) Brown Stink Bug Nymph, 5.) Southern Green Stink Bug Adult, 6.) Southern Green Stink Bug Nymph, 7.) Redshouldered Stink Bug Adult, 8.) Redshouldered Stink Bug Nymph, 9.) Redbanded Stink Bug Adult, 10.) Redbanded Stink Bug Nymph, 11.) Spined Soldier Bug Adult, 12.) Spined Soldier Bug Nymph.