Status of Redbanded Stink Bugs in 2018 Soybean Crop
Recently, I posted an article titled “An Example of the Disease Triangle at Work”. The subject of the article was how the environment during the 2018 crop season apparently was conducive to an unusually high incidence of southern blight, caused by the pathogen Sclerotium rolfsii, in soybeans. This finding by pathologists contradicts the normal very minor effect of this disease in the Midsouth soybean crop.
I am not aware of a formal “insect triangle”. However, it stands to reason that such a triangle that describes insect infestations can actually exist. Specifically, if an insect pest and a suitable host are present in the same environs, then environmental conditions–i.e. food supply, temperature, etc.–that are conducive to the proliferation of that injurious insect will likely promote a high infestation by that insect that will result in subsequent injury to the host plant. The below discussion about the redbanded stink bug is based on this premise.
In an article titled “Redbanded Stink Bug–A Growing Menace to Midsouth Soybeans” that I posted on Aug. 30, 2017, the challenge presented by the redbanded stink bug (RBSB) (Piezodorus guildinii) to the 2017 Midsouth soybean crop was documented. The incursion of this insect pest into the upper reaches of the Midsouth in 2017 was a relatively new occurrence.
In an article titled “What Will Cold Temperatures Mean for Redbanded Stink Bug This Year?” that was posted on the MCS blog site on Jan. 20, 2018, MSU Entomologists Drs. Catchot, Cook, and Gore presented temperature data they had collected from several known habitats for RBSB overwintering. They found that 6 habitats out of the 7 they measured reached below-freezing temperatures of a duration known to be lethal to RBSB. They surmised that this could lead to a large reduction in RBSB populations in the 2018 growing season.
In an article titled “Redbanded Stink Bug Ditchbank Survey 5/10/2018“, the above three MSU authors reported results from their annual ditchbank survey that was conducted in May 2018. In that article, they state “...with RBSB, finding them in the spring in substantial numbers is an indication of how far north and in what numbers they successfully overwintered.” “Unlike other pests, ditch bank samples for RBSB are a strong indicator of the potential problem and this in fact did materialize into a greater issue last year (2017).” From this survey, “...RBSB are present at low levels in isolated areas at this time. Soybeans planted in the normal planting window will likely have no or very low incidence of the pest. It will take some time for these numbers to build to threatening levels and only very late-planted beans may experience any problems.” Thus, from this survey conducted in May of 2018, they surmised that the low numbers of RBSB they found then could indicate a relatively low infestation during the 2018 growing season.
Now to a Sept. 20, 2018 article by David Bennet in the Delta Farm Press. In that article, Dr. Todd Spivey, LSU Extension Soybean Specialist states “...the growing season had some real positives. Because of the cold weather we had last winter, the redbanded stink bug populations were way down. That was certainly a blessing. In 2017, a lot of growers had to treat for the pest three times–some even four times. In 2018, though, some growers never treated for stink bugs even once. Others treated once and knocked them out and they didn’t have many issues the rest of the year.”
I contacted Dr. Angus Catchot, MSU Extension Entomologist, on Friday, Sept. 21, 2018 and asked “What have you seen in Miss.? I know you did some temperature work last winter and determined that most of the measured habitats got to cold for the RBSB to survive the winter.”
Dr. Catchot replied “Best I can tell we have only treated 4-5 fields this year for RBSB, and those were below (south of) I-20. As we are cutting a lot of beans now, they can be found in the greener spots as they (the RBSB) are on the move, but numbers are very low on average. This has been a good thing for our growers this year. However, if we do not have a cold winter this year (as in 2017-18), we will have a problem next year (2019), again because they (the RBSB) are in the system...”.
All of this indicates the following to me.
• Both the off- and in-season environment can affect infestation potential of insect pests that cause economic injury to soybeans.
• Monitoring the environment that harbors overwintering insects that can cause injury to soybeans during the following growing season is an important task that can provide results for producers to use to anticipate injurious levels of those insects.
• This, like disease and insect surveys, is a case of observational research that can be used to provide important information for soybean producers as they make pest management plans.
• It appears that the incidental research conducted by the MSU entomologists in the winter of 2017-2018 has provided valuable information that proved to be true. This is information that might only be gathered infrequently when certain conditions exist, so it is fortuitous that it was recorded this past winter.
The MSPB is continuing to fund a project titled “Management of Redbanded Stink Bug (RBSB) in Miss. Soybean Production Systems (Project No. 58-2018)” that is designed to determine RBSB damage potential by soybean growth stage, determine insecticidal efficacy to control RBSB, and determine insecticide termination timing to protect soybean yield from RBSB infestations when they occur. Results from this research should provide guidelines for managing RBSB in Miss. soybean fields to prevent yield and seed quality losses.
Composed by Larry G. Heatherly, Sept. 2018, larryheatherly@bellsouth.net