Southeast cotton producers have a new tool – a pocket-sized scouting decision aid to help them assess and manage stink bug damage based on thresholds for different cotton growth stages.
The decision aid was developed by Southeast entomologists to encourage enhanced stink bug scouting in cotton for better field identification of stink bug-induced boll damage symptoms and to reinforce the use of recommended scouting procedures.
“The idea is to get more people into scouting and make scouting more accurate and efficient,” says Jack Bacheler, entomologist with North Carolina State University, who served as lead on the project. “We tried to make it visually appealing, but useful, with the latest dynamic threshold for stink bugs in cotton based on week of bloom.
The Decision Aid
The pocket scouting decision aid, which has the Extension logo of the producer’s individual state, provides the following: a table of the dynamic threshold by week of bloom; recommended scouting procedures; measuring holes to help select the correct boll size range for damage assessments; and images of internal and external stink bug-induced boll damage.
Entomologists say the aid should greatly improve stink bug management because the dynamic threshold is based on cotton growth stages when the crop is most susceptible to stink bug damage, thereby targeting insecticide when it’s needed and avoiding unnecessary applications during periods of low risk from stink bugs.
Other entomologists collaborating on the decision aid were Ames Herbert, Virginia Tech; Jeremy Greene, Clemson University; Phillip Roberts and Michael Toews, University of Georgia; and Eric Blinka, Monsanto, Dyersburg, Tenn.
Bacheler says every state has had a threshold in the past of either 10 or 20 percent internal boll damage, even though it was known that the cotton crop was more susceptible to stink bugs at certain times.
In a series of 47 replicated tests in North Carolina, South Carolina and Georgia, the dynamic threshold was compared to the different static thresholds. The tests were divided into three categories based on whether the individual test was treated two or more times at the 20 percent threshold (high/moderate stink bug levels), one time at the 20 percent threshold (low/moderate levels) or not treated at the 20 percent level (low levels).
The static 10 percent and 30 percent thresholds did not result in good economic returns. In all cases, the dynamic threshold offered the best return, taking into account both the respective yields and the cost of application.
Rise Of Stink Bugs
Stink Bug Scouting
Decision Aid Provides:
Stink bugs have become an increasing problem for Southeast producers.
Bacheler says that the main reason for the greatly expanded pest status of stink bugs in the Southeast has been the significant drop in insecticide use for caterpillar pests such as bollworms and tobacco budworms. Also, some of the newer caterpillar chemistry is not effective against bug species.
Phillip Roberts, UGA entomologist, says the new decision aid will be distributed in the coming weeks at field days and scouting schools. For stink bugs, as with many pests, every year can be different.
“Although the cost of controlling stink bugs was low in 2009, these pests can be very damaging to cotton bolls in some years and at some locations,” Roberts says.
Bacheler says green stink bugs are more common in the upper Southeast, while southern green stink bugs are more prevalent in the lower Southeast.
Correct identification is important as brown stink bugs are not as effectively controlled by pyrethroids as are the two green species.
Contact Amanda Huber at (352) 486-7006 or firstname.lastname@example.org.