By Nick Seiter, Extension Entomologist
Kudzu bugs have been found more readily in soybeans in Arkansas this year, and we have had a few fields near Helena reach our economic threshold of 25 nymphs in 25 sweeps (Fig. 1). We followed one field in particular to demonstrate our management recommendations and test several products for efficacy (thanks to Phillips County Extension Agents Robert Goodson and Shawn Payne for helping us identify and monitor the field, and to Hank Chaney for helping us organize several demonstrations). In our test, bifenthrin and lambda-cyhalothrin (Discipline and Karate) were particularly effective alone or in combination with other materials, and acephate (Orthene) provided good control as well (Fig. 2). This is similar to what has been observed in other states since this insect was first found in the U.S. in 2009; overall, this has not been a difficult insect to kill.
Data from states that have been dealing with the kudzu bug for some time now demonstrate that it is the nymphs, not the adults, which are driving yield losses. The field we monitored at Helena had approximately 200 adults in 25 sweeps on June 29 – enough to alarm just about any consultant or grower who has not dealt with this insect before (Fig. 3). However, it took almost an entire month (July 25) before economic threshold was reached and a
treatment was applied. When you combine the relatively slow cycle of infestation with the type of damage that kudzu bugs do (indirect stress placed on the plant due to feeding on vascular fluid), there is a wider time window for a control to be applied than with pests like stink bugs or bollworms that damage the seeds and pods directly.
During our evaluations, we noticed the presence of a fungal disease (Beauveria bassiana) infecting and killing kudzu bugs (Fig. 4). This disease has been widely observed throughout the kudzu bug’s distribution in the U.S., and has been credited by some of our colleagues with helping to reduce kudzu bug populations from their peak levels a few years ago.
Kudzu bugs are a new pest that needs to be on your radar if you are scouting soybeans. However, we do not expect them to be all that challenging to manage; our educational push now is to stress proper identification of the life stages and targeting of the nymphs rather than the adults for control. If we use the recommendations that have been developed in other states that have been dealing with kudzu bugs for a while now, we should be able to take this pest in stride.