Arkansas IPM Report – July 1, 2022

by Glenn Studebaker - Extension Entomologist, IPM Coordinator - July 3, 2022

Moth Trap Sites

We now have a webpage dedicated to pheromone trap catches for bollworm, tobacco budworm and southwestern corn borer. Trap catches for each species can be viewed by county. Users can click on the county to access a drop-down menu for each species. Updated moth numbers are posted as county agents report their numbers. You can access this information on the 2022 County Trap Catchespage of the University of Arkansas Division of Agriculture, Cooperative Extension website.

Southwestern Corn Borer

Pheromone trap catches for southwestern corn borer continue to increase in south Woodruff County. See a table of the Woodruff County trap catches, and you can also see the Monroe County trap catches. Some traps caught over 600 moths this week. Trap catches in other areas of the state continue to remain low. Growers with non-Bt hybrids in the area of south Woodruff County and Monroe County should consider applying an insecticide with a long residual for southwestern corn borers. Products containing chlorantraniliprole as the active ingredient (Besiege, Elevest, Prevathon, Vantacor) or methoxyfenozide (Intrepid, Intrepid Edge, Invertid, TurnStyle, Vexer, Inspirato, Zylo) will give longer residual control. Some are asking what rate will give the longest residual. The short answer to that question is higher rates give longer residual control. We can expect 2 to 3 weeks of residual from lower rates of products containing chlorantraniliprole and about 3 weeks from products containing the mid-range rate (8 oz) of methoxyfenozide. The table below shows a list of residual insecticides (Table 1). For a complete list of recommended insecticides for corn insects, see the corn section of MP144 Insecticide Recommendations for Arkansas.

Table 1. Insecticide recommendations for corn growers.

Bollworm

Bollworm numbers have begun to drop off this week, but are still fairly high in some areas. Trap catches by county can be found on the 2022 Trap Catches webpage.  Some soybean fields have hit threshold this week. The threshold for bollworm in soybeans is dynamic and changes with the cost of control and crop value. See the table below for the bollworm threshold (Table 2). 

Table 2. Bollworm Dynamic Threshold in Soybeans.

When considering using the virus Heligen, remember applications should be made before reaching the economic threshold and should target small larvae. Once larvae reach a size of over ½-inch, Heligen may not be as effective, and growers should switch to a conventional insecticide. For more information on using a biopesticide such as Heligen, consult publication AG1306. Consult publication MP144 Insecticide Recommendations for Arkansas for a list of recommended insecticides and treatment thresholds.

Stink Bugs in Soybean

We are seeing treatment-level stink bugs in some soybean. These are predominantly in fields that have begun to put on pods, and most appear to be green stink bug species that are easily controlled with pyrethroid insecticides. The treatment level for stink bugs in soybean is when 9 or more stink bug nymphs and/or adults are found per 25 sweeps sampled with a 15-inch diameter sweep net. Consult the soybean section of MP144 for recommended insecticides.

“This work is supported by the Crop Protection and Pest Management Program [grant no. 2021-70006-35512/project accession no. 1027188] from the USDA National Institute of Food and Agriculture.”