Overview of Insect Pests in Maturing Soybean Fields in Central Kentucky

From September 8 to September10, we scouted for insect pests on 14 commercial soybean fields across several central Kentucky counties, including Nelson, Hardin, Breckenridge, Hancock, Davies, and McLean counties. Tallies were conducted using nets, and soybeans were in the R3 to R5 (double crop) and R5 to R8 (full-season) growth stages.

Many of these fields had been sprayed for stink bugs or other insects (i.e., caterpillars, bean leaf beetles, or three-cornered alfalfa) and populations were low. However, there were a couple of fields where three insect pests were present in great numbers (Table 1), namely stink bugs, grasshoppers-katydids, and flea beetles

In Henderson County, we sampled at least two fields, but there was one that had an average of 110 stink bugs per 100 sweeps. In this field, most of the stink bugs collected were the brown marmorated stink bug (95 individuals/100 sweeps), followed by the green stink bug and brown stink bug.

In Nelson County, a field had an average of 96 grasshopper and katydids per 100 sweeps (Figure 1). Both grasshopper and katydid species were observed causing damage to soybean crops (Figure 1A). However, the number of these insects was slightly higher in full season soybean (96 individuals/100 sweeps) than in double crop systems (60/100 sweeps). See Figure 1B-D.

Table 1. Highest numbers of insect pests found in commercial soybean fields in Central Kentucky

Also, a field in Breckinridge County had extremely large numbers of flea beetles. These flea beetles might have moved from adjacent corn fields that had senescent leaves.

Additionally, caterpillars (green cloverworm, loopers, silver spotted skipper, etc), bean leaf beetles, and alfalfa three-cornered hoppers were observed, but their numbers did not require control measures.

Figure 1. A) Soybean leaflet damaged by orthopterans. B-C) Grasshopper species, and D) katydid species found in a commercial soybean field in Nelson Co. (Photos: Armando Falcon-Brindis, UK)

By Armando Falcon-Brindis, Entomology Research Analyst, and Raul T. Villanueva, Entomology Extension Specialist.

Posted in Grains
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