This year in soybean it is always something. Now, false chinch bugs. Dave Bowlin (Heartland Cooperative, Indianola) found a soybean field in which false chinch bugs were killing seedling soybean plants. The field was no-till with a serious shepardspurse infestation. When these weeds were killed with a herbicide, false chinch bugs moved onto the soybean. The chinch bugs did not feed on the cotyledons, or at least they did not initially kill them, but they did kill the trifoliate leaves, including the newly developing leaves. There were probably 200 or 300 nymphs per square foot in the weedy areas of this field.
The nymphs are only 1-3 millimeters in length, red or gray, and run rapidly. The adults are 3-4 millimeters in length, gray with white wings, and fly quickly. The adults are very difficult to spot and seldom sit still on the soybean. Adults live 2-4 weeks and there are 4-6 generations per year.
|Soybean leaves killed by false chinch bugs.|
The false chinch bug is not reported as a pest of soybean in the Handbook of Soybean Insect Pests  so this gives us some idea of the frequency of the problem in soybean. The Handbook of Corn Insects (both handbooks are published by the Entomological Society of America ) states that these unpleasant-smelling bugs are generalist feeders that prefer to feed on plants in the mustard and beet families and that they are rarely pests of corn. Outbreaks are associated with drought, causing false chinch bugs to abandon spring hosts in early to midsummer and move in hordes into no-till corn and soybean. In this field, the herbicide that killed the shepardspurse acted like a drought by killing the weeds.
For no-till soybean fields with weed problems, false chinch bugs now can be added to the list of future potential pests. Insecticides labeled for use in soybean could be used to control this pest.
Soybean field with plants in background killed by false chinch bugs. Foreground shows healthy soybean where no shepardspurse had grown.
This article originally appeared on page 147 of the IC-486(18) -- July 16, 2001 issue.