STEM BORING OF SOYBEAN BY DECTES TEXANUS (COLEOPTERA: CERAMBYCIDAE) AND THE NATURE OF ITS IMPACT ON YIELD - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 121

Observations in our laboratory suggest that soybean stem diameter is only weakly
correlated with the size of D. texanus pupae and adults that mature within them; although the
largest adults tend to emerge from the largest stalks, some large stalks also yield very small
individuals (A.K. Grant, unpublished data). Oviposition in smaller soybean plants might
entail substantial mortality for D. texanus . Although very small larvae are often numerous in
samples of soybean stalks, many small pupae produce non-viable adults that die prior to
reproductive age in the laboratory. Nevertheless, weights of D. texanus pupae can vary from 5
mg to 50 mg indicating substantial genetic variance for body size. Since the smallest size
classes of insects maturing in soybean still have very low apparent fitness, exploitation of
soybeans by D. texanus may be associated with ongoing selection for reduced body size and a
lower critical size threshold for adult viability.
A CKNOWLEDGMENTS
This work was partially funded by USDA, CSREES, Northcentral Region IPM Mini-
grants Program. The manuscript was improved by commentary from Dr. L. Buschman.
Contribution No. 08-54-J of the Kansas State Agricultural Research Station. Voucher
specimens No. 178 are located in the Kansas State University Museum of Prairie Arthropod
Research.
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