In greenhouse studies, three soybean cultivars and one breeding line were planted at 3- or 4-d intervals. When the plants were in the R-2, R-3, or R-4 reproductive stage of development, they were infested with one fourth-instar bollworm, Heliothis zea (Boddie), or tobacco budworm, Heliothis virescens (F.). Larvae were allowed to feed and develop to prepupae on the plants. On 'Bragg' soybeans, an average of 91, 83, 76, 51, and 30 seeds were destroyed per bollworm larva when infestation began in the following five periods of plant development: 3 d before pods were visible, first appearance of pods, and 3, 6, and 9 d after the first appearance of pods, respectively. The numbers of seeds destroyed by bollworms and tobacco budworms in a given treatment did not differ significantly. Bollworms destroyed significantly fewer seeds per larva on a commercial cultivar and a breeding line that had shown resistance to insect feeding on foliage than on a susceptible cultivar when the beginning of the infestation coincided with the first appearance of pods; however, the number of seeds destroyed did not differ significantly when 4- and 8-d-older plants were infested.
Document Type: Research Article
Publication date: June 1, 1987
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