Soybean Yield Interaction between Helicoverpa zea Infestation and Simulated Frost Injury
- Craig S. Eckel ,
- J. R. Bradley and
- John W. Van Duyn
Soybean, Glycine max (L.) Merr., yields may be reduced by corn earworm, Helicoverpa zea (Boddie), feeding and by early frosts. One consequence of H. zea feeding can be a delay in pod development. A consequence of frost injury can be shortening of the seed fill duration. The objective of 12 experiments conducted at multiple locations from 1984 to 1987 was to evaluate the potential for an interaction between H. zea feeding damage and early frost. Insecticides were used to establish varying levels of H. zea populations in soybean and paraquat (1,1′.dimethyl-4,4′-bipyridinium dichloride) was used to simulate frost injury. Significant yield differences between levels of H. zea populations were detected in eight experiments, and paraquat treatments significantly reduced yields in 11 experiments. A significant interaction between H. zea population level and paraquat treatment time occurred in three experiments. In these experiments, yield reduction due to paraqnat was greater where H. zea populations were larger. Although soybean can compensate for a delay in pod set caused by H. zea feeding in most years, when seed fill period is shortened, as would occur with early frost, a delay in pod set can contribute to yield loss. Identifying one of the many factors that lead to variation in yield loss from a particular level of H. zea infestation, is a step towards more effective management of this pest.
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