Anitha Chirumamilla, Laurence Charlet, Janet Knodel, Theresa Gross, and Brent Hulke
Abstract: The banded sunflower moth is a key pest of sunflower in the northern Plains. Female moths deposit eggs on the outer surface of the bracts of the sunflower head. Larval feeding in the heads causes seed loss and lower oil content resulting in reduced yield. Upon reaching maturity larvae drop to the ground and overwinter in the soil. Host plant resistance is a plant mechanism used to defend against attack and reduce damage from pest species. The present study was conducted to evaluate sunflower lines that had been rated as resistant to the banded sunflower moth for numbers of larvae attacking the head, seed damage caused by larval feeding and to determine the mechanisms contributing to insect resistance. We also investigated the relationship between trichome densities on sunflower bracts and susceptibility of sunflower lines to infestation by the moth. Results showed that avoidance to egg laying (antixenosis) and toxicity of the plant to the larvae (antibiosis) were probably the two mechanisms contributing to resistance in the sunflower lines tested. Preliminary observations on the effect of density of hair-like structures (trichomes) on the sunflower bracts on the susceptibility of sunflower lines to the banded sunflower moth showed that an increase in hair density on the bracts increased the susceptibility of sunflower lines to moth infestation. Based on these results, a greenhouse study will be conducted to determine the relationship between hair density on the bracts and egg laying preference of the banded sunflower moth.
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