PLANT STAGE SUSCEPTIBILITY AND ECONOMIC INJURY LEVEL FOR TARNISHED PLANT BUG, Lygus lineolaris (Heteroptera: Miridae), ON CONFECTION SUNFLOWER

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), feeding on developing sunflower seed causes kernel brown spot, a serious problem in confection sunflower. The purpose of this research was to determine the eco-nomic injury level and plant stage susceptibility for confection sunflower in greenhouse and field studies using sunflower heads artificially infested with L. lineolaris adults. Greenhouse experiments showed each adult damaged 38 seeds per head. Field studies showed a lower average damage in heads infested with seven adults compared with heads with five adults, possibly due to inter-ference among the adults and nymphs. The regression equation used to predict the number of kernel brown spot damaged seeds per head based on adults per head was Y=-0.86+33.54X. Thus, feeding resulted in 32.7 damaged seeds per head per adult. Approximately 5 % of seeds in a head were damaged per adult. Damage to sunflower heads was approximately twice as severe when L. lineola-ris infestation occurred at growth stages R4 and R5 compared with stages R6 and R7. Thus, protection of sunflower plants from infestation by tarnishe