PLANT STAGE SUSCEPTIBILITY AND ECONOMIC INJURY LEVEL FOR TARNISHED PLANT BUG, Lygus lineolaris (Heteroptera: Miridae), ON CONFECTION SUNFLOWER / FASE SENSIBLE DEL DESARROLLO Y EL NIVEL DEL IMPACTO ECONÓMICO DEL INSECTO LYGUS LINEOLARIS (Heteroptera: miridae) EN EL GIRASOL DE CONFITERÍA / PHASE SENSIBLE DU DÉVELOPPEMENT ET NIVEAU DES PERTES ÉCONOMIQUES PROVOQUÉES PAR L’INSECTE Lygus lineolaris (Heteroptera: miridae) DANS LE TOURNESOL INDUSTRIEL
2014
Charlet, Laurence D.
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 economic 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 interference 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. lineolaris infestation occurred at growth stages R4 and R5 compared with stages R6 and R7. Thus, protection of sunflower plants from infestation by tarnished plant bug, until they have completed blooming, may prevent economic loss. The economic injury level for tarnished plant bug was one adult per 10 to 15 plants, each head averaging 500 to 600 seeds, for a damage level of 0.5%. Thus, tarnished plant bug management should be initiated between the R4 to R5.1 stage if adult densities approach the economic injury level. Also, fields need to be monitored until bloom is completed to reduce incidence of kernel brown spot damage to confection sunflower
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