Distribution of Tarnished Plant Bug (Lygus lineolaris) Infestations and the Effects of Spray Timing in Mid-Atlantic Cotton

Economically damaging populations of Lygus lineolaris (Palisot de Beauvois), the tarnished plant bug (TPB), were rare and sporadic in Mid-Atlantic cotton prior to 2010. Recent widespread infestations have dramatically increased insecticide use in Virginia, with a majority of acres sprayed at least twice in 2016. Given the lack of information on this pest in the Mid-Atlantic, we sought to provide growers with regionally specific recommendations to help minimize yield losses and reduce insecticide use. Experiments were conducted in Virginia in 2017 to evaluate 1) the spatial and temporal distribution of TPB populations, 2) when TPB infest cotton and the extent of damage these infestations cause, and 3) optimal insecticide spray timing for management. Distribution of TPB was determined by sampling twenty-three commercial cotton fields in eight Virginia counties using sweep net and drop cloth sampling. To determine when cotton plants are most susceptible to TPB feeding, adults were placed in screen-caged field plots at different growth stages. A separate experiment controlled natural infestations of TPB with insecticides during different cotton growth stages. Tarnished plant bug density, plant injury (i.e., square retention and internal boll injury) and lint yield were measured. We found TPB across Virginia’s cotton-growing region throughout the season (May through September). Optimal spray timing for TPB in the Mid-Atlantic is similar to the Mid-South (i.e., the critical window for crop protection is the second through the fourth week of bloom). Lint yield was also higher for early-planted cotton (1 May) compared to late-planted cotton (1 June). Higher plant injury and percent yield loss observed in cages exposed to TPB in the first through third weeks of bloom confirms the early weeks of flowering are critical for TPB management in Mid-Atlantic cotton. Findings from this study and future work will continue to develop management recommendations to protect yield potential and reduce unnecessary or ineffective insecticide applications.