Fusarium Hardlock Associated With <i>Lygus lineolaris</i> (Hemiptera: Miridae) Injury in Southeastern Cotton

The tarnished plant bug, <i>Lygus lineolaris</i> (Palisot de Beauvois), is an important insect pest in cotton that feeds on reproductive fruit, contributing to yield loss. Economically damaging infestations of <i>L. lineolaris</i> have doubled in Virginia since 2013. Escalation of <i>L. lineolaris</i> abundance may increase Fusarium hardlock disease observed in this region, compounding economic losses. Research has linked Fusarium hardlock with fungal species <i>Fusarium verticillioides</i> and <i>F. proliferatum</i>. Field and greenhouse experiments were performed to investigate (i) Fusarium hardlock occurrence in field plots managed and unmanaged for <i>L. lineolaris</i>, (ii) severity of <i>F. verticillioides</i> infection of cotton bolls with and without the presence of <i>L. lineolaris</i> feeding in a greenhouse setting, and (iii) <i>Fusarium</i> species composition and prevalence within field-collected <i>L. lineolaris</i> and cotton lint with and without insect feeding injury and hardlock symptoms present. Nearly twice the amount of hardlock (i.e., proportion of hardlocked locules) occurred in field-collected bolls with <i>L. lineolaris</i> feeding symptoms (0.40 ± 0.02) compared with bolls without (0.21 ± 0.01). Based on real-time quantitative PCR, cotton bolls exposed to <i>F. verticillioides</i> inoculum and caged with <i>L. lineolaris</i> adults had greater levels of <i>F. verticillioides</i> DNA compared with untreated bolls. <i>F. proliferatum</i>, <i>F. verticillioides</i>, and <i>F. fujikuroi</i> were isolated from field-collected <i>L. lineolaris</i> and hardlocked cotton lint at harvest. These findings suggest that the presence of <i>L. lineolaris</i> is associated with an increased risk of Fusarium hardlock in Southeastern cotton, and both should be carefully managed using timely insecticide applications and cultural control practices to minimize yield loss.