Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 14, 2012
Publication Date: September 1, 2012
Citation: Brewer, M.J., Armstrong, J.S., Medrano, E.G., Esquivel, J.F. 2012. Association of Verde plant bug, Creontiades signatus (Hemiptera: Miridae), with cotton boll rot. Journal of Cotton Science. 16(3):144-151. Interpretive Summary: Verde plant bug was the dominant boll-feeding sucking bug species (>98% of insects collected using a beat bucket) from peak to late bloom in cotton fields near the coast along the Coastal Bend of South Texas, from Port Lavaca to the Lower Rio Grande Valley in 2010 and 2011. It was common in fields within 8 km of coastal waters (average of 0.42 bugs per plant during peak to late bloom), while it was not detected in inland fields. Cotton boll rot was found on up to 25% of the open bolls inspected; the disease was concentrated in coastal fields where the verde plant bug was found, and it was the major contributor to boll damage. Results from field surveys and verde plant bug feeding on caged plants supported the positive association of verde plant bug presence and subsequent harvest-relevant cotton boll rot in open bolls at harvest. Based on our findings, we recommend in-season monitoring of verde plant bug to aid in assessing the likelihood of subsequent boll damage from cotton boll rot, especially for fields close to coastal waters. Additional inspection of signs of internal feeding by cracking green bolls (no greater than quarter-sized bolls) may be useful to verify that feeding is occurring in the soft tissue inside the boll, but we caution that inspection for early signs of cotton boll rot in green bolls may be a poor indicator of final disease expression and resulting boll damage. Based on our work, in-season monitoring of the verde plant bug using the beat bucket is currently the best indicator of harvest damage caused by these bugs and potentially magnified by cotton boll rot.
Technical Abstract: Cotton along the Gulf Coast of south Texas has experienced loss from cotton boll rot especially during the last 10 to 15 years, and stink bugs and plant bugs (Hemiptera: Pentatomidae and Miridae) that feed on cotton bolls have been suspected in introducing the disease. A replicated grower field survey was done to capture a representation of these sucking bug species and subsequent boll injury, including cotton boll rot, in 2010 and 2011. This survey was paired with a controlled field cage experiment that isolated feeding by verde plant bug, Creontiades signatus Distant (Hemiptera: Miridae). Verde plant bug was the dominant boll-feeding sucking bug species (~99% of insects collected) during peak to late bloom in cotton fields within 8 km of coastal waters (average of 0.42 bugs per plant), while it was not detected in inland fields. Cotton boll rot was found on up to 25% of the open bolls inspected, the disease was concentrated in coastal fields where verde plant bug was found. The proportion of green bolls with signs of cotton boll rot estimated at the same time as insect monitoring was not linearly related to the number of verde plant bug per plant (P = 0.91), but the subsequent proportion of open bolls with signs of cotton boll rot near harvest was linearly related to the number of verde plant bug per plant during peak to late bloom (adjusted r2 = 0.53, P = 0.007). Isolating verde plant bug feeding further implicated it in introducing cotton boll rot. Verde plant bug-infested plants had significantly higher incidence of insect-punctured bolls and locules (15-35% in infested plants) and disease symptom incidence (5-27% in infested plants) than uninfested plants. All bolls with symptoms of disease tested positive for bacteria. From a pest and disease monitoring viewpoint, an in-season insect monitoring program is justified and needed most critically for fields close to coastal waters, and companion in-season detection of rot within the bolls must be done with great care.