Title: Relationship between piercing-sucking insect control and internal lint and seed rot in Southeastern cotton (Gossypium hirsutum) Authors
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2014
Publication Date: N/A
Interpretive Summary: Previously, using greenhouse cotton, we showed that a disease of immature green cotton bolls in the southeastern Cotton Belt states is caused by infective microbe(s) vectored by boll-piercing insects such as stink bugs. Boll damage traditionally associated with stink bugs is actually dependent on whether or not the insects harbor and transmit cotton pathogens. Here, we sampled field–grown bolls from stink bug management plots in four South Atlantic coast states (North Carolina, South Carolina, Georgia, and Florida) to determine the incidence of the disease in the field and its association with the activities of piercing-sucking insects. The aim of collecting bolls throughout the southeast region was to determine if the observations made in the controlled greenhouse studies could be confirmed in the field. By far the greatest incidence of disease was found on bolls that had been punctured. Further investigations directed toward developing basic management strategies to reduce losses to emerging cotton boll rot pathogens are ongoing to provide guidance for judicial use of insecticides for control only when cotton pathogen-carrying vectors are identified in the field. Stinkbugs that are not harboring pathogens cause negligible boll damage.
Technical Abstract: In 1999 crop consultants scouting for stink bugs (several Hemiptera spp.) in South Carolina discovered a formerly unobserved seed rot of cotton that caused yield losses ranging from 10 to 15% in certain fields. The same symptoms were subsequently reported in fields throughout the southeastern Cotton Belt. The exterior of diseased bolls appear undamaged, but cross-sections of the immature, green fruit reveal pink to dark brown, damp, deformed lint and, discolored and dead seeds. A pathogenic strain of the bacterium, Pantoea agglomerans, along with other opportunistic microbes isolated from diseased, field-grown bolls, were used in greenhouse experiments to determine the vector capacity of boll-piercing stink bugs. Following laboratory demonstration of transmission of P. agglomerans by the southern green stink bug (Nezara viridula L.), green bolls were sampled from stink bug management plots in four South Atlantic coast states (NC, SC, GA and FL) to determine the incidence of the disease in the field and its association with the activities of piercing-sucking insects. A logistic regression analysis of the boll damage data revealed that disease was 24 times more likely to occur in bolls collected from plots in FL, where evidence of pest pressure was highest, than in bolls harvested in NC plots with the lowest detected insect pressure. Fruit from insecticide protected plots that reduced stink bug numbers, were less likely to be diseased than bolls from unprotected sites. Overall, punctured bolls were 142 times more likely to also have disease symptoms than non-punctured bolls irrespective of whether or not the plots were protected with insecticides. These data, and related findings reported by the authors, strongly suggest that piercing-sucking pests such as stink bugs, including Nezara virdula, vector boll pathogens. Much of the damage to cotton bolls that is commonly attributed to stink bug feeding may be in actuality the effect of pathogens vectored by stink bug probing and feeding.