ABSTRACT

The ability of grain sorghum to serve as a trap crop for the southern green stink bug (SGSB), Nezara viridula (L.), in cotton was investigated in Mystic, GA in 2002. Three 150 ft x 12 rows of sorghum (sorghum trap) and cotton (cotton trap) were planted along a single edge of a cotton field adjacent to corn. SGSB populations were monitored in the sorghum trap, in the cotton trap, in field cotton associated with the sorghum trap, and in field cotton associated with the cotton trap. A statistically significant difference in mean number SGSBs per 3 ft. of row occurred between the sorghum and cotton trap for almost every date. SGSBs began moving into Row 1 of field cotton adjacent to each trap crop on 9/6. More SGSBs moved into the cotton field adjacent to the cotton trap than into cotton adjacent to the sorghum trap. Only on this one date were SGSBs at economic threshold in field cotton. No insecticide applications were necessary for control of this pest in the 16-acre cotton field over the whole cotton-growing season, and thus, the trap crop provided a seasonal refuge for natural enemies of the SGSB. Mortality of SGSB eggs by the parasitoid, T. basilis, and the two predators, O. insidiosus and G. punctipes was moderately high (57%) during the 2nd peak in SGSG population in the sorghum trap, and began to fall as the SGSB population began to fall in this trap crop. Parasitization of SGSB nymphs and adults by T. pennipes was moderately high (69%) during the first SGSB peak and very high (98%) during the second SGSB peak in the grain sorghum trap crop. These results indicate that the trap crop was effective in conserving and enhancing these natural enemies. Trap cropping for SGSBs in cotton offers the potential to provide an IMP system that could improve sustainability by reducing pesticide and other off-farm inputs and expenses.