Passive transmission of sorghum ergot (Claviceps africana) by four species of adult stink bugs

The ability of Oebalus pugnax (F.) (rice stink bug), Acrosternum hilare (Say) (green stink bug), Nezara viridula (L.) (southern green stink bug), and Euschistus servus (Say) (brown stink bug) to passively carry and transmit Claviceps africana spores from diseased to non-infected plants was evaluated at the USDA-ARS, Southern Plains Agricultural Research Center (SPARC), College Station, Texas. Following exposure to ergot-infected sorghum panicles in the field for 30 minutes, stink bugs were captured and subsequently released in cages containing panicles of healthy green-house-grown sorghum plants of male-sterile line ATx623 in full bloom. The highest level of disease severity was 14.1% when greenhouse-grown ATx623 plants were exposed to ergot contaminated rice stink bugs for 30 minutes; whereas, the lowest ergot infection (2.8%) was exhibited by panicles exposed to ergot contaminated brown stink bugs. Estimates of the mean number of C. africana spores adhering to the external body parts of ergot contaminated stink bugs after being used as vectors on healthy sorghum panicles also was recorded. The highest mean concentration of adhering C. africana spores (2.2 x 10 super(5) spores/ml) was recovered from ergot-contaminated rice stink bugs, while the lowest mean concentration of 6.2 x 10 super(4) spores/ml was from contaminated green stink bugs. No significant differences in mean count of external spore concentration recovered between southern stink bugs and rice stink bugs were noted; however, these mean spore counts were significantly higher than the amounts found on green and brown stink bugs. No ergot infection was evident on ATx623, and no spore was recovered from non-contaminated stink bugs.