Transmission of Claviceps africana Spores from Diseased to Non-Infected Sorghum by Corn Earworm Moths, Helicoverpa zea

Abstract

ABSTRACT The potential of corn earworm moths Helicoverpa zea, an important pest of sorghum in Texas, as a passive vector of sorghum ergot, Claviceps africana was assessed. Laboratory-reared (females and males) and field-moths trapped in sex pheromone traps were confined in screen cages with potted male-sterile sorghum line AT×623 that had been artificially infected with sorghum ergot and was producing massive amounts of honeydew that contained spores of the fungus. In the cages, moths were observed feeding on the honeydew. When laboratory-reared moths contaminated with C. africana spores were released for 12 or 48 h in cages containing healthy greenhouse- or field-grown male-sterile sorghum plants at anthesis, the levels of ergot severities on the panicles ranged from 0.5–90%, per panicle. The levels of ergot infection on greenhouse- and field-grown AT×623 exposed to ergot contaminated field-trapped males for 48 h ranged from 0–81.7%. Mean external contamination of laboratory-reared and field-trapped moths placed in a soapy wash was 1.4 × 105 and 4.7 ×104 conidia/ml, respectively. This study demonstrated that contaminated adult corn earworm could transmit the sorghum ergot from diseased to healthy panicles when environmental conditions are favorable for infection. Thus, migrating moths and other highly mobile pest species have the potential to transport C. africana over relatively large distances.