Submitted to: Journal of Sustainable Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2003
Publication Date: January 1, 2003
Citation: PROM,L.K., LOPEZ,J. ., LATHEEF,M.A., TRANSMISSION OF CLAVICEPS AFRICANA SPORES FROM DISEASED TO NON-INFECTED SORGHUM BY CORN EARWORM MOTHS, HELICOVERPA ZEA, JOURNAL OF SUSTAINABLE AGRICULTURE, 2003. Interpretive Summary: Sorghum ergot is a fungal disease that attacks sorghum and that can result in major losses to farmers because it reduces both the yield and quality of the grain produced by the plant. Sorghum ergot is a new disease in the United States, and it is important to learn as much about it as possible to help develop good and cost-effective control methods. We have shown both in greenhouse and field tests that corn earworm moths, which visit growing sorghum plants to drink nectar from sorghum flowers, can transmit the reproductive components (called spores) of sorghum ergot from diseased plants to healthy plants, thus spreading the disease. These studies are important because they show that highly mobile flying insects such as the corn earworm can be a major factor in spreading sorghum ergot over many miles from diseased sorghum fields to non-diseased fields. Reducing the impact of ergot in sorghum production may require the development of methods to minimize or avoid spread of the disease by flying insects.
Technical 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 Frederickson, Mantle, And de Milliano, was assessed. Laboratory-reared females and males and field-moths trapped in sex pheromone traps were confined outdoors in screen cages with potted male-sterile sorghum line ATx623 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 hours in cages containing healthy greenhouse- or field-grown male-sterile sorghum line ATx623 plants at anthesis, the levels of ergot severities on the panicles reanged from 2-90%, 5-90%, and 0.5-50% per panicle. THe levels of ergot infection on greenhouse -and field-grown ATx623 exposed to ergot contaminated field-trapped moths for 48 hours ranged from 0.8-38.8% and 0-81.7%, respectively. Mean external contamination of laboratory-reared and field-trapped moths placed in a soapy wash was 1.1 X 10**5 and 4.7 X10**4 conidia/ml, respectively. This study demonstrated that contaminated adult corn earworm can 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.