Monday, 10 July 2006

Reducing Plant Water Stress from Attacks of Greenbugs, Corn Leaf Aphids and Virus Disease in Dryland Sorghum.

Hong Li, William A. Payne, Jerry Michels, and Charles M. Rush. Texas A&M University, 2301 Experiment Station Rd., Bushland, TX 79012

Greenbugs, corn leaf aphids (CLA) and maize draft mosaic virus (MDMV) disease are recognized as the most damaging pest and virus disease to many forage crops including grain sorghum (Sorghum bicolor (L.) Moench). A study of dryland grain sorghum was conducted in a Pullman clay loam on the High Plain of Texas during 2002-2005. The objective was to reduce plant insect, disease, and water stress using the relationships of sorghum canopy temperature, grain yield, greenbugs, CLA, MDMV, and soil water content (SWC) in space and time. Canopy temperature was detected 24 hours per day at a 10-minute interval using infrared thermocouple sensors (IRt/c) at 18 sites along transect across the field. Monthly greenbugs, CLA, MDMV and SWC were determined at each site across the field. The data showed that greenbugs, CLA and MDMV occurred at the beginning of July and the populations peaked at the beginning of August. Sorghum grain yield decreased with increase of greenbugs and CLA populations ( P < 0.05). The canopy IRt/c temperature decreased with SWC but increased with greenbugs, CLA, and MDMV disease incidence with a coefficient of determination of 56-64%. It was suggested that attacks by insects and virus disease resulted in plant water stress and yield loss. Because the insect and virus disease incidence was related to relative humidity and air temperature, adjusting planting day would be an option to reduce sorghum plant water stress and yield loss related to insect attacks and disease incidence.

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