GREENBUG (HOMOPTERA, APHIDIDAE) FEEDING AFFECTS NONSTRUCTURAL CARBOHYDRATE-LEVELS IN SEEDLING SORGHUM

Changes in nonstructural carbohydrate (NSC) levels in seedling sorghum, Sorghum bicolor (L.) Moench, caused by the feeding of greenbug, Schizaphis graminum (Rondani), were examined. Plants were grown hydroponically in Hoagland's solution at 25-degrees-C for 14 d, then subjected to a 7-d greenbug infestation maintained at 15 aphids per plant. Nonstructural carbohydrates were extracted with water from root and shoot samples of seedlings and analyzed by high-performance liquid chromatography. Greenbug feeding significantly reduced plant growth. Greenbug honeydew represented a major loss to the plant and accounted for 18 +/- 4.7& (mean +/- SE, n = 4) of the dry weight loss of the infested plants. Concentrations (dry weight basis) of glucose and starch in the shoots and sucrose in the roots tended to be higher in infested than uninfested plants. However, total nonstructural carbohydrates concentrations in roots and shoots clearly were not significantly different between infested and uninfested seedlings.