ENHANCED TOXICITY OF SUGAR ESTERS TO THE TOBACCO APHID (HOMOPTERA, APHIDIDAE) USING HUMECTANTS

Eighteen humectants were evaluated in the laboratory and in the field to determine if they enhanced the insecticidal activity of natural and synthetic sugar esters against the tobacco aphid, Myzus nicotianae Bl ackman. Sugar esters included 3 types of mixtures of sucrose eaters an d glucose esters extracted from Nicotiana gossei Domin, N. palmeri Gra y, and N. glutinosa L., and 4 types of synthetic sucrose esters. A lea f spray technique was used to apply sugar eaters and treatment combina tions in the laboratory Sugar esters from N. gossei also were evaluate d alone and in combination with certain humectants in the field by usi ng a CO2 hand-held sprayer and a high-clearance sprayer fitted with a compressed air system. Toxicities of all sugar eaters to tobacco aphid s were significantly improved by certain humectants. Improved efficacy was related to the concentration of humectants and the type of sugar esters and humectants. The addition of humectants Volpo G-31, Incromec tant AMEA 100, Aqua-Tein C, Incromectant AMEA 70, Incromectant LQ, Inc romectant LAMEA, Incromectant AQ, Hydrolactin 2500, Crosilk 10,000, an d Cromoist CS at a 5% concentration to a solution of N. gossei sugar e sters at a concentration of I mg/ml resulted in >90% aphid mortality. Aphid mortality from the sugar esters alone was only 12%. Aphid mortal ity increased as the concentration of humectants with sugar esters inc reased. Field evaluations showed that 5 humectants also were effective in enhancing the toxicity of N. gossei sugar esters against the tobac co aphid. Sugar esters applied with a CO2 hand-held sprayer in the fie ld gave higher aphid control than a high-clearance sprayer. Humectants alone were not toxic to tobacco aphids.