Enhanced Toxicity of Sugar Esters to the Tobacco Aphid (Homoptera: Aphididae) Using Humectants

Abstract

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 nicotiatnae Blackman. Sugar esters included 3 types of mixtures of sucrose esters and glucose esters extracted from Nicotiana gossei Domin, N. palmeri Gray, and N. glutinosa L., and 4 types of synthetic sucrose esters. A leaf spray technique was used to apply sugar esters and treatment combinations in the laboratory. Sugar esters from N. gossei also were evaluated alone and in combination with certain humectants in the field by using a CO2 hand-held sprayer and a high-clearance sprayer fitted with a compressed air system. Toxicities of all sugar esters to tobacco aphids 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, Incromectant AMEA 100, Aqua-Tein C. Incromectant AMEA 70. Incromectant LQ, Incromectant LAMEA. Incromectant AQ. Hydrolactin 2500. Crosilk 10.000, and Cromoist CS at a 5% concentration to a solution of N. gossei sugar esters at a concentration of 1 mg/ml resulted in >90% aphid mortality. Aphid mortality from the sugar esters alone was only 12%. Aphid mortality increased as the concentration of humectants with sugar esters increased. Field evaluations showed that 5 humectants also were effective in enhancing the toxicity of N. gossei sugar esters against the tobacco aphid. Sugar esters applied with a CO2 hand-held sprayer in the field gave higher aphid control than a high-clearance sprayer. Humectants alone were not toxic to tobacco aphids.