Toxicity of Synthetic Sucrose Esters Against the Tobacco Aphid (Homoptera: Aphididae)

Four synthetic sucrose esters were evaluated in the laboratory and field to determine their insecticidal activity on the tobacco aphid, Myzus nicotianae Blackman. Synthetic sucrose esters provided moderate to good insecticidal activity against tobacco aphids in laboratory evaluations. Octanoyl sucrose esters were most toxic, and decanoyl sucrose esters were least toxic to aphids. Only the octanoyl sucrose esters at a 2 mg/ml rate were as toxic to aphids as the natural sugar esters from Nicotiana gossei Domin. They were also the most effective synthetic sucrose esters against aphids when a CO₂ hand-held sprayer was used. All of the synthetic sucrose esters demonstrated significantly higher aphid mortality at a rate of 2 mg/ml than at 1 mg/ml. Heptanoyl and octanoyl sucrose esters provided significantly higher aphid control under wet conditions than under dry conditions in the laboratory. Results from field tests were inconsistent. Field evaluations conducted in 1995 showed that the four synthetic sucrose esters were moderately toxic at a rate of 4 mg/ml using a CO₂ hand-held sprayer and low to moderately toxic using a high clearance sprayer. The addition of a surfactant (Volpo G-31, Silwet L-77 or Volpo G-31 plus Silwet L-77) significantly improved the efficacy of octanoyl sucrose esters when a CO₂ hand-held sprayer was used. Relatively low aphid control was obtained with octanoyl sucrose esters in the field even though two surfactants were added when a high clearance sprayer was used at rates of 840 L/ha and 1400 L/ha.