TOXICITY OF SYNTHETIC SUCROSE ESTERS AGAINST THE TOBACCO APHID (HOMOPTERA, APHIDIDAE)

Four synthetic sucrose esters were evaluated in the laboratory and fie ld to determine their insecticidal activity on the tobacco aphid, Myzu s nicotianae Blackman. Synthetic sucrose esters provided moderate to g ood insecticidal activity against tobacco aphids in laboratory evaluat ions. Octanoyl sucrose esters were most toxic, and decanoyl sucrose es ters 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 s ucrose esters against aphids when a CO2 hand-held sprayer was used. Al l of the synthetic sucrose esters demonstrated significantly higher ap hid mortality at a rate of 2 mg/ml than at 1 mg/ml. Heptanoyl and octa noyl sucrose esters provided significantly higher aphid control under wet conditions than under dry conditions in the laboratory. Results fr om 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 (V olpo G-31, Silwet L-77 or Volpo 0-31 plus Silwet L-77) significantly i mproved the efficacy of octanoyl sucrose esters when a CO2 hand-held s prayer was used. Relatively low aphid control was obtained with octano yl 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.