Ovicidal Activity from Different Spray Droplet Attributes, 1989

Abstract

Abstract Combinations of 2 insecticides, 3 spray rates (AI), and 2 nozzle types were compared for percent mortality of TBW eggs and neonate larvae. Cotton plants were grown in the greenhouse, 2 plants/pot, to average heights of 16-22 inches. TBW eggs (0-24 h old) were collected from a susceptible strain of laboratory-reared moths and transferred to the cotton plants with a small brush. Plants were sprayed in a laboratory spray chamber and then returned to the greenhouse for further treatment and evaluation. A factorial arrangement of treatments with a split plot in time for ovicide rate was used to determine the effect of droplet size and density and AI rate of Larvin and Ovasyn on control of TBW eggs and neonate larvae. Droplet sizes, Dv0.5, of 285 and 180 |xm with corresponding droplet densities of 25 and 70 drops/cm2 were obtained in selected sections of the spray plume of Spraying Systems 8002E and 650033 nozzles, respectively. AI rates were 0.057, 0.125, and 0.250 lb/acre in 1.12 and 2.38 gal/acre for the 650033 and 8002E nozzles, respectively. Fifty-four eggs were placed on 6 fully-expanded terminal leaves in each potprior to spraying. Eggs were similarly placed on other sprayed plants 1 and 2 d after spraying. This 2 × 2 × 3 (nozzle × ovicide × days posttreatment) experiment with 3 replications was duplicated for the 0.125 and 0.250 AI rates; a single experiment was conducted for the 0.057 AI rate. Six d after egg placement, the plants were examined for egg hatch and larval mortality. The percentage eggs hatched and the percentage larval recovery from hatched eggs were converted to percent mortality compared to an untreated check by Abbott's formula. Data were transformed by arcsine X.