Tests of Some Recently Developed Insecticides in Control of the Grape Leafhopper and Oriental Fruit Moth

Abstract

Certain of the more recently developed insecticides including emulsions of pyrethrum, derris, coconut fatty acids, orthotoluidine, wormseed oil, and carbon disulphide were tested in comparison with nicotine sulfate and sodium fluosilicate, colloidal arsenate of lead, and coated arsenate of lead in comparison with dry arsenate of lead. Early in the season the emulsions, and sodium fluosilicate were sprayed on the nymphs and on foliage containing eggs of the grape leafhopper (Typhlocyba comes Say). Pyrethrum soap emulsion killed the nymphs equally as well as nicotine sulfate and prevented the hatching of eggs. Derrisol also killed the nymphs but was not so effective as an ovicide. Sodium fluosilicate killed the nymphs but burned grape foliage unless combined with hydrated lime or Bordeaux mixture. Combinations of these materials with Bordeaux mixture did not seem to affect their toxicity to leafhopper nymphs. Later in the season twigs containing larvae of the oriental fruit moth (Laspeyresi.a molesta Busck), were sprayed with the emulsions mentioned and although no killing resulted it was observed that the younger larvae which left twigs sprayed with pyrethrum soap emulsion were stunned and unable to re-enter. Further tests with this material were made in the laboratory using sprayed peaches and larvae of graded sizes. When combined with sodium fluosilicate and Bordeaux mixture this insecticide was very effective in preventing larvae from entering the fruit. A dust of pyrethrum powder, hydrated lime, and sodium fluosilicate was also quite effective and sodium fluosilicate combined with hydrated lime and used as a spray or dust killed a large percentage of the larvae. In field tests sodium fluosilicate-lime dust, and pyrethrum soap emulsion, with Bordeaux mixture were superior to arsenicals and nicotine in reducing the percentage of wormy fruit.