Insecticidal activity of castor oil on Diaphania nitidalis (Stoll) (Lepidoptera: Pyralidae)

Abstract

The pickleworm, Diaphania nitidalis (Lepidoptera: Pyralidae), is a pest of considerable economic importance, because attack all parts of the vegetative and reproductive plants, including the fruits of cucurbits. Thus, this work aimed to evaluate toxicity of Ricinus communis L. (castor beans) emulsions against D. nitidalis caterpillars. In the experiments, we used the seed oil of R. communis in emulsions at concentrations 1; 2; 3; 4 and 5% (v/v). The spraying was accomplished in two ways: (i) application on the food (pumpkin leaves) of caterpillars and (ii) application on the second instar caterpillars. Evaluations were performed 24, 48 and 72 h after the application of emulsions. The design was completely randomized, with five replications in a triple factorial (two way application x three phases of evaluation x five concentrations). Castor oil acts by contact and ingestion, and exposure time to emulsion and the concentration of emulsion may interfere in the increased mortality of D. nitidalis caterpillars. The application way by ingestion had a higher mortality. The concentration of 1% was sufficient to cause mortality of 92% of D. nitidalis caterpillars after 48 h.