Toxicity of some new and conventional insecticides on Trichogramma chilonis Ishii and Bracon brevicornis Wesmael under laboratory condition

Abstract

Aim: Insecticides that are widely used to suppress various pests also disrupt the effectiveness of various natural control agents. After application of insecticides, predators and parasitoids may acquire insecticides via host, direct contact or by ingesting floral nectar and pollen. The main objective of the study was to find out the adverse effect of some new and conventional insecticides on Trichogramma chilonis Ishii and Bracon brevicornis Wesmael under laboratory condition. Methodology: Experiments were carried out on T. chilonis and B. brevicornis in Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India. The eggs of Corcyra cephalonica Stainton were used as host for laboratory rearing of T. chilonis, whereas full grown larvae were used for rearing of B. brevicornis. Three doses (half of the recommended, recommended and double the recommended dose) of pyridalyl 10EC, indoxacarb 14.5SC, chlorfenapyr 10SC, triazophos 40EC and chlorpyriphos 20EC were used along with control treatment. Persistent toxicity study was carried out only with recommended dose of each insecticide. The mortality data of different natural enemies were analyzed following CRD. The corrected percentage mortality was calculated for persistent toxicity study. Results: Chlorpyriphos was highly toxic to T. chilonis with no emergence followed by triazophos (1.32- 10.44% emergence) and chlorfenapyr (4.22-13.63% emergence). Pyridalyl and indoxacarb were relatively safe towards T. chilonis with 70.11-77.38 and 71.51-74.94 % adult emergence. Toxicity trend towards B. brevicornis was similar to T. chilonis. Persistent toxicity study revealed that pyridalyl and indoxacarb had short persistency, chlorfenapyr was moderately persistent while conventional insecticides (triazophos and chlorpyriphos) were highly persistent. Interpretation: This study suggests that pyridalyl and indoxacarb can be used safely whereas chlorfenapyr, triazophos and chlorpyriphos should be used with caution in integrated pest management.