Effects of diflubenzuron on a field population of the coconut black-headed caterpillar, Nephantis serinopa Meyrick (Lepidoptera: Gelechiidae), and its parasite, Parasierola nephantidis (Muesebeck) (Hymenoptera: Bethylidae), in India

Abstract

AbstractDiflubenzuron was applied once at 2·5–20 g a.i. in 10 litres of water to coconut palms infested with larvae of Nephantis serinopa Meyr. in Tamil Nadu, India. The entire field population of larvae was eliminated within 14 to 18 days, depending on the dose. The mortality due to moulting inhibition in larvae treated in the field and then brought into the laboratory ranged from 77·4 to 88·8%. The higher the dosage, the higher was the inhibition of transformation to the pupal and adult stages. Diflubenzuron also apparently had an antifeedant effect on the larvae. The compound directly or indirectly affected the development of Parasierola nephantidis (Mues.), a parasite of N. serinopa. The preference of female parasites for parasitising host larvae and oviposition in and the number of progency produced from a single host larva that had been treated with diflubenzuron in the field were significantly reduced. The percentage of normal adults produced from treated parasite larvae ranged from 17·3 to 43·0% as against 99·1% from untreated larvae. Treatment of mature parasite larvae directly with diflubenzuron in the laboratory affected development and caused morphological deformities in the adults.