MSc

The joint action of diflubenzuron in combination with deltamethrin and carbaryl was assessed against pests of brinjal using laboratory trials, pot culture experiments and micro plot trials in the field. Standard bioassay technique was adopted in the laboratory studies using grubs of H. vigintioctopunctata and nymphs of A. gossypii as test insects. Based on these LC50, LC25, LC10 values were computed using the dose mortality regression equations. The joint action of diflubenzuron and deltamethrin/carbaryl, mixed in the above doses, was assessed using H. vigintioctopunctata as test insect and expressed in terms of co-toxicity factor (Mansour et al., 1966).
A pot culture experiment was conducted for studying the effect of simultaneous and sequential applications of chitin synthesis inhibitor and insecticides against grubs of H.vigintioctopunctata.
A microplottrial was conducted in the field for assessing the efficacy of two effective combinations of IGR and insecticides for the control of the pests of brinjal.
Laboratory studies showed antagonistic, additive and potentiating effects in the combinations of diflubenzuron with deltamethrin/carbaryl. Potentiation effect was obtained in combincations of diflubenzuron and deltamethrin at ratios 1:0.15, 1:0.58 and 1:1.98 with the mortality percentages of 100, 93.33 and 83.33 respectively. In case of diflubenzuron with carbaryl the ratio 1:0.36 produced maximum potentiation with a mortality per cent of 83.30.
The applications of diflubenzuron and deltamethrin with a higher proportion of the insecticide and the application of diflubenzuron and carbaryl with a higher ratio of diflubenzuron were more effective (100 and 73.33 per cent mortality respectively) in the pot culture experiment against H. vigintioctopunctata. As there was no significant difference between simultaneous and sequential applications of diflubenzuron and deltamethrin, simultaneous applications of the toxicants was selected for field evaluation. The simultaneous application of both the combinations were evaluated in microplots in the field against pests of brinjal.
The combinations were superior to carbaryl 1500 ppm (standard) against grubs of epilachna beetle and larvae of fruit and shoot borer. Against sucking insects the cobninations were inferior to the standard except for the lacewing bug for which significant control was obtained. The combinations significantly reduced the population of S. docilis from 14 th day after spraying and it was on par with carbaryl.
The combinations provided prolonged control for the grubs of H. vigintioctopunctata, U. hystricellus, L. orbonalis and S. docilis when compared with the extent of control obtained with carbaryl.