Residual toxicity period of insecticides against citrus leaf miner, Phyllocnistis citrella stainton in nursery

Four granular insecticides namely cartap hydrochloride, chlorpyriphos, phorate and fipronil were evaluated under field conditions against, Phyllocnistis citrella. The pest population in all the treatments was minimum between 3–4 weeks after application and thereafter, the population started increasing. Fipronil (0.06 kg a.i. ha−1) and phorate (2.0 kg a.i. ha−1) were the most effective insecticides (76% reduction in pest population). Lower dosages had lesser persistence period compared to their higher dosages. Phorate (2.0 kg a.i. ha−1) was comparatively more persistent (5 weeks) compared to other insecticides. In another set of study, 6 sprayable insecticides, viz., monocrotophos, fenvalerate, deltamethrin, cypermethrin, imidacloprid and carbosulfan were evaluated. Monocrotophos at 0.2% after 2 days had 100% larval mortality of P. citrella and population started increasing 14 days after application. All the synthetic pyrethroids (fenvalerate, deltamethrin and cypermethrin) also showed the same trend of persistence as that of monocrotophos. Imidacloprid @ 0.008% (100.0%) took slightly more initial time to produce its toxic effect but remained effective for about 15 days while carbosulfan @ 0.2% (94.6%) was effective for 13 days and thereafter, the population started increasing.