Neem derivatives based integrated pest management of cotton.

Abstract

Field and laboratory experiments were conducted to see the effect of neem (Azadirachta indica A. Juss) oil at 1, 2% and neem seed water extract at 2, 4% alone, in combination with bio-control agents (Trichogramma chilonis and Chrysoperla carnea) with that of synthetic chemicals viz. Actara 24WG (60gmha-1), Imidacloprid 25%WP (625 gmha-1), Fenpropathrin 20EC (750mLha-1), Polytrin-C 440EC (1250mLha-1) and proclaim 19EC (500mLha-1) against sucking insects i.e. whitefly (Bemisia tabaci Genn.), Jassid (Emrosca devastans Dist.), thrips (Thrips tabaci Lind,) and chewing insects i.e. spotted bollworm (Earias insulana Boisd.), american bollworm (Helicoverpa armigera Hubner) and pink bollworm (Pectinophora gossypiella Saund.) of cotton (CIM-499). Crop was sprayed 5 times during the cotton season. First spray was carried out 45 days after the date of sowing of crop and repeated at an interval of 15 days of first spray and so on. Data of population dynamics of sucking insects were recorded 24 hours before and then, 24, 168 and 336 hours after each spray. The data for American and spotted bollworms infestation were recorded 168 and 336 hours after each spray while for Pectinophora gossypiella, the bolls were collected on 15th of August, 14th September and 15th October 2005 and 2006 and dissected in the Laboratory to calculate the infestation. For the yield of seed cotton, the picking was started when 50 % bolls were open/ready for picking and was continued up to end of crop. Overall, after synthetic insecticides, neem oil 2%+bio-control agents (Trichogramma chilonis and Chrysoperla carnea) reduced significantly (p<0.05) % population of sucking insects (thrips. whitefly and jassid) and % infestation of bollworms (American and spotted) of cotton (168 hours after each spray). In case of pink bollworm, the bolls collected on 15th August, 15th September and 15th October, effect of treatmentsand time period/observations were found significant (p<0.05) on % damage/infestation of pink bollworm.The lowest mean % damage (5.00%) recoded in the treatment treated with insecticides followed by N2+B (8.89 %), N1+B (10%) and W4+B (11.11%) which performed similar while the highest mean % damage recorded in W2 with 22.78 % and N1 with 21.11 % which performed similar compared with control (25.56%). Neem oil 2 % (14.44 %) and W4 (17.18%) gave similar results. Best results were received from the bolls collected during 15th August (8.83%) damage. Maximum yield of seed cotton (1494 kg) was received in the plot treated with N2+B after insecticide (1895 kg). Neem derivatives at all tested concentrations have significant negative effect on settling response of whitefly and jassid on cotton leaves as compare with that in their respective control (untreated). Significantly lower numbers of test insects settled on neem derivatives treated leaves except N1 and W2 in spotted bollworm as compare with that in their respective control. Intensity of numbers of test insects settled on neem derivatives was lower at higher concentrations of neem derivatives due to repellent/deterrent effect of neem derivatives. Neem derivatives at all concentrations affected development (larvaeandpupae) of spotted bollworm. Significantly minimum survival of larvae and maximum larval mortality and less pupal formation was observed in Fenpropathrin 20EC application due to its toxic effect while neem derivatives at higher concentration also affected survival of larvae and resulted into larval mortality due to toxic effect of neem derivatives. Pupal formation was affected at higher tested concentrations of neem derivatives due to growth regulating effect of neem derivatives. Adult formation was not significantly affected by any treatment. The longest larval and pupal duration were observed at higher concentrations of neem derivatives due to growth regulating effect of neem derivatives. In laboratory trials, all the neem derivatives (indirect effect) had non-significant differences on the parasitism by Trichogramma chilonis on Helicoverpa eggs. Though, in the N2 treatment, % parasitization was significantly lower (P<0.05) than % parasitization in W2 treatment (indirect and direct effect). Adult emergence of T. chilonis was not affected by the concentrations of neem derivatives. Percent parasitization of Helicoverpa eggs by T. chilonis were inhibited (indirectand direct effect) in treatment of Proclaim 19EC (Insecticide) along with adult emergence too due to toxic effect of Proclaim 19EC. Neem derivatives at different concentrations and insecticide have significantly altered feeding/consumption ability of predator (p<0.05). The highest % consumption of aphids by Chrysoperla carnea was observed in the treatments of low concentrations of neem derivatives while the lowest % consumption of aphids was noted in the treatments in insecticide and higher concentrations of neem derivatives. Aphid % consumption by Chrysoperla carnea at different prey (aphids) densities were significantly different (p<0.05). Percent consumption of 75.87% was recorded when offered 16 aphids day-1 to predator. No significant differences were observed in % consumption when offered 32, 48, 64 and 80 aphids day-1 to predator. Effect of treatments (neem derivatives at different concentrations and insecticide) and different instars of Chrysoperlacarnea were found significant (P<0.05) on % consumption/feeding of aphids. The highest reduction in prey % consumption rate by Chrysoperla carnea was observed in Imidacloprid 25%WP application (31.77%) followed by N2(69.19%) and W4 (70.61%) while the lowest reduction in prey % consumption rate by Chrysoperla carnea was observed in the treatment of N1 (91.77%) and W2 (91.44%) as compared with control (94.94%). The highest % consumption of aphids was observed by the 2nd instar larvae (75.94%) followed by 1st instar (74.82%) of Chrysoperla carnea.