The present study was performed to assess the individual and combined potential of 3 different concentrations of Trichoderma sp. (Ts) and Bacillus thuringiensis (Bt) to control brinjal insect pests. Tested formulations were applied on larval and adult stages of the pest. The Trichoderma laboratory bioassays revealed 73% mortality of the aphid species, Aphis gossypii (Glover), and 53% mortality of the cotton leafhopper (Jassids) Amrasca bigutulla bigutulla (Ishida), while opposite results were observed in case of Bt at the highest concentration (1 × 108 cfu ml−1) used. In vivo results revealed that Ts caused a significant population reduction of the aphid (87%) than the jassid (72%), 7 days of post-treatment, at the highest concentration, while non-significant results were observed at the lowest concentrations. A. gossypii was significantly found more susceptible to the mixture of Trichoderma + Bt than the jassid (62%) and brinjal shoot and fruit borer (65%) even after 48 h of treatment application. The combined application (Trichoderma + Bt) showed maximum population reduction of jassid (88%), aphid (95%), and BSFB (96%), respectively, 7 days post-applications. The positive correlation among time and concentration was observed. The result may imply that consortium of these microbial organisms could be effective and can be incorporated in IPM programs for effective control of sucking and chewing insect pests of brinjal.
The tropical armyworm, Spodoptera litura Fabricius (Noctuidae; Lepidoptera), is among the most harmful pests causing economic loss in the quality and production of a variety of crops, particularly cotton. Entomopathogens play an important role in insect pest management. The nuclear polyhedrosis virus (NPV) isolate of S. litura (V-SpltNPV) was isolated from infected larvae in a cotton crop, and viral occlusion bodies were confirmed, using an inverted microscope. The pathogenicity of V-SpltNPV against 2nd, 3rd, and 4th larval instars of S. litura was evaluated at various concentrations (1 × 10 4 to 1 × 10 8 OBs/ml). Mortality rate was high (37.65-96.82%) in early instar larvae against tested concentrations. LC 50 and LT 50 values increased with increasing larval age. There was 689,865 times increase in LC 50 value (1.35 × 10 2 OBs/ml) for 2nd instar larvae to LC 50 value (6.90 × 10 5 OBs/ml) for 4th instar larvae. LT 50 values enhanced from 4.99 days for 2nd instar larvae to 7.49 days for 4th instar larvae, due to a decrease in efficacy of NPVs with the increasing age of larvae. In a greenhouse experiment, a combined application of spinosad with V-SpltNPV (1 × 10 8 OBs/ml) caused (100%) mortality of 2nd instar larvae. A single application of V-SpltNPV (1 × 10 8 OBs/ml) resulted to mean mortality (52.63%) of tested larvae. The native isolate V-SpltNPV seems to have a potential to be used in integrated manner with other IPM tactics to significantly reduce the use of toxic chemical pesticides.
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