Mahesh S. Yandigeri

The predation efficiency of adult and larval stages of two coccinellid species, Coccinella transversalis Fabricius and Cheilomenes sexmaculata Fabricius (Coleoptera: Coccinellidae), against two aphid species, Aphis craccivora Koch and Aphis gossypii Glover (Hemiptera: Aphididae) was evaluated under laboratory conditions. Daily predation rates were recorded for adult Coccinella predators on A. craccivora and for larval predators on A. gossypii . Adult stages of C. transversalis consumed more number of A. craccivora (19.95 ± 0.87 aphids/day) than C. sexmaculata adults (18.28 ± 1.40 aphids/day); on the other hand, the larvae of C. sexmaculata exhibited higher consumption rates on A. gossypii (20.73 ± 1.71 aphids/day) as compared to C. transversalis with a mean consumption of 18.09 ± 1.42 aphids/day. The Area Under Predation Curve (AUPC) values supported these findings and revealed that adult C. transversalis (AUPC = 240.3 ± 3.36) outperformed adult C. sexmaculata (221.3 ± 7.84); whereas larval C. sexmaculata (210.0 ± 10.60) was significantly better compared to larval C. transversalis (180.2 ± 3.80). The findings of this study confirms the stage-specific predation strategy is necessary to achieve sustainable management of aphids using coccinellid predators.

The influence of five different wastes namely, vegetable, fruit, kitchen, fish slaughter, and rice moth rearing (wastes), was evaluated on the multiplication, development, and waste reduction potential of black soldier fly, Hermetia illucens under laboratory conditions. The survival rate of larvae, prepupae weight per unit weight of wastes, adult fecundity, and longevity were the highest in kitchen and vegetable wastes. The lowest rate of survival and least weight of prepupae was recorded in the fish slaughter wastes. Kitchen wastes and rice moth rearing wastes recorded the lowest feed conversion ratio and residence time requirement. Bioconversion rate, pupal weight, and survival percentage of pupae were recorded to be the highest in kitchen waste. The results indicated that black soldier fly larvae could degrade kitchen and rice moth rearing (wastes) wastes and these parameters can be used to upscale the biomass production of this detritivore insect with suitable development parameters.

Biological control by using microbial inoculants is adopted as the best alternative to chemical pesticides to manage plant diseases. In the present study, a microbial consortia based management strategy involving the microbes Bacillus velezensis MB101 (BV), Streptomyces atrovirens N23 (SA) and Trichoderma lixii NAIMCC-F-01760 (TL), was evaluated for the management of Rhizoctonia solani (RS), the causal agent of tomato root rot. The efficacy of these microbial inoculants was evaluated in glasshouse and field experiments. Plant defense-related enzymes were assayed in the glasshouse, and biocontrol effect was evaluated in the field with RS infected soil. In the glasshouse experiment, co-inoculated SA + TL treated plants showed maximum disease resistance in comparison to control. Also, the plant defense-related enzymes such as chitinase, β-1,3-glucanase, peroxidases, polyphenol oxidase, and phenylalanine ammonia lyase were increased in this treatment. Furthermore, three application methods were assessed in the field, and SA + TL showed maximum disease reduction (76%) by the dual application. Based on glasshouse and field study results, it was concluded that co-inoculation of SA + TL activated plant defense against RS as compared to the individual microbes, and co-inoculation could be a new effective strategy to manage the root rot pathogen in an eco-compatible manner.

A chitinolytic actinomycete Streptomyces vinaceusdrappus S5MW2 was isolated from water sample of Chilika lake, India and identified using 16S rRNA gene sequencing. It showed in vitro antifungal activity against the sclerotia producing pathogen Rhizoctonia solani in a dual culture assay and by chitinase enzyme production in a chitin supplemented minimal broth. Moreover, isolate S5MW2 was further characterized for biocontrol (BC) and plant growth promoting features in a greenhouse experiment with or without colloidal chitin (CC). Results of greenhouse experiment showed that CC supplementation with S5MW2 showed a significant growth of tomato plants and superior disease reduction as compared to untreated control and without CC treated plants. Moreover, higher accumulation of chitinase also recovered in the CC supplemented plants. Significant effect of CC also concurred with the Analysis of Variance of greenhouse parameters. These results show that the a marine antagonist S5MW2 has BC efficiency against R. solani and chitinase enzyme played important role in plant resistance.

The ability of two diazotrophic cyanobacteria Westiellopsis prolifica and Anabaena variabilis were examined to solubilize extracellular insoluble tricalcium phosphate (TCP) and Mussorie rock phosphate (MRP). The two strains exhibited a differential response to insoluble forms of phosphorus used. W. prolifica showed better growth in presence of MRP while A. variabilis proliferated better in presence of TCP. Biological nitrogen fixation measured in terms of acetylene reduction (AR) activity showed significant variation among the concentrations of TCP or MRP and time of incubation. W. prolifica and A. variabilis showed maximum AR activity on 14 and 21 days of incubation respectively. In general AR activity in presence of MRP was always less than that in presence of TCP at all concentrations. Among the two cyanobacteria A. variabilis was best in terms of P-solubilization and nitrogen fixation and TCP (20 mg P l⁻¹) was the best source of insoluble P rather than MRP or K₂HPO₄.