Foliar application of microbial consortium formulations suppresses Phomopsis leaf blight, promotes vegetative growth, and modulates biochemical defence in strawberry (Fragaria × ananassa Duch. cv. Camarosa) under protected cultivation.
Abstract
Background Strawberry (Fragaria × ananassa Duch. cv. Camarosa) cultivation under protected shade-net structures in South India is increasingly constrained by Phomopsis leaf blight and concurrent foliar insect infestations. Microbial formulations and consortia may provide sustainable alternatives to intensive synthetic pesticide use. Objectives This study evaluated four commercial microbial formulations, applied individually and as a consortium at 5 and 10 mL L-1, for their effects on Phomopsis leaf blight severity, foliar insect incidence, vegetative growth, and biochemical traits of strawberry under shade-net conditions. Methods Eleven treatments were arranged in a completely randomised design with three replications (132 plants). Treatments were applied after natural development of characteristic symptoms consistent with Phomopsis leaf blight. Disease and insect scores were recorded before spraying and 14 days after treatment. Vegetative and biochemical parameters were assessed two weeks after treatment. Disease severity was visually assessed using the rating approach. Data were analysed by least squares ANOVA followed by Tukey HSD at α = 0.05. Key results The 10 mL L-1 complete consortium (T10) reduced disease severity to 0.00 compared with 2.56 in the untreated control and produced the highest plant spread (26.88 cm), plant height (16.33 cm), leaf area (97.37 cm²), and number of leaves (25.33). The microbial disease-control formulation at 10 mL L-1 (T9) produced the highest tannin, chlorophyll a, and carotenoid concentrations. The 10 mL L-1 treatments generally produced stronger responses than their corresponding 5 mL L-1 treatments. Conclusion The complete consortium at 10 mL L-1 showed favourable performance in reducing symptom-based Phomopsis leaf-blight severity and improving vegetative growth. As pathogen isolation and molecular confirmation were not performed, the disease diagnosis should be regarded as symptom-based rather than definitive pathogen confirmation. Further validation is required before wider recommendation.