Integrated disease management of bull's eye pathogen infecting lycopersicon esculentum (Tomato)

Abstract

Early blight disease in Lycopersicon esculentum (Tomato) caused by Alternaria solani is a disease posing economical threat to tomato cultivation worldwide. The efficacy of fifteen plant extracts (Polyalthia longifolia, Azadirachta indica, Datura stramonium, Ocimum sanctum, Calotropis procera, Crotalaria juncea, Eucalyptus obliqua, Cassia fistula Agele marmelos, Croton bonplonadium, Pergularia daemia, Cleome viscose, Phyllanthus amarus, Bauhinia purpurea and Euphorbia hirta), five Trichoderma harzianum strains (T1, T2, T3, T4 and T5) and seven de oiled cakes (neem cake, castor cake, karanj cake, mustard cake, groundnut cake, salmeal cake and mahua cake) were investigated in vitro and in vivo conditions. In laboratory conditions, all the treatments inhibited the mycelium of A. solani. T5 strain of Trichoderma harzianum (81%), Eucalyptus obliqua (80.7% at 15% concentration) among plant extracts and karanj cake (48.6% at 10% concentration) among de oiled cakes recorded maximum mycelium inhibition of the pathogen. Pot culture experiments were further conducted to check the combined effect of selected plant extracts and de oiled cakes (from laboratory conditions) with Trichoderma harzianum. All the three compatible constituents were further evaluated in the field conditions. The combination of T5 + Eucalyptus obliqua + karanj cake recorded maximum inhibition of (59.8%) against A. solani and was comparable with fungicide mancozeb (71.8%). Foliar spray application of tomato plants with all the combined constituents has significantly reduced the early blight infection as compared to untreated control. Thus, it could be concluded that the synergistic effect of combined constituents may be an efficacious treatment against Alternaria solani as an invulnerable option to synthetic agrochemicals.