Late blight is highly variable adapting to new fungicides and overcoming host resistance. The objective of the study was to determine efficacy of Trichoderma asperellum against Phytophthora infestans and its compatibility with fungicides. T. asperellum at 33% (3 × 106), 66% (7 × 106) and 100% (1 × 107 CFU/mL; g/L), Ridomil® (Metalaxyl 4% + Mancozeb 64%) and Mistress 72® (Cynamoxil 4% + Mancozeb 64%) were plated alongside P. infestans in vitro and detached leaflets assay. Results indicated that Ridomil® and Mistress 72® completely inhibited mycelial growth of P. infestans in vitro and in detached leaves. The 33% T. asperellum concentration had the lowest inhibitory power (38.0%) while 66% (91.10%) and 100% (91.30%) T. asperellum concentrations were not significantly different (P=0.05). Lesion sizes were not significantly different in 66% T. asperellum (1.91 cm2) and 100% (1.89 cm2) concentration while 33% concentration (3.5 cm2) and untreated (3.55 cm2) did not differ significantly. Ridomil® and Mistress 72® had no significant effect on T. asperellum mycelial growth. The results suggest that T. asperellum at 66% was effective in managing late blight. Results further indicate that T. asperellum could be used in combination with fungicides for effective and economical option.
Key words: Trichoderma asperellum, Phytophthora infestans, detached leaf assay, in vitro.