Impact of fungicides and plant extracts on biocontrol agents and side-effects of Trichoderma spp. on rice growth

The sensitivity of the biocontrol agents for plant disease control, Trichoderma , Talaromyces and Bacillus to 27 fungicides at the recommended rate and half the recommended rate, and 10 plant crude extracts at 10 and 50 g L −1 were evaluated. The results showed that the same fungal species exhibited sensitivity to or compatibility with each fungicide in the same way. Trichoderma harzianum strains displayed the highest resistance on potato dextrose agar mixed with each fungicide followed by T. asperellum , T. hamatum , T. reesei , T. viride , Talaromyces flavus and T. tratensis , respectively. Carbendazim, prochloraz, propiconazole, tebuconazole, fluopyram + tebuconazole, tebuconazole + trifloxystrobin, thiophanate-methyl and triforine at both rates tested inhibited mycelial growth by 100% in all Trichoderma and Talaromyces species tested. Meanwhile, Bacillus amyloliquefaciens showed more compatibility with fungicides and crude plant extracts than B. subtilis strains. The extracts of Syzygium aromaticus and Piper betle completely inhibited all antagonistic microbe growth whereas all antagonists tested grew normally on P. longum extract even at 50 g L −1 . Moreover, the results revealed a negative effect of Trichoderma species on rice seedling germination and growth; they inhibited rice germination up to 80% when applied as seed treatment at 10 6 spores/ g. The results of this study indicate the sensitivity of antagonistic Trichoderma , Talaromyces and Bacillus strains to fungicides and crude plant extracts. The results provide useful data for integrated disease management using combinations of fungicides, crude plant extracts and biocontrol agents. The study also cautions the application of Trichoderma as seed dressing in rice.