Performance of Selected Philippine Species of Trichoderma as Biocontrol Agents of Damping Off Pathogens and as Growth Enhancer of Vegetables in Farmers' Field

摘要

The use of Trichoderma species (T. parceramosum, T. pseudokoningii and a UV-irradiated strain of T. harzianum) as biological control (biocon) agents of damping off pathogens of vegetables was demonstrated in a farmers' field in Laguna province, Philippines. Improved Trichoderma pellets introduced into the soil at a rate of 100 g per m~2 2 wk before seed sowing in beds or direct seeding in the field, a much increased dosage compared to that used in a previous work, were used. With these innovations, one-time soil introduction of the antagonist minimized activity of Pythium spp., Sclerotium rolfsii and Rhizoctonia solani, thus damping off disease caused by these pathogens was effectively controlled. Soil population density of Trichoderma monitored 6 wk after application was highly correlated with the increased percentage seed germination and percentage seedling survival of the test crop, Bras-sica chinensis (pechay). Performance of biocon agents was compared with that of the chemical fungicide mancozeb. More seeds germinated in Trichoderma-treated plots and, consequently, more healthy seedlings were available for transfer to the field by using biocon than by using chemical fungicide. Growth of Brassica chinensis (pechay) and Lycopersicon esculentum(tomato) seedlings was significantly enhanced in seedbeds treated with Trichoderma pellets but not in mancozeb-treated seedbeds and the control. Field application in Benguet, a high altitude province in northern Philippines, also showed growth enhancement in Apium graveolens (celery). Solanum melongena (eggplants) grown directly in biocon-treated plots produced more fruits that were bigger and heavier than those from the control plots and from plots sprayed with the chemical fungicide mancozeb. A significantly lower number of viable sclerotial bodies of Rhizoctonia solani was recovered in biocon-treated plots compared with the other treatments. A lower incidence of the disease could be expected in the next cropping season. Use of biocon pellets of Trichoderma did not only reduce the incidence of damping off but also enhanced growth and resulted in higher yield of crops.