Integrated control of soilborne and bulbborne pathogens in Iris

Coating iris bulbs with a preparation of Trichoderma harzianum was highly effective under greenhouse conditions in reducing incidence of diseases caused by Rhizoctonia solani and Sclerotium rolfsii. In field experiments with irises for bulb production, the incidence of R. solani in plants and bulbs was effectively reduced (up to 93%), and the yield increased (by 35-41%), by applying T. harzianum either as a bulb coating or broadcast application (biological treatment), treating soil with pentachloronitrobenzene (PCNB; quintozene) (chemical treatment), or solarizing the soil by mulching it with transparent polyethylene sheets (physical treatment) prior to planting. Combined treatments, i.e., chemical-biological or physicalbiological, were the most effective. T. harzianum bulb treatment and broadcast application in field plots increased Trichoderma population density in the soil by 4-27 times.