Gliocladium catenulatum as a Potential Biological Control Agent of Damping‐off in Bedding Plants

Hyphal interactions between the antagonist Gliocladium catenulatum and the soil‐borne plant pathogenic fungi, Pythium ultimum and Rhizoctonia solani, were investigated in dual culture by scanning electron microscopy. Gliocladium catenulatum hyphae grew along and sometimes coiled loosely around those of the pathogens. Appressorium‐like structures were produced by the antagonist which aided in holding and penetrating the hosts’ hyphae. Partial destruction of these was observed in the later stages of parasitism. A wettable powder formulation of the antagonist was then evaluated for biological control of damping‐off in bedding plant seedlings grown in a peat‐based growing medium, artificially infested with P. ultimum or R. solani. A growing medium incorporation or drench of the formulation were, in general, equally effective in reducing damping‐off and, in most cases, as effective as fungicide drenches of propamocarb HCl or tolclofos‐methyl. Populations of G. catenulatum survived well in the pathogen‐infested growing medium with levels of >106 colony forming units/cm3 being detected 28 days after application. Survival of G. catenulatum in the formulation and subsequent ability to reduce damping‐off was unaffected by storage for 48 weeks at ≤ 5°C. Further, agar tests with fungicides showed that furalaxyl, propamocarb HCl and fosetyl‐aluminium were minimally detrimental to the growth of the antagonist. The commercial implications of the results are discussed.