Establishment of an active Trichoderma population in the phylloplane and its effect on grey mould (Botrytis cinerea )

Biological control of grey mould caused by Botrytis cinerea is achieved by Trichoderma harzianum under commercial greenhouse conditions. The establishment of populations of Trichoderma in the phylloplane of treated plants was studied. After several applications of a formulated preparation, a level of 10 super(5) cfu per leaf was established. High relative humidity (r.h.) but not saturation favoured establishment and biocontrol activity of T. harzianum. T. harzianum) affected the level of natural bacterial and fungal populations, resulting in an increase or decrease in comparison with nontreated leaves. However, r.h., temperature, plant nutrition, plant species, and leaf age influence the effect of the biocontrol agent on the indigenous microflora. It is suggested that microclimatic conditions affect Trichoderma establishment more than does plant nutrition.