SURVIVAL IN THE PHYLLOPLANE OF AN INTRODUCED BIOCONTROL AGENT (TRICHODERMA-HARZIANUM) AND POPULATIONS OF THE PLANT PATHOGEN BOTRYTIS-CINEREA AS MODIFIED BY ABIOTIC CONDITIONS

Leaf populations of Trichoderma were studied on tomato, pepper and geranium plants incubated under various conditions. Treatments involved high (>90%) or lower (75-85%) relative humidity (r.h.), temperatures of 15+/-3 degrees C or 25+/-3 degrees C, and soil fertilization with formulations of 2,2,5%, 3,3,8% or 5,3,8% NPK. The size of populations on leaves treated with the fungus Trichoderma harzianum differed according to plant species, leaf age, length of incubation, atmospheric conditions, and plant nutrition. T. harzianum populations were promoted in many cases by high r.h. and by 3,3,8% NPK. Interactions of introduced populations of Botrytis cinerea with populations of T. harzianum on tomato leaves under combinations of the above conditions showed that the population of B. cinerea was ca tenfold lower in the presence of T. harzianum than in the absence of this fungus.