GROWTH AND SURVIVAL OF THE MYCOPARASITE CONIOTHYRIUM-MINITANS ON LETTUCE LEAVES IN CONTACT WITH SOIL IN THE PRESENCE OR ABSENCE OF SCLEROTINIA-SCLEROTIORUM

Lettuce leaves co-inoculated with Sclerotinia sclerotiorum and Coniothyrium minitans and controls were placed on, or buried in, soil for a period of two weeks to study development and survival of C. minitans. On S. sclerotiorum-infected leaves on the soil surface, the number of colonies of C minitans recovered was about 40% of the number of pycnidiospores applied. When buried in the soil there was a reduction to about 2% of the spores applied. When C. minitans was applied on healthy lettuce leaves, which were subsequently placed on or in soil, the recovery was about 4%. It is argued that these figures indicate multiplication of C. minitans on S. sclerotiorum-infected lettuce leaves on the soil, and good survival in all other cases.