THE BEHAVIOUR OF THE ENTOMOPATHOGENIC FUNGUS VERTICILLIUM LECANII (ZIMM) VIEGAS IN SOIL .2. LONGEVITY OF V-LECANII IN SOIL AND MINERAL WOOL AND THE OPTIMIZATION OF ITS SURVIVAL BY ADDITION OF PROMOTING ORGANIC SUBSTANCES

摘要

The behaviour of Verticillium lecanii was investigated in two soils of different composition, in mineral wool, and under addition of promoting substances. High initial spore concentrations of V. lecanii in soil, the influence of composition and ingredients of the soil, as well as the addition of organic substances were tested for their ability to maintaining a high concentration of fungal units over longer periods, as would be necessary for an effective control of soil-borne stages of Thysanoptera. In soil containing more humus substances, the survival of the entomopathogen was much higher at the same level of water saturation than in soil with a lower content of organic substances. Moreover, growth and multiplication of V. lecanii was detectable when promoting organic substances were added to soil. Highest promotion of the growth was caused by the addition of soyflour, glycerol or both. Within 5 days, the cfu increased between 5- and 30-fold and remained at this level for at least 40 days. The promotion of V. lecanii was found to depend on the applied soyflour concentration in the range between 0.1 and 1 % (soil dry matter basis) and amounted between 10- and 100-fold after 14 days.