Persistence of the entomopathogenic fungus Lecanicillium muscarium Zare & Gams under ambient conditions in the field.

Positive results of laboratory trials, which proofed the effectiveness of the entomopathogenic fungus L. muscarium against endophytic larvae of the horse chestnut leafminer moth Cameraria ohridella DESCHKA et DIMIC, led to outdoor trials. One aspect of these trials was to determine the persistence of the fungus, which was used as commercial product Mycotal (Koppert, NL) and as strain V24 from the section Phytomedicine. In different variants several spore concentrations and the influence of an oil-containing adjuvant (Koppert, NL) were tested. The persistence of the fungus was determined through the number of colony forming units (cfu) after impressing the leaves on agar plates. The fungus could be detected until 14 days past application (dpa), with differences between the variants, despite most unfavourable weather conditions, like above-average of temperature and hours with sunshine as well as low humidity and heavy rainfall. In all variants were found dead and moulding larvae within the mines.