INDUCTION OF TRAPS BY OSTERTAGIA-OSTERTAGI LARVAE, CHLAMYDOSPORE PRODUCTION AND GROWTH-RATE IN THE NEMATODE-TRAPPING FUNGUS DUDDINGTONIA FLAGRANS

Biological control of parasitic nematodes of domestic animals can be a chieved by feeding host animals chlamydospores of the nematode-trappin g fungus Duddingtonia flagrans. In the host faeces, D. flagrans develo p traps that may catch nematode larvae. In experiments on agar, D. fla grans had a growth rate between 15 and 60 mm/week at temperatures betw een 20 and 30 degrees C. The presence of nematodes induces the fungus to produce traps. The rate of trap formation in D. flagrans has an opt imum at 30 degrees C, producing 700-800 traps/cm(2)/2 days, when induc ed by 20 nematodes/cm(2) on agar. Approaching 10 and 35 degrees C the ability to produce traps is gradually reduced. The response of chlamyd ospore production on agar to changes in temperature is the same as tha t for trap formation. On agar, at 10, 20 and 30 degrees C D. flagrans loses its trap inducibility after 2-3 weeks. During the ageing process , increasing numbers of chlamydospores are produced up to a certain li mit. The time for reaching maximum chlamydospore concentration coincid ed with the time for loss of induction potential. The implications of these results in relation to biological control in faeces are discusse d.