[In vitro predatory activity of a strain of Arthrobotrys oligospora Fres. Against a zooparasitic nematode].

The in vitro predatory activity of Arthrobotrys oligospora Fres. against larvae of Haemoncus contortus (Rudolphi) Cobb. was investigated on sheepdung agar. The technique employed is described and discussed. The data and observations presented indicate that temperature and number of larvae added to the fungus appear as important factors regulating the capturing efficiency. High trapping percentages were observed at 15 degrees C and 22 degrees C after a 24 hours' contact period, whereas at 10 degrees C a highly significative predatory effectiveness is not observed until 72 hours. In all experiments, where the plates contained more than 3 or 4 nematodes per square centimetre, the trapping percentage exceeds 50 p. cent after a 7 days' contact period. The response of the fungus to an increase in the number of larvae is not univocal : at 10 degrees C and 22 degrees C the nematode-trapping efficiency does not seem to depend upon the larval dnesity of the inoculum; at 15 degrees C, on the contrary, the nematodes are all the more trapped as their concentration is high. At this temperature with 35 larvae p. square centimetre, a trapping percentage of 90 p. 100 can be observed.