Laboratory experiments to evaluate the ability of Arthrobotrys oligospora to destroy infective larvae of Cooperia species, and to investigate the effect of physical factors on the growth of the fungus.

Laboratory investigations were designed to study the influence of temperature, pH and oxygen tension on the growth of Arthrobotrys oligospora, a nematode-trapping microfungus. Experiments were performed to evaluate the potential role of A. oligospora in destroying third-stage larvae of Cooperia spp. on agar plates and in cattle faeces. The fungus had a growth rate optimum at 23 degrees C and pH 6. Anaerobic cultivation for 23 hours at 23 degrees C and 39 degrees C inhibited fungal growth, but it did not destroy the fungus, which regained growth upon a subsequent shift to aerobic conditions at 23 degrees C. Under experimental conditions in petri-dishes containing agar, the nematode-trapping efficiency of the fungus was striking in that 100% of a population of third-stage larvae of Cooperia spp. was captured within three days of the experiment. The trapping efficiency in faeces was shown to depend upon the inoculation level. At a concentration of approximately 2500 conidia per g faeces, 99% of the larvae were destroyed. The possibilities of using nematode-trapping fungi in controlling animal-parasitic nematodes are discussed.