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

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Abstract
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°ree;C and pII 6. Anaerobic cultivation for 23 hours at 23°ree;C and 39°ree;C inhibited fungal growth, but it did not destroy the fungus, which regained growth upon a subsequent shift to aerobic conditions at 23°ree;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 arc discussed.