The ability of the nematode-trapping fungus Duddingtonia flagrans to reduce the transmission of infective Ostertagia ostertagi larvae from faeces to herbage

The ability of two isolates of the nematode-trapping fungus Duddingtonia fl agrans to reduce the numbers of gastrointestinal nematode larvae on herbage was tested in three plot studies. Artificially prepared cow pats containin g Ostertagia ostertagi eggs, with and without fungal spores, were deposited on pasture plots two or three times during the grazing season in 1995, 199 6 and 1997. The herbage around each pat was sampled fortnightly over a peri od of 2 months and the number of infective larvae was recorded. At the end of the sampling period, the remainder of the faecal pats was collected to d etermine the wet weight, dry weight, and content of organic matter. The inf ective larvae remaining in the pats were extracted. Faecal cultures showed that both fungal isolates significantly reduced the number of infective lar vae. Significantly fewer larvae were recovered from herbage surrounding fun gus-treated pats compared with control pats in all three experiments, refle cting the ability of the fungus to destroy free-living larval stages in the faecal pat environment. After 8 weeks on pasture there were no differences between control and fungus-treated pats with respect to wet weight, dry we ight, and organic matter content. This indicates that the degradation of fa eces was not negatively affected by the presence of the fungus.