A new isolate of the nematophagous fungus Duddingtonia flagrans as biological control agent against free-living larvae of horse strongyles

An experiment was carried out in 1997 to test the efficacy of an isolate of the microfungus Duddingtonia flagrans against free-living stages of horse strongyles under conditions in the field and to assess the eventual effect of the fungus on the normal degradation of faeces. Faecal pats were made fr om faeces of a naturally strongyle infected horse, which had been fed funga l material at a dose level of 10(6) fungal unit/kg bwt. Control pats withou t fungi were made from faeces collected from the same animal just before be ing fed fungi. Faecal cultures set up for both groups of faeces to monitor the activity of the fungus under laboratory conditions showed that the fung us significantly reduced the number of infective third-stage larvae (L-3) b y an average of 98.4%. Five faecal pats from each batch of faeces were depo sited on pasture plots at 3 times during spring-summer. The herbage around each pat was sampled fortnightly to recover L-3 transmitted from faeces. Th e results showed that the herbage infectivity around fungus-treated pats wa s reduced by 85.8-99.4%. The remaining faecal material at the end of each s ampling period was collected, and the surviving L-3 were extracted. Signifi cantly fewer larvae were recovered from the fungus-treated pats. Analysis o f wet and dry weight of the collected pats, as well as their organic matter content, were performed to compare the degradation of faeces of both group s. The results indicated that the presence of the fungus did not alter the degradation of the faeces.