Efficacy of the nematode-trapping fungus Duddingtonia flagrans against three species of gastro-intestinal nematodes in laboratory faecal cultures from sheep and goats.

The ability of the nematode-killing fungus Duddingtonia flagrans to reduce number of infective larvae of three species of gastro-intestinal parasitic nematodes developing in dung was investigated in both goats and sheep. Groups of lambs and kids (12-20 weeks old) were given mono-specific infections of Haemonchus contortus, Ostertagia (Teladorsagia) circumcincta or Trichostrongylus colubriformis. Following patency of the infections (t1) faecal samples were collected for determination of faecal nematode egg count (FEC) and culture of parasite larvae. Groups of animals were then dosed on 2 consecutive days with one of the two dose rates of the fungus (250,000 or 500,000 spores/kg liveweight). One (t2) and 5 (t3) days after the second dose of fungus samples were again collected for FEC and culture. The number of larvae recovered from the faecal cultures at t1 and t3 were used as controls to assess the efficacy of the experimental treatment at t2. Average efficacy was 78% with group means ranging from 40 to 93%. Dose rate of fungus appeared to influence efficacy against O. circumcincta but not against H. contortus or T. colubriformis. Overall, there were no differences in the efficacy of the fungus against any of the parasite species or in either host animal. The results of this trial indicate the potential use of this fungus as a broad spectrum anti-parasite agent for use in both goats and sheep.

Influence of nematophagous fungi, earthworms and dung burial on development of the free-living stages of Ostertagia (Teladorsagia) circumcincta in New Zealand.

Biological options for nematode parasite control are being sought, as the long-term efficacy of conventional anthelmintics comes increasingly under threat from drug-resistant parasites. Three biological methods with the potential to reduce pasture contamination by parasitic nematode larvae were examined: (a) killing of larvae developing in dung by nematophagous fungi; (b) removal of dung through earthworm ingestion; (c) burial of dung in soil as might occur through the action of dung beetles. Field trials with the test bio-control agents were carried out in autumn and spring by adding dung from sheep infected with Ostertagia (Teladorsagia) circumcincta to pots of ryegrass/white clover. The factorial treatment structure included five fungal treatments (individual applications of Duddingtonia flagrans, Monacrosporium gephyropagum and Harposporium helicoides, a combination of all the three fungi together and an untreated control), two dung burial treatments (dung buried or deposited on the soil surface) and two earthworm treatments (earthworms present or absent). D. flagrans and H. helicoides, individually or in combination, reduced recovery of infective stage larvae in experiment 1, while only H. helicoides reduced recovery in experiment 2. In both the experiments, dung burial increased the total number of larvae recovered, while the number of infective larvae were reduced by the action of earthworms. Increased recovery following burial, along with the fact that larvae moved rapidly from soil onto herbage, suggests that soil may provide a protective reservoir for infective larvae infesting herbage.

Isoflavonoids as insect feeding deterrents and antifungal components from root ofLupinus angustifolius.

Crude extracts of the root of the resistant legume,Lupinus angustifolius, showed feeding deterrent activity toCostelytra zealandica andHeteronychus arator larvae. Nine 5-hydroxyisoflavones were isolated from an active fraction and their feeding deterrent activity and antifungal activity was measured. High feeding-deterrent activity was associated with high antifungal activity with some exceptions.