Influence of temperature and light on growth, capture and predation of Haemonchus contortus by Arthrobotrys oligospora

Influence of factors including temperature and light on growth and predation profiles of Chhattisgarh isolate of Arthrobotrys oligospora on Haemonchus contortus of caprine origin was studied. Maximum growth of the fungus was obtained at 26°C on 23^rd day of incubation whereas, lowest growth was observed at 4°C even after 23^rd day of incubation. While temperatures between 4^o and 30°C clearly affected ring structure and trophic hyphal development, attachment of H. contortus larvae to adhesive hyphae of A. oligospora was not affected. Optimum temperature for fairly effective attachment of the larvae, ring structure formation and formation of trophic hyphae inside the nematode body and mortality was 26°C where 100% of baited larvae were captured on day 21 by various trapping structures with resultant trophic hyphal development and mortality on day 28. Significantly higher mortality percentage of baited larvae could be observed on day 9 and reached 100% level on day 20 in CMA plates incubated at 26°C. Growth of the fungus though initially sluggish in dark, remained similar to the growth in constant artificial light from day 9 of incubation onwards. Larval attachment with adhesive hyphae, ring structures and trophic hyphae formation was more pronounced in light where 100% of larvae were found filled with trophic hyphae by day 28. Significantly higher mortality percentage of baited larvae could be observed on day 9 onwards and reached 100% level on day 20 in CMA plates incubated at 26°C in presence of light. Mortality of larvae appeared to be sluggish and reached a maximum of 51% in plates incubated in dark.