The ecology of nematode‐trapping fungi in the soil

SUMMARY The decomposition of sucrose in non‐sterile soil stimulates an increase in both the population of free‐living nematodes and the activity of indigenous nematode‐trapping fungi. After sucrose decomposition reaches a certain stage the fungi cease to trap the nematodes still present in the soil. Increasing the amount of sucrose added to the soil stimulates greater increases in nematode population but results in a decrease in predacious activity of the fungi. Experiments using nematode‐free soil suggest that the presence of nematodes is necessary to initiate the formation of trapping organs, but that the fungi are incapable of remaining in a predaciously active state in the absence of an organic energy source other than the nematodes. The significance of this is discussed.