FIGURE 4.12 Interactions among the bark beetle, Ips cembrae, the wood wasp, Urocerus gigas, and the two larch fungal pathogenic fungi, Ceratocystis lariciola and Amylostereum chailletti, showing how the severity of the diseases depends on interactions between the two insects. Source: From Redfern (1989).

In natural ecosystems, entomopathogenic fungi may be important density-dependent population regulators (Kamata, 2000). Hajek and Leger (1994) reviewed the literature on the biology and ecology of entomopathogenic fungi. Blakwell (1994) has specifically reviewed the literature on the Laboulbenales. Kamata (2000) considered the effect of the pathogenic fungus Cordyceps militaris in conjunction with avian predators, parasitoids, and abiotic factors on the population of the beech caterpillar Syntypistis punctatella. He concluded that the periodic population fluctuations of these larvae were caused by delayed density-dependent regulators. The fungus was the prime suspect. This causal agent was suspected as the disease started to induce population decline before it reached outbreak densities, but the delayed induced defensive response of the trees was not as closely related to the changes in the insect population (Fig. 4.13). Cordyceps is also reported as frequently occurring on insects in tropical forest