Interactions of the microsporidium Vairimorpha necatrix with a bacterium,virus, and fungus in Heliothis zea

Interactions between Vairimorpha necatrix and three other pathogens of Heliothis zea were evaluated with dose-mortality studies in order to find a synergistic combination which could be tested for field control of H. zea. The effect of the microsporidium combined with the bacterium Bacillus thuringiensis was at least additive, with indications of synergism. The interaction between V. necatrix and Heliothis nuclear-polyhedrosis virus was antagonistic except that the highest microsporidian dose overcame the antagonism with a resultant independent action. The interaction between V. necatrix and the fungus Nomuraea rileyi was additive, though response varied some-what with different proportions of the two pathogens. Even though none of these interactions is likely to be valuable in microbial control, V. necatrix has the potential to synergize or antagonize any biological or chemical agent that acts on the midgut epithelium of host insects.