Biological Control and Pathogens

Project personnel: Jeff Lord, Paul Flinn, James Throne, Jim Campbell

    Bacillus thuringiensis var. kurstaki (Btk) is the only entomopathogen that has been in operational use on post-harvest food crops in the US. While there is some continued application on stored peanuts and corn, use on small grains has declined from already-modest levels. There are two reasons for this. First, Btk targets only moths, which are not the major insect pests in stored grain. A variety of small beetles infest stored grain, and pest control personnel are not inclined to use a material that does not include the beetles in its spectrum of activity. Secondly, high natural variation in the susceptibility of both Indianmeal moth and almond moth to Btk toxins allowed for rapid resistance development.

    Two other entomopathogens, Plodia interpunctella granulosis virus and Mattesia trogodermae, a protozoan pathogen of dermestid beetles, have been successfully tested in simulated field conditions but have little commercial potential. Both of these pathogens have a very narrow host range and are expensive to produce. Beauveria bassiana has self-life, producibility, and host range attributes that would seem to give it a substantial advantage over other pathogens. Importantly, it also has a registration that would permit use in stored products and an exemption from residue tolerances. The perception has been that the humidity in food processing and storage environments is not conducive for this fungus to be effective. We have shown that B. bassiana can infect many stored- product beetles under such conditions. Furthermore, we have shown, on a laboratory scale, that the fungus is synergistic with diatomaceous earth (DE), another non-toxic stored grain insect control agent. Primarily due to its detrimental effects on grain test weight and flow characteristics, DE use has been limited. Application of DE at low, problem-free rates with B. bassiana may be an efficacious, safe way to control many beetles. Our plan is to identify other synergistic materials and to scale up testing of B. bassiana with DE and other synergists to demonstrate operational practicality.