Much has been said and written about the potential for pests to develop resistance to biopesticides. I think we can all agree that, when used properly, the likelihood of this is low. However, not all microbial biopesticides work the same, even if they are the same species (there can be significant differences between strains). Indeed, the probability for resistance development can differ greatly between biopesticides due to differences in their modes of action. For example, the most common biopesticide products used today contain the bacterium Bacillus thuringiensis (Bt) as the active ingredient. Bt produces a family of toxins that act on a specific site in the insect gut; this is known as a single-site mode of action. Resistance to some Bt strains has been well-documented for many years.  

Products such as BotaniGard® that utilize multiple modes of action are less likely to cause the development of resistance in the host population. BotaniGard contains spores of the fungus Beauveria bassiana strain GHA, a generalist pathogen of insects. Being a generalist means that this strain attacks a wide variety of hosts, AND that the mechanisms used to attack and kill hosts are broad-based. Another way to put this is: BotaniGard utilizes multiple modes of action. First, BotaniGard attacks the cuticle of the host with a group of broad-spectrum enzymes that dissolve the soft portions of the insect skin. Once inside the insect, the fungus grows rapidly and moves throughout the host's body. The rapidly growing fungus consumes insect tissues, causing death. The fungus also produces the metabolite beauvericin, which aids in killing the host. These combined modes of action work together to control arthropods and are difficult for pest populations to defeat.

The development of resistance to BotaniGard in insect populations is less likely compared to traditional pest control materials. However, we should not foolishly assume that it is impossible. We recommend that BotaniGard be rotated with other pest control materials with unrelated modes of action in order to reduce the likelihood of resistance developing in insect and mite pest populations.

Contact a BioWorks representative to recommend IPM programs that include BotaniGard for your pest control needs.

"All methods of spraying will have an impact, but complete spray coverage is very important on the undersides of the leaves where the pathogen enters the plant and disease develops. Starting early with preventative sprays in the growing cycle is your best defense.

Plant suppliers and seed companies have developed spray programs with chemical recommendations for the prevention and control of downy mildew. BioWorks products CEASE and MilStop are both labeled for downy mildew control and may have an impact in preventing the disease. They can be used together or alternated to prevent downy mildew." 

-- Rich Reineke, Great Lakes Technical Sales Manager, BioWorks.

Also see Technical Bulletin: Tank-mixing Cease & MilStop