Utah Pests News Spring 2007

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Beyond Bt:  Using Microbial Pesticides

Bactur, Bactospeine, Bioworm, Dipel, Javelin, Topside – All names for a commonly used microbial pesticide, Bacillius thuringiensis (Bt). Bt has been used commercially since 1961, when it was first registered by the EPA. Today there are over 187 microbial pesticides on the market, and many are used successfully to control a variety of insects and diseases in landscape and agricultural settings. These materials are great alternative to synthetic, broad-based chemical pesticides.

Microbial pesticides are made from bacteria, fungi, protozoa, viruses, and other organisms (or their toxins) that cause death or disease of insects or plant pathogens. They are sold as dusts, wettable powders, sprays, granules, etc. and are applied in the same way as conventional pesticides.

The greatest advantage to using these products is that they are safe for the environment. They target a certain pest or pest group and are thus non-toxic to humans and other life not related to the target pest. For example, the microbial insecticides do not harm predatory and parasitic insects because the toxin that a given organism produces is harmless on its own, and only becomes activated when it encounters a specific "receptor site" on its host.

Other advantages:

  • Can be applied almost up to harvest date.
  • Useful in locations where synthetic chemicals cannot be used such as near wetlands, schools, and in parks.
  • If necessary, can be used in conjunction with synthetic chemical insecticides (follow label directions).
    • Can be applied almost up to harvest date.
    • Useful in locations where synthetic chemicals cannot be used such as near wetlands, schools, and in parks.
    • If necessary, can be used in conjunction with synthetic chemical insecticides (follow label directions).

There are a few caveats to using microbials. Some require multiple applications, and correct timing of application is crucial. They also have a short shelf life, and must be protected from exposure to UV light and excessive heat. Most of the products that control insects must be ingested to be effective. And finally, some materials are costly due to their time-consuming production and difficulty in large-scale production.

Bacillius thuringiensis is the most common organism used in microbial products. Several strains have been discovered, each targeting the larvae of specific pests. One strain targets beetles, specifically Colorado potato beetle, elm leaf beetle, and cottonwood beetle. Another strain targets only mosquito, black fly, and fungus gnat larvae, but not house fly larvae. Research continues to identifying other strains. The table below lists several microbial products available to Utah growers and landscapers.

So why do synthetic pesticides still significantly outnumber bio-pesticides? One reason is the "caveats" listed above. More likely, the pest control industry has not heard a large enough demand from consumers. The need for a wider variety of organic and alternative pest control treatments will certainly drive the product development in the future.

Table of microbial pesticides available for Utah growers and homeowners.
Those with an italics (*) are available for home use.

Active Ingredient Product Names Target Pest and Notes
Bacillus sphaericus Vectolex CG, Vectomax mosquito larvae Remains effective in stagnant or turbid water
Bacillus subtilis Pro-Mix, Rhapsody, Serenade* many diseases including leaf spots, anthracnose, blights, powdery mildew, and root rots
Bacillus thuringiensis subsp. kurstaki Biobit, Caterpillar Killer*, Dipel*, Foray, Green Light*, Safer Garden Dust, Thuricide*, Xentari foliage-feeding caterpillars Deactivates rapidly in sunlight; apply in the evening or on overcast days and direct some spray to lower surfaces or leaves
Pseudomonas fluorescens A506 Blightban protection against fire blight, bunch rot, and botrytis rot on a variety of fruits and nuts
Streptomyces griseoviridis Mycostop protection against fusarium root rot, alternaria, botrytis, phytophthora root rot and more
Streptomyces lydicus Actino-Iron, Actinovate protection against a variety of root and foliar diseases including damping-off, alternaria leaf spot, pythium and phytophthora root rot, take-all, verticillium, and more
Beauveria bassiana Botanigard, Naturalis aphids, fungus gnats, mealy bugs, mites, thrips, whiteflies
Myrothecium verrucaria   nematodes, including cyst, dagger, root-knot, and stunt Made from dried fermentation solids and solubles of the fungus
Trichoderma harzianum PlantShield, Root Shield, T-22 HC protection against botrytis, root rots, powdery mildew
Nosema locustae NOLO Bait grasshoppers and Mormon crickets Useful for rangeland grasshopper control.
Codling moth granulosis virus (GV) Cyd-X, Carpovirusine, Virosoft codling moth caterpillars Active only if ingested; subject to rapid breakdown in ultraviolet light

-Marion Murray, IPM Project Leader