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I:X'I'OXNET PIP- BACILLUS THURINGIENSIS `ltp://ace.orst.edu/cgi-bin/mfs/ol/pips/bacillus.htm • Effects on birds: B.t. is not toxic to birds [8,150]. The LD50 in bobwhite quail is greater than 10,000 mg/kg. When autopsies were performed on these birds, no pathology was attributed to B.t. Field observations of 74 bird species did not reveal any population changes after aerial spraying of B.t. formulation [148]. • Effects on aquatic organisms: B.t. is practically nontoxic to fish [150]. Rainbow trout and bluegills exposed for 96 hours to B.t. at concentrations of 560 and 1000 mg/L did not show adverse effects. A small marine fish (Anguilla anguilla) was not negatively affected by exposure to 1000 to 2000 times the level of B.t. expected during spray programs. Field observations of populations of brook trout, common white suckers, and smallmouth bass did not reveal adverse effects 1 month after aerial application of B.t. formulation [148]. However, shrimp and mussels may be affected adversely [8]. • Effects on other organisms: Applications of formulated B.t. are not toxic to most beneficial or predator insects [148]. Treatment of honeycombs with B.t. var. aizawai does not have a detrimental effect upon bees, nor on the honey produced [151]. Very high concentrations (108 spores/ ml sucrose syrup) of B.t. var. tenebrionis, which is used against beetles such as the Colorado potato beetle, reduced longevity of honey bee adults but did not cause disease [151]. B.t. applied at rates used for mosquito control may cause the death of some non-target species [8]. Users of B.t. are encouraged to consult local officials or the nearest EPA regional office responsible for protecting endangered species before using B.t. products in counties where susceptible endangered species of Lepidoptera are known to be present [146]. It did not have negative effects on frogs and salamanders [150]. Environmental Fate: • Breakdown in soil and groundwater: B.t. is a naturally-occurring pathogen that readily breaks down in the environment. Due to its short biological half-life and its specificity, B.t. is less likely than chemical pesticides to cause field resistance in target insects. B.t. is moderately persistent in soil. Its half-life in suitable conditions is about 4 months [152]. B.t. spores are released into the soil from decomposing dead insects after they have been killed by it. B.t. is rapidly inactivated in soils that have a pH below 5.1 [148]. Microbial pesticides such as B.t. are classified as immobile because they do not move, or leach, with groundwater. Because of their rapid biological breakdown and low toxicity, they pose no threat to groundwater. • Breakdown in water: The EPA has not issued restrictions for the use of B.t. around bodies of water. It can be effective for up to 48 hours in water. Afterwards, it gradually settles out or adheres to suspended organic matter [150]. • Breakdown in vegetation: B.t. is relatively short-lived on foliage because the ultraviolet (UV) light of the sun destroys it very rapidly. Its half-life under normal sunlight conditions is 3.8 hours [153]. It is not poisonous to plants and has not shown any adverse effect upon seed generation or plant vigor [150]. Physical Properties: • Appearance: The insecticidal action of B.t. is attributed to protein crystals produced by the bacterium. The vegetative cells of B.t. are approximately 1 micron wide and 5 microns long, and are motile [146]. The commercial product contains about 2.5 x 10^11 viable spores per gram. B.t. products lose some of their effectiveness when stored for more than 6 months [8]. B.t. is incompatible with alkaline materials. Formulated products are not compatible with captafol, dinocap, or, under some conditions, leaf(or foliar) nutrients [8]. 3 of 4 5/11,100 4:15 PM