STP1268

    Influence of Droplet Sizes of Deposits on Persistence of Bacillus Thuringiensis Applied as an Aqueous Flowable, and Azadirachtin Applied as a Nonaqueous Solution, Onto Oak Foliage

    Published: Jan 1996


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    Abstract

    The effect of droplet sizes of deposits on foliage on persistence of Bacillus thuringiensis var. (BTK) applied as an aqueous flowable (Study I), and of azadirachtin applied as a nonaqueous solution (Study II), was investigated under greenhouse conditions. In Study I, uniform droplets, 42 to 250 μm in diameter, of a BTK formulation, Foray 48B, were applied onto foliage of oak seedlings. Leaves were clipped at different intervals of time after treatment, the toxic protein was extracted, and the extracts were bioassayed using fourth instar gypsy moth larvae. The mean half-lives of BTK inactivation (DT50) in foliage were about 26 h for the largest droplets (250 μ m), and about 12 h for the smallest droplets (42 μm). The DT50's for the 42 and 73 μm droplets were significantly lower than for the 103 and 132 μm droplets, which in turn were lower than for the 160 to 250 μm range. An upper limit in the 130 to 160 μm range was indicated beyond which the rate of inactivation was independent of droplet sizes applied. In Study II, uniform droplets, 95 to 450 μm in diameter, of an azadirachtin formulation, Margosan-O®, containing a tracer dye, were applied onto foliage of oak seedlings. Leaves were clipped at different intervals of time after treatment, azadirachtin was extracted, and the extracts were analyzed by high-performance liquid chromatography. The DT50's ofazadirachtin loss from foliage was about 19 h regardless of the droplet sizes applied.

    Keywords:

    Bacillus thuringiensis, azadirachtin, photoinactivation, sunlight-mediated inactivation, effect of droplet sizes on persistence


    Author Information:

    Sundaram, KMS
    Natural Resources Canada, Canadian Forest Service, Forest Pest Management Institute, Sault Ste. Marie, ON

    Sundaram, A
    Natural Resources Canada, Canadian Forest Service, Forest Pest Management Institute, Sault Ste. Marie, ON


    Paper ID: STP16029S

    Committee/Subcommittee: E35.22

    DOI: 10.1520/STP16029S


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