Volume 17 Part 1 Article 46: Managing Sciarid Flies with Bacillus thuringiensis var. israelensis

Volume 17 Part 1 Article 46
Year 2008
Title: Managing Sciarid Flies with Bacillus thuringiensis var. israelensis
Authors: D.L. Rinker and G. Alm


The potential for Bacillus thuringiensis var. israelensis (Bti) as a mushroom sciarid fly (Lycoriella mali) control was proposed over two decades ago. Although recently registered for mushroom use as Gnatrol® DG in North America, its effectiveness on mushroom farms has been questioned. The basic question addressed in the research reported here is ‘How can Bti be used most effectively against the mushroom sciarid fly, Lycoriella mali?’ In a series of experiments, Bti formulations, rates within formulations and timings of application with respect to fly infestation time were evaluated. Bti was incorporated into compost or casing or drenched onto casing, and gravid adult female flies were introduced under a mesh canopy that covered the experimental unit (0.25 m2). Gnatrol® DG, Vectobac®12AS and a technical powder, when incorporated into the casing with flies introduced at casing, demonstrated that product formulation was not a critical issue and that increasing rates within the formulation increased fly control, such that a Gnatrol® DG application of 5.2 kg per 100 m2 (about 3.5 times the label rate) reduced emerging adults by 83%. Incorporation of Gnatrol® DG in the casing with a fly introduction on the same day and a drench application of Bti 6 or 12 days later showed that an application or combination at day 6 was superior in control to any other application. Similarly, when flies were introduced at casing and with Gnatrol® DG drenched at 1 kg per 100 m2 on day 4, 6, 8 and 10 after casing, Bti was most effective on days 4 and 6. Percentage rates of control were 87, 75, 8 and 0, respectively. The most efficacious use of Gnatrol® DG is to apply the product as a drench when the fly larvae are expected to be young.

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