Screening for control agents for Trichoderma green mould in commercial mushrooms

Project Code SCR06-002

Project Lead

James Coupland - FarmForest Research

Objective

Find alternative products to control Trichoderma Green Mould in commercial mushrooms by doing in vitro and in vivo screening of selected fungicides against Trichoderma aggressivum and by evaluating the efficacy and phytotoxicity of successful candidates

Summary of Results

Trichoderma green mould (Trichoderma aggressivum f. aggressivum; Taa) is one of the most destructive fungi in the commercial mushroom industry. The number of currently available chemical fungicides that inhibit the growth of Trichoderma but allow the growth of commercial mushrooms (Agaricus bisporus; Ab) is very limited. Senator 70WP, one of the few fungicides effective against Trichoderma, has been used in Canada since 2003 under an emergency registration. Alternative products to control Trichoderma would be greatly appreciated by producers.

In a study at Pennsylvania State University that ended in December 2004, researchers screened approximately 180 products and/or formulations against Trichoderma by conducting in vitro tests on agar plates. The results of this research were used as a starting point by Dr. Danny Lee Rinker (University of Guelph) and Dr. James Coupland (FarmForest Research, Almonte) for selecting products that demonstrated some degree of efficacy for more in-depth evaluation.

The first stage of the project consisted of in vitro screening of 26 fungicides from the Pennsylvania study. These fungicides were incorporated in the culture medium (agar) at various concentrations (5, 10, 20 and 40 ppm). The fungi Trichoderma (the pathogen) and Agaricus (the commercial mushroom) were cultured on agar plates and mycelial growth was evaluated. Six fungicides from this first stage were chosen for the next stage.

In the second stage, the six selected fungicides were evaluated using in vivo testing. Bags filled with compost, containing the commercial mushrooms and inoculated with the pathogenic fungus, were used. Various fungicide concentrations were tested: 500, 1000 and 1500 ppm. In this stage of the test, four fungicides proved to be potentially effective, namely Fungazil, Mertect, Rovral and Senator.

The last stage consisted of verifying the efficacy of the four potential fungicides under commercial growing conditions. The mycelium of the commercial mushrooms was inoculated with the pathogenic fungus and then sprayed with the fungicides. The concentrations used were 500 ppm for Fungazil, 1500 ppm for Mertect, 500 ppm for Rovral and 875 ppm for Senator.

The fungicides that demonstrated the greatest efficacy in inhibiting the growth of the pathogenic fungus were Fungazil 100 SL (imazalil sulfate), Mertect SC (thiabendazole) and Senator 70WP (thiophanate-methyl). These fungicides provided excellent Trichoderma control and had no adverse effects on production yields.

Fungazil 100 SL (500 ppm) and Mertect SC (1500 ppm) are not yet registered in Canada. These two products are promising, but additional studies on rates, mycotoxicity and residues left on commercial mushrooms are needed.

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