Mushrooms: Inhibiting fungicide degradation in casing, and evaluating fungicides, biopesticides and diseased area covering methods for fungal disease control

Summary: Sporgon (a.i. prochloraz-manganese) is currently the only approved fungicide used in the UK mushroom industry. Degradation of prochloraz results in the production of inactive by-products, thereby reducing the efficacy of an applied dose in controlling wet and dry bubble diseases. This project aims to reduce degradation of prochloraz in the casing by reducing casing pH (which inhibits chemical breakdown) and/or stimulating a microbial population in the casing that is antagonistic to the microbes that degrade prochloraz. Casing treatments that are effective in inhibiting degradation of prochloraz will then be tested against standard casing for control of wet and dry bubble disease in pot and on-farm experiments. 

Parallel tests in in vitro agar plate tests and in vivo casing experiments on the sensitivity of Verticillium and Mycogone isolates to prochloraz will be conducted. This will enable the results from rapid agar plate tests on pathogen isolates to be translated into effective Sporgon application rates on casing.

Benefits to Industry: 

• Reduced degradation of prochloraz in the casing with improved control of wet and dry bubble diseases

• Enable growers to determine the required rate of Sporgon and its likely disease control efficacy in relation to the prochloraz sensitivity of the on-farm pathogens determined from agar plate tests

• Minimise the use of Sporgon with reduced risk of prochloraz residues in the mushrooms and in the SMC

• Determine the conditions that affect prochloraz degradation to reduce the persistence of prochloraz in SMC.

Aims and Objective: 

(i) Project aim(s): 

1. Manipulate the casing pH and microbial population to inhibit the degradation of prochloraz to improve wet and dry bubble disease control

2. Calibrate the results of in vitro agar plate tests for prochloraz sensitivity of pathogen isolates so that they relate to levels of disease control achieved with prochloraz concentrations in casing in vivo.

(ii) Project objective(s):

1. Determine the effect of the following casing factors on prochloraz degradation and control of wet and dry bubble:

(a) casing pH

(b) casing additives (cooked-out spent casing, bark, green waste compost)

(c) bacterial inoculum (Bacillus subtilis) and supplements. 

2. Calibration of in vitro plate test results for prochloraz sensitivity of Mycogone perniciosa and Lecanicillium (Verticillium) fungicola isolates against in vivo bubble disease control achieved with prochloraz concentrations in casing materials.