Dose Curves of Disinfestants Applied to Plant Production Surfaces to Control Botrytis cinerea

Lethal dose curves were calculated using probit analysis for six disinfestants (chlorazene hydrosol, hydrogen dioxide, hydrogen peroxide, iodine, quaternary ammonium chloride, sodium hypochlorite) when applied on seven substrates (galvanized metal, stainless steel, polyethylene ground fabric, polyethylene pot plastic, pressure-treated pine, exterior latex-painted pine, raw pine) that had been inoculated with Botrytis cinerea conidia. Mortality was determined by percentage of ungerminated versus germinated conidia that had been rubbed off of a substrate onto half-strength potato dextrose agar (hPDA) 16 to 24 h previously. Based on overlapping confidence limits (95% CL) of the lethal doses resulting in 90 and 50% mortality (LD₉₀ and LD₅₀, respectively) and significance of slopes, differences occurred between substrates with all six disinfestants. LD₉₀ values ranged from 0.21 to 4.54 g a.i./liter for chlorazene hydrosol, 4.99 to 40.3 g a.i./liter for hydrogen dioxide, 63.0 to 233.1 g a.i./liter for hydrogen peroxide, 0.42 to 2.45 g a.i./liter for iodine, 0.64 to 6.46 g a.i./liter for quaternary ammonium chloride, and 0.87 to 6.84 g a.i./liter for sodium hypochlorite. For hydrogen dioxide, quaternary ammonium chloride, and sodium hypochlorite, a binomial lethal dose (LD_b) was calculated by plating the inverted inoculated substrates on hPDA, then recording the presence or absence of B. cinerea mycelial growth over 7 days. Lethal doses resulting in the absence of mycelial growth (LD_b100) were equal to or greater than the LD₉₀ values for most disinfestants and substrates. Results demonstrate for the six disinfestants that dose should be selected based on the substrate being disinfested of B. cinerea conidia.