Poster: Biology & Disease Mgmt: Chemical Control
Quantification of the mortality of conidia of Botrytis cinerea and Penicillium digitatum in peracetic acid.
J. Smilanick (1), L. Grant (2) (1) consultant, U.S.A.; (2) Jet Harvest Solutions, U.S.A.
Peracetic acid (PAA) is common sanitizer, but information about its fungal toxicity is sparse. PAA toxicity was assessed to conidia of Botrytis cinerea and Penicillium digitatum, causes of gray mold and citrus green mold, respectively. They were immersed in PAA, entrapped on a glass fiber filter, rinsed with dH2O, and placed on PDA to observe germination, then the time (LT95) or concentration (LD95) when 95% mortality occurred were estimated by probit analysis. Two 100 mg/l (= ppm) solutions were used, one from 4.9% PAA + 26.5% H2O2 and the other from 15.0% PAA + 22.0% H2O2. Mortality was similar in both therefore due to PAA with little or no H2O2 contribution. ET95 of B. cinerea and P. digitatum conidia in 100 mg/l PAA was 5.4 and 2.4 minutes, respectively. ET95 of B. cinerea and P. digitatum conidia in 500 mg/l PAA was 17.2 and 9.8 seconds, respectively. LD95 of B. cinerea and P. digitatum conidia during a 24-hour PAA exposure was 24.7 and 3.3 mg/l, respectively. LD95 of P. digitatum conidia during 10 or 30-minute PAA exposure was 50 and 41 mg/l, respectively. Although PAA resistance was markedly higher in B. cinerea than P. digitatum, label rates of PAA are adequate to control conidia of both pathogens. PAA can be mixed with fungicides, label rates are relatively high (650 mg/l preharvest and 85-100 mg/l postharvest), is USDA Organic Program organic rules, and its disinfection by-products are of minimal concern.