Interaction of monoterpenoids, methyl jasmonate, and Ca2+ in controlling postharvest brown rot of sweet cherry

The banning of synthetic fungicides for postharvest use on fruits in Canada has prompted a search for alternative control strategies for postharvest b rown rot caused by Monilinia fructicola (Wint.) Honey on sweet cherry (Prun us avium L.). Thymol and carvacrol were the two most potent fungicides amon g the monoterpenoids tested. The brown rot incidences of M. fructicola-inoc ulated cherry dipped in 1000 mug.mL(-1) thymol and carvacrol were 24 % and 23 %,respectively, compared with 81% for the control. The effects of thymol and carvacrol were not significantly enhanced by the addition of CaCl2 or CaB'y(R), a foliar calcium fertilizer. Decco(R)282 significantly reduced th e activity of thymol. Methyl jasmonate, an elicitor of plant defense mechan isms, did not reduce brown rot by itself, and did not increase the efficacy of thymol and carvacrol when used as an additive in dipping or fumigation experiments. Thymol and carvacrol caused stem browning of cherry fruits in the fumigation experiment, however, 69% and 73%, respectively, of the brown ing was prevented when methyl jasmonate was used as a co-fumigant. Chemical names used: 5-methyl-2-(1-methylethyl)phenol (thymol); 2methyl-5-(1-methyl ethyl)phenol (carvacrol); methyl 3-oxo-2-(2-pentenyl)cyclopentane acetate ( methyl jasmonate).