Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2006
Publication Date: 10/1/2006
Citation: Smilanick, J.L., Mansour, M., Mlikota, G.G., Goowdwine, W.R. 2006. The effectiveness of pyrimethanil to inhibit germination of spores of penicillium digitatum and to control citrus green mold after harvest. Postharvest Biology and Technology. 42:75-85. Interpretive Summary: Citrus fruit often rot after harvest during storage and marketing. A new reduced-risk fungicide, pyrimethanil, was approved for use on citrus fruit after harvest to control postharvest rot and we showed what rates of the material are needed and how to minimize the amount needed, mainly by combining its use with sodium bicarbonate. This work shows how the fungicide, which replaces older fungicides not of the “reduced-risk” class, can best be used while minimizing residues that reach consumers.
Technical Abstract: Pyrimethanil (PYR) has recently been approved for postharvest use on citrus fruit to control green mold, caused by Penicillium digitatum. The EC50 of PYR to inhibit germination of P. digitatum spores was 0.2 to 0.4 microg/ml and was similar from pH 4 to 7. Green mold on citrus fruit was reduced more than 90% by PYR at 500 microg/ml or higher applied by immersing for 30 s or drenching the fruit, while its application in wax over rotating brushes at 1000 or 2000 microg/ml reduced green mold about 65%. Control of sporulation by PYR in aqueous solutions was better than the same concentration applied in wax, but it was inferior to imazalil. An imazalil-resistant P. digitatum isolate was controlled by PYR. The addition of sodium bicarbonate improved PYR performance. PYR was not compatible with chlorine. An increase in the temperature of the PYR solution slightly but significantly improved its effectiveness to control green mold, although its residues on fruit were greatly increased by heat; they approximately doubled for each 5C increase in solution temperature above 30C. PYR was very effective when applied up to 24 h after inoculation, but much less effective when it was applied before inoculation. PYR effectively controls green mold and is needed to control isolates of P. digitatum resistant to other fungicides.