Inhibition of Citrus Postharvest Pathogens by Vapor of Citral and Related Compounds in Culture

The vapors of citral, its isomers geranial and neral, and its related compounds were examined for their effect on Penicillium digitatum, Penicillium italicum, and Geotrichum candidum, the major fungi responsible for postharvest spoilage of citrus. Vapor of citral and its two isomers generated from 15 μL L-1 aqueous solutions in Petri dishes inhibited development of the three pathogens, with concentrations of 2−6 μL L-1 also being effective against P. italicum. Vapors of citral and geranial from 15 μL L-1 solutions were fungicidal to P. digitatum and G. candidum, while neral was fungicidal to G. candidum. Citral-related compounds were much less effective, with effectiveness decreasing from citronellal to citronellol and citronellic acid. R and S isomers of these three citral-related compounds generally had similar effects on the fungi tested. Keywords: Citral; geranial; neral; vapor; Penicillium digitatum; Penicillium italicum; Geotrichum candidum citrus race; Geotrichum candidum var. citri-aurantii