Effect of method of application on antifungal efficacy of citral against postharvest spoilage fungi of citrus in culture

Three methods of challenging Penicillium digitatum, P. italicum and Geotrichum candidum with citral in culture were examined. All three species failed to grow when spores were spread on neutral Dox-yeast (NDY) agar mixed with 3000, 6000 or 15000 muL/L citral in 400 muL/L TritonX emulsifier, but development progressed normally in the absence of citral. Mixing of spores with citral solutions of 3000-15000 muL/L for 1 h before plating, to simulate dipping of fruit, reduced viability of P. italicum, and growth of G. candidum was completely inhibited by 6000-15000 muL/L citral. Citral solutions of 15000 muL/L inhibited all three species completely. Exposure of spores to citral in the volatile phase, simulating fumigation, completely prevented growth of all three fungi at headspace concentrations of 16000-40000 muL/L. The potential of citral in the volatile phase to control postharvest spoilage of citrus is discussed.