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Effect of Nonanal, Citral, and Citrus Oils on Germination of Conidia of Penicillium digitatum and Penicillium italicum. R. C. French, Plant Disease Research Laboratory, P.O. Box 1209, Frederick, MD 21701; R. K. Long(2), F. M. Latterell(3), C. L. Graham(4), J. J. Smoot(5), and P. E. Shaw(6). (2)U. S. Horticultural Research Laboratory, 2120 Camden Road, Orlando, FL 32803; (3)(4)(5)(6)Citrus and Subtropical Products Laboratory, P.O. Box 1909, Winter Haven, FL 33880. Phytopathology 68:877-882. Accepted for publication 15 December 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-877.

Suspensions of nonanal in 1% water agar stimulated germination and swelling of conidia of Penicillium digitatum Sacc. (33% at 500 μliter/liter, 5 days, control 0%) and P. italicum Wehmer (35% at 500 μliters/liter, 3 days, controls 4.5%). Nonanal was the most active of the C6-C12 aldehydes studied. Decanal and dodecanal were very effective in causing swelling of spores. Citral was about as stimulatory as nonanal. Mixtures of citral and nonanal were more stimulatory to germination, or induced more swelling, than either compound alone. Suspensions of oils (1,000 μliters/liter in 1% water agar) from orange, lemon, lime, grapefruit, and tangerine, which contain these compounds along with many related compounds, were more stimulatory than nonanal, citral, or mixtures, and germination was more rapid.