Influence of Single Applications of Fungicides on Net Photosynthesis of Pecan. B. Wood, Horticulturist, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008. T. Gottwald, Pathologist, J. Payne, Entomologist, USDA, Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008. Plant Dis. 68:427-428. Accepted for publication 9 December 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/PD-68-427.

Single-fungicide spray treatments were applied to mature leaves of greenhouse-grown pecan seedlings. Six of eight fungicides tested reduced net photosynthesis (PN) 1 day after treatment by 25–35%. These six fungicides continued to reduce PN 9 days after the single spray treatment. Propiconazole and etaconazole had no effects on PN. Benomyl reduced PN 1 day after treatment but had no effect after 9 days. Triphenyltin hydroxide (wettable powder and flowable), fenarimol, chlorothalonil, and dodine had relatively long-term detrimental effects.

Keyword(s): carbon exchange, Carya illinoensis, Cladosporium caryigenum, net assimilation rate, pecan scab.