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Removal of Fentin Hydroxide from Pecan Seedlings by Simulated Rain. KATHERINE L. REYNOLDS, Department of Plant Pathology, University of Georgia, Athens 30602-7274. CHARLES C. REILLY and MICHAEL W. HOTCHKISS, USDA-ARS Southeastern Fruit and Tree Nut Research Laboratory, 111 Dunbar Road, Byron, GA 31008; and FLOYD F. HENDRIX, Department of Plant Pathology, University of Georgia, Athens 30602-7274. Plant Dis. 78:857-861. Accepted for publication 7 June 1994. 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, 1994. DOI: 10.1094/PD-78-0857.

A rainfall simulator was used to examine the influence of a synthetic latex spray adjuvant and pecan cultivar on removal of fentin hydroxide (TPTH) from pecan foliage. Six-week-old pecan seedlings were sprayed with TPTH with or without adjuvant, allowed to dry, and exposed to 0, 0.25, 1.27, 2.54, or 5.08 cm of simulated rain. The initial concentration of tin on sprayed leaves was normally distributed, with greater variation on leaves sprayed with TPTH without adjuvant. In most cases the fungicide was removed at a constant rale with increasing rainfall. Addition of the spray adjuvant resulted in significantly greater fungicide tenacity after relatively light rains of 2.54 cm or less, although after an additional 2.54 cm, there was no significant difference between fungicide residues on leaves treated with or without adjuvant. Removal of fungicide by rain was examined on seedlings of 13 pecan cultivars. The percentage of tin removed after 5.08 cm of rain did not differ significantly among cultivars in the first run of the experiment. In the second run, significantly less tin was removed from leaves of seedlings of cultivars Moneymaker and Moore than the other cultivars. Differences in leaf surface characteristics among pecan cultivars have been reported and may be responsible for observed differences in fungicide tenacity.