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Systemic Activity and Fungitoxicity of Iprodione and E-0858 (N-[5-(2-methoxypyridinyl)]-Cyclopropane-Carboxamide) in Almond Blossoms to Monilinia laxa. J. M. Osorio, Department of Plant Pathology, University of California, Davis 95616, Current address: Facultad de Agronomia, University of Panama, David, Chiriqui; J. E. Adaskaveg(2), J. M. Ogawa(3), R. M. Bostock(4), and A. D. Jones(5). (2)(3)(4)Department of Plant Pathology, University of California, Davis 95616; (5)Facility for Advanced Instrumentation, University of California, Davis 65616. Phytopathology 84:656-660. Accepted for publication 21 March 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-656.

The structure of the experimental fungicide E-0858 was identified and affirmed as N-[5-(2-methoxypyridinyl)]-cyclopropane-carboxamide (molecular mass = 192 Da). The compound is a heterocyclic, anilide derivative with an empirical formula of C10H12N2O2 and represents a new class of fungicides. Translocation of iprodione and E-0858 into almond floral tissues was demonstrated by autoradiography, thin-layer chromatography (TLC), and combustion to radioactive carbon dioxide of blossoms treated with 14C-E-0858 and 14C-iprodione. These fungicides were applied either to the petals or the sepals of closed blossoms on detached shoots from 5-yr-old Drake and 10-yr-old Thompson almond trees, as well as 3-yr-old potted plants of Ne Plus Ultra almond. Translocation of 14C-E-0858 into stamens and pistils of blossoms on detached shoots ranged from 4 to 8% of the recovered radioactivity, whereas the recovered radioactivity of 14C-iprodione in the same tissues ranged from 1 to 3%. On potted plants, translocation of fungicide into internal floral parts ranged from 1 to 2% for E-0858 and was 1% for iprodione. Higher radioactive counts were detected in stamens and pistils when fungicides were applied to sepals rather than to petals. Separation of constituents in extracts of 14C-E-0858–treated blossoms by TLC yielded three radioactive spots, but only the parent compound was fungitoxic to mycelium of Monilinia laxa. Some of the 14C-iprodione was converted into three radioactive products in almond blossoms, with the parent compound and one metabolite showing fungitoxic activity against mycelial growth of M. laxa. In bioassays, E-0858 and iprodione applied to closed blossoms provided stamen protection similar to that of the systemic fungicide benomyl.

Additional keywords: brown rot blossom blight, dicarboximides, fungicide translocation.