VIEW ARTICLE

Disease Control and Pest Management

Factors Influencing the Uptake of Fenarimol and Flusilazol by Apple Leaves. A. L. O’Leary, Department of Botany and Plant Pathology and Pesticide Research Center, Michigan State University, East Lansing 48824, Present address: Ricerca, Inc., P.O. Box 1000, Painesville, OH 44077; A. L. Jones, Department of Botany and Plant Pathology and Pesticide Research Center, Michigan State University, East Lansing 48824. Phytopathology 77:1564-1568. Accepted for publication 14 July 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1564.

The influence of temperature, light, leaf age, leaf surface, and fungicide concentration on the uptake of fenarimol and flusilazol by apple leaf disks was studied under controlled conditions using ¹⁴C-labeled fungicides. Penetration of both fungicides through adaxial and abaxial leaf surfaces was temperature-dependent. After 24 hr, approximately 12, 40, and 60% of the ¹⁴C-fenarimol and 15, 32, and 54% of the ¹⁴C-flusilazol applied to the abaxial surface of leaf disks from fully expanded leaves were absorbed at 10, 20, and 30 C, respectively. Uptake through the adaxial surface was also temperature-dependent, but the rate of penetration was slower than for the abaxial surface. Penetration into young, partially unfolded leaves was significantly higher than into fully expanded leaves. Although uptake of the ¹⁴C-label increased with increases in temperature from 5 to 30 C, there was a shift to a higher rate of uptake between 15 and 20 C. Uptake of ¹⁴C-fenarimol and ¹⁴C-flusilazol increased linearly as the concentration of fungicide in the solution applied to the adaxial leaf surface was increased. Light did not affect uptake of the fungicides through either leaf surface. The results indicate that ergosterol biosynthesis-inhibiting fungicides are readily absorbed by the leaf and that absorption is controlled more by physical properties of the cuticle than by metabolism of the leaf.