Evaluation of a Microemulsion Formulation of Fenarimol for the Control of Apple Scab Caused by Venturia inaequalis. T. B. Sutton, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. J.-S. Huang, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Plant Dis. 73:716-719. Accepted for publication 3 March 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0716.

Microemulsion (ME) and emulsifiable concentrate (EC) formulations of fenarimol were equally effective in greenhouse trials in controlling apple scab (caused by Venturia inaequalis) when applied 48, 72, 96, or 120 hr after inoculation. The percent of surface area affected with chlorotic and sporulating lesions did not differ significantly between the two formulations at 10, 20, or 30 microng a.i./ml. There was a significant positive linear relationship between time of fungicide application after inoculation and percent of leaf surface covered with sporulating lesions or chlorotic flecks. Uptake of ¹⁴C-label from radiolabeled fenarimol from leaves treated with the EC formulation was significantly greater than uptake of the label from leaves treated with the ME formulation at 10 and 30 ?g a.i./ml. Autoradiographs indicated that leaves on seedlings treated with ¹⁴C-labeled fenarimol in the EC formulation had greater radioactivity than those treated with the ME formulation. Fenarimol movement was acropetal and some ¹⁴C-label of both formulations could be detected in the four or five leaves immediately above the treated leaf.