Poster Session: Disease Control and Pest Management - Chemical Control

165-P

Effects of chemical class and physical properties on the translaminar activity of fungicides.
C. J. R. KLITTICH (1), S. L. Ray (1)
(1) Dow AgroSciences LLC, Indianapolis, IN, U.S.A.

The translaminar activity of 61 fungicides in three classes was examined using cucumber powdery mildew as a model system. Application rates were normalized to foliar LC50 and formulation was identical for all compounds. Lipophilicity and water solubility were the most predictive parameters in multiple and logistic regression models. Foliar LC50 was a key third parameter for predicting size of the control zone. Triazole and strobilurin fungicides fell into four groups: moderate translaminar movement/small zone of control (pyraclostrobin, fluoxastrobin); moderate translaminar movement/large zone of control (propiconazole, epoxiconazole, tebuconazole); strong translaminar movement/large zone of control (picoxystrobin, fenbuconazole, myclobutanil, prothioconazole); very strong translaminar movement/large zone of control (cyproconazole, azoxystrobin). Although triazoles as a class produced significantly larger control zones than the other fungicide classes, individual strobilurins can have very strong translaminar movement. When triazole and strobilurin fungicides were compared for lipophilicity and water solubility they were distributed across the range of physical properties with no retention of the translaminar group clustering. Although lipophilicity and water solubility were the most predictive factors in our models, other (unknown) physical properties must also affect the translaminar redistribution of strobilurins and triazoles.