Advances in the potentiometric determination of pka and log kow of pesticides

The phenylpyrrole fungicide fenpiclonil inhibited the metabolism of glucose in mycelium of Fusarium sulphureum Schlecht at a concentration which only slightly inhibited mycelial growth (EC₁₅). At the same concentration, fenpiclonil also inhibited accumulation and, to a greater extent, phosphorylation of 2-deoxyU-¹⁴C]glucose in starved mycelium loaded with unlabelled 2-deoxyglucose. Fenpiclonil did not affect cell-free phosphorylation of 2-deoxyglucose or the ATP content of mycelium. Therefore, the primary mode of action of the fungicide may be based on inhibition of transport-associated phosphorylation of glucose. This may cause a cascade of metabolic events which eventually lead to fungal growth inhibition and death. One major event affected by inhibition of transport-associated phosphorylation is the accumulation of polyols, such as glycerol and mannitol, in mycelium. This was not observed in an osmotically sensitive, fenpiclonil-resistant laboratory isolate of the fungus.