Studies of the in vivo activity of esters of o-coumaric and cinnamic acids against apple scab

Abstract

The preparation of new esters of o-coumaric and cinnamic acids is described. Spray applications of o-coumaric acid were inactive in vivo against Venturia inaequalis on immature leaves but alkyl esters of the acid penetrated intact leaves more readily and reduced the incidence of disease. Isobutyl o-coumarate was the most active compound. In contrast to o-coumaric acid, cinnamic acid gave some measure of control but esters of this acid were not consistently better. The most satisfactory formulation mixture for these materials contained acetone, Tween 80 and Triton X-100, giving a fine crystalline suspension.Systemic action of isobutyl o-coumarate in shoots of the apple variety Cox's Orange Pippin was demonstrated, and its presence in the upper epidermis of the first five leaves above those to which it had been applied was shown by thin-layer chromatography of extracted material.

Greenhouse evaluation of chemicals for control of powdery mildews. V. Tests with unsaturated compounds*

“…For barley tests, the percentage of Triton X-IOO was reduced to 0.01 %; on this host, seedlings dipped in the formulation mixture developed sometimes fewer and sometimes more lesions than the undipped seedlings. Cinnamic and o-coumaric acids were commercial specimens, and the esters, other than those already mentioned, were prepared from them by a variety of methods described by Kirkham & Hunter (1965).…”

“…Two other groups of unsaturated compounds recently reported (Pianka, 1963;Bates, Spencer & Wain, 1963) to be highly toxic to various fungi were also included; compounds in the first group were derived from P-nitrostyrene, and in the second from the simpler nitroalkenes. Although a few esters of cinnamic acid had been tested and found of no value in the first series, the continuing interest in this acid and in the closely related o-coumaric acid, especially as esters, for the systemic control of apple scab (Kirkham & Hunter, 1964), led us to include both these acids and most of the esters tested by Kirkham & Hunter (1965). Most of the compounds used in the second series of mildew tests were also tested for activity against Venturia inaequalis (Cke.)…”