ABSTRACT
The biological decay of the stalks and dead roots of some grasses and shrubs liberates materials that are phytotoxic to vicinal vegetative species. A low contact angle will reduce the wettability by water as well as the rate of biodegradation. The forerunner of controlled release combinations prepared by covalently linking a pesticide to a substrate was the inorganic ester Fenone, tris(2,4-dichlorophenoxethyl)phosphite, which was introduced in 1956. Actually, pure pesticides absorbed on carriers represent a very time-abbreviated form of controlled delivery. The polymeric product, which may contain sulfonamide or imine linkages, was free of uncombined amitrole, and yet exhibited the characteristic herbicidal activity of this chemical in pot tests. Phenoxy carboxylic acids and the hydroxy-rich natural polymers, such as cellulose, chitin, chitosan, lignin, starch, alginic acid or lignocellulosic bark, make convenient reaction partners for the synthesis of practical controlled release systems useful as herbicides for both land and sea plants.
