Fuente: WIPO "tomato" An oil-ester composition is shown and described herein. The oil-ester composition is suitable as a rainfastening agent for application to a biological substrate. The oil-ester composition may be employed in conjunction with agrochemicals to apply agrochemicals to a biological substrate. The oil-ester composition exhibits excellent rainfastness to prevent significant run off of an agrochemical upon exposure to water after application to a substrate.