EFFECTS OF VARIOUS SYNTHETIC SUCROSE ESTERS ON WEED SEED-GERMINATION AND CROP GROWTH - STRUCTURE-ACTIVITY AND DOSE-RESPONSE RELATIONSHIPS

Twelve synthetic sucrose ester (SE) products with C-7-C-10 chain lengt hs and various degrees of esterification (DE) were tested for their in fluence on seed germination of prosomillet and velvetleaf and on growt h of broccoli and bell pepper plants. At 100 ppm most SE caused virtua lly total inhibition of germination; at lower concentrations dose-resp onse and structure-activity relationships were apparent. Sucrose ester s with seven and eight carbon acyl groups were most effective, and act ivities decreased for nonanoyl and decanoyl esters, respectively. With respect to DE, products high in di-, tri-, and tetraacyl esters were most active. Increased DE caused decreasing activities; however, the l owest DE (higher in monoacyl esters) was also less active. The biologi cally most active SE product was characterized by mass spectrometric t echniques. The product consisted of 7.5% monoheptanoyl and 20.7% di-, 33.5% tri-, 23.6% tetra-, 7.7% penta-and 1.3% hexaheptanoyl esters. St ructure-activity relationships with respect to published insecticidal activities paralleled their germination inhibitory effects. Growth of young broccoli and bell pepper plants, the leaves of which were treate d with the 12 SE samples, was not affected by concentrations far above those used for effective insecticidal action. Since the SE products a re nontoxic to humans and higher animals, fully biodegradable, and not harmful to the crops tested, they appear to be good candidate insecti cides. Potentials for suppression of weed seed germination need field evaluation.