improved release - extending compositions are provided for encapsulation of bioactive agents which exhibit reduced release rates of the bioactive agent from the composition matrix when compared with conventional encapsulated formulations , most preferably employed in agricultural applications for insect and weed control . the compositions of the invention from about 25 - 75 wt . % native , undenatured starch , from about 25 - 75 wt . % biodegradable synthetic polymer , and from about 1 - 40 wt . % bioactive agent .