EFFICACY OF STARCH-ENCAPSULATED FORMULATIONS OF ATRAZINE CONTAINING 2OR 3 HERBICIDES IN SAME GRANULE

Field experiments were conducted in 1990, 1991, and 1992 to evaluate a nd compare the efficacy of commercial herbicide formulations with star ch encapsulated granules that contain one, two, or three herbicides. A trazine in combination with alachlor or metolachlor composed the two-c omponent granules and the addition of dicamba to both composed the thr ee-component granules. All starch-encapsulated formulations were produ ced by twin screw extrusion technology and evaluated in two granule si zes, 1.4 to 0.5-mm (14 to 20 mesh) and 0.85 to 0.43-mm (20 to 40 mesh) . Active ingredient rates applied were selected for the existing soil conditions and combination granules contained active ingredients propo rtional to premixed commercial formulations available or suggested for tank mixes. Evaluations were performed under conventional, chisel, an d no-tillage systems. PRE and PPI applications of starch encapsulated two-component (atrazine-alachlor) in 1990 controlled giant foxtail (ex cept at the low rate with large granule size), redroot pigweed, and co mmon lambsquarters excellently but control of velvetleaf was fair to p oor. Smaller-sized granules were generally more effective for controll ing weeds than the larger-sized granules. In 199 1, starch-encapsulate d two-component (atrazine-metolachlor) granules applied both PRE and P PI in conventional, chisel, and no-till systems gave results similar t o 1990 with the small granules more effective on velvetleaf. The addit ion of dicamba in the granule to form three-component starch-encapsula ted granules in 1992 resulted in control of velvetleaf, ivyleaf mornin gglory, and jimsonweed statistically equal to commercial formulations except in one case of no-till com. In our experiments, herbicide formu lations (granular vs. commercial) had no significant effect on com yie ld in 28 out of 31 treatments. These data indicate that if the experim ental three-component starch-encapsulated formulations of com herbicid es used in these studies were optimized they could become as efficacio us as commercial formulations presently on the market. This is the fir st report of research containing data on two- and three-component star ch-encapsulated granular formulations.