|Dailey Jr, Oliver|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 22, 1998
Publication Date: N/A
Interpretive Summary: In the last two decades, concern over the contamination of groundwater and surface water by pesticides has mounted. The chief objectives of our research are to develop herbicide formulations that will maintain or increase efficacy on target weeds and that will not adversely impact on the environment. The herbicide cyanazine has been frequently implicated in groundwater and surface water contamination. Cyanazine was microencapsulated within several different polymers by the solvent evaporation process, and herbicide efficacy studies on five weed species were conducted under greenhouse conditions. Poly(x-methylstyrene) formulations and several ethyl cellulose formulations of cyanazine were consistently comparable or superior to the commercial formulation in herbicidal activity over time. This research benefits formulation chemists, agronomists, and the agrochemical industry in that it identifies polymers suitable for further studies in the preparation and evaluation of formulations of cyanazine and other herbicides. Microencapsulated herbicides should be safer to handle, reduce the total amount of herbicide used, and have reduced potential for leaching in the soil while maintaining effective biological activity.
Technical Abstract: In two separate studies, the herbicide cyanazine was microencapsulated within polymers by the solvent evaporation process using 88% hydrolyzed polyvinyl alcohol (205 indicates low viscosity, 523 indicates medium) as emulsifier. Cyanazine formulations were prepared with: cellulose acetate butyrate (CAB); ethyl cellulose of two different viscosities (EC22 and EC100); low and medium molecular weight poly(methyl methacrylate) (PMML and PMMM); poly(alpha-methylstyrene) (PMS). Pesticide efficacy studies on five weed species (barnyardgrass, smallflower morningglory, crowfootgrass, Florida beggarweed, and Palmer amaranth) were conducted under greenhouse conditions over a period of 12 weeks for Study 1 and 25 weeks for Study 2, using the commercial formulation Bladex 90 DF for comparison purposes. In the first study of polymeric formulations of cyanazine, the following order of herbicidal activity was observed: Bladex 90DF = EC22-205 = PMS-205 = PMS-523> CAB-523 = EC100-205> CAB-205> PMMM-523> PMMM-205 = PMML-205. The first three formulations exhibited high activity comparable to the commercial formulation throughout the 12 weeks. The following order of herbicidal activity was observed in Study 2: EC100-205 greater than or equal to PMS-205 greater than or equal to EC22-523 greater than or equal to PMS-523 = Bladex 90 DF > CAB-205 = EC22-205>EC100-523> greater than or equal to CAB-523. For three weed species, EC100-205 and PMS-205 were more efficacious than Bladex 90DF. In both studies, the poly(alpha-methylstyrene) formulations were consistently comparable or superior to the commercial formulation in long term control.