Strategies for reduction of herbicide application in sugar beet

In order to investigate the limits and possibilities of herbicide reduction in sugar beet, trials were conducted during 2003 to 2006 in Germany on five sites yearly using several strategies of herbicide applications. Pre- and post-emergence applications of different active ingredients including herbicide mixtures (up to six herbicides) were tested. Weed coverage of untreated control, herbicide efficacy, yield, and quality of sugar beet, application index, and the treatment costs were determined. Both, site-specific and a mixture of reduced herbicide application (reduction rate on average 75%) with an amount of 1.6 kg/ha of active ingredients showed the best weed control and the highest white sugar yield. Herbicide reduction of approx. 90% of the maximum registered application rate as well as the application of foliar herbicides only proved insufficient for weed control (efficacy <= 95 % averaged over all locations). The white sugar yield of all herbicide treatments was significantly higher compared to the untreated control, but not among the different treatments. A significant correlation between the application index and herbicide efficacy could not be determined. However, with an increasing application index also the safety of an efficient weed control increased.