Efficiency of chemical weed control in maize (<i>Zea mays</i>) in Bavaria

Abstract

A total of 321 field trials in the period from 1991- 2016 provided 4203 data sets for different herbicide treatments. In maize in Bavaria we found on average four different weed species at every field sites. Pigweed (Chenopodium sp.), knotweed (Polygonum sp.), barnyardgrass (Echinochloa crus-galli) and black nightshade (Solanum nigrum) were found most frequently. The occurrence of geranium species (Geranium sp.) increases rapidly in the last years. Difficult-to-control weeds were green foxtail (Setaria viridis), wild buckwheat (Fallopia convolvulus), crabgrass (Digitaria sp.), black-grass (Alopecurus myosuroides) and geranium species.
Over all treatments, an average herbicide efficiency of 91% was detected. Treatments with an index of 1.5 – 2.0 achieved a weed control efficiency of > 95% in the half of all cases. Herbicide treatment with terbuthylazine as the basic active ingredient provided higher weed control and specific control of wild buckwheat and geranium. S-metholachlor achieved higher over all weed control efficiency. With triketones there is a higher efficiency in control of barnyardgrass and black nightshade. Sulfonylureas with grass weed activity are excellent to control black-grass in maize.
Currently there is a risk of losing herbicides for weed control in maize. As a result there is a need of a novel integrated weed management with secure efficiency in weed control and compatibility of environment. The Bavarian Plant Protection Service will support this progress with specific field trial programs in future.