Sweet Corn Response to Linuron Herbicide

Atrazine is the standard broadleaf herbicide for sweet corn in the Midwestern U.S.  The USEPA is reviewing atrazine because of its potential environmental impacts. The use of atrazine has been restricted in some sandy soil areas and resistant weed genotypes are a problem. There are few acceptable alternative herbicides. Linuron was used on sweet corn until 1995 when re-registration resulted in the label being voluntarily withdrawn. Recently the herbicide was purchased by TKI NovaSource who is interested in expanding the label. Our objective was to determine the tolerance to linuron of “Synergy’, an example of a bi-color synergistic sweet corn cultivar, and the weed management with linuron alone or combined with low rates of atrazine. Linuron from 0.26 to 0.84 kg/ha alone or combined with atrazine or mesotrione did not reduce sweet corn emergence, height, or yield. Linuron at 0.26 kg/ha or greater controlled common purslane (Portulaca oleracea L.); waterhemp and pigweed species (includes Amaranthus albus, tumble pigweed; A. blitoides S. Wats., prostrate pigweed; A. hybridus L., smooth pigweed; A. powellii S. Watts, Powell amaranth; A. retroflexus, redroot pigweed; A. rubis Sauer, common waterhemp; and A. tuberculatus (Moq.) Sauer, tall waterhemp), velvetleaf (Abutilon theophrasti Medik.); common lambsquarters, (Chenopodium album L.); other broadleaf weeds (includes jimsonweed, Datura stramonium L.; and ivyleaf morningglory, Ipomoea hederacea Jacq. ); and grass (includes large crabgrass Digitaria sanguinalis (L.) Scop.; fall Panicum, Panicum dichotomiflorum Michx.; and giant foxtail, Setaria faberi Herrm.) similar to atrazine at 1.56 kg/ha. Linuron may allow atrazine use to be reduced on sweet corn without decreasing weed control. Further research is needed to determine the tolerance of linuron on a range of sweet corn cultivars.