An herbicide formulation that combines 2,4-dichlorophenoxyacetic acid (2,4-D) choline salt and glyphosate can stay on the US market, a federal appeals court ruled July 22. A three-judge panel rejected claims by the National Family Farm Coalition and other petitioners that the herbicide combination would lead to an increase in the use of glyphosate and that the Environmental Protection Agency had failed to evaluate the ability of 2,4-D to drift to off-target plants. The judges, however, did agree with petitioners that the EPA did not properly evaluate the risks to monarch butterflies of increased 2,4-D use on milkweed in target fields. Monarch caterpillars feed exclusively on milkweed. Rather than ordering the EPA to cancel the herbicide’s registration, however, the court directed the agency to review the evidence regarding harm to monarch butterflies from killing milkweed. The herbicide, marketed under the name Enlist Duo by Corteva Agriscience, formerly Dow AgroSciences, is approved for killing weeds on corn, soybean, and cotton fields.