Evaluations of pre- and postemergence herbicides for dodder management in cranberry

Dodder (Cuscuta spp.), an obligate parasitic plant, is one of the most problematic weeds for Massachusetts cranberry growers. Despite the fact that dodder has been prevalent on farms for over half a century and that numerous research projects have been directed towards its control over the years, the need for efficacious management strategies still exists. Fifteen herbicides (chlorimuron-ethyl, flumioxazin, imazethapyr, indaziflam, mesotrione, metribuzin, metsulfuron, oryzalin, oxyfluorfen, pendimethalin, pyroxasulfone, two formulations of quinclorac, rimsulfuron, and trifluralin) were screened for preemergence control in greenhouse trials, applied in 3,742 L ha^-1 of water to simulate application by chemigation. Eight herbicides were screened for postemergence control (chlorimuron-ethyl, dipotassium salt of endothall, mesotrione, metsulfuron, quinclorac, rimsulfuron, sodium salt of acifluorfen, and an herbicide that is a combination of sodium salt of bentazon and sodium salt of acifluorfen) applied as spot treatments in 281 L ha^-1 in greenhouse trials. Two herbicides (imazethapyr and rimsulfuron) were also screened in the field for postemergence control in simulated chemigation applications. Seven herbicide-rate combinations (365 and 730 mL ha^-1 of a 19.05% a.i. indaziflam formulation, 4.7 ha^-1 of a 22.3% a.i. oxyfluorfen formulation, 4.7 and 9.4 ha^-1 of a 38.7% a.i. pendimethalin formulation, and 280 and 420 g ha^-1 of a 51% a.i. flumioxazin formulation) suppressed dodder seed germination under preemergence-greenhouse conditions. Flumioxazin is currently being evaluated for crop safety and field efficacy in fall/spring applied field trials. Imazethapyr (438 mL ha^-1 of a 22.87% a.i. formulation) was identified as a possible postemergence control.