LAUSR

Abstract Carolina redroot is a common weed of New Jersey cranberry beds that competes with crops for nutritional resources but also serves as a food source for waterfowl. Greenhouse studies were conducted in 2017 in Chatsworth, NJ, to determine control of Carolina redroot aboveground vegetation and rhizome production with 10 herbicide active ingredients. Herbicides were applied as a single application on 10- to 15-cm-tall plants. Diquat at 560 g ai ha-1and mesotrione at 280 or 560 g ai ha-1controlled more than 90% of emerged shoots at 63 d after treatment (DAT). Aboveground vegetation control at 63 DAT reached 87% with 2,4-D and flumioxazin but was limited with glyphosate, not exceeding 40%. Mesotrione at 560 g ai ha-1provided 98% control of roots and rhizomes (root/rhizome) at 63 DAT, a 10% increase compared with 280 g ai ha-1; and 2,4-D (90%), glyphosate (87%), diquat (86%), and flumioxazin (85%) also showed excellent root/rhizome control. The greatest reduction of plant biomass compared with the nontreated check (UNT) was noted with 2,4-D, mesotrione at 280 g ai ha-1and 560 g ai ha-1, and diquat, with decreases from 73% to 80% for shoots and from 82% to 88% for roots/rhizomes. Glyphosate had less impact on shoot biomass reduction (-56%) but similar effect on root/rhizome dry weight (-79%) compared with 2,4-D, mesotrione, and diquat. Flumioxazin and fomesafen significantly reduced root/rhizome biomass by 78% and 72%, respectively. Concurrently, 2,4-D, flumioxazin, fomesafen, and diquat reduced the number of secondary shoots 70% to 90% compared with the UNT, whereas glyphosate and mesotrione completely inhibited emergence of new shoots. These data suggest that mesotrione applied POST provides excellent control of Carolina redroot. Future research should evaluate field applications of mesotrione in early summer when Carolina redroot regrowth occurs following the dissipation of PRE herbicide activity. Nomenclature:2,4-D; diquat; flumioxazin; fomesafen; glyphosate; mesotrione; Carolina redroot, Lachnanthes caroliniana (Lam.) Dandy.; cranberry, Vaccinium macrocarpon Ait