Herbicide Programs for Large Crabgrass and Goosegrass Control in Kentucky Bluegrass Turf

Abstract

Low rates of preemergence herbicides were applied with postemergence herbicides as sequential applications or as tank-mixed applications for large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.] control in Kentucky bluegrass (Poa pratensis L.). In 1991, a higher percentage of large crabgrass control (83%) was obtained in late August from sequential applications of oxadiazon at 2.2 kg·ha-1 applied in early March and followed by fenoxaprop at 0.20 kg·ha-1 in June than when oxadiazon (62%) or fenoxaprop (11%) was applied alone. During this period, sequential applications of oxadiazon at 2.2 kg·ha-1 and monosodium salt of MAA (MSMA) at 2.2 kg·ha-1 achieved 79% control of large crabgrass, while the control was at ≤46% when MSMA or fenoxaprop was applied to plots previously treated with pendimethalin at 1.7 kg·ha-1 or dithiopyr at 0.28 kg·ha-1. There was no advantage from sequential applications of preemergence and postemergence herbicides for large crabgrass control in 1992, when compared with postemergence herbicides applied alone. Large crabgrass control in late August was higher over 2 years from tank-mixes of pendimethalin at 1.7 kg·ha-1 with fenoxaprop at 0.14 kg·ha-1 (80%) than when pendimethalin (28%) or fenoxaprop (55%) was applied alone at the same rates. The control was also higher from tank-mixes of pendimethalin at 1.7 kg·ha-1 with MSMA at 2.2 kg·ha-1 (92%), when compared with MSMA (77%) alone. The response was similar from tank-mixes of dithiopyr at 0.28 kg·ha-1 with fenoxaprop at 0.14 kg·ha-1 (98%) or with MSMA at 2.2 kg·ha-1 (98%), when compared with dithiopyr applied alone (81%) at the same rate. Quinclorac applied alone at 0.84 kg·ha-1 controlled large crabgrass as effectively as when applied to plots previously treated with preemergence herbicides or when applied tank-mixed with preemergence herbicides. None of the preemergence herbicides applied at low rates with postemergence herbicides (fenoxaprop, MSMA, or quinclorac) controlled goosegrass. Chemical names used: S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate (dithiopyr); (±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]-phenoxy]propanoic acid (fenoxaprop); 3-[2,4-dichloro-5-(1-methylethoxy)-phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzen-amine (pendimethalin); and 3,7-dichloro-8-quinoline-carboxylic acid (quinclorac).