Turfgrass Weed Research Articles

Sequential Herbicide Treatments for Large Crabgrass and Goosegrass Control in Bermudagrass1

AbstractLarge crabgrass [Digitaria sanguinalis (L.)] and goosegrass [Eleusine indica (L.) Gaertn.] are predominant summer weeds in most turfgrasses. A system for chemically controlling these weeds in late spring and early summer with the least amount of herbicide and labor is needed. Experiments were conducted to determine whether sequential herbicide treatments could be applied in June for control of emerged weeds present in bermudagrass [Cynodon dactylon (L.) Pers.] and prevent further germination of weed seeds during the remainder of the season. Combinations of preemergence and postemergence herbicides were applied in each of 2 years at Gritfin or control of large crabgrass and at Atlanta, Georgia for control of goosegrass. Sequential treatments of metribuzin [4‐amino‐6‐tert‐butyl.3‐(methylthio)‐as‐triazin‐b(4H)‐one] at 1.1 kg/ha with either bensulide [0,0‐diisopropyl phosphorodithioate S‐ester with N‐(2‐mercaptoethyl) benzenesulfonamide], oxadiazon [2‐tert‐butyl‐4‐(2,4. dichloro‐ 5‐isopropoxyphenyl) ‐ Δ2‐ 1,3,4‐oxadiazolin‐5‐one], butralin [4‐(1,1‐dimethylethyl)‐N‐(1‐methylpropyl)‐2,6‐dinitrobenzenamine], or napropamide [2‐(α‐naphthoxy)‐N,N‐diethylpropionamide] controlled a higher percentage of large crabgrass than when either chemical was applied alone. Single treatments of MSMA (monosodium methanearsonate) or methazole [2‐(3,4‐dichlorophenyl)‐4‐methyl‐1,2,4‐oxadiazolidine‐3,5‐dione] provide excellent control of large crabgrass. Goosegrass control was greater from sequential treatments of MSMA with oxadiazon, napropamide, or profluralin [N‐(cyclopropylmethyl)‐α,α, α‐trifluoro‐2,6‐dinit ro‐N‐propyl‐p‐toluidine ] than with MSMA alone. Methazole and metribuzin each controlled goosegrass almost completely.

Herbicides for Seasonal Weed Control in Turfgrasses1

AbstractCommercially available preemergence herbicides do not consistently control weeds in turfgrasses satisfactorily in the Southeast. New herbicide tests to determine if weed control could be improved were conducted on several soil types over a 3‐year period. Several herbicides were applied in early spring and evaluated for the control of large crabgrass (Digitaria sanguinalis L. Scop) in bermudagrasses [Cynodon dactylon (L.) Pers.] and Kentucky bluegrass (Poa pratensis L.) turf or they were applied in early fall and evaluated for the control of annual bluegrass (Poa annua L.) and other winter annuals in a bermudagrass turf. Soil types were Cecil sl and Cecil scl (Typic Hapludult), Appling loamy sand and Appling scl (Typic Hapludult), Madison scl (Typic Hapludult), Hatboro 1 (Typic Fluvaquents), and Davidson scl (Rhodic Paleudult). Oxadiazon [2‐tert‐butyl‐4‐(2,4‐dichloro‐5‐isopropoxyphenyl)‐ Δ2‐1,3,4‐oxadiazolin‐5‐one] applied in early spring at 4.5 kg/ha was better than with other herbicides tested for large crabgrass control. Oxadiazon was the only herbicide that consistently controlled large crabgrass at all locations. Parsley‐piert (Alchemilla microcorpa Boissier Reuter), a broadleaf winter annual not previously reported, was controlled satisfactorily when oxadiazon was applied preemergence in the fall. No other herbicide controlled parsley‐piert as well as oxadiazon.

Turfgrass Tolerance and Weed Control with Methazole and Metribuzin

Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] were evaluated in separate experiments for postemergence control of large crabgrass [Digitaria sanguinalis(L.) Scop.] and goosegrass [Eleusine indica(L.) Gaertn.] and on tolerance of centipedegrass [Eremochloa ophiuroides(Munro) Hack.], St. Augustinegrass [Stenotaphrum secundatum(Walt.) Kuntze], and bermudagrass [Cynodon dactylon(L.) Pers. ‘Common’]. Methazole was also evaluated on tolerance of Kentucky bluegrass (Poa pratensisL. ‘Common’). Metribuzin applied at 0.6 kg/ha and methazole at 1.1 kg/ha as single treatments controlled 82 and 87% goosegrass, respectively. Repeated treatments were needed for similar control of large crabgrass. These treatments did not permanently injure bermudagrass or centipedegrass. St. Augustinegrass was severely injured when treated with single applications of methazole at 1.1 kg/ha or metribuzin at 0.6 kg/ha while Kentucky bluegrass was severely injured by methazole applied at any rate. Methazole caused moderate to severe injury to bermudagrass when applied at 2.2 kg/ha in each of two applications and to centipedegrass when applied at 4.4 kg/ha in each of two applications.