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  • Author or Editor: Garvin Crabtree x
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Abstract

Plants of red-osier dogwood (Cornus sericea L.) treated with 2,4-dichlorophenoxy-acetic acid (2,4-D) or l,1’-dimethyl-4,4’-bipyridium ion (paraquat) after reaching vegetative maturity were much less affected by the herbicides than plants treated earlier. Data support the hypothesis that vegetative maturity is a distinct physiological stage in the development of woody plants, and that inconsistencies in herbicide efficacy can, in part, be explained by this phenomenon.

Open Access

Competition between perennial ryegrass (Lolium perenne L. `Manhattan II') sod and wine grapes (Vitis vinifera L. `Chardonnay') for mineral nutrients was investigated with three methods of vineyard floor vegetation management (bare floor, mowed, and unmowed sod) and three rates of urea application (0, 137, and 274 kg N/ha). Sod decreased N concentration of grape leaves in both 1986 and 1987; Fe concentration in 1986; and S, Ca, B, and Mn in 1987. Sod also reduced total content of all measured nutrients in grape leaves. Mowing did not alleviate this reduction in leaf nutrient content. A high rate of urea (274 kg N/ha) compensated for N reduction in grape leaves caused by sod competition. Chemical names used: 2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2 -cyclohexen-1-one (sethoxydim); N,N-diethyl-2-(1-naphthalenyloxy)propanamide (napropamide).

Free access

Abstract

In a greenhouse experiment, lettuce (Lactuca sativa L.) showed considerable tolerance to N-(l,l-dimethylpropynyl)-3,5-dichlorobenzamide (pronamide) with a safety factor greater than 2 × compared to susceptible weeds. The crop and weed tolerance was greater in a silty clay loam and a muck soil than in a sandy soil. Barnyardgrass [Echinochloa crus-galli (L.) Beau v.] was more susceptible to pronamide than redroot pigweed (Amaranthus retroflexus L.) and wild turnip (Brassica campestris L.).

Open Access

Abstract

Five weed-control treatments (unweeded; hand-weeded; bensulide and naptalam; bensulide, naptalam, and paraquat; black polyethylene mulch) were combined factorially with three row-cover treatments (no cover, spun-bonded polyester, highly perforated polyethylene) in a 2-year experiment. Slicing cucumbers (Cucumis sativus L.) were transplanted 26 (1985) or 23 (1986) days after application of the bensulide-naptalam. This combination of herbicides provided weed control for up to 4 weeks after transplanting, but was less effective in 1986 than in 1985. Row covers reduced herbicide efficacy. Spraying paraquat through the covers 2 to 3 days before setting transplants significantly improved weed control and cucumber yield. Soil crusting was reduced, and earliness and total yield were enhanced by mulch and row covers. Greatest yields and estimated net economic return in both years occurred with row covers with mulch followed by mulch alone in 1986 and by mulch alone or hand-weeding with row covers in 1985. Weed control, earliness, and yield were not affected significantly by type of row cover in either year. Chemical names used: O,O-bis(1-methylethyl)-S-[2-(phenylsulfonyl)amino]ethyl]phosphorodithioate (bensulide); 2-[(1-napthalenylamino)carbonyl]benzoic acid (naptalam); 1,1′-dimethyl-4,4′-bipyridinium salts (paraquat).

Open Access

Abstract

Close plant spacing in bush snap beans (Phaseolus vulgaris L.), sweet corn (Zea mays L.), and onions (Allium cepa L.) resulted in less weed competition, as measured by crop plant reproductive parts, than wider row spacings. Early weed competition was important in all crops but weed competition at any time reduced onion yields significantly. Corn required 2 weeks and bush snap beans 3 weeks of cultivation after emergence to eliminate losses due to weed competition. Fresh weights of weed at harvest time were significantly less (0.8 kg) in plots of bush snap beans at the narrow row spacing than in plots with the medium and wide spacings (2.8 and 2.4 kg) in an 0.81 m2 area.

Open Access