Mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl] amino] phenyl] acetamide}+bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] at 0.14 + 0.84 kg ai/ha was the most injurious of five herbicide treatments applied once to one- to two-leaf red rice (Oryza sativa L. ♯3 ORYSA). The most injurious treatment to five-to six-leaf red rice was DPX Y6202 {ethyl [2-[4-[6-chloro-2-quinoxalinyl]oxy]phenoxy] propionate} at 0.56 kg ai/ha. Two applications, regardless of red rice growth stage, of all treatments except fluazifop {[±]-butyl-2-[4-[[5-trifluoromethyl]-2-pyridinyl] oxy] phenoxy] propanoate} resulted in 86 to 99% injury.

Under greenhouse conditions, approximately 50% visible control of bermudagrass [Cynodon dactylon (L.) Pers. ♯3 CYNDA], quackgrass [Agropyron repens (L.) Beauv. ♯ AGRRE], and wirestem muhly (Muhlenbergia frondosa L. ♯ MUHFR) was obtained using 0.56 kg/ha glyphosate [N-(phosphonomethyl)glycine], CGA-82725 {2-propynyl-2-[4-([3,5-dichloro-2-pyridinyl] oxy) oxy)phenoxy propanoate}, 0.28 kg/ha fluazifop-butyl {(±)-butyl 2-[4-[(5-(trifluoromethyl)-2-pyridinyl)oxy] phenoxy] propanoate}, sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, and 0.11 kg/ha haloxyfop-methyl [methyl 2-(4-((3-chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoate]. Except for quackgrass, sethoxydim and fluazifop-butyl reduced shoot regrowth in plants clipped 3 to 6 h after treatment Sethoxydim required a 24-h duration on quackgrass foliage to reduce growth. Fresh weights of haloxyfop-methyl- and CGA-82725-treated plants required a 12- to 24-h clipping for reduced regrowth in all species. For all herbicides and species tested, little or no regrowth occurred when plants were clipped 48 h after treatment. A 1-h interval between split applications of sethoxydim and a 24-h interval between split applications of fluazifop-butyl and haloxyfop-methyl reduced fresh weights of bermudagrass regrowth when compared to an equivalent single rate. Regrowth of treated quackgrass indicated a 24-h interval was required for reductions with split applications of sethoxydim, fluazifop-butyl, and haloxyfop-methyl. Wirestem muhly regrowth was reduced after a 1-h interval between applications. In all species, superior control was obtained using two half-rate applications compared to one full-rate application.

Toxicities of the isopropylamine salt of glyphosate [N-(phosphonomethyl)glycine], SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate), and SC-0545 (trimethylsulfoxonium carboxymethylaminomethylphosphonate) were similar to hard red winter wheat (Triticum aestivum L. ‘Centurk 78′) at equal dosages, carrier volumes, carrier water qualities, and sulfuric acid concentrations in the greenhouse and field at Lincoln, NE. Toxicity of HOE-00661 [ammonium (3-amino-3-carboxypropyl)-methylphosphinate] was less than the other herbicides at equal dosages. Rate of development of injury to wheat was similar at 0.4 kg/ha for glyphosate, SC-0224, and SC-0545, but greater for HOE-00661 up to 4 days after application and less thereafter. Reductions in carrier volume from 190 to 96 L/ha resulted in improved phytotoxicities for glyphosate, SC-0224, and SC-0545 at 0.1 kg/ha and HOE-00661 at 0.4 kg/ha. Addition of 0.25% (v/v) concentrated sulfuric acid to 190 L/ha of well water carrier resulted in improved phytotoxicities for glyphosate, SC-0224, and SC-0545 at 0.1 kg/ha and HOE-00661 at 0.4 kg/ha. Carrier water with reduced levels of polyvalent cations resulted in increased phytotoxicities of glyphosate, SC-0224, and SC-0545 at 0.1 kg/ha in 190 L/ha. Phytotoxicity of HOE-00661 was not affected by carrier water quality. Glyphosate, SC-0224, and SC-0545 at equal rates and HOE-00661 at a 4 X rate showed similar toxicity to wheat.

Solutions containing 24 or 120 g ae/L of amine or salt formulations of glyphosate [N-(phosphonomethyl) glycine], triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, and picloram (4-amino-3,5,6-trichloropicolinic acid) were applied to small shrubs with a carpeted roller. Glyphosate reduced the live canopy cover of false broomweed (Ericameria austrotexana M.C. Johnston) by 83 to 87% at one site but only by 37 to 58% at another location. The lower concentration of picloram reduced false broomweed cover by at least 92%, and the higher concentration completely controlled the weed at both study sites. Effectiveness of triclopyr was usually intermediate between glyphosate and picloram. Removing a scraper designed to abrade stems prior to herbicide deposition reduced the effectiveness of picloram but not other herbicides. The herbicides reduced canopy cover of common goldenweed [Isocoma coronopifolia (Gray) Greene ♯3 IOCCO] by 92 to 100%. Common goldenweed was also controlled by 2,4-D [(2,4-dichlorophenoxy)acetic acid] amine applied with the carpeted roller. In glasshouse experiments, 1.2 to 60 g ae/L of 2,4-D amine reduced live canopy dry weight of common goldenweed by 73 to 88% at 5 months after application with a carpeted roller.

Losses due to weeds in the United States and the cost of their control are now more than $20 billion annually (35). Of this total, $13 billion represents a 10% annual loss in agricultural production that includes not only the direct competition of weeds to reduce crop yields but also the reduced quality of produce, livestock losses, and increased cost of fertilizer, irrigation, harvesting, grain drying, transportation, and storage. In addition, farmers spend more than $7.2 billion to control weeds each year. About 43% of the expenditures to control weeds is the retail cost of herbicides, $3.1 billion, in 1980 (15). The value of herbicides sold in 1984 will probably be about 15% higher than in 1980. An additional $4.1 billion represents the cost of tillage and hand labor required for weed control (35). The total loss of over $20 billion represents an indirect annual weed tax of about $85 on each individual living in the United States.