Quizalofop controlled 2- to 3-leaf and 5- to 6-leaf red rice better than fluazifop-P, haloxyfop, or sethoxydim applied alone. Red rice control increased when acifluorfen was tank mixed with haloxyfop, fluazifop-P, or sethoxydim. Antagonism was most severe when imazaquin was tank mixed with any of the grass herbicides. The efficacy of sethoxydim, fluazifop-P, and haloxyfop was reduced when applied with chlorimuron or bentazon. In greenhouse experiments, all of the grass herbicides, except for fenoxaprop, reduced fresh weight of red rice 71% or more. Based on fresh weight reduction, acifluorfen, fomesafen, and lactofen only reduced the activity of fluazifop-P, while imazaquin decreased the activity of all grass herbicides.

Duncecap larkspur was not killed by triclopyr, picloram, or clopyralid applied once at recommended rates. Triclopyr at 1.1, 1.7, 2.2, and 4.6 kg ae/ha applied twice to the same plots in two consecutive years reduced duncecap larkspur density from 29 to 64%. However, the higher rates of triclopyr left 2 plants/m2, an unacceptable level for preventing cattle poisoning.

Four experiments were conducted in 1985 and 1986 at three locations to assess weed control efficacy and phytotoxicity of several preemergence herbicides applied between beds (row middles) of polyethylene-mulched cauliflower grown on raised beds. Efficacy of most herbicide treatments varied among the four experiments; however, 4.5 kg ai/ha diethatyl and tank mixes of oxyfluorfen with cinmethylin consistently controlled weeds best. Plant stand, yield, and cauliflower curd size were not affected by treatment for any of the varieties used at any of the locations.

Two 5-yr experiments in a winter wheat-grain sorghum rotation were conducted near Hesston, KS, to evaluate selected foliage-applied herbicides to control honeyvine milkweed in the fall after wheat harvest. Herbicides that suppressed honeyvine milkweed stem populations 9 months after treatment included glyphosate, glyphosate plus dicamba, glyphosate plus 2,4-D, picloram, and four combinations of picloram plus 2,4-D. Honeyvine milkweed had regrown sufficiently by 24 months after herbicide application to require retreatment. Stem populations were suppressed following repeat treatments. Herbicide treatments increased yields of grain sorghum planted 9 months later but did not increase yields of winter wheat planted 13 months or longer after herbicide application.

Six, 9, and 12-mm diam dicalcium phosphate tablets were evaluated for their release of acetochlor, metolachlor, and metribuzin. Greenhouse bioassays with Italian ryegrass demonstrated that herbicides from the smaller tablets did not control grass as long as from the larger tablets. Italian ryegrass was controlled within a 5- to 7-cm diam circle around the 12-mm diam tablet and a 5-cm diam circle around the 6-mm diam tablet. All tested herbicides responded in a similar fashion. Six-mm diam tablets released metolachlor for 11 weeks, while the 12-mm tablet was active for 28 weeks.

The objective of this study was to determine how selected herbicides affect sod tensile strength and rooting of mature and immature turfs of ‘Tifway’ bermudagrass. Both immature and mature turf had 100% ground cover, but only mature turf had tensile strength adequate for harvesting and handling. Sod tensile strength at 2, 4, and 8 weeks after application generally was unaffected by herbicide treatment, although imazapyr killed bermudagrass top growth. Root number and root length initially were depressed by imazapyr, bensulide, napropamide, sethoxydim, and sulfometuron at most rates and intervals tested. Eight weeks after treatment, root length, root number, and sod tensile strength for all treatments, except those with imazapyr, were similar to that of the untreated control.

The potential diversity in tolerance of eight commercial sugarcane cultivars to metribuzin, terbacil, and hexazinone was investigated. Herbicides were applied preemergence in the fall after planting and postemergence to the crop in the spring each year over the 3-yr crop cycle. Reductions in shoot counts and heights were not observed with any of the herbicide treatments in the fall following planting. Cultivar differences in growth and yield responses were obtained, particularly in the plant cane year of the 3-yr crop cycle. Metribuzin was the least phytotoxic and hexazinone the most phytotoxic. Reductions in sugar yields (kg/ha) were attributed to reductions in stalk populations and, to a lesser extent, to reductions in stalk height and sugar (sucrose) content. Cultivars sensitive to hexazinone either were equally sensitive to terbacil or were less sensitive to terbacil. Terminal fluorescence (FT)3 measurements indicated that photosynthesis following postemergence applications of terbacil and hexazinone was no longer inhibited 5 weeks after treatment in the tolerant cultivars, CP 70–321 and CP 74–383, but continued to be reduced in the cultivars showing sensitivity, CP 65–357 and CP 48–103. The order of cultivar tolerance to hexazinone and terbacil from least tolerant to most tolerant is CP 48–103 < CP 65–357 ≤ CP 72–370 < CP 70–321 = CP 70–330 < CP 72–356 = CP 73–351 = CP 74–383.

Field experiments were conducted in 1986 and 1987 to evaluate the effect of herbicide rate (two-thirds and maximum labeled rate) and timing of application before soybean planting on common cocklebur control. In 1986, chlorimuron plus metribuzin at 50 plus 320 and 80 plus 480 g ai/ha and imazaquin at 90 g ai/ha applied at planting controlled common cocklebur better than when applied 4 weeks before planting (WBP). Imazaquin at 140 g/ha applied at planting controlled common cocklebur better than when applied 6 WBP. All treatments at two-thirds of the labeled rate applied at planting controlled common cocklebur comparable to the full labeled rate applied 2, 4, or 6 WBP. In 1987, all treatments applied 2 WBP controlled common cocklebur better than when applied 4, 6, or 8 WPB.

Germination stimulants were tested for effectiveness on velvetleaf seed imbibition and germination and concurrent microbial attack of seed to deplete weed seed in soil. Several chemicals increased in vitro seed germination and decreased the numbers of hard, viable seed. The proportion of nonviable seed, 5% with Fusarium oxysporum (Schlech.), was enhanced to 40% by adding ethephon at 100 μg/ml. Fungal density on seedling roots and imbibed (nonviable seed) was increased by chemical treatment. Seedling emergence was reduced 15% when ethephon or carbofuran was applied to soil with the fungus. Shoot dry weight decreased and root infection increased with all treatments regardless of fungal inoculation. Butylate and carbofuran increased infection of imbibed seed in soil by F. oxysporum while ethephon and AC94377 increased infection by other soil fungi.

Wheat that emerged with alfalfa seeded in the field in late August grew for 20 days after planting without suppressing the alfalfa but reduced yields if allowed to grow with alfalfa for 30 or more days. Uncontrolled wheat reduced the first cutting yield of alfalfa by 80% or more. Sethoxydim at 0.4 kg ai/ha, fluazifop at 0.2 kg ai/ha, and haloxyfop at 0.2 kg ai/ha controlled wheat selectively in alfalfa. Herbicides applied 20 days after seeding protected alfalfa from suppression by wheat. Control of wheat was equal when herbicides were applied 30 days after seeding, but in 1 of 2 yr, the wheat had suppressed the alfalfa enough to reduce yields the following May.

Multiflora rose was defoliated completely 320 days after spring foliar application of metsulfuron. Metsulfuron and 2,4-D plus dicamba spring foliar applied controlled multiflora rose equally. Metsulfuron applied to soil using a spotgun at 20 mg per m diam of multiflora rose in the spring resulted in 95% control 320 days later in one study but only 50% control in another. Control was less when lower rates of metsulfuron were soil-applied with a spotgun. Tebuthiuron spring soil-applied completely controlled multiflora rose. All spring-applied foliar and soil applications seemed to control multiflora rose better than fall treatments.

Five perennial cool-season grasses: Kentucky bluegrass, creeping red fescue, tall fescue, orchardgrass, and perennial ryegrass were treated at the 2- to 3-leaf, 3- to 4-leaf, 4- to 6-leaf, and 6- to 7-leaf growth stages with four rates (0, 0.14, 0.28, and 0.56 kg ai/ha) of the butyl ester of fluazifop. Creeping red fescue was not injured by any rate at any growth stage. Reduction in shoot dry weight increased linearly with increasing fluazifop rate for the remaining four species, except for the 6- to 7-leaf stage in Kentucky bluegrass and the 4- to 6-leaf stage in tall fescue and perennial ryegrass. Significant differences between growth stages within each rate varied with species. In general, tolerance increased at the 4- to 6-leaf and 6- to 7-leaf growth stages.

In 1986 and 1987, imazethapyr at 0.11 or 0.14 kg ai/ha and metolachlor plus imazaquin at 1.4 plus 0.16 kg/ha, applied preplant incorporated, controlled greater than 85% of red rice in soybeans. Red rice was controlled similarly by standard herbicide treatments of alachlor at 2.8 kg ai/ha, metolachlor at 2.2 kg ai/ha, and alachlor plus imazaquin at 2.5 plus 0.14 kg ai/ha. Eighty-four percent or more of red rice was controlled with single postemergence herbicide treatments of DPX-Y6202-31 at 0.14 kg ai/ha or imazethapyr at 0.11 kg ai/ha or by sequential postemergence treatment of DPX-Y6202-31 (0.07 plus 0.07 kg ai/ha) or clethodim (0.1 plus 0.1 kg ai/ha). Soybean injury was insignificant, and yields from treated plots were superior or equal to those from untreated plots.

Leafy spurge control with picloram and various 2,4-D formulations was evaluated to determine the optimum treatment combination and carrier volume for aerial application using a microfoil boom. Leafy spurge control was similar when the same herbicide treatments were applied at 94 and 47 L/ha but declined at 23 L/ha. Leafy spurge control was better when similar herbicide treatments were applied with a one-row microfoil nozzle boom compared to a two-row nozzle. Leafy spurge control 12 months after treatment tended to be better with picloram at 0.28 and 0.56 kg ae/ha applied with 2,4-D mixed amine compared to picloram plus 2,4-D dimethylamine or oil-soluble amine formulations during average growing conditions. However, picloram plus 2,4-D oil-soluble amine was the best formulation in dry conditions.

Horseweed is a major weed in conservation tillage production systems. Herbicides were evaluated for horseweed control at two growth stages, rosette and 10- to 15-cm tall. Horseweed was controlled at the rosette stage with the 2,4-D ester, 2,4-D amine, dicamba, 2,4-D plus glyphosate, and glyphosate. Higher rates were needed for control at the 10- to 15-cm stage. Paraquat did not effectively control horseweed at any stage.

Florida beggarweed germination in laboratory experiments was highest between 21 and 38 C and at osmotic potentials above −0.2 MPa, with complete germination inhibition below −0.8 MPa. Patterns of seedling emergence in the field corresponded to timing and size of rainfall events in relation to the time of soil disturbance. Smaller percentage total seasonal emergence was observed following large rainfall events where soil had not been disturbed compared with plots recently disturbed, and soil disturbance not followed by rainfall did not promote major weed flushes.

Mon 4620 at 2.8 kg ai/ha, paclobutrazol plus mefluidide at 1.1 plus 0.4 kg ai/ha, and flurprimidol plus mefluidide at 1.1 plus 0.4 kg ai/ha were applied on four dates to determine their influence on highly maintained tall fescue turf. Seedhead suppression was good to excellent by Mon 4620 applied March 1 or 18 and by paclobutrazol plus mefluidide and flurprimidol plus mefluidide applied anytime from March 1 until April 1. None of the plant growth regulators (PGRs) suppressed seedheads effectively when applied April 15 when the grass was near the end of the rapid growth cycle and just before seedhead emergence. Vegetative growth of mowed tall fescue was suppressed for 8 weeks in 1987 when PGRs were applied March 1 immediately after full green-up. Application dates were not as important in 1988 as in 1987. Tall fescue was injured the least by Mon 4620 applied in March and by flurprimidol plus mefluidide applied on March 18. Paclobutrazol plus mefluidide injured the turf severely regardless of application date.

A cropping system of soybeans and rice grown in alternate years for 4 yr controlled red rice when combined with effective herbicide treatments applied to the soybean crop. Effective herbicide treatments in soybeans were preplant incorporated applications of alachlor, metolachlor, or alachlor plus trifluralin each followed by postemergence over-the-top applications of bentazon plus mefluidide, postemergence directed applications of paraquat, or sequential applications of postemergence over-the-top bentazon plus mefluidide and postemergence directed paraquat. Control of red rice in soybeans reduced red rice infestations in the subsequent rice crop. Red rice infestations were lower in rice grown the fourth year than in rice grown the second year. Postemergence over-the-top or directed herbicide treatments used alone or combined with preplant incorporated applications of trifluralin did not control red rice in soybeans with subsequent red rice infestations in the rice crop.

Studies were conducted to determine the usefulness of HOE-39866 (HOE-00661) in chemical fallow systems on the Canadian prairies. HOE-39866 at 0.5 to 1.0 kg ai/ha controlled Russian thistle, kochia, green foxtail, wild oats, and wheat comparable to paraquat, glyphosate, and glyphosate plus the isopropylamine salt of 2,4-D. However, control of barley with HOE-39866 was unacceptable. HOE-39866 was compatible in tank mixtures with ammonium sulfate, paraquat, chlorsulfuron, and metsulfuron. Ammonium sulfate improved weed control when HOE-39866 was applied at 0.25 kg/ha but not at 0.75 kg/ha. Adding paraquat at 0.07 to 0.21 kg ai/ha to HOE-39866 improved control of grass species over HOE-39866 alone. Adding chlorsulfuron and metsulfuron to HOE-39866 provided greater initial control of certain species as well as residual control of many weeds. HOE-39866 alone or in conjunction with other herbicides is an alternative to the herbicides used in chemical fallow systems.

Larvae of the leafy spurge hawk moth were sprayed with and/or were fed leafy spurge plants sprayed with 2,4-D or picloram. Larval survival was not affected from contact with the chemicals, from feeding on contaminated foliage, or from a combination of both. Viable second-generation adult moths were produced in all treatments. Thus, leafy spurge infested with the leafy spurge hawk moth can be sprayed with 2,4-D or picloram without injury to larvae that have reached the fourth or fifth instar stages.