Experiments were conducted in 1985 and 1986 at three locations in eastern Arkansas to evaluate red rice control in soybeans with postemergence grass herbicides and plant growth regulators applied singly or sequentially at early to late-tillering growth stages of red rice. Haloxyfop at 0.21 kg ai/ha and quizalofop at 0.14 kg ai/ha applied singly or sequentially and fluazifop at 0.21 kg ai/ha applied sequentially consistently controlled red rice and suppressed seedhead production in soybeans. Mid-season treatments were not beneficial when high soil moisture stress conditions existed. Mefluidide or sethoxydim applied singly or sequentially or amidochlor applied singly provided erratic control and seedhead suppression of red rice in soybeans.

Effects and interactions of two soil temperatures, 19 ± 1 and 27 ± 3 C, and seven soil-applied herbicide treatments on the morphological development and concentrations of eight essential nutrients in leaves, stems, and roots of pinto beans were determined. Soil temperature did not affect overall plant morphology but did affect some nutrient concentrations in the roots, stems, and leaves. Combinations of alachlor plus trifluralin at 2.2 plus 0.28 kg ai/ha and EPTC plus trifluralin at 2.2 plus 0.28 kg ai/ha caused greater negative effects than when the herbicides were applied separately. Oryzalin at 0.56 kg ai/ha and EPTC at 3.4 kg ai/ha induced the least number of morphological effects, while alachlor at 3.4 kg ai/ha, chloramben at 2.2 kg ai/ha, and trifluralin applied at 0.56 kg ai/ha produced an intermediate number. Alachlor, trifluralin, and combinations of alachlor plus trifluralin and EPTC plus trifluralin inhibited nodule growth. Each herbicide affected different nutrients. Alachlor plus trifluralin affected the level of each nutrient in at least one plant tissue. Many herbicide-soil temperature interactions occurred.

Field studies were conducted on a Crowley silt loam under weed-free conditions to determine herbicidal tolerance of ‘Centennial’ soybeans. Early season phytotoxicity and mature plant height reductions were caused by imazaquin at 140 g ai/ha applied preemergence (PRE) followed by imazaquin applied postemergence (POE) at both 140 (labeled rate) and 280 g/ha and for metribuzin plus chlorimuron at 360 plus 60 g ai/ha PRE followed by chlorimuron POE at 18 g/ha (double rate). Soybean yields, averaged across 3 yr, were reduced only for metribuzin plus chlorimuron PRE followed by chlorimuron POE at both 9 and 18 g/ha (10 and 15%, respectively).

Field studies were conducted to determine if oxyfluorfen alone or combined with other herbicides could be applied between black polyethylene mulch without injuring muskmelon. Oxyfluorfen at rates up to 1.1 kg ai/ha did not injure muskmelon provided adequate rain or irrigation occurred to incorporate the oxyfluorfen thereby minimizing vapors that could injure muskmelon. Using this practice, muskmelon yields from oxyfluorfen-treated plots were the same as yields from untreated cultivated plots.

Two field studies were conducted to compare bentazon tolerance in “Bohemian Chili” (BCH) and “Keystone Resistant Giant” (KRG) with other pepper cultivars and plant introductions (PIs). In the first study, BCH, KRG, “Santaka” (SA), and “Sweet Banana” (SB) were treated with five rates of bentazon from 1.1 to 9.0 kg ai/ha. Based on foliar injury, the cultivars ranked BCH = SA < KRG < SB; based on yield tolerance to bentazon, they ranked KRG ≤ SB < SA ≤ BCH. In the second study, the response of BCH, KRG, SA, SB, and five PIs to 4.5 kg/ha bentazon showed that 3 PIs (127445, 163187, 246123) tolerated bentazon similarly to BCH and SA.

The effect of three rates of metolachlor on ‘Prime Time’ and ‘Tastie’, early maturing, fresh-market cabbage was evaluated in two geographically distinct regions of New York in 1986 and 1987. Metolachlor, when applied at 1.1, 1.7, and 2.2 kg ai/ha either pretransplant or 48 h after transplanting, caused no observable negative effects on either cabbage variety in either year when grown on sandy loam soils on Long Island. On a central New York silt loam soil, injury from metolachlor at 1.7 and 2.2 kg/ha applied post-transplant was negligible and transient. Metolachlor applied post-transplant caused a delay in maturity of Tastie cabbage in both years but not Prime Time; however, total yields equalled those of the weed-free controls with both varieties. Metolachlor applied pretransplant frequently caused excessive and persistent injury and often reduced cabbage yields.

A survey of 146 fields was conducted to investigate herbicide performance in winter wheat-producing areas of southwestern Nebraska during August and September of 1986. Only 55% of the fields received an excellent rating for weed control and stubble quality; one third rated as unacceptable. Weed control after wheat harvest was improved by planting ‘Bounty 310’, ‘Siouxland’, ‘Vona’, and ‘Centura’ winter wheat cultivars rather than ‘Mustang’, ‘Hawk’, ‘Pioneer 2656’, and ‘Wings'. Fertilizing winter wheat in the fall, planting wheat at the optimum date, high wheat stem density, using a winter wheat-corn-fallow rotation, not spraying herbicides after wheat harvest on days that it rained or air temperature exceeded 35 C, and spraying weeds when they were small also improved weed control in wheat stubble. Nine months after wheat harvest, fields treated with atrazine before July 16 had more volunteer wheat than fields treated later.

Seasonal variations in tolerance of jack pine and white spruce to glyphosate and triclopyr were investigated in field and growthroom studies. Foliar injury was higher in both species following field applications of herbicides in July during periods of active growth than in September and October when the plants were not growing actively. Herbicides applied to trees in the growthroom 3 weeks after bud break caused greater injury than applications either before or 14 weeks after bud break. White spruce tolerated both glyphosate and triclopyr better than jack pine. Triclopyr injured both species more than glyphosate. Chemical analysis and electron micrographs showed that the cuticular wax deposition on both species was greater in field-grown trees than in growthroom-grown trees and was greater at 14 weeks after bud break than at 3 weeks. Increased wax deposition with time after bud break may reduce herbicide uptake and may account partially for the increased tolerance of both species to glyphosate and triclopyr.

Field experiments were conducted in 1982 through 1986 to evaluate the effect of six postemergence grass herbicides, clethodim, the methyl ester of diclofop, the butyl ester of fluazifop-P, the methyl ester of haloxyfop, the methyl ester of quizalofop, and sethoxydim, on 31 seedling grass species. All herbicides except diclofop controlled most of the species tested. None of the herbicides controlled rattail fescue or red fescue. Only clethodim and haloxyfop controlled annual bluegrass.

Weed control with thiameturon applied postemergence at 8 to 32 g ai/ha varied with species, growth stage, addition of surfactant, and environmental conditions. Pennsylvania smartweed control was excellent, velvetleaf control ranged from poor to excellent, and common lambsquarters control was poor with thiameturon applied without surfactant. When surfactant was added to the thiameturon spray mixture, velvetleaf and common lambsquarters control was >85% at 8 g/ha when weeds were growing actively and at 16 g/ha when weeds were under moisture stress. However, in weed-free studies, corn yields were reduced by 35 kg/ha for each 1 g/ha thiameturon applied in 1986 and by 10 kg/ha for each 1 g/ha thiameturon applied in 1987 when surfactant was added to the spray mixture. When no surfactant was added, yields were reduced 12 kg/ha for each 1 g/ha thiameturon applied in 1986 but were not reduced in 1987.

Experiments are conducted to evaluate the tolerance of three deciduous species: black locust, honeylocust, apple, and three coniferous species: Douglas fir, ponderosa pine, and Japanese black pine, in the seedling stage to napropamide. Deciduous species were more susceptible to napropamide than coniferous species. Domestic apple had the slowest seed germination and root development and was more susceptible. The deciduous species had more secondary roots in the shallow soil layer which contained most of the herbicide than the coniferous species. The roots of all woody species tested in vitro were inhibited significantly by contact with the herbicide, but only shoot growth of domestic apple and black locust was inhibited. Injury to woody nursery crop seedlings may be avoided by delaying herbicide application.

Field studies were conducted in 1984, 1985, and 1986 to compare standard flat fan nozzles, low-volume flat fan nozzles, rotary controlled droplet applicators, and air-assisted nozzles for postemergence weed control in onions with oxyfluorfen and fluazifop-P. Herbicides applied with flat fan nozzles at 47 or 190 L/ha controlled broadleaf and grass weeds as good or better than with the other nozzles. Oxyfluorfen applied with flat fan nozzles controlled common lambsquarters and ladysthumb best. None of the nozzles improved control of the difficult marsh yellowcress. Carrier volume had minimal effect on weed control. Nozzle and carrier volume did not affect onion yield.

A decision criterion is presented for postemergence johnsongrass control in soybeans. Models derived from actual data describing the relationship between johnsongrass density (X) and soybean yield loss are used to develop the decision criterion for soybeans planted in 0.25- and 1-m row spacings. The yield loss equations are L1 = 424–424 exp (-0.023X2) for 0.25-m row spacing and L2 = 643-643 exp (−0.004X2) for 1-m row spacing. When combined with the cost of control (Px) and the expected price of soybeans (Py), these equations can be used to find the density thresholds where johnsongrass control becomes profitable. For the 0.25-m row spacing, this relationship was Px = Py [424–424 exp (−0.023X2) or more simply Px = Py L1, which equates the cost of control to the value of the soybean yield increase from control. The johnsongrass density (X) that satisfies this equality is the threshold (X*) above which control is profitable.

Combinations of grass and legume mulches were planted in growing corn during the fall in 1985 and 1986, and the following spring no-till corn was planted into these living mulches. Mulch treatments consisted of a single species or grass plus legume mixtures. Fluazifop-P, 2,4-D, and atrazine were broadcast applied in late April to suppress the mulches and reduce their competition with corn. Chewings fescue and ladino clover competed least with dryland corn. Weed growth associated with chewings fescue and the ladino clover mulches was similar to that in the conventional disk-plant treatment, but corn yields were lower. Hairy vetch mulch was killed by 2,4-D. The winter rye mulch competed with corn and reduced yield.

Linuron, metribuzin, oryzalin, and dinoseb were evaluated for weed control in conventional (CT) and rye-stubble reduced-tillage (RT) systems for potatoes. Early season control of weeds was equivalent for all herbicides in both tillage systems. In 1985, redroot pigweed populations were significantly greater in RT than in CT control plots. Populations of common lambsquarters were equivalent, regardless of the tillage system. In 1986, the rye mulch reduced early emergence of both species in untreated RT plots when compared to the untreated CT controls. During both seasons, potato stands decreased 16% with RT. In 1985, total yields did not differ between tillage systems; however, in 1986, total potato yields in RT plots decreased an average of 22% compared to yields in CT plots.

A surface-roller wiper that rotates by direct contact with the ground was developed to apply herbicides to broadleaf weeds in turf. The free-wheeling roller 1.8 m wide consists of a 30-cm diam PVC pipe covered with a 1.3-cm thick carpet The herbicide is delivered by gravity to the carpet through a pipe manifold. Broadleaf weeds in turf were effectively controlled with 2,4-D roller applied once as a 2% solution (2.2 kg ae/ha) or twice as a 1% solution (1.1 kg/ha). Herbicide drift was avoided with the roller applicator as indicated by lack of injury to tomato plants downwind from 2,4-D roller applied as a 5% (5.6 kg/ha) solution.

Imazethapyr at 0.05 to 0.14 kg ai/ha applied preplant incorporated, preemergence, and postemergence was evaluated alone and with complementary herbicides in the field for weed control in soybean. Imazethapyr controlled 90% or more smooth pigweed regardless of application method or herbicide rate. Imazethapyr at 0.05 kg/ha controlled jimsonweed 30% better postemergence compared to soil applications. Imazethapyr at 0.10 kg/ha controlled 90% or more velvetleaf regardless of application method. The addition of alachlor to soil-applied imazethapyr enhanced giant foxtail, jimsonweed, and velvetleaf control. Adding acifluorfen or bentazon to postemergence imazethapyr antagonized weed control. Adding sethoxydim to postemergence imazethapyr was not beneficial.

Field experiments were conducted from 1983 through 1987 to evaluate various postemergence grass herbicides on bermudagrass in peanuts. Fluazifop, haloxyfop, and SC-1084 applied once effectively controlled common bermudagrass when less than 8 cm tall, but resulted in variable control when applied to bermudagrass 15 cm or taller. Sethoxydim effectively controlled common bermudagrass one of 2 yr. ‘Coastal’ bermudagrass required two applications of BAS 517, fluazifop-P at 0.21 or 0.28 kg ai/ha, and haloxyfop for control of better than 88%. Clethodim and sethoxydim provided poor to fair control, respectively.

Cold stress and field studies were conducted to determine the effects of alachlor, metolachlor, butylate plus dichlormid, and EPTC plus dichlormid on germination and seedling vigor of 30 sweet corn cultivars with three commercially important endosperm mutants (su, se, and sh2). Seedling emergence from cool soils was best when treated with EPTC plus dichlormid and alachlor and was decreased 11% by metolachlor and butylate plus dichlormid. The se and sh2 endosperm mutants were injured the most by the herbicides. Plant size was reduced by the thiocarbamate herbicides but not by the chloracetamides.

When centipedegrass was unmowed, seedhead suppression generally was better with imazethapyr than with mefluidide either alone or with flurprimidol, but these treatments were not effective for 8 weeks. In several instances, imazethapyr at 0.30 kg ai/ha and MH at 2.2 and 4.5 kg ai/ha severely injured (>30%) centipedegrass. Mowing weekly did not control seedhead development effectively, and none of the plant growth regulator plus mowing treatments effectively suppressed seedheads for 12 weeks. To effectively suppress seedhead production for 8 weeks, centipedegrass treated with mefluidide required mowing 3 weeks after treatment, while centipedegrass treated with imazethapyr or flurprimidol plus mefluidide required mowing at 3 and 6 weeks.