Fenoxaprop applied between late winter and mid-spring selectively controlled roughstalk bluegrass in perennial ryegrass grown for seed in Oregon. Fenoxaprop applied after the arrival of warmer weather in late March had enhanced effectiveness against roughstalk bluegrass compared to earlier application. However, additional delay into April increased damage to perennial ryegrass. Optimum application date coincided with a 15- to 18-cm perennial ryegrass canopy height. Mixed stands of seedling and established roughstalk bluegrass were more consistently controlled by 0.28 kg ai/ha fenoxaprop than by lower rates.

Preplant applied herbicides were compared for their effect on three varieties of sugarbeets when seeds were planted at six depths during 1987 through 1989. More sugarbeet seedlings emerged and at a faster rate as the depth of seeding decreased from 4.5 to 1.6 cm. Herbicide injury to sugarbeet seedlings increased as depth of seeding increased from less than to greater than 2.5 cm. Herbicide treatments reduced sugarbeet stand and decreased early season sugarbeet height but had little effect on root yield or sucrose content.

Seed capsules of field-grown jimsonweed were harvested 2, 4, 6, and 10 weeks after anthesis. Degree day accumulation from anthesis and weeks after anthesis were equal in predicting the time required for nondormant jimsonweed seed production and seed dry weight. Seed germination increased as capsule age increased from 2 to 6 weeks. No additional increase in germination was observed in seed from capsules collected 10 weeks after anthesis. Maximum seed weight was obtained from capsules 6 and 10 weeks old in 1986 and 1987, respectively. Germination was correlated highly with seed weight.

Experiments were conducted in each of two seasons to determine possible effects of diclofop, difenzoquat, dinoseb, and mecoprop on the incidence of take-all disease and grain yield of winter wheat. All of the herbicides, especially mecoprop, reduced incidence of take-all. Treatments increased grain yields the first year but not the second, compared to the inoculated weed-free control. None of the herbicides tested increased incidence or severity of take-all disease in either of the two seasons. The technique of inoculating disease-free soil was successful in obtaining uniform and reproducible incidence of disease.

Hereford cows and their spring-born calves grazed an irrigated grass pasture containing about 13% dandelion based on dry weight yield. Grazing treatments were 1) no grazing, 2) 4 days of grazing just before clipping, and 3) long-term grazing just before clipping. In clippings taken in June and July after the grazing treatments, the percentage dandelion in the forage was similar in all three grazing treatments, indicating that cattle used dandelion as readily as grass. The protein and mineral contents of dandelion were at appropriate levels to meet the established requirements of beef cattle.

Chlorsulfuron, metsulfuron, clopyralid, 2,4-D, picloram, and dicamba plus 2,4-D were spring-applied to musk thistle in rosette, bolting, bud, and early flower growth stages. All treatments reduced viable achene production at all musk thistle growth stages at Mcgrew, NE, and Longmont, CO. However, differences occurred at Evergreen, CO, among treatments and growth stages. No achenes developed at Evergreen when herbicides were applied during the rosette stage with dicamba plus 2,4-D, picloram, or metsulfuron at 21 g ai/ha or during bolting with chlorsulfuron or metsulfuron at 21 g/ha. Chlorsulfuron applied during early bloom reduced viable achene production over 99% compared to untreated plants and the picloram treatment.

The effect of common cocklebur interference on snap beans was investigated at Bridgeton, NJ, in 1987 and 1988. Snap bean yields were reduced by increasing weed densities. Yields were reduced 8 to 44% in 1987 and 2 to 55% in 1988 by full-season in-row weed densities ranging from 0.5 to 8/m2. One weed and 4 weeds/m2 were the damage-threshold populations of common cocklebur with full-season interference in 1987 and 1988, respectively. The weed-free requirement, after planting, was to the unifoliolate stage of snap beans. Common cocklebur at 4 weeds/m2 did not affect yield when snap beans were maintained weed free until the unifoliolate stage of snap beans. The critical duration of interference for common cocklebur emerging with snap beans was between the emergence and full-bloom stage of snap beans. Snap bean yield was not reduced with weed removal at full bloom.

Both alachlor at 3.6 kg ai/ha and metolachlor at 2.8 kg ai/ha applied preplant incorporated consistently controlled red rice 82% and 90%, respectively, over a 3-yr period. Averaged across years, only mefluidide at 0.14 kg ai/ha plus bentazon at 0.84 kg ai/ha, haloxyfop at 0.28 kg ai/ha, and quizalofop at 0.14 kg ai/ha applied postemergence controlled red rice comparable to the preplant herbicide treatments. High rates of sethoxydim and fluazifop (0.56 kg ai/ha), haloxyfop (0.28 kg ai/ha), and quizalofop (0.14 kg ai/ha) were needed to obtain soybean yields equivalent to alachlor and metolachlor.

Field experiments were conducted in Oklahoma to determine the effects of row spacing, cultivar, seeding rate, and water or ammonium polyphosphate fertilizer injection in the row at seeding, on the competitiveness of hard red winter wheat with cheat. Decreasing row spacing from 23 to 8 cm increased yield of weed-free wheat at two of three locations and cheat-infested wheat in six of ten experiments. Increasing seeding rate from 265 to 530 seeds m-2 increased wheat yield. Injecting water at 20 ml m-1 of row at seeding did not increase wheat emergence or yield. Cheat seed production was not consistently suppressed by any one cultivar. Juvenile growth habit was unrelated to wheat competitiveness.

The control of wild oat, volunteer wheat, and volunteer barley in a flax crop with sethoxydim was enhanced 20 to 27% by orienting the spray nozzles forward 45°. Control of annual grasses was not influenced by the time of day sethoxydim was applied. However, injury to flax from a tank mixture of sethoxydim and bromoxynil/MCPA (1:1) was greatest when applied between 0500 and 1100 h, and least when applied between 1500 and 2300 h. Flax injury and reduced seed yields also resulted when sethoxydim was applied when air temperatures exceeded 30 C regardless of stage of crop growth.

Field studies were conducted in 1987 and 1988 to investigate the control of common lambsquarters in pea and snap bean following preplant incorporated, preemergence, and postemergence applications of imazethapyr at 36 to 69 g ai/ha. The residual activity of imazethapyr on rotational crops of sweet corn, grain sorghum, and cucumber was evaluated. All rates of imazethapyr provided good (>80% initially) control of common lambsquarters. Although imazethapyr caused some injury to both pea and snap bean, yields were not reduced except for snap bean following postemergence applications. Imazethapyr residues resulting from the applications of 36 to 69 g/ha caused visible injury and fresh weight reductions to all three rotational crops.

Effects of a 28% N solution containing urea and ammonium nitrate (28% UAN) and a nonionic surfactant on efficacy, uptake, and translocation of chlorimuron ethyl ester in soybean and broadleaf weeds were investigated. Chlorimuron applied postemergence at 8.8 and 13 g ai/ha with either nonionic surfactant at 0.25% (v/v), 28% UAN at 9.4 L/ha, or nonionic surfactant plus 28% UAN controlled weeds better than without additives. Chlorimuron with nonionic surfactant and with 28% UAN controlled weeds similarly but with 28% UAN injured soybeans least. Chlorimuron with nonionic surfactant plus 28% UAN controlled velvetleaf best but injured soybeans most. Less than 2% of applied 14C-chlorimuron was absorbed in velvetleaf 84 h after treatment (HAT) when no additive was present, but adding nonionic surfactant, 28% UAN, and nonionic surfactant plus 28% UAN resulted in 21, 9, and 32% uptake, respectively, 84 HAT. Nonionic surfactant plus 28% UAN also increased translocation (primarily acropetal) of the 14C. Adding 28% UAN increased 14C-chlorimuron uptake in velvetleaf grown at low fertility but had no effect under high fertility.

Pyridate was evaluated alone and as a component in herbicide systems for weed control and peanut tolerance. Pyridate at 1.0 and 1.5 kg ai ha-1 applied postemergence controlled 79 and 96% of Florida beggarweed, respectively. Pyridate was less effective on sicklepod than 2,4-DB. Peanuts exhibited no visible foliar injury or yield reduction with pyridate at 1.5 kg ha-1, the highest rate evaluated. Comprehensive weed control and maximum yield required that pyridate be tank mixed with 2,4-DB at 0.22 kg ae ha-1.

Experiments were conducted in Massachusetts and New York to evaluate the potential influence of plant growth stage, spray volume, nozzle type, additional surfactant, and herbicide formulation on smooth and large crabgrass control in turf with fenoxaprop. At a well-watered site, crabgrass control with fenoxaprop was equal to or greater than with MSMA. On an irrigated, fertilized site, crabgrass growth stage did not influence fenoxaprop efficacy. Excellent control of up to 5-tiller smooth crabgrass was obtained with 0.20 kg/ha of fenoxaprop. On nonirrigated turf, fenoxaprop was less effective on tillered crabgrass than on 2- to 5-leaf weeds. Under very dry conditions, fenoxaprop was ineffective regardless of growth stage. Control with MSMA was less affected by drought than was fenoxaprop. Spray volumes, between 140 and 1120 L/ha, did not affect fenoxaprop efficacy; however, high volume applications (1120 L/ha) with floodjet nozzles were less effective than flat fan nozzle treatments in two of three tests. Added surfactant did not improve efficacy except with floodjet nozzles on a droughty site. No differences were observed between the water-based and the emulsifiable concentrate formulations of fenoxaprop. Fenoxaprop caused temporary phytotoxicity (≤20% reduction in turf quality) to established Kentucky bluegrass and perennial ryegrass.

Studies on the efficacy and economic analysis of Texas panicum management systems in corn were conducted in Georgia on a loamy sand soil in 1987, 1988, and 1989. Management systems that included butylate, EPTC, atrazine plus tridiphane, atrazine plus pendimethalin, atrazine plus trifluralin, paraquat, or ametryn acceptably control Texas panicum. Corn yields were not affected significantly by the Texas panicum management systems. Overall net returns calculated for corn production indicated that systems which included postemergence applications of atrazine, pendimethalin, trifluralin, paraquat, ametryn, or cultivation alone gave the highest net returns. Systems which included butylate, EPTC, or tridiphane frequently had significantly lower net returns.

An experimental plot sprayer, with a new mixing chamber and water measuring system, was developed to minimize operator exposure to pesticides during mixing and rinsing. Premeasured herbicide samples in 50-ml capped test tubes are emptied into the mixing chamber, and water is measured, rinses the test tube, and drains into the chamber to produce the spraying volume. This system eliminates operator contact with the chemicals and can be flushed quickly between plots to eliminate contamination. Rinsing efficiency with atrazine was greater for a suspension than a wettable powder formulation but less than 0.1% of the initial concentration was detected in water following the first or second rinsing.

Field experiments were conducted on six loam and sandy loam soils to study the influence of various soil parameters on atrazine, cyanazine, alachlor, metolachlor, and pendimethalin efficacy. Herbicidal activity was highly correlated to the soil organic content. Humic matter content was equally or better correlated (r = 0.70 to 0.91) with herbicide bioactivity than was organic matter content (r = 0.66 to 0.84). Regression equations were determined which allow herbicide rate recommendations for 80% weed control to be calculated based on soil humic matter or organic matter levels.

Field experiments were conducted over a 3-yr period to evaluate the efficacy and crop yield response of selected herbicides to control loose silky bentgrass in fall rye. Loose silky bentgrass was controlled 18 to 100% with trifluralin preemergence incorporated at 0.4 to 0.6 kg ai ha-1, chlorsulfuron preemergence at 0.024 kg ha-1 and metsulfuron early postemergence at 0.006 to 0.024 kg ha-1. Rye yield was unaffected by these herbicides 2 of 3 yr. In a farm demonstration trial trifluralin preemergence incorporated at 0.4 kg/ha controlled loose silky bentgrass.

Weed free field experiments were conducted for 3 yr at one location to measure the response of cotton to glyphosate spot applied once, twice, and three times. Glyphosate treatments frequently used for silverleaf nightshade control were applied at specified intervals after cotton emergence to in-row, uniformly spaced densities of “simulated” weeds. The number and application timing influenced cotton injury each year. Frequently, cotton lint yields following treatments applied once at four, six, or eight sites/9 m of row were not reduced significantly compared to the untreated plots; however, average yield reductions ranged from 10 to 14%. Glyphosate, applied more than once generally, caused more crop injury and reduced lint yields by 13 to 39%.

AC 222,293, a postemergence herbicide for wild oat control in wheat, barley, and sunflower, was applied at five rates at three locations in Montana in the spring of 1985. Twelve and 11 crops were seeded into treated soil in 1985 and 1986, respectively. Sugarbeet, lentil, and rape were injured by residual levels of AC 222,293 14 months after application. Injury was significantly greater at one location, indicating herbicide bioavailability varied by location. Soil pH was correlated negatively with crop injury, indicating the herbicide persists longer on lower pH soils.