Growth chamber experiments were conducted to determine if certain genetic, environmental, and chemical factors or their interactions promote chloroacetamide herbicide injury to corn seedlings. Greater chloroacetamide injury occurred with ‘Pioneer 3320’ than with ‘Pioneer 3780’ hybrid corn, with 15 C than with 30 C soil temperature, with soil moisture at 105% field capacity (FC) than at 75% FC, with alachlor than with metolachlor, and with a herbicide rate of 2.2 kg/ha than with 1.1 kg/ha. Covering the plant containers with clear plastic until seedling emergence caused alachlor to be more phytotoxic to corn than metolachlor. Most factors evaluated increased the injury to corn in an additive manner.

Field experiments were conducted from 1983 through 1985 to evaluate the influence of tridiphane at 0.3, 0.6, 1.1, and 2.2 kg ai/ha when tank mixed with propanil at 2.2 or 3.4 kg ai/ha on control of 3- to 4-leaf or 4- to 6-leaf barnyardgrass in rice. Tridiphane at 0.6 kg/ha or greater tank mixed with propanil at 2.2 or 3.4 kg/ha enhanced control of 3- to 4-leaf barnyardgrass compared to propanil applied alone at 3.4 kg/ha. Rates of tridiphane at 1.1 kg/ha or greater plus propanil at 3.4 kg/ha were necessary to control 4- to 6-leaf barnyardgrass. ‘Starbonnet’ rice injury was minimal for all treatments.

A mixture of 2,4-D with either thiameturon, DPX-L5300, or DPX-R9674 controlled common chickweed in winter wheat better than 2,4-D alone. None of these herbicides affected wheat height, lodging, or yield. Similarly, no significant differences in wheat height or lodging occurred among seeding rates. Wheat sown near South Charleston, OH, at a seeding rate of 67 kg/ha yielded significantly less than that sown at 100 or 134 kg/ha; however, there was no difference in wheat yield among seedling rates at a second location near Columbus, OH.

Field studies were conducted for 3 yr to evaluate the persistence of metolachlor and alachlor applied to ‘Centennial’ soybean and to determine their residual effect on ‘Mars' rice. At labeled use rates of metolachlor at 2.8 kg ai/ha and alachlor at 3.9 kg ai/ha, soil residue levels in the fall 5 months after application on Crowley and Midland silt loam soils averaged 0.04 and 0.05 ppmw, respectively. Metolachlor fall soil residues averaged 3.5 times higher when applied at 5.6 and 11.2 kg/ha compared to 2.8 kg/ha, but residues for labeled and double rates of alachlor were similar. In the spring 9 months after herbicide application, soil residues averaged over years did not exceed 0.06 ppmw. The 3-yr rice yields were not affected by residual metolachlor or alachlor.

This study was conducted to determine if ‘Pensacola’ bahiagrass, a major weed in turf and pastures in the southeastern United States, could be eliminated selectively from centipedegrass and ‘Tifway’ bermudagrass turf and a ‘Coastal’ bermudagrass pasture by treating with sulfometuron. Established Pensacola bahiagrass usually was controlled satisfactorily in Tifway bermudagrass and centipedegrass turf and in a Coastal bermudagrass pasture with sulfometuron at 210, 160, 105 g ai/ha applied twice, respectively. Bahiagrass seedlings were eliminated from both newly planted centipedegrass and Tifway bermudagrass turf with 105 g/ha sulfometuron applied once.

The influence of pH on the behavior of metribuzin and ethyl-metribuzin in soil and nutrient solution was studied. Toxicity of both herbicides to oats decreased as soil pH decreased from 8.4 to 4.2 in a sandy loam. Herbicide adsorption increased as soil pH decreased. In nutrient solution, pH did not change the phytotoxicity of either herbicide, indicating that pH primarily influences herbicide availability in soil and not plant uptake.

Johnsongrass control in the field was greater with fenoxaprop or haloxyfop than with sethoxydim in 1985 and 1986. Johnsongrass control was reduced under field and greenhouse conditions by adding a dimethylamine salt of 2,4-D. Generally, the antagonism was overcome by increasing the rate of fenoxaprop, haloxyfop, or sethoxydim. Sethoxydim showed less antagonism from 2,4-D than did fenoxaprop or haloxyfop in the greenhouse.

Preliminary evaluation of 11 pepper genotypes indicated a high degree of variability in bentazon tolerance. ‘Bohemian Chile’ and ‘Santanka’ hot pepper tolerated bentazon similarly in subsequent greenhouse and field experiments. Yields or shoot fresh weights of these two cultivars were not reduced by up to 9.0 kg ai/ha bentazon in the field. ‘Keystone Resistant Giant’ sweet pepper was more susceptible to bentazon compared to the tolerant cultivars, but it was more tolerant than the highly susceptible cultivar, ‘Sweet Banana’. An F1 hybrid of Keystone Resistant Giant and Santanka tolerated bentazon better than Keystone Resistant Giant but slightly less than Santanka. Thus, bentazon tolerance in this genotype is genetically transferrable, and increasing bentazon tolerance through conventional plant breeding techniques may be possible.

The duration and intensity of unicorn-plant interference on lint yield of cotton were evaluated in the field. Random densities of 5.5 ± 1.1 unicorn-plant/m2 reduced lint yield by 41 kg/ha or about 5% for each week that unicorn-plant was present. Interference by 4, 8, and 12 weeds/10 m row decreased yield by 22, 49, and 56 kg/ha, respectively, for each week of weed interference. Each 1 kg/ha of unicorn-plant dry weight reduced lint yield by 0.26 kg/ha. Linear regression of weed dry weight could be used to predict cotton lint yield changes regardless of duration or intensity of weed interference.

Nine field experiments were conducted from 1984 through 1988 to determine the effect on rice of imazaquin applied to soybeans the previous growing season. Imazaquin was applied preplant incorporated, preemergence, or postemergence at rates ranging from 70 to 560 g ai/ha. ‘Bond’, ‘Lemont’, ‘Mars', ‘Newbonnet’, and ‘Tebonnet’ rice were planted the following year. Across all locations, years, cultivars, soil series, methods of application, and imazaquin rates, rice injury symptoms were not observed, and rice grain yields were not reduced by imazaquin residues.

Several labeled herbicide treatments reduced winter wheat height and grain yield when applied at different growth stages in 1984 and 1985. Yield reductions were related to reduced spike production. Wheat height and yield generally were greatest when herbicides were applied at Zadoks' Stage 29 and lowest at Stage 13. Herbicide treatments did not affect wheat kernels per spike, kernel weight, volume weight, or germination either year. However, most herbicide treatments either increased or decreased seed protein content, depending on the year.

The economic feasibility of four Wyoming big sagebrush control methods: burning, spraying with 2,4-D, plowing and seeding, and rotocutting was analyzed. Perennial grass response to big sagebrush treatment was measured to estimate a treatment response function for each control method which provided the biological informational base to develop cost and benefits. Annualized present values of net additional returns for single 2,4-D and burning treatments were $1.10/ha and $1.16/ha, respectively. When big sagebrush was retreated at optimal intervals, 2,4-D and burning generated annualized net additional returns of $2.88/ha and $2.57/ha, respectively. Rotocutting was marginally feasible, and plowing was not feasible.

Acifluorfen, chlorimuron, and thiameturon were compared in single and sequential treatments for cowpea control in soybean. Chlorimuron applied once at 8.8 g ai/ha at 14, 21, and 28 days after cowpea emergence controlled 80% or more of cowpea. Control was greater at 14 and 21 than at 28 days after emergence in one of three experiments. Cowpea control by chlorimuron was similar with single and sequential treatments. Soybean injury was lower, and soybean seed yields generally were higher with chlorimuron than with thiameturon or acifluorfen. Thiameturon and acifluorfen controlled less than 60% of cowpea. Three weedy cowpea cultivars responded the same to chlorimuron, but cowpea recovery was substantial in 1 of 3 yr.

Chlorsulfuron at 0.018 kg ai/ha, metsulfuron at 0.0045 kg ai/ha, and 2,4-D at 1.1 kg ae/ha plus dicamba at 0.28 kg ae/ha were applied over snow-covered winter wheat to study the feasibility of combining herbicides with a graphite snow-removal treatment. Chlorsulfuron or metsulfuron applied on snow effectively controlled annual broadleaf weeds when tank mixed with urea ammonium nitrate (UAN) at 28 kg N/ha and graphite powder at 20 kg/ha. Over-snow treatments of 2,4-D plus dicamba plus UAN did not control weeds. There was no antagonism or synergism among herbicides, UAN, or graphite.

Several plant growth regulators applied to established sod driveways in an apple orchard suppressed growth of the ground cover sufficiently to eliminate one to three mowings. MH at 4.5 or 6.7 kg ai/ha applied spring and fall reduced the growth of a single species sod cover crop, ‘Kentucky 31’ tall fescue, the year after treatment. MH at both rates also reduced the dandelion population growing in the mixed species orchard sod. Paclobutrazol or EPTC applied in the spring before or during initial grass growth reduced dry matter production in the fescue sod cover crop and the number of mowings compared to the mowed and non-mowed control plots.

Imazaquin and imazethapyr were applied postemergence to soybeans for control of 8- to 12-leaf rhizome johnsongrass and pitted morningglory in the field. At 8 weeks, johnsongrass control was 70% with 70 g ai/ha imazaquin plus 105 g ai/ha imazethapyr but was no more than 50% with a single application of either herbicide. Imazaquin at 70 g/ha plus imazethapyr at 35 g/ha interacted synergistically to provide 90% pitted morningglory control, while 140 g/ha imazaquin controlled 77%. Imazaquin at 70 g/ha with imazethapyr from 18 to 105 g/ha controlled both weed species equal to or better than that obtained with 140 g/ha imazaquin.

The effect of glyphosate applied as a desiccant to field bindweed-infested alfalfa in the final year of seed production was examined in field experiments near Lovelock, NV. Glyphosate at 2.5 and 5.0 kg ae/ha flat fan applied was equal to and/or superior to dinoseb for desiccation of foliage, respectively. Alfalfa seed yield and quality following glyphosate treatment were similar to that of dinoseb-treated alfalfa. Glyphosate treatment reduced some alfalfa and field bindweed stands. A beneficial interaction between low-volume control droplet application (CDA) and glyphosate was not evident.

A scentless plant bug feeds on velvetleaf seeds. Fungi, dominated by the genera Fusarium and Alternaria, were isolated from insect-attacked seeds at levels related to insect density on the plants. The combined effects of insect feeding and fungal infection decreased seed germination. Burial of insect-attacked seeds in soil for 24 months reduced seed survival and increased Fusarium infection. Decreases in velvetleaf seed viability and survival in soil caused by a seed-feeding insect and associated seed fungi suggests that subsequent infestations by velvetleaf can be decreased through integrated use of the two biological control agents.

Spring-applied herbicides were evaluated in field studies conducted in 1985 through 1987 in western Nebraska for selective weed control in irrigated established alfalfa. Imazethapyr, norflurazon, pendimethalin, and prodiamine did not injure alfalfa but varied in their weed control spectrums. Overall weed densities were lowest in plots treated with norflurazon at 2.8 kg ai/ha and diuron at 1.8 kg/ha.

The potential interactive effects between metolachlor [0, 0.1, 0.5, and 1.0 ppm (w/w)] and the air pollutant ozone (O3) [0.2 and 0.4 ppm (v/v)], on growth of corn, bean, and soybean were examined under controlled conditions. At both concentrations, O3 alone reduced corn and bean dry weights but only affected bean at 0.4 ppm (v/v). Shoot dry weight of corn was reduced by O3 plus metolachlor more than expected, thus indicating synergism. The expected dry weights of bean and soybean treated with metolachlor plus O3 were similar to or higher than expected, thus indicating additive or antagonistic interactions.