Fourteen field experiments were conducted from 1988 to 1991 in Oklahoma to evaluate herbicides for red horned poppy control in winter wheat. Chlorsulfuron applied alone PRE at 9 to 26 g ai ha-1 or with metsulfuron controlled red horned poppy 90 to 100% in four of five locations. MCPA at 420 g ae ha-1 and MCPA + bromoxynil at 140 + 140 g ae ha-1 applied POST in mid November controlled red horned poppy 100%. All herbicides applied POST in mid March failed to control the weed consistently.

This paper describes the application of a relatively new remote sensing tool, airborne video imagery, for distinguishing weed and brush species on rangelands. Plant species studied were false broomweed, spiny aster, and Chinese tamarisk. A multispectral video system that acquired color-infrared (CIR) composite imagery and its simultaneously synchronized three-band [near-infrared (NIR), red, and yellow-green] narrowband images was used for the false broomweed and spiny aster experiments. A conventional color camcorder video system was used to study Chinese tamarisk. False broomweed and spiny aster could be detected on CIR composite and NIR narrowband imagery, while Chinese tamarisk could be distinguished on conventional color imagery. Quantitative data obtained from digitized video images of the three species showed that their digital values were statistically different (P = 0.05) from those of associated vegetation and soil. Computer analyses of video images showed that populations of the three species could be quantified from associated vegetation. This technique permits area estimates of false broomweed, spiny aster, and Chinese tamarisk populations on rangeland and wildland areas.

Field observations in 1986 indicated that increased injury to soybean could occur from clomazone plus metribuzin and clomazone plus linuron compared with metribuzin or linuron alone. Field experiments to measure this response were conducted in 1988, 1989, and 1990 at two locations in Michigan. Atrazine at 0, 1120, 2240, and 3360 g ha-1 was applied the year previous to soybean planting to determine if atrazine residues in the soil influenced soybean response. Herbicide treatments in soybean included clomazone, metribuzin, linuron, alachlor, clomazone plus metribuzin or linuron, alachlor plus metribuzin or linuron, and an untreated control. Additive and synergistic responses in soybean to clomazone plus linuron and clomazone plus metribuzin, regardless of atrazine application rate, occurred in some field environments. Experiments in the greenhouse demonstrated that soybean shoot weight was reduced synergistically from clomazone plus metribuzin compared with either herbicide alone, and the response was greater on a soil with 2.5% organic matter compared with a soil with 4.4% organic matter. Clomazone plus metribuzin reduced leaf area and shoot dry weight, regardless of placement, while leaf area and shoot dry weight were reduced more when clomazone plus linuron- and atrazine plus metribuzin-treated soil was placed in the same zone as the soybean seed. The synergistic interaction in soybean to clomazone plus metribuzin occurred under both cool and warm temperature regimes in growth chamber studies.

Field studies were conducted from 1985 to 1989 on a Sharkey clay to examine injury to a semi-dwarf rice cultivar, ‘Lemont’, from triclopyr or triclopyr plus propanil. Triclopyr applied in the booting stage reduced yield two of three years, with the observed yield reduction possibly caused by epinasty of the rice flag leaf. Triclopyr application to three- to four-leaf rice caused hyponasty. Triclopyr did not reduce plant height, seed weight, germination, or total milling yield. Triclopyr plus propanil caused more leaf burn that triclopyr alone, but yields were not reduced compared with the untreated control. This research indicated that triclopyr and triclopyr plus propanil can be used in rice production with the semi-dwarf cultivar, Lemont, with the potential to minimize drift to non-target crops due to the greater flexibility in application timing compared with 2,4-D application.

The effect of metribuzin at six rates of application was evaluated on four soybean (Glycine max L.) cultivars and on common hempnettle (Galeopsis tetrahit L.) over a three-yr period (1985 to 1987). The cultivars Maple Amber and Baron were susceptible to metribuzin whereas the cultivars Maple Isle and KG-20 were tolerant of metribuzin. Metribuzin caused progressively greater reductions in plant stands and loss in yield in the susceptible cultivars as rate of application increased. Metribuzin at 0.5 kg ha-1 or higher controlled over 90% of common hempnettle.

Field experiments were conducted during 1982 to 1988 in Virginia to evaluate BAS 517, CGA 82725, clethodim, cloproxydim, fenoxaprop, fluazifop, fluazifop-P, haloxyfop, paraquat, quizalofop, SC-1084, sethoxydim, sethoxydim plus thifensulfuron, and terbacil for control of annual grasses in alfalfa. Herbicides were applied to alfalfa and grasses 2 to 30 cm in height after the first and/or second cuttings. Overall, the herbicides were highly effective in controlling fall panicum, giant foxtail, barnyardgrass, and large crabgrass. Alfalfa yields were not increased with herbicide treatments in several experiments. Only paraquat, applied later than recommended after cutting in one experiment, and sethoxydim plus thifensulfuron at one location reduced alfalfa yields.

Dicamba, 2,4-D, picloram, and commercially available premixes of glyphosate plus 2,4-D or glyphosate plus dicamba were evaluated alone and in combination for field bindweed control in a winter wheat-fallow system in Colorado, Wyoming, Kansas, and Montana. Approximately one year after application, herbicide mixtures containing picloram at 0.14 or 0.28 kg ai ha-1 provided the best control. In five of seven locations, the control provided by picloram in herbicide mixtures was greater than the control provided by glyphosate plus 2,4-D, 2,4-D, or dicamba when these products were mixed with picloram. Glyphosate plus 2,4-D or glyphosate plus dicamba premixes, or 2,4-D added to dicamba were less effective for long-term control of field bindweed than mixtures containing 0.14 kg ai ha-1 or more of picloram. Under drought conditions in Kansas in 1988, picloram did not control field bindweed as well as in Colorado, Wyoming, or Montana where rainfall was normal.

‘Vernal’ alfalfa response was evaluated when chlorsulfuron, thifensulfuron, 2,4-D, glyphosate, bromoxynil, and selected combinations of those herbicides were applied at rates simulating spray drift during the fourth trifoliolate leaf stage following the first cutting in 1990 and 1991. The order of phytotoxicity was 2,4-D > chlorsulfuron > thifensulfuron > glyphosate > bromoxynil. By the end of each growing season, alfalfa had recovered from injury caused by all herbicides except the highest rates of 2,4-D and 2,4-D plus glyphosate. The alfalfa stand was reduced only by 2,4-D and 2,4-D plus glyphosate. All herbicides caused characteristic symptoms, but some specific symptoms were similar among different herbicides or resembled symptoms caused by disease, mineral imbalance, and adverse weather conditions.

Field and container studies were conducted to determine effects of prodiamine on Florida betony and leatherleaf fern. Effects of Florida betony competition on leatherleaf fern frond yield and quality were also determined. Seed germination and growth and flowering of established Florida betony decreased with increasing prodiamine application rates; 4.5 kg ai ha-1 or higher prevented seed germination and eliminated or nearly eradicated established betony one year after treatment. Prodiamine treatments up to 6.7 kg ai ha-1 did not affect leatherleaf fern growth, frond yield (number, fresh weight) or quality (color, size, vase life). When leatherleaf fern and Florida betony were grown together in containers for 7 mo, fern frond yield and quality were reduced.

This study was conducted to determine the tolerance of three cultivars of rice (‘Lemont’, ‘Mars', and ‘Tebonnet’) to bromoxynil and triclopyr. The effects of two rates of application (the labeled rate and twice the labeled rate) at three different growth stages (two- to three-leaf stage, four- to five-leaf stage, and panicle initiation) on percent visible injury rating and percent grain yield reduction of rice were investigated. Percent visible injury ratings for triclopyr averaged across all rates and application times, were 15, 16, and 25% (LSD = 3%) for Tebonnet, Mars, and Lemont, respectively, whereas ratings for bromoxynil were 11, 8, and 7% injury (LSD = 2%). Tebonnet was more tolerant than Lemont to triclopyr with an average percent grain yield reduction, across treatments, of 6% compared with 9% for Mars and 12% for Lemont (LSD = 4%). Bromoxynil did not decrease the average yield of any of the three cultivars.

This study evaluated the response of sweet cherry to different herbicides applied at rates simulating drift. Chlorsulfuron, thifensulfuron, bromoxynil, 2,4-D, glyphosate, and a combination of 2,4-D and glyphosate were applied on one side of one- and two-year-old established cherry trees at 1/3, 1/10, 1/33, and 1/100 of the maximum rate for small grain production. The order of herbicide phytotoxicity was chlorsulfuron > 2,4-D > glyphosate > 2,4-D + glyphosate > thifensulfuron > bromoxynil. Trees recovered from injury caused by all treatments except higher rates of chlorsulfuron, 2,4-D, and glyphosate. The herbicides caused characteristic symptoms, but some resembled disease, mineral deficiency, and environmental stress symptoms. Therefore, any allegations about herbicide drift based on chronic symptoms should be supported by analysis of plant tissue.

Yellow nutsedge control with rust (Puccinia canaliculata (Schw.) Lagerh.) collected in Salisbury, MD., was evaluated alone or in combination with pebulate at 1.7 or 3.3 kg ai ha-1 in transplanted tomato. Foliar applications of urediniospores in mid-June did not affect the yellow nutsedge population; however, tuber biomass was reduced 32%. In July, yellow nutsedge infection was manifest as an increase of phytotoxicity from 2.3 to 4.1 (0 to 10) and of disease incidence increase from 3 to 37%. Pebulate, 3.3 kg ha-1 reduced the yellow nutsedge population and ground cover by 79 and 90%, respectively, in June, with a 48% reduction of both tuber population and biomass in September. Tomato yields were not increased by rust or pebulate treatments. Marketable tomato yield was increased 46% by handweeding. Yellow nutsedge control was not enhanced by the combination treatments of pebulate followed by rust inoculation.

Experiments were conducted in 1989 and 1990 to study the effects of 220 g ai ha-1 AC 263,222, 840 g ai ha-1 glufosinate, 560 g ai ha-1 glyphosate, and 840 g ai ha-1 paraquat on sicklepod seed production and quality when applied at R5, R6, R7, and R8 growth stages of sicklepod. No seed were produced on plants treated at R5 with paraquat and glufosinate; glyphosate was the least effective herbicide at this growth stage. Although sicklepod seed germinated after AC 263,222 application at R5, no seedling emergence occurred. Normal seedlings, seedling emergence, and seedling radicle length were reduced by all herbicides applied to parent plants at R5, R6, and R7 growth stages. AC 263,222 applied at R7 reduced normal seedlings and seedling emergence more than any other herbicide. No effects were observed on any of the variables investigated when herbicides were applied at R8.

Field studies were conducted in 1988 and 1989 to examine the interrelations of cultivation and herbicide band width in controlling pitted morningglory and sicklepod in soybean. Alachlor + imazaquin PRE followed by imazaquin + surfactant POST were not applied or were applied on bands 15, 30, 45, 60, 75 cm wide or were broadcast. Plots were cultivated zero, one, two, or three times. Without cultivation, at least a 60-cm wide band was needed to achieve maximum soybean seed yields. A slight linear increase in soybean seed yield in response to increasing band width was observed with one cultivation. With two cultivations, soybean seed yields were similar with and without herbicides, but a 15-cm wide herbicide band was needed to achieve maximum production with three cultivations. Greatest gross returns exclusive of weed management costs were realized with two or three cultivations and a 15-cm wide band.

When applied correctly, atrazine can be used safely in certain areas of the United States for weed control in winter wheat, but persistence in the soil may injure wheat replanted after crop failure. Studies were conducted at Moro, OR, in 1989–90 and 1990–91 to determine the effect of September preplant applications of atrazine at 0.56, 1.12, and 2.24 kg a.i. ha-1 (1X, 2X, and 4X label rates) on wheat seeded at that time and on wheat re-seeded 2 or 6 mo later. Yield of winter wheat re-seeded in November following September atrazine applications was not reduced at any rate. The September-planted wheat was killed with glyphosate in the spring to simulate winter killing, then plots were re-seeded to spring wheat. The commercial rate of atrazine, 0.56 kg ha-1, caused only minor injury to spring wheat, but injury at the 2X and 4X rates was excessive.

Field studies were conducted in 1989 and 1990 to determine the potential interaction of terbufos and nicosulfuron on corn. Terbufos applied in-furrow at planting interacted with nicosulfuron applied POST to cause significant injury 25, 30, 40, 50, and 60 d after planting in 1989 and 1990. Injury decreased significantly when nicosulfuron was applied at later growth stages of corn. Plant population was not affected by terbufos and nicosulfuron regardless of the growth stage of corn at application of nicosulfuron in either year. Corn ear number and grain yield in 1989 and 1990 were lower in plots treated with terbufos at planting and nicosulfuron applied at the three leaf stage than in plots treated with only nicosulfuron. There were no differences in the height of corn, ear number, or grain yield when nicosulfuron was applied at the seven-leaf stage regardless of terbufos application in 1989 or 1990.

A survey conducted to determine the distribution of red horned poppy in western Oklahoma identified infestations in 14 Oklahoma and 3 Texas counties. Soil pH from infested fields ranged from 7.0 to 8.5. Red horned poppy grew as an annual, germinating in fall, spring, or summer. Plants that emerged in the fall survived −25 C, flowered in April and produced mature seed in June. Plants that emerged in April, flowered in June and produced mature seed in July. Corolla color varied from red to yellow with time of anthesis.

Field experiments were conducted in 1990 and 1991 near Artesia and Las Cruces, NM to evaluate directed POST treatments of oxyfluorfen for the control of broadleaf weeds that emerge after thinning chile peppers. At Artesia, Wright groundcherry and prostrate pigweed reduced red pepper yield by 33% in untreated plots in 1990 and clusterflower reduced yield by 19% in 1991. At Las Cruces, Wright groundcherry, Palmer amaranth and common lambsquarters reduced yield by 61% in 1990 and by 76% in 1991. A sequential treatment of oxyfluorfen at 0.14 kg ai ha-1 2 wk after thinning, when the peppers were 15 cm tall, followed by 0.14 kg ha-1 4 wk after thinning controlled all species except common lambsquarters without injuring the peppers.

Low-spatial resolution satellite imagery from the NOAA-10 polar-orbiting meteorological satellite was analyzed to determine if central New Mexico grasslands infested by broom snakeweed could be discriminated from unaffected areas. Distinctive phenological characteristics of broom snakeweed, including an early season growth flush and late season flowering, enable moderate to heavily infested areas to be separated from grasslands having few or no weeds present. The procedure used shows promise as a tool for locating and monitoring brown snakeweed and other weeds growing on shortgrass prairie.

Experiments were conducted to evaluate the effect of tillage, rye residue levels, and control strategies on weed suppression and potato yield. Reduced tillage (RT) yields in 1989 were lower than in conventional tillage (CT) due to high hairy galinsoga populations. However, in 1990, potato yields were greater in RT when early emerging weeds were suppressed. Increasing residue levels up to 2300 kg ha-1 had no effect on weeds or yields in either year. In a separate study, preemergence herbicides (linuron plus metolachlor, 1.7 kg ai ha-1 each) applied 10 d after planting (DAP) in reduced tillage controlled weeds for 6 wk, but efficacy decreased after hilling. Metribuzin applied postemergence (0.19 kg ai ha-1) 7 d after hilling controlled late germinating weeds. Potato yields were greatest when the preemergence herbicides were applied.