Herbicidal control of triazine-resistant (TR) kochia was evaluated in no-till grain sorghum. Herbicides were applied early preplant (EPP) or POST. In EPP experiments, herbicides plus nonionic surfactant at 0.25% v/v were applied 7, 2, or 0 wk before planting (WBP). Fluorochloridone at 0.8 kg ai/ha applied 7 or 2 WBP, pyridate at 1.0 kg ai/ha applied 2 WBP, and paraquat at 0.4 kg ai/ha applied 0 WBP controlled 94 to 99% of TR kochia; a prepackaged mixture of glyphosate plus 2,4-D at 0.3 plus 0.6 kg ae/ha and paraquat at 0.4 kg/ha applied 7 or 2 WBP controlled 71 to 82% of TR kochia; and 2,4-D ester at 0.6 kg ae/ha applied 2 WBP controlled 75% of TR kochia. Linuron at 0.8 kg ai/ha and atrazine at 2.2 kg ai/ha were ineffective. In the POST herbicide experiments, where paraquat plus metolachlor at 0.6 plus 1.7 kg ai/ha were applied 17 d before planting, various combinations and rates of bentazon plus atrazine, bromoxynil, and dicamba with adjuvants provided good control of TR kochia that was less than 8 cm tall.

Metham was applied in the dormant season to established cranberry for the control of false lily-of-the-valley. Rates of 108 to 214 kg ai/ha controlled false lily-of the-valley, but there were inconsistent results between years and fields. Soil temperature, organic matter content, and amount of water used for incorporation appeared to be important factors in determining results. The phytotoxicity of metham sodium to cranberry was sporadic, ranging from moderate at 214 kg ai/ha to severe at 108 kg ai/ha. The 142 kg ai/ha rate usually resulted in an acceptable level of crop injury. Sanding the bog after application reduced phytotoxicity and heat stress increased it.

Absorption of 14C-bentazon from the leaf surfaces of common cocklebur and velvetleaf was rapid and most occurred within 4 h after foliar application. Greater 14C in the epicuticular wax (ECW) did not correlate with higher radioactivity in the leaf tissue. There was significantly less ECW on the “mature” leaves of common cocklebur and “juvenile” leaves of velvetleaf. However, the “mature” leaves exhibited greater 14C absorption for both species. The use of 28% urea ammonium nitrate increased 14C-absorption when compared with crop oil concentrate and with no adjuvant.

Research was conducted in central Georgia to determine the influence of norflurazon on bermudagrass stand and production when applied to newly sprigged bermudagrass and in the spring to dormant bermudagrass. Norflurazon at rates up to 1.12 kg ai/ha on newly sprigged bermudagrass caused moderate chlorosis to the emerging leaves but did not adversely influence stand density or ground cover at 60 and 90 days after treatment (DAT). Norflurazon applied to dormant bermudagrass the spring of 1993 resulted in greater than 50% foliage chlorosis at rates ≥ 1.68 kg/ha. Foliage chlorosis was 94% on bermudagrass treated with 3.36 kg/ha 30 DAT and at spring growth initiation. However, chlorosis level was reduced when bermudagrass began rapid growth. Forage production was not influenced by the early season chlorosis when compared to nontreated areas or areas treated with diuron at 1.12 kg/ha and the weed free check.

DC X2-5309 organosilicone adjuvant added at 1% (v/v) spray solution increased the efficacy of bentazon, pyridate, and terbacil on kochia in greenhouse trials. DC X2-5309 decreased the rain-free period needed after application of bentazon and bromoxynil to 6 and 1 h, respectively, and increased the uptake of 14C-bentazon and 14C-bromoxynil by kochia at 1, 3, 6, and 24 h after application compared with crop oil concentrate (COC). In field trials, bentazon and bromoxynil rates required to control equal amounts of kochia were reduced by half when adding DC X2-5309 compared with adding crop oil concentrate. DC X2-5309 added at 0.5% (v/v) spray solution with bentazon did not injure spearmint and controlled kochia equal to or better than bentazon with COC added at 1% (v/v) spray solution.

Field studies were conducted in 1988/89 and 1989/90 at two locations to determine the effect of rye, wheat, and triticale cover crop mulches on weed emergence patterns, weed biomass, and soybean development. Redroot pigweed and common lambsquarters emergence patterns were not altered by mulches. Early in the season, mulches reduced weed biomass; however, the results were inconsistent between locations and years. Under weed-free conditions, the cover crop mulches had no detrimental effects on soybean development and yields were not different from bare soil controls.

Field research was conducted at Rosemount, MN in 1990 and 1991 to determine the effect of starch encapsulation on weed control in corn with alachlor, metolachlor, and atrazine under two weed densities. At low weed densities (122 total plants/m2), giant foxtail and Pennsylvania smartweed control were not different with full rates of herbicide applied in starch encapsulated or commercial formulations. Velvetleaf control was less with starch-encapsulated than commercial formulations regardless of velvetleaf density. At high giant foxtail densities (740 plants/m2), control was not affected by formulation with full rates of alachlor plus atrazine. However, giant foxtail control was less with starch-encapsulated formulations than commercial formulations with 75% rates of alachlor plus atrazine and both 75 and 100% rates of metolachlor plus atrazine. At low weed densities, corn yield was not different with any treatment, except starch-encapsulated metolachlor plus atrazine at 75% rates, compared to the weed-free control. Alachlor plus atrazine at full rates was the only starch-encapsulated treatment to result in corn yield not different from the weed-free control at high weed densities. Conversely, all commercial formulation treatments resulted in corn yields not different from the weed-free control at high weed densities.

Two field experiments were conducted between 1990 and 1992 under sprinkler irrigation at the Research and Extension Center, Torrington, WY to determine the influence of mixed densities and durations of kochia and green foxtail interference in sugarbeet. Sugarbeet root yield and top weight generally decreased as densities of green foxtail and kochia increased whether alone or in combination. Reductions in sugarbeet root yield and above ground biomass from mixed densities of kochia and green foxtail were additive at the low and intermediate density but less than additive at the high density of either species. Sugarbeet root yield decreased as the duration of interference after sugarbeet emergence from a mixed density of kochia and green foxtail increased. Since sugarbeet plants were irrigated to avoid water stress and adequate nutrients were applied, it appears that kochia and green foxtail interfered with sugarbeet primarily for light, based on light and height measurements. Season-long as well as duration of interference did not show any significant effect on sucrose content. Based on regression analysis the lowest densities of kochia and green foxtail required to reduce root yield were approximately 0.3 and 0.06 plants/m of row, respectively. The minimum duration of time that 0.5 kochia and 3.0 green foxtail plants/m of row can interfere with sugarbeets before root yield is economically reduced was approximately 3.5 wk after sugarbeet emergence.

The leaves of tall morningglory, giant duckweed, and common purslane were treated with nine surfactants at a concentration of 0.1% and examined after 24 hr using cryo-scanning electron microscopy for phytotoxicity as evidenced by tissue damage and epicuticular wax morphology changes. In some instances, tissue damage could be discerned; however, the effects of a particular surfactant were not uniform across the three species. Morphological alteration of epicuticular waxes was not observed. Gas chromatographic analyses of the epicuticular waxes of the species used in the study reveal component differences and may, in part, explain the lack of uniform response across species for a particular surfactant.

Cultivation timings and postemergence applications of AC 263,222 were evaluated for sicklepod and pitted morningglory control in soybean. Cultivation alone controlled each less than 35% season-long. A cultivation made 7 d after POST applications of AC 263,222 more consistently improved sicklepod and pitted morningglory control than a cultivation made 3 d before, immediately after, or 3 d after the POST application. Imazaquin PRE followed by 18 g ai/ha AC 263,222 controlled sicklepod 88% or more and pitted morningglory 83% or more two of three years. A cultivation made immediately after AC 263,222 POST resulted in reduced soybean yields in several instances compared to the same treatment without cultivation. A cultivation made 7 d after application of AC 263,222 increased soybean yields the most in several instances compared to all other timings.

The Spurgia esulae gall midge was introduced in North Dakota in 1986 as a biocontrol agent for leafy spurge. Spurgia esulae causes stem tip galls thereby decreasing seed production and it has been most successful near wooded areas. However, a second control method is needed to reduce the leafy spurge infestation and prevent spread from roots. Imazethapyr, 2,4-D, or picloram application did reduce the number of S. esulae galls but not the number of larvae per gall. Long-term S. esulae population was not affected by herbicide application. The integration of herbicides with S. esulae would prevent leaf spurge spread from a wooded area and would reduce seed production within an area where herbicides generally cannot be used.

Field experiments were conducted in 1990, 1991, and 1992 to evaluate and compare the efficacy of commercial herbicide formulations with starch encapsulated granules that contain one, two, or three herbicides. Atrazine in combination with alachlor or metolachlor composed the two-component granules and the addition of dicamba to both composed the three-component granules. All starch-encapsulated formulations were produced by twin screw extrusion technology and evaluated in two granule sizes, 1.4 to 0.5-mm (14 to 20 mesh) and 0.85 to 0.43-mm (20 to 40 mesh). Active ingredient rates applied were selected for the existing soil conditions and combination granules contained active ingredients proportional to premixed commercial formulations available or suggested for tank mixes. Evaluations were performed under conventional, chisel, and no-tillage systems. PRE and PPI applications of starch encapsulated two-component (atrazine-alachlor) in 1990 controlled giant foxtail (except at the low rate with large granule size), redroot pigweed, and common lambsquarters excellently but control of velvetleaf was fair to poor. Smaller-sized granules were generally more effective for controlling weeds than the larger-sized granules. In 1991, starch-encapsulated two-component (atrazine-metolachlor) granules applied both PRE and PPI in conventional, chisel, and no-till systems gave results similar to 1990 with the small granules more effective on velvetleaf. The addition of dicamba in the granule to form three-component starch-encapsulated granules in 1992 resulted in control of velvetleaf, ivyleaf morningglory, and jimsonweed statistically equal to commercial formulations except in one case of no-till corn. In our experiments, herbicide formulations (granular vs. commercial) had no significant effect on corn yield in 28 out of 31 treatments. These data indicate that if the experimental three-component starch-encapsulated formulations of corn herbicides used in these studies were optimized they could become as efficacious as commercial formulations presently on the market. This is the first report of research containing data on two- and three-component starch-encapsulated granular formulations.

Several herbicides control common ragweed postemergence in soybean. However, weed response may be altered if herbicides are tank-mixed and the choice of additive may also influence the degree of weed control. Imazethapyr and thifensulfuron could be tank-mixed with bentazon for broadleaf weed control and visual crop injury reduced compared to a bentazon plus acifluorfen tank-mix. Experiments determined common ragweed control with these herbicides and herbicide combinations when applied with various additives. In the greenhouse, bentazon at 560 g ai/ha reduced common ragweed dry weight 95 to 97%. Common ragweed control with imazethapyr at 35 g/ha increased by 13 and 7% when 28% urea ammonium nitrate was applied with nonionic surfactant or petroleum oil adjuvant, respectively. Tank-mixing imazethapyr with bentazon did not change dry weight of common ragweed compared with bentazon. Bentazon plus thifensulfuron plus nonionic surfactant required the addition of 28% urea ammonium nitrate to reduce dry weight of common ragweed comparable to that with bentazon. In field research, bentazon at 1120 g/ha reduced common ragweed dry weight 78 to 81%. Tank-mixing bentazon with thifensulfuron at 4.5 g/ha or imazethapyr at 71 or 35 g/ha reduced common ragweed dry weight at 14 d after treatment by 89 to 91%, thus enhancing control compared to each herbicide applied alone. Adding 28% urea ammonium nitrate to bentazon plus imazethapyr or bentazon plus thifensulfuron tank-mixes did not increase control compared to these treatments applied with either nonionic surfactant or petroleum oil adjuvant. By 28 d after treatment only imazethapyr at 35 or 71 g/ha plus 28% urea ammonium nitrate plus nonionic surfactant or petroleum oil adjuvant and bentazon plus imazethapyr tank-mixes provided 85% or more control of common ragweed in 1991, and only imazethapyr at 71 g/ha plus 28% urea ammonium nitrate plus petroleum oil adjuvant or imazethapyr at 71 g/ha plus bentazon provided greater than 78% common ragweed control in 1992. Soybean yield was not different from the handweeded control only where bentazon plus 71 g/ha of imazethapyr or acifluorfen at 560 g/ha was applied.

In greenhouse experiments, unrefined corn oil was tested as an adjuvant with the mycoherbicidal fungus, Colletotrichum truncatum. A1:1 (V/V) fungus/corn oil tank mixture extended by at least 70 h the period of time in which the fungus remains infective between inoculation and the onset of dew. This formulation also reduced the dew period requirements for optimal weed pathogenesis and mortality from 12 h to 2 h, and reduced the required spray volume by 100-fold, from 500 L/ha to 5 L/ha. These results suggest that formulating C. truncatum in unrefined corn oil greatly improves the bioherbicidal potential of this pathogen.

Field experiments were conducted in Michigan, Minnesota, and Wisconsin to evaluate injurious interactions between nicosulfuron herbicide applied POST and nine insecticides applied at planting on ‘Pioneer 3751’ field corn in 1991. Insecticides were applied in-furrow, T-band, and surface band at planting. Corn injury from nicosulfuron and terbufos applications was more severe in Wisconsin than in Michigan. No corn injury was observed in Minnesota. Terbufos 15% ai granule (15G) or 20% ai controlled release granule (20CR) increased nicosulfuron injury to corn in Wisconsin. Nicosulfuron at 35 g ai/ha caused the greatest vigor reduction following terbufos 15G, intermediate vigor reduction following terbufos 20CR, phorate 20G, or phorate 20CR, and the least vigor reduction following fonofos, chlorpyrifos, chlorethoxyfos, tefluthrin, or carbofuran in Wisconsin.

Herbicide efficacy trials in field corn, sweet corn, and soybean were conducted at three locations in Wisconsin over a 6-yr period. Percent weed pressure (WP) was determined by visually estimating the contribution of all weed species present to the total crop and weed volume in each plot. Crop yields in each plot were measured. Percent crop yield reduction (YLDRED) was calculated by comparing mean yields of individual treatments with those of the highest yielding treatment in each trial. Linear regression analyses of YLDRED and WP data from 1640 field corn and 138 sweet corn treatments were significant. Nonlinear regression analysis of YLDRED and WP data from all 1374 soybean treatments was significant; however, a linear regression of those 1154 soybean treatments with WP ratings of 30 or less produced a more easily interpreted regression equation.

Field studies were conducted in 1990 and 1991 at Davis and Five Points, CA to evaluate weed control with napropamide and hand-weeding and the effect on yield and profitability in transplanted bell pepper. Weed cover 8 wk after transplanting averaged less than 10% in plots hand-weeded biweekly for 6 wk after transplanting. Weed cover at harvest was less than 30% in plots hand-weeded at 8 wk after transplanting. Napropamide treatment reduced weed cover at 8 wk after transplanting an average of 34% compared to untreated plots, but differences declined to 14% at harvest. Time required to hand-weed plots was greater if the interval between weeding was 4 instead of 2 wk. The time needed to hand-weed plots was reduced from 38% to 71% by napropamide treatment. When weeds were excluded by hand-weeding for the entire season, bell pepper yielded 25 810 kg/ha and was 4% to 18% higher than other treatments. Net returns were greater for plots that were hand-weeded the entire season or when napropamide was combined with hand-weeding at 4 and 8 wk after transplanting, compared to other treatments.

The response of ‘Florico,’ ‘Victoria,’ and 'Stan II’ triticale to 2,4-D, dicamba, 2,4-D plus dicamba, diclofop, and thifensulfuron plus tribenuron applied POST during the tillering stage was examined. At rates twice those recommended for application to wheat, Victoria and Stan II were not injured, and injury to Florico was less than 10%. None of the herbicides or combinations adversely affected plant height at maturity, tiller or spike production, grain weight/spike, kernel weight, kernels/spike, yield, or test weight of any cultivar. Cultivars varied in tiller production, height, yield, test weight, kernel weight, and kernels/spike.

Various combinations of methods were evaluated for the control of ivyleaf morningglory growing in cotton. The combinations included chemicals incorporated to two depths or tanked-mixed as postemergence treatments and cultural methods that included in-row cultivation and hand weeding. The most effective combinations of methods included a herbicide such as cyanazine or prometryn in some treatments resulting in reduced ivyleaf morningglory population and improved cotton yields. Cultural methods without chemical assistance gave little or no control of ivyleaf morningglory based on weed populations and cotton yield. Statistically the best combinations had lint yields equal to the weed-free treatment, but the yields were reduced from 114 to 372 kg/ha. Also, most combination treatments had enough plant debris in the lint to reduce fiber grade.

Spent spearmint hay from mint that had been treated with clopyralid in the fall or spring injured ‘Russet Burbank’ potato planted into loamy sand soil amended with 50 g hay/kg soil. Lowering the ratio of mint hay to soil from 50 to 3.1 g/kg reduced, but did not eliminate, the injury to potato. Potato was inured by clopyralid at concentrations as low as 3 ppbw in soil.