Weed removal experiments in dry edible beans were conducted during 1992 and 1993 at Crookston and Staples, MN. Ten manual weed removal treatments were studied to determine when a natural infestation of weeds first reduced dry bean yield, and when weed removal could be discontinued without further loss of seed yield. Major weeds in order of average biomass production on weedy check plots at dry bean harvest over locations and years were wild mustard, foxtail spp., redroot pigweed, common ragweed, wild buckwheat, hairy nightshade, and common lambsquarters. Hairy nightshade also emerged late in the growing season and could negatively affect harvest efficiency and stain navy beans. Weed removal treatments had little effect on dry bean stands or 100-seed weights of harvested dry bean seed. The critical period for weed control in dry beans was 3 to 5 or 6 weeks after planting (WAP). Thus, weed control practices should begin no later than 3 WAP and continue until at least 5 or 6 WAP for maximum dry bean yields.

Broadleaf weed control ranged from 80% with clomazone at 0.14 kg/ha to 100% with clomazone at 1.12 kg/ha. Broadleaf weed control was higher with clomazone than naptalam or ethalfluralin. The combination of clomazone at 0.14 kg/ha and naptalam at 5 kg/ha or ethalfluralin at 1.25 kg/ha gave more than 90% broadleaf weed control. Clomazone caused chlorosis and bleaching on cucumber leaves but plants rapidly recovered. Cucumber yields were higher in plots treated with clomazone alone at 0.14 to 0.56 kg/ha than with ethalfluralin or naptalam alone. Clomazone dose response studies were conducted in weed-free plots with five cucumber varieties. The 0.28 kg/ha rate caused low levels of visible injury and did not decrease yields. Cultivar differences were more pronounced at higher clomazone rates. The five cucumber cultivars were, in order of increasing clomazone tolerance, ‘Sunre 3537,’ ‘Pioneer,’ ‘Quest,’ ‘Prince,’ and ‘Calypso.’ We concluded that clomazone is an effective and selective herbicide for broadleaf weed control in pickling cucumber.

Pathogenicity of four Colletotrichum coccodes isolates to potato, eastern black nightshade, and hairy nightshade was evaluated in greenhouse studies. Three Idaho isolates, AC-14, AC-28, and AC-44, and an isolate obtained from Mycogen Corporation, AC-Myc, produced lesions on potato foliage. Plants inoculated with AC-14, AC-28, and AC-44 also showed wilt symptoms similar to those produced by Verticillium dahliae as potatoes were beginning to senesce. Infection by AC-44 reduced tuber fresh weight and specific gravity. All isolates colonized eastern black and hairy nightshade, although some isolates caused little or no symptom development. Thus, both species may serve as sources of primary inoculum for C. coccodes isolates that are pathogenic to potatoes. Only AC-Myc substantially injured the leaves of both nightshade species. AC-Myc was more pathogenic to eastern black than to hairy nightshade, and to plants inoculated at the 3- to 4-leaf versus the 7- to 8-leaf stage.

Information on the effects of multiple weed management tactics in corn is needed to develop integrated weed management systems. The effectiveness and compatibility of an in-row cultivator as compared to a standard interrow cultivator used with reduced rates of a soil-applied herbicide, rotary hoeing, and/or a bioeconomic model for POST herbicide selection was examined. Weed control with a single rotary hoeing at corn emergence controlled annual weeds similarly to two rotary hoeings. One-third recommended use rate of alachlor controlled weeds similarly to a two-thirds rate. Reduced rates of alachlor controlled more weeds than rotary hoeing over 2 yr. The in-row cultivator required early-season weed control (rotary hoeing or reduced alachlor rate) for optimum efficacy. The in-row cultivator provided better weed control than the standard cultivator while the cost of operating the two cultivators was similar. Thus, the in-row cultivator was more efficient than the standard cultivator. Furthermore, less intensive early-season weed control was required with the in-row cultivator for maximum weed control as compared to the standard cultivator. Rotary hoeing plus the in-row cultivator provided similar weed control to other weed management tactics that required both soil-applied and POST herbicides. Gross margin was influenced more by corn yield than cost of weed management tactics.

Field research was conducted during the summers of 1981 and 1982 in order to determine relative infection and population increase of lesion nematodes (Pratylenchus spp.) on seven weed species that commonly occur in field-bean (Phaseolus vulgaris L.) fields in western Nebraska. Weeds were grown at three densities with and without fieldbeans. A representative sample of the root systems from plants in each plot was removed in August and the nematodes were extracted and counted. No difference in nematode infection rate was found among weed population levels. Nematodes per gram of dry root were not different in weeds grown with or without fieldbeans. Weeds grown with fieldbeans had smaller root systems, and consequently total nematodes per root system were less than in weeds grown in the absence of fieldbeans. There was a significant difference among most weed species when nematodes per gram of dry root were estimated. Hairy nightshade (Solanum sarachoides Sendt. ♯3 SOLSA) and barnyardgrass [Echinochloa crus-galli (L.) ♯ ECHCG] supported the highest numbers of nematodes per g oven-dry roots, redroot pigweed (Amaranthus retroflexus L. ♯ AMARE) and common cocklebur (Xanthium pensylvanicum Wallr. ♯ XANPE) had least numbers of nematodes/g oven-dry roots, and infestation levels on other weed species were variable but generally intermediate.

Field studies were conducted to determine the influence of annual herbicide treatments plus cultivation on weed populations and corn yields in ridge-till corn during a 3-yr period at Mitchell, NE, and a 7-yr period at North Platte, NE. When the experiment was initiated at North Platte, no weeds were present before corn planting. It took 4 yr before triazine-resistant kochia became a problem before corn planting in plots treated with atrazine, but these were controlled by other operations prior to corn harvest. In the cultivated check, green foxtail densities before harvest increased from 0 in 1985 to 32 plants 100 m−2 in 1991. Annual applications of dicamba plus 2,4-D 10 d early preplant followed by cultivation controlled triazine-resistant kochia and velvetleaf, but common lambsquarters, nightshade species, and green foxtail increased. Volunteer corn was controlled with cultivation. After 3 yr at Mitchell, the annual weed population increased 10-fold in the cultivated check. Thus, corn yields were reduced 64% with two cultivations compared with an annual early preplant application of dicamba plus 2,4-D followed by alachlor plus cyanazine PRE and two cultivations. With two cultivations under low annual weed populations at North Platte, grain yield from the cultivated check treatment was not different from annual treatments of herbicides after 7 yr. Metolachlor plus atrazine occasionally caused a reduction in corn grain yields.

Alfalfa (Medicago sativa L. ‘Vernal′) was seeded broadcast or in drill rows spaced 18 cm apart in the same operation that EPTC (S-ethyl dipropylcarbamothioate) was applied. For broadcast seeding, EPTC was applied as herbicide-treated crop seed, as granules mixed with crop seed, or as granules applied with the crop seed, but with the seed and granules carried in separate boxes on the seeder. For drill-row seeding, EPTC was applied between the rows in subsurface lines as a liquid or granular formulation; and within the rows as herbicide-treated seed, as granules mixed with the seed, or as granules carried in a box separate from the seed. Weed control and crop tolerance with the more effective simultaneous applications of EPTC were similar to those with conventional preplant-incorporated applications. To seed alfalfa (either broadcast or in drill rows) and apply EPTC in one operation, the methods wherein untreated seed and a granular formulation of EPTC were applied together but from separate boxes on the seeder were the most practical, because the mechanical components, the seed, and the formulated herbicide are all commercially available.

Spring-applied herbicides were evaluated in the field in 1982 through 1984 in western Nebraska for selective weed control in irrigated seedling alfalfa (Medicago sativa L. ‘Appollo’). Weed densities were least in plots treated preplant with benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine] in combination with postemergence applications of 2,4-DB [4-(2,4-dichlorophenoxy) butyric acid]. Combinations of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} with bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) and fluazifop-butyl {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} with bromoxynil provided less grass control than sethoxydim or fluazifop-butyl applied alone. Annual weeds did not reduce alfalfa stand density.

Studies were conducted to determine the effects of tillage level on weed control and yield of asparagus grown on a sandy loam soil under sprinkler irrigation. Without herbicides, horseweed and kochia populations increased in no-till asparagus production over a 3-yr period, compared to asparagus that was rototilled either once in the spring or once in the spring and again at layby. Without herbicides, hairy nightshade populations increased most when asparagus was rototilled both in the spring and at layby. Volunteer asparagus was controlled best when herbicides and tillage were combined in the spring and again at layby. Common groundsel was controlled without herbicides by rototilling both in the spring and at layby. Diuron at 1.4 kg ai/ha plus prodiamine at 1.4 kg/ha or metribuzin at 0.9 kg/ha plus norflurazon at 2 kg/ha controlled all weeds under all three tillage levels when split-applied in the spring and at layby. Tillage level had no effect on total asparagus spear number or weight if tillage was performed in mid March before asparagus emergence.

Changes in the weed seedbank due to crop production practices are an important determinant of subsequent weed problems. Research was conducted to evaluate effects of primary tillage (moldboard plowing and chisel plowing), secondary tillage (row cultivation), and herbicides on weed species changes in the soil seedbank in three irrigated row crop rotational sequences over a 3-yr period. The cropping sequences consisted of continuous corn for 3 yr, continuous pinto beans for 3 yr, or sugarbeets for 2 yr followed by corn in the third year. Cropping sequence was the most dominant factor influencing species composition in the seedbank. This was partly due to herbicide use in each cropping sequence producing a shift in the weed seedbank in favor of species less susceptible to applied herbicides. A comparison between moldboard and chisel plowing indicated that weed seed of predominant species were more prevalent near the soil surface after chisel plowing. The number of predominant annual weed seed over the 3-yr period increased more rapidly in the seedbank after chisel plowing compared to moldboard plowing unless effective weed control could be maintained to produce a decline in seedbank number. In this case, seedbank decline was generally more rapid after moldboard plowing. Row cultivation generally reduced seedbanks of most species compared to uncultivated plots in the pinto bean and sugarbeet sequences. A simple model was developed to validate the observation that rate of change in the weed seedbank is influenced by type of tillage and weed control effectiveness.

Management systems for direct-seeded and transplanted sugarbeets (Beta vulgaris L. ‘Mono Hy D2′) were compared for weed control and sugarbeet selectivity from 1983 through 1985 in western Nebraska. Broadleaf weed density was similar, but yellow foxtail [Setaria glauca (L.) Beauv. # SETLU] density was lower in transplanted compared to direct-seeded sugarbeets. Preplant soil-incorporated applications of cycloate (S-ethyl cyclohexylethylcarbamothioate) plus trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] at 3.3 plus 0.6 kg ai/ha or ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] plus trifluralin at 2.2 plus 0.6 kg/ha was noninjurious to transplanted sugarbeets but caused severe injury to direct-seeded sugarbeets. The combination of cycloate or ethofumesate with trifluralin improved weed control over that obtained when cycloate or ethofumesate was used alone. By combining the improved weed control obtained from cycloate plus trifluralin or ethofumesate plus trifluralin with the transplanting crop establishment technique, a superior sugarbeet weed control program was developed.

Two species of annual nightshades were commonly found as agronomic weeds in Minnesota. Eastern black nightshade (Solanum ptycanthum Dun.), the most common species, was found throughout the southern half of the state. Hairy nightshade (Solanum sarrachoides Sendt. ♯3 SOLSA) was found only in a few scattered locations. Eastern black nightshade seedling emergence began in mid-April or early May, and more than 80% of the total yearly emergence occurred before June. Hairy nightshade emergence began in May, but less than 70% of its total yearly emergence occurred before June. Eastern black nightshade berries first contained viable seeds 4 to 5 weeks after flowering of the plants and a week or more before the berries began to turn black. Hairy nightshade generally required a week longer than eastern black nightshade for viable seed production after flowering.

Weed management experiments with kidney beans were conducted at one irrigated site in 1991 and at two irrigated sites near Staples, MN during 1992. Green foxtail was the most difficult weed to control at the three research sites which agrees with survey results from dry bean growers regarding their worst weed problems. Hairy nightshade increased rapidly when weed management methods were reduced. Dry bean seed yields were highest in cultivated check plots on the farmer's field and in conventional practices plots at the Irrigation Research Center. Net economic returns, averaged over 1991 and 1992, for producing kidney beans at the Irrigation Research Center were $899/ha using conventional practices, $791/ha with cover crop practices, $734/ha with cultivated checks, $690/ha with herbicides only, and $208/ha on weedy checks. Kidney beans are an economical crop for North Central growers, but adequate weed management technologies are necessary for profitable production.

Field studies were conducted to identify herbicides suitable for improved control of hairy nightshade, redroot pigweed, and common lambsquarters in pinto beans. Fomesafen at 0.25 kg ai ha-1 did not adequately control these weeds. Clomazone at 0.5 kg ai ha-1 controlled common lambsquarters but only suppressed the growth of redroot pigweed and hairy nightshade. Ethalfluralin at 0.84 to 1.1 kg ai ha-1 gave excellent initial control of these weeds but did not control later flushes of hairy nightshade. Imazethapyr applied PPI or POST at 50 to 75 g ai ha-1 controlled hairy nightshade, redroot pigweed, and common lambsquarters throughout the growing season. Imazethapyr combined with ethalfluralin gave superior weed control and resulted in greater yields than the most commonly used herbicides in pinto beans in western Canada.

Field studies were conducted to examine weed control efficacy and crop injury with SAN 582 (proposed name, dimethenamid) in irrigated ‘Russet Burbank’ potato. SAN 582 applied preemergence (PRE) at 1.1 to 1.7 kg ai/ha controlled light to moderate infestations of redroot pigweed, common lambsquarters, and hairy nightshade > 90%. Season-long control of these species with mixtures of SAN 582 plus metribuzin or rimsulfuron was > 98% and was similar to or better than registered mixtures. Green foxtail control with SAN 582 alone ranged from 83 to 100%, depending on rate and year. SAN 582 mixtures with metribuzin or rimsulfuron usually controlled green foxtail > 90%. In weed-free plots, SAN 582 was applied alone PRE or early postemergence (EPOST) at rates up to 3.4 kg/ha. SAN 582 applied EPOST usually caused 10 to 30% more potato injury than when applied PRE, but U.S. No. 1 yield was not reduced by SAN 582 applied either PRE or EPOST. SAN 582 shows good potential for PRE use in irrigated potato.

Under irrigated field conditions at Prosser, WA, Russian thistle [Salsola kali (L.) var. tenuifolia Tausch. ♯3 SASKR] began to emerge by mid-March each year and usually had completed its emergence by May 1. Common lambsquarters (Chenopodium album L. ♯ CHEAL) was the next to appear, usually during the third or fourth week of March. Barnyardgrass [Echinochloa crus-galli (L.) Beauv. ♯ ECHCG], redroot pigweed (Amaranthus retroflexus L. ♯ AMARE), hairy nightshade (Solarium sarrachoides Sendt. ♯ SOLSA), black nightshade (5. nigrum L. ♯ SOLNI), eastern black nightshade (S. ptycanthum Dun.), and cutleaf nightshade (S. triflorum Nutt. ♯ SOLTR) generally began to emerge during the first 2 weeks of April and emergence generally peaked mid-April to mid-May. Russian thistle and cutleaf nightshade had the most restricted emergence patterns, whereas seedlings of common lambsquarters, redroot pigweed, hairy nightshade, and black nightshade emerged each month from April through September. Shallow tillage at monthly intervals increased the overall emergence of common lambsquarters, redroot pigweed, black nightshade, and eastern black nightshade; decreased the emergence of barnyardgrass; and had no effect on the emergence of Russian thistle, cutleaf nightshade, or hairy nightshade.

Field studies were conducted to evaluate potato injury and weed control with postemergence-directed (PDIR) bromoxynil, glufosinate, or monocarbamide dihydrogen sulfate (MCDS). All three herbicides controlled hairy nightshade, common lambsquarters, redroot pigweed, and kochia ≥ 85%, depending on rate, with either mid- or late-PDIR treatment. Bromoxynil or MCDS caused 5 to 6% more initial injury with mid- than with late-PDIR treatment, but total yield and yield of U.S. #1 tubers were not reduced by either herbicide. PDIR glufosinate caused moderate injury at 0.84 kg ha−1, the rate needed for acceptable (≥ 85%) weed control. Total yield was reduced 10% and U.S. #1 yield was reduced 30% by PDIR glufosinate at 0.84 kg ha−1. Thus bromoxynil and MCDS showed potential for use as PDIR treatments in potatoes, but glufosinate did not.

Field studies were conducted to examine hairy nightshade control with, and potato tolerance to, bentazon or bentazon plus nonionic surfactant (NIS), petroleum oil concentrate (POC), methylated seed oil (MSO), BCH-815, or urea-ammonium nitrate (UAN). Bentazon treatments were applied early or late POST. Hairy nightshade control with bentazon at 0.56 kg ha–1 plus POC, MSO, BCH-815, or UAN was equal to or better than bentazon alone at 1.12 kg ha–1 regardless of time of application. Potato injury with bentazon plus additives applied late POST was sometimes greater than with bentazon alone, but use of additives did not reduce potato yield or quality. Yield of US ♯1 tubers was lower when bentazon was applied late POST than when applied early POST in one of two years.

Reductions in yields of processing tomatoes (Lycopersicon esculentum Mill. ‘H2653’ and ‘Earlirouge′) caused by interference from eastern black nightshade (Solanum ptycanthum Dun. # SOLPT) and hairy nighthsade (S. sarrachoides Sendt. # SOLSA) were estimated for transplanted and seeded tomatoes at two locations in southern Ontario. Tomato yield losses were significantly greater in seeded than in transplanted tomatoes. Stomatal conductance and transpiration rates of seeded tomatoes decreased more rapidly with increased nightshade density than did those of transplanted tomatoes. Percent yield losses also differed between sites. Seeded tomatoes grown at high density in twin rows (33 300 and 45 000 plants/ha) had higher yields and lower percent yield losses than did tomatoes grown at low density in single rows (12 500 to 22 500 plants/ha). Nightshade dry weight and seed production decreased per plant but increased per unit area with increasing nightshade density. Nightshade dry weights and seed production did not vary with site or method of tomato establishment. A hyperbolic model provided an excellent fit to data on both tomato yield losses and nightshade seed production as a function of nightshade density.

Eight accessions of weedy nightshades representing five species were evaluated for response to four herbicides applied preemergence in growth chamber studies and four herbicides applied postemergence in greenhouse studies. Species differed in susceptibility to all herbicides evaluated. The largest differences were found with postemergence applications of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide}; hairy nightshade (Solanum sarrachoides Sendt. ♯ SOLSA) was relatively susceptible, but eastern black nightshade (S. ptycanthum Dun.) was very tolerant. S. ptycanthum, however, was one of the more susceptible species. It was always more susceptible than black nightshade (S. nigrum L. ♯ SOLNI) to all other herbicides evaluated.