Landsat-5 Thematic Mapper spectral data and field survey information were combined to identify specific land cover types associated with 1741 dyers woad infestation points on the Cache National Forest in northern Utah. Ten of 60 possible cover types were strongly associated with current dyers woad infestations, and therefore considered highly suited to establishment and survival of the weed. Non-infested land of the same “highly suited” cover types comprised an additional 24 714 ha within the 149 021-ha study area, suggesting the potential for an eventual 124-fold increase in dyers woad incidence on the forest.

Intact soil columns were evaluated as a screening technique to determine the effect of tillage on herbicide movement through soil. Alachlor was applied at 3.3 kg ai ha-1 to intact surface 0- to 10-cm and subsurface 10- to 20-cm soil columns (15-cm diam) taken from long-term no-till and conventional tillage plots and leached with 11.6 pore volumes (7 L; 39 cm) of water at a rate that did not create ponding. Leachate was collected in 0.07 pore volume fractions. Twice as much alachlor leached from surface no-till than from surface conventional tillage columns. The differences in leaching patterns from the surface soil can be attributed to the effect of tillage on soil physical and chemical properties. Using intact soil columns in the laboratory can be a useful rapid screening technique to evaluate tillage impacts on herbicide movement.

Tolerance of two metribuzin-tolerant and two metribuzin-sensitive early maturing soybean cultivars to two rates of acifluorfen, imazethapyr, metribuzin, and thifensulfuron was evaluated under weed-free conditions. Acifluorfen at 1120 g ai ha-1 reduced plant height by 3 cm and thifensulfuron at 18 and 35 g ai ha-1 delayed physiological maturity by 3 d. No herbicide treatment reduced soybean yield when compared with a weed-free check. Soybean yield of the two metribuzin-tolerant and the two metribuzin-sensitive cultivars did not change as metribuzin rate was increased from zero to 280 to 560 g ai ha-1.

Cotton response to triclopyr was evaluated when it was applied over-the-top at simulated drift rates to pin-head square and early bloom cotton growth stages in 1987 and 1988. The herbicidal effects of triclopyr were most evident after a lag period of 10 to 15 d. Triclopyr at 60 g ai ha-1 applied at pin-head square reduced cotton height in 1987, but not in 1988. Triclopyr applied at pin-head square and early bloom reduced cotton flowering initially, as measured by white bloom counts, in both years. Total blooms were reduced in 1987, but not in 1988. Cotton maturity was delayed by triclopyr application during early bloom, as shown by a decrease in percent open bolls, and a decrease in first pick cotton yields. Cotton yield was lower in plots receiving triclopyr, with the greatest yield reduction caused by a 60 g ha-1 triclopyr application at early bloom.

Greenhouse and laboratory experiments were conducted to evaluate the influence of clopyralid formulation, spray droplet size, and spray volume on deposit of clopyralid on greenhouse-grown honey mesquite. The addition of surfactant WK at 0.5% (v/v) of the spray solution caused a twofold increase in deposition of spray of the monoethanolamine salt (MEA) of clopyralid but not the oleylamine salt (OLA). There were no differences in spray deposit between spray droplet size spectrums of 160 or 330 μm Dv.5 or spray solution applications of 47 or 187 L ha-1. Dye and gas chromatography measurements of spray deposit of clopyralid compared favorably except where surfactant WK was used with the OLA formulation.

Field experiments were conducted to determine the efficacy of fluazifop-P-butyl for the control of green foxtail, wild oat, barley, and wheat in flax as influenced by spray nozzle orientation, time of day, and growth stage. Under drought conditions in 1988, control of wild oat, wheat, and barley with fluazifop-P-butyl was enhanced 75%, 53% and 78%, respectively, when nozzles were oriented to spray forward 45°. Under adequate soil moisture conditions enhancement of control was minimal. Green foxtail control improved when fluazifop-P-butyl was applied from 1700 to 2100 h, but time of day had no effect on control of wild oat, barley, or wheat. Fluazifop-P-butyl effectiveness was reduced when applied 4 d after flax emergence due to late emerging grass seedlings. Green foxtail was the most tolerant to fluazifop-P-butyl, whereas wild oat, wheat, and barley were the most susceptible.

A 2-yr field study was conducted to evaluate the efficacy of ICIA-0051 for the control of annual grass and broadleaf weed species in conventional tillage corn. Treatments consisted of postemergence applications of ICIA-0051 alone and in combination with cyanazine or atrazine. ICIA-0051 at 0.6 kg ha-1 alone and in combination with cyanazine or atrazine at 1.1 kg ha-1 controlled large crabgrass, yellow foxtail, fall panicum, common lambsquarters, and redroot pigweed effectively (over 90%). The addition of cyanazine or atrazine at 1.1 kg ha-1 to the lowest rate (0.3 kg ha-1) of ICIA-0051 also improved large crabgrass, yellow foxtail, and fall panicum control by 9, 7, and 26%, respectively. None of the treatments of ICIA-0051 except the highest rate (1.1 kg ha-1) reduced either silage or grain yields of corn.

Horsenettle was described quantitatively in two grazed bermudagrass pastures for two years. Six times from April through October, plants were counted, phenologically documented, and tops were harvested for estimation of above-ground phytomass. Roots were sampled for carbohydrate, N fraction, and macronutrient analyses. Top growth, flowering, fruiting, and chemical composition were similar between sites within years, but differed between years. Starch and total non-structural carbohydrates in roots increased following reproductive periods both years. Root concentrations of protein and non-protein N increased and concentrations of P decreased in August and September in one year only. Analysis of the relationship between seasonal trends in carbohydrate fluctuation and pasture management practices suggests that systemic herbicide application in mid-summer may lead to more effective control than application in spring.

Optimal rates and time of application of glyphosate for control of the native perennial bluejoint reedgrass [Calamagrostis canadensis (Michx.) Nutt.] were determined from 1986 to 1989 near Delta Junction, AK. Applications were made 2 wk apart from late May or early June to September. Glyphosate did not provide control before June 15 or after September 1. Bluejoint reedgrass was controlled best when glyphosate was applied from late July to mid-August. Ammonium sulfate (2.2 kg ha-1) or nonionic surfactant (0.5% v/v) increased control except on the earliest and latest application dates. Control was consistently better with 1.1 than 0.6 kg ha-1 (ai) of the isopropylamine salt of glyphosate.

An experiment was conducted to evaluate the translocation pattern of 14C-glyphosate and 14C-quizalofop in five quackgrass biotypes at two stages of growth. Whole plant translocation differed between stages for each herbicide. The percentage of 14C-glyphosate and 14C-quizalofop in the leafwash and in the treated leaf did not differ among biotypes, but differences occurred for the translocation to the underground parts. The partitioning of the 14C-glyphosate and 14C-quizalofop in the treated crown, other crowns, propagating rhizomes, and other rhizomes differed among biotypes. On a disintegration per minute (DPM) mg-1 basis, differences among biotypes were found with 14C-glyphosate but much less with 14C-quizalofop. Metabolism of 14C-quizalofop in the treated leaf was similar in the two biotypes tested except for the percentage of polar metabolites 1 d after treatment. The percentage of 14C-quizalofop available for translocation was the same in both biotypes.

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.

This study examined the response of corn to clomazone, chlorimuron, imazaquin, and imazethapyr the year following their application to soybeans. Herbicides were surface-applied from one-half to three times the labeled application rates. Soybeans were planted the year of application and crop tolerance was evaluated. Corn was planted in rotation the following season. Soybeans were tolerant of all four herbicides. The highest rates of clomazone, chlorimuron, and imazaquin injured the corn early in the season. Imazethapyr did not influence corn growth. Visual estimates of clomazone injury were as high as 39% chlorosis. Seedling dry weight reductions at the highest chlorimuron and imazaquin rates were 32% and 24%, respectively. Although corn was injured by higher rates of clomazone, imazaquin, and chlorimuron at the 3-leaf stage, none of the herbicides significantly reduced grain yield. This study suggests that these herbicides can carry over and injure corn, especially if labeled application rates are exceeded. However, low to moderate early season injury to corn may not affect grain yield.

Sweet corn was grown with a living mulch of white clover, a dead mulch of rye, and without mulch, in both till and no-till conditions. Unplanted controls were also included in the experimental design. Corn yields were highest in clover treatments early in the experiment but lowest in later years. The declining yields in the clover living mulch were related to the strip application of glyphosate which allowed establishment of perennial and biennial weeds, notably dandelion and horseweed. These overwintering weeds apparently prevented effective control of summer annuals, especially redroot pigweed, common lambsquarters and large crabgrass, by atrazine and metolachlor. Presence of a rye mulch decreased weed biomass and had no detrimental effect on corn yield. In general, corn yield was not affected by tillage, although the number of marketable ears was reduced in the no-till treatments during the drought year of 1988. The much greater weed biomass in the unplanted control treatments showed the importance of crop competition for weed control in sweet corn cropping systems.

Kikuyugrass was analyzed for nitrate (expressed as KNO3) and soluble oxalate concentration after it was grown for 8 wk in nutrient solution supplemented with KCl, NaCl, or NH4NO3; fertilized in the greenhouse with urea and KNO3 at 112 kg N ha-1; and fertilized in the field in Hawaii and Panama with urea at 56 and 112 kg N ha-1. Both treated and untreated kikuyugrass grown in nutrient solution contained toxic levels of nitrates and soluble oxalates. Plants treated with urea in the greenhouse contained 0.4% nitrate (nontoxic) 72 h after treatment whereas those treated with KNO3 contained 2.36% nitrate (highly toxic). Fertilization of kikuyugrass with urea in Panama and Hawaii did not significantly affect soluble oxalate concentration, but nitrate concentration increased to potentially lethal levels (over 1.5% as KNO3, dry wt) in plants from Hawaii.

Field studies were conducted to determine the most effective rate of several herbicides applied at various growth stages to control downy brome in conservation fallow programs. Downy brome growth stage affected the efficacy of all herbicides. All herbicides were less effective when application was delayed until the boot stage of downy brome. Fluazifop-P and sethoxydim must be applied prior to tillering to effectively control downy brome. Glyphosate, the commercial mixture of glyphosate plus 2,4-D, paraquat, and HOE-39866 consistently controlled downy brome up to the 3- to 5-tiller stage. Glyphosate at 180 to 200 g ha-1, paraquat at 250 to 300 g ha-1, and the commercial mixture of glyphosate plus 2,4-D at 600 to 660 g ha-1 controlled downy brome 80 to 90%. The effective rates were lower than rates currently registered for downy brome control in western Canada, and thus there is potential for making conservation fallow programs more economical when downy brome is the predominant weed.

Carpetgrass is a warm season grass used in the south as low maintenance turf, especially in wet areas where other turf species do not persist. The response of carpetgrass to postemergence (POST) herbicides currently available for turf producers has not been thoroughly investigated and was the objective of four experiments conducted over a 2-yr period. Slight reduction in turf quality followed application of atrazine (2.2 kg ai ha-1), bentazon (2.2 kg ai ha-1), imazaquin (0.4 and 0.6 kg ai ha-1), mecoprop (1.1 kg ai ha-1), triclopyr (0.6 kg ai ha-1), metsulfuron (0.2 kg ai ha-1), 2,4-D (1.1 kg ai ha-1), 2,4-D plus dicamba (0.8 + 0.3 kg ai ha-1), and 2,4-D plus dicamba plus mecoprop (0.9 + 0.1 + 0.5 kg ai ha-1). Marginally acceptable turf quality followed sulfometuron (0.2 kg ai ha-1), sethoxydim (0.3 and 0.6 kg ai ha-1), and diclofop (2.2 kg ai ha-1) treatments. Unacceptable turf quality resulted from asulam (2.2 kg ai ha-1) and MSMA (1.1 and 2.2 kg ai ha-1) treatments. Carpetgrass tolerated most POST broadleaf and sedge herbicides but was sensitive to most POST grass herbicides used in other turf species, with the exception of sethoxydim.

Crambe has gained interest as an alternative crop for industrial oil production. No herbicides are currently registered in crambe and weed control strategies need to be identified if crambe is to become a viable crop. Field experiments were conducted to determine crambe tolerance to several herbicides. Crambe was tolerant to soil-applied trifluralin, pendimethalin, and cinmethylin, or DPX-A7881 applied postemergence. Postemergence applications of chlorimuron or imazethapyr were injurious to crambe.

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.

The effectiveness of soil solarization with black (BPE) and clear polyethylene mulches (CPE), 0.04 and 0.06 mm thick, respectively, was tested during the 1986 to 1990 growing seasons for controlling Egyptian broomrape, hemp broomrape and nodding broomrape in heavily infested fields. Solarization for 6 wk reduced or eliminated broomrape infestation and improved crop yields. The CPE started to show splitting and deterioration after 4 to 5 wk of solarization. The BPE lasted in usable conditions throughout the growing season. Deep soil tillage with the hand hoe, after solarization, caused broomrape to reappear. Crops grew best in plots after solarization with BPE if they were planted through the same mulch after it was perforated. Soil solarization with BPE or CPE in large tomato field trials, completely eliminated both nodding and hemp broomrapes during the growing season. However, greenhouse pot experiments indicated that solarization significantly reduced weed seedling numbers, but did not significantly reduce the dry weights of the broomrape plants that emerged in the soil samples taken from solarized plots.