Multiflora rose is a serious weed pest in West Virginia. There are cultural and chemical means for control, but expense and environmental consequences often preclude their use. Limited information is available concerning biotic agents with potential for multiflora rose biocontrol. A literature search, contacts with scientists in Asia where multiflora rose originated and apparently is not a pest, and disease and insect surveys in West Virginia indicate this plant is healthy and, generally, pest free. However, three insects in West Virginia and one disease occurring in the midwestern United States were of special interest. The rose hip borer, Grapolita packerdi Zeller, which consumes the hypanthium tissues of the hips; the rose seed chalcid, Megastigmus aculeatus var. nigroflavus Hoffmeyer, which destroys the seeds within the achenes; and the raspberry cane borer, Oberea bimaculata Oliv., which kills canes, were found in West Virginia. The disease, rose rosette, not found in West Virginia, is killing multiflora rose in Arkansas, Indiana, Kansas, and Missouri. There is little information on the biology and/or host ranges of these insects or the disease. However, finding three insects in West Virginia adversely affecting growth and/or reproduction of multiflora rose and learning of a disease that kills this plant suggest there are biotic agents that might help manage multiflora rose.

Weed population models can serve as a framework to organize weed biology information and to develop weed control strategies. Models help to identify information gaps, to set research priorities, to develop hypotheses pertinent to weed population regulation, and to suggest control strategies. A population simulation model of leafy spurge (Euphorbia esula L. # EPHES) was used to demonstrate the applicability of population models to weed science. Sensitivity analysis of an existing leafy spurge model indicated that transition from basal buds to vegetative shoots, survival of vegetative shoots, and survival of basal buds over winter were important transition parameters influencing population growth of this weed species. Possible mechanisms (intraspecific competition and environmental factors) that influence the transition from basal buds to vegetative shoots were shown. Intraspecific density effects on basal bud transition and production were included to show model refinement and second-generation model development. Four control strategies were simulated and were compared to field studies to show the predictive and management potential of the modeling approach. Simulations of population response to foliage feeding herbivores was highly correlated (r = 0.98) with field data for sheep grazing on leafy spurge. Simulation of picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) applied to leafy spurge also was correlated (r = 0.97) with field results.

Japanese honeysuckle (Lonicera japonica Thunb. # LONJA) vines can smother young trees, presenting problems in nursery, parkland, and woodlot management. The tardy-deciduous nature of honeysuckle provides an application window for its selective control with glyphosate [N-(phosphonomethyl)-glycine] or dichlorprop [(±)-2-(2,4-dichlorophenoxy)propanoic acid] plus 2,4-D [2,4-dichlorophenoxy)acetic acid] immediately after fall defoliation of hardwood species. Glyphosate at 1.5% v/v (5.4 g ae/L) applied in December killed mature, woody honeysuckle vines and eliminated most regrowth from basal and subterranean buds 28 months after treatment. Dichlorprop plus 2,4-D at 1.5% v/v (3.6 g ae/L of each herbicide), when applied shortly after the first freezing temperatures in October, was as effective as glyphosate but was less effective when applied in December. Tuliptree (Liriodendron tulipifera L.), American beech (Fagus grandifolia Ehrh.), and Scotch pine (Pinus sylvestris L.) suffered minimal and temporary injury from these herbicides.

In field experiments over a 3-yr period, quizalofop {(±)-2-[4-[(6-chloro-2-quinoxalinyl)oxy)phenoxy] propanoic acid} at 100 to 150 g ae/ha effectively controlled several annual grass weeds and volunteer barley (Hordeum vulgare L. # HORVX) in flax (Linum usitatissimum L. ‘Linott’). Quizalofop applied when flax was 10 cm tall generally was more effective on wild oats (Avena fatua L. # AVEFA) and green foxtail [Setaria viridis (L.) Beauv. # SETVI] than when flax was 4 cm tall. Volunteer barley was controlled at both stages of flax growth. Weed interference in untreated plots adversely affected flax quality factors such as seed size, seed weight, percent oil, and iodine value of the oil but not in quizalofop-treated plots.

Field studies were conducted from 1982 to 1984 to evaluate the effectiveness of SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] for quackgrass [Agropyron repens (L.) Beauv. # AGRRE] control. The herbicides were compared 1) in different rates and carrier volumes, 2) on several spring and fall application dates, and 3) with varying time intervals between application and moldboard plowing. Glyphosate and SC-0224 controlled quackgrass equally well at carrier volumes of 25 to 400 L/ha. Both herbicides generally provided similar control as fall and spring applications and with time intervals of 12 to 96 h between application and plowing. Occasionally the low rate of SC-0024 gave less quackgrass control the next season than the same rate of glyphosate. Adding nonionic surfactant at 0.5% (v/v) did not influence the phytotoxicity of these herbicides at the rates and carrier volumes tested. These herbicides controlled quackgrass comparably and greater than 85% when applied under appropriate environmental conditions.

The effects of rainfall on the efficacy of 11 foliar-applied herbicides were evaluated for their control of seedling johnsongrass [Sorghum halepense (L.) Pers. # SORHA] in greenhouse experiments during 1984 and 1985 at Stoneville, MS. Time intervals between herbicide application and rainfall (at 1.27 cm in 10 ± 0.5 min) ranged from 5 to 60 and 30 to 240 min depending on herbicide classification. In general, the phosphonic acid herbicides glyphosate [N-(phosphonomethyl)glycine] and SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) at 0.99 kg ai/ha required rain-free periods ≥240 min to control seedling johnsongrass effectively. The selective postemergence grass herbicides generally required ≥60 min to control seedling johnsongrass effectively when control without rainfall was ≥85%. Among the selective herbicides tested, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoic acid} and DPX-Y6202 {ethyl[2-[4-(6-chloro-2-quinoxalinyl)oxy] phenoxy] propionic acid} at 0.06 kg ae/ha required the shortest time between herbicide application and rainfall to be effective. As herbicide rates were reduced, the effects of rainfall increased.

A technique based on the relationship between leaf area index (LAI) and the transmittance of direct sunlight was developed for the in situ study of competition for light between plant species. Field studies were conducted in 1984 and 1985 using monocultures and mixtures of rapeseed (Brassica napus L.), wild mustard (Sinapis arvensis L. # SINAR), and common lambsquarters (Chenopodium album L. # CHEAL). LAI estimated nondestructively by this method agreed closely with LAI determined by conventional destructive techniques. Light measurements at several heights in the canopy were used to determine the vertical distribution of canopy leaf area. Combining this information with species heights allowed the separation of the canopy LAI into individual species LAI, from which light competition could be estimated by calculating the sunlit LAI of each species. The technique permits many detailed measurements in the same canopy throughout the growing season. The light sensor required is not costly and is simple to operate and to maintain.

In a 3-y field study, the isopropylamine salt of glyphosate [N-(phosphonomethyl)glycine] at 1.7 kg ai/ha and sulphosate [trimethyl sulfonium salt of N-(phosphonomethyl)glycine] at three rates, a split application of 0.6 + 0.6 or single applications of 1.1 or 1.7 kg ai/ha satisfactorily controlled swamp dodder (Cuscuta gronovii Willd. ex R. & S. # CVCGR) in cranberry (Vaccinium macrocarpon Ait.). While none of these treatments decreased cranberry yield, sulphosate at 1.1 or 1.7 kg/ha did increase yield. Glyphosate at 0.4 kg/ha applied late in the life cycle of carrot (Daucus carota L.) when swamp dodder was in full flower satisfactorily controlled swamp dodder while increasing yield of carrot roots. Glyphosate applied early in the life cycle of carrot and dodder controlled swamp dodder but lowered yield of carrot roots.

Backcross-derived isolines of soybean [Glycine max (L.) Merr.] cultivars with and without the Rps1-k gene for resistance to Phytophthora rot (Pythopthora megasperma f. sp. glycinea) were grown in hydroponic culture with and without metribuzin [4-amino-6-(1,1-dimethylethyl)-3-3(methylthio)-1,2,4-triazin-5(4H)-one] added at 0.15 mg L−1. A marked tolerance to metribuzin was associated with Rps1-k possibly from an allele at the Hm/hm locus which is known to be linked closely with the Rps1 locus. This improved tolerance could reduce the occurrence of injury from metribuzin applications.

Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was evaluated as a pretreatment for eastern redcedar (Juniperus virginiana L. # IUPVI) before spring burning in tallgrass prairie. Wetting sprays of paraquat at 0.3 g ai/L or 0.6 g/L were applied to crowns of small (0.8 to 1.5 m), medium (1.5 to 2.5 m), and large (2.5 to 5.0 m) eastern redcedar trees in August 1983 and 1984 before prescribed burns in the springs of 1984 and 1985. Paraquat alone at the 0.6 g/L concentration killed about 90% of the crown of small trees but as little as 30% of the crown of large trees. Paraquat pretreatments increased post-fire damage to small- and medium-size trees and partially compensated for light fine fuel loading.

Desmedipham applied at 0.5 kg ai/ha at the 4-leaf stage of common buckwheat controlled wild mustard over 90%. Desmedipham at 1.0 kg/ha at the 2- and 6-leaf stages also controlled wild mustard approximately 90%, at least in 1985, but significantly injured the crop. Fluorochloridone controlled wild mustard over 90% when applied preplant incorporated at 1.0 kg ai/ha or preemergence at 0.28 to 0.56 kg/ha. Fluorochloridone applied postemergence at 0.10 to 0.20 kg/ha also controlled wild mustard over 90% but injured common buckwheat by 41 to 57%.

Field studies were conducted in 1985 and 1986 to determine the influence of herbicide rate, carrier, and carrier volume on off-site movement of clomazone {2-[2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxalidinone} using sunflower (Helianthus annuus L. ‘HY-894’) and wheat (Triticum aestivum L. ‘Caldwell’) as indicator plants. Clomazone applied at the lowest rate (0.56 kg ai/ha) had less off-site movement than higher rates. Off-site movement was similar among water carrier volumes applied at each clomazone rate but was less when clomazone was impregnated onto dry fertilizer.

Canada thistle [Cirsium arvense [L.] Scop. # CIRAR] is a major weed problem in birdsfoot trefoil (Lotus corniculatus L. ‘Norcen’) seed production in northern Minnesota. Several systemic herbicides applied with selective applicators (roller and ropewick) were evaluated for Canada thistle control in birdsfoot trefoil. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), and glyphosate [N-(phosphonomethyl)glycine] controlled Canada thistle better than MCPA [(4-chloro-2-methylphenoxy)acetic acid] and dicamba (3,6-dichloro-2-methoxybenzoic acid). Glyphosate and MCPA did not injure birdsfoot trefoil foliage or bloom, whereas, picloram, clopyralid, and dicamba injured both. Although selective applications of glyphosate controlled Canada thistle for a short term with the least birdsfoot trefoil injury, long-term Canada thistle control in birdsfoot trefoil does not appear feasible with selective herbicide applications.

Sicklepod control with one or two cultivations or postemergence (POE) directed-spray applications of linuron or metribuzin plus 2,4-DB was less than 50% in August evaluations when no soil-applied herbicide had been used. However, sicklepod control greater than 75% was noted through August when two cultivations or metribuzin plus 2,4-DB applied POE followed either metribuzin applied preplant incorporated (PPI) and preemergence (PRE) or metribuzin plus alachlor applied as a PRE treatment. One cultivation after these soil-applied herbicide treatments did not reduce sicklepod populations compared to the chemical treatments alone. Soybean yields more than doubled over yields in untreated plots when a combination of soil-applied herbicides and two cultivations or metribuzin plus 2,4-DB applied POE were used.

Third-year heights, third-year root-collar diameters, and 3 yr volume growth of loblolly pine seedlings were examined in relation to a) root-collar diameter class at time of planting and b) herbaceous weed control. Treatments were a) no weed control and b) complete control for 2 yr. For both weed control treatments, means for third-year heights, groundline diameters, and volume growth were related positively to initial seedling diameter. The influence of initial seedling diameter on third-year diameters and heights did not differ among weed control treatments. However, the influence of initial diameter on volume growth did differ among weed control treatments. Thus, when using herbaceous weed control, additional gains in early volume growth can be realized by planting seedlings with large root-collar diameters.

Residents in Stillwater County, MT, used a weed bounty program as an educational tool to promote awareness, detection, and control of spotted knapweed (Centaurea maculosa Lam. # CENMA) on range and noncropland. Many people became involved with the weed control effort, weed awareness was increased, spotted knapweed was controlled, and the program was cost effective. The success of a weed bounty program is influenced by 1) the enthusiasm and innovations of the county extension agent, weed supervisor, or other key individual or group in the community; 2) the choice of the weeds selected; and 3) good media coverage of the bounty program. With proper planning and organization, weed bounty programs effectively promote awareness and action in other areas of public concern.

Agriprofessionals and technical college students took an examination without and with simple dichotomous keys. Without keys, only 15% and 30% of the agriprofessionals identified 71% or more of the grass and morningglory species (Ipomoea spp. # IPOZZ), respectively; 97% scored in this range for both weed groups with keys. Without keys, no student scored higher than 40% or 30% on grass and morningglory species, respectively. With keys, all students identified more than 60% and 50% of the grasses and morningglories, respectively. For grasses, only 3% of the agriprofessionals and none of the students achieved an excellent (>90%) score without keys, while 56% and 8% did with keys. Twelve percent and 65% of the agriprofessionals achieved an excellent score on the morningglory species without and with keys, respectively; 42% of the students scored higher than 80% with keys.

Potential herbicide loadings to groundwater are determined by soil, chemical, management, and climatic factors. Several simple assessment procedures to rank pesticides according to their potential impact on groundwater are available. Most of these procedures are not specific to any climatic region, cropping practice, or soil. Using a continuous simulation model, GLEAMS (Groundwater Loading Effects of Agricultural Management Systems), to assess potential herbicide leaching allows more condition-specific assessment. Simple relationships for relative comparisons in a specific soil/climatic setting were developed by relating simulated 50-yr mean leaching losses to the herbicide half-life/Koc ratio. Other criteria of herbicide leaching potential such as 50-yr maxima or other values based on probability distributions could be used. Although differences in soils were demonstrated in this exercise, the same procedures could be applied to different management systems.