Joseph C. Neal

Response of Japanese Stiltgrass (Microstegium vimineum) to Application Timing, Rate, and Frequency of Postemergence Herbicides1

Japanese stiltgrass is a nonnative invasive grass that occurs in a variety of habitats and is widely distributed throughout the eastern United States. In natural areas such as forests, herbicide options that selectively control Japanese stiltgrass while preserving native herbaceous and woody vegetation may be desired. The efficacy of three selective postemergence herbicides (fenoxaprop-P, imazapic, and sethoxydim) applied early season, midseason, or late season on monoculture understory stands of Japanese stiltgrass in forests was examined in an experiment conducted at a site in North Carolina and a site in Virginia from 2002 to 2004. The herbicides, averaged across application timings, controlled Japanese stiltgrass at the end of the growing season 83 to 89% and seedhead production 79 to 94% compared with nontreated plants. Seedling emergence was reduced in the spring of 2004 by 89, 70, and 78% by fenoxaprop-P, imazapic, and sethoxydim, respectively, applied in 2003. In another experiment at the North Carolina site in 2002 and 2003, fenoxaprop-P or sethoxydim applied twice (4 wk apart) at half-registered rates controlled Japanese stiltgrass. This study demonstrates that land managers have multiple POST herbicide and application timing, rate, and frequency options for Japanese stiltgrass control. Nomenclature: Fenoxaprop-P; imazapic; sethoxydim; Japanese stiltgrass, Microstegium vimineum (Trin.) A. Camus #3 MCGVM. Additional index words: Invasive plant, annual jewgrass, bamboograss, flexible sesagrass, Japanese grass, Marys grass, Nepalese browntop. Abbreviations: 1X, maximum use rate.

Preemergence and Postemergence Control of Japanese Stiltgrass (Microstegium vimineum)1

Preemergence (PRE) and postemergence (POST) herbicides registered for large crabgrass control were evaluated for control of Japanese stiltgrass, an invasive, nonnative C4 annual grass. Benefin plus oryzalin, dithiopyr, isoxaben plus trifluralin, oryzalin, oxadiazon, pendimethalin, prodiamine, or trifluralin applied PRE controlled Japanese stiltgrass 87% or greater 8 wk after treatment. Benefin plus trifluralin, metolachlor, or napropamide applied PRE were less effective (78, 39, and 59% control, respectively). Single POST applications of clethodim, fenoxaprop-P, fluazifop-P, or sethoxydim controlled Japanese stiltgrass 50 to 88%. These herbicides applied twice provided 82 to 99% control. Single POST applications of glufosinate controlled Japanese stiltgrass 82 to 85%, whereas two applications provided complete control. Single POST applications of glyphosate were just as effective as two applications in controlling Japanese stiltgrass. Dithiopyr, MSMA, and quinclorac applied POST were ineffective on Japanese stiltgrass. All PRE and POST herbicides tested were equally or more effective on Japanese stiltgrass than on large crabgrass, with the exception of metolachlor applied PRE and dithiopyr or quinclorac applied POST. Nomenclature: Benefin; clethodim; dithiopyr; fenoxaprop-P; fluazifop-P; glufosinate; glyphosate; isoxaben; metolachlor; MSMA; napropamide; oryzalin; oxadiazon; pendimethalin; prodiamine; quinclorac; sethoxydim; trifluralin; Japanese stiltgrass, Microstegium vimineum (Trin.) A. Camus #3 MCGVM; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA. Additional index words: Annual jewgrass, bamboograss, flexible sesagrass, invasive plant, Japanese grass, Marys grass, Nepalese browntop. Abbreviations: DAT, days after treatment; POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

3,7-Dichloroquinolinecarboxylic Acid Inhibits Cell-Wall Biosynthesis in Maize Roots

The mode of action of the herbicide 3,7-dichloroquinolinecar-boxylic acid (quinclorac) was examined by measuring incorporation of [14C]glucose, [14C]acetate, [3H]thymidine, and [3H]uridine into maize (Zea mays) root cell walls, fatty acids, DNA, and RNA, respectively. Among the precursors examined, 10 [mu]M quinclorac inhibited [14C]glucose incorporation into the cell wall within 3 h. Fatty acid and DNA biosynthesis were subsequently inhibited, whereas RNA biosynthesis was unaffected. In contrast to the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile, quinclorac strongly inhibited cellulose and a hemicellulose fraction presumed to be glucuronoarabinoxylan. However, the synthesis of (1–>3),(1–>4)-[beta]-D-glucans was only slightly inhibited. The degree of inhibition was time- and dose-dependent. By 4 h after treatment, the concentration that inhibited [14C]glucose incorporation into the cell wall, cellulose, and the sensitive hemicellulose fraction by 50% was about 15, 5, and 20 [mu]M, respectively. Concomitant with an inhibition of [14C]glucose incorporation into the cell wall, quinclorac treatment led to a marked accumulation of radioactivity in the cytosol. The increased radioactivity was found mostly in glucose and fructose. However, total levels of glucose, fructose, and uridine diphosphate-glucose were not changed greatly by quinclorac. These data suggest that quinclorac acts primarily as a cell-wall biosynthesis inhibitor in a susceptible grass by a mechanism that is different from that of 2,6-dichlorobenzonitrile.

A Survey of Weed Scientists' Perceptions on the Significance of Crabgrasses (Digitaria spp.) in the United States1

A survey was conducted to document the significance of crabgrass species among cropping systems and geographical regions in the continental United States. Surveys were mailed to 117 weed scientists, at least one in each state, including, where possible, extension weed scientists with responsibilities in each of the major agronomic and horticultural crops plus turfgrass systems. A 62% response rate was achieved. Large, smooth, and southern crabgrasses were considered at least occasionally important, with India and blanket crabgrasses considered rarely or not important. Smooth crabgrass and large crabgrass were considered to be important species in most of the latitudinal range, whereas southern crabgrass was considered to be important only in the southern states. Crabgrasses were considered to be more problematic in turf than in other cropping systems. From a regional perspective in turf, large crabgrass was the most important species in the Southeast, followed by southern crabgrass and smooth crabgrass. In the Northeast, smooth crabgrass was perceived as the more important species, but large crabgrass was more important in the north-central states. Nomenclature: Blanket crabgrass, Digitaria serotina (Walt.) Michx. #3 DIGSO; crabgrass, Digitaria spp.; India crabgrass, Digitaria longiflora (Retz.) Pers. # DIGLO; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; smooth crabgrass, Digitaria ischaemum (Schreb.) Muhl. # DIGIS; southern crabgrass, Digitaria ciliaris (Retz.) Koel. # DIGSP. Additional index words: Geographic distribution, turfgrass.

Japanese Stiltgrass (Microstegium vimineum) Management for Restoration of Native Plant Communities

Abstract Japanese stiltgrass is a nonnative invasive grass occupying a range of habitats in the eastern United States. Conventional management recommendations include hand-removal, mowing, or a nonselective herbicide application in autumn prior to flowering. However, no study has directly compared the ecological impacts of long-term management strategies on Japanese stiltgrass populations or recruitment and establishment of native flora. An experiment was initiated in 2002 and continued for three growing seasons in mixed pine-hardwood forests in central North Carolina. Conventional treatments included hand-removal, mowing, or an application of glyphosate (1.1 kg ai/ha) once in autumn, and selective removal by hand or fenoxaprop-P (0.19 kg ai/ha) season-long as needed. All treatments were compared to nontreated plots. Percent vegetation cover by species was recorded twice annually. Data were aggregated into five classes; Japanese stiltgrass, other exotic plants, native forbs, native monocots, and native woody plants. The soil seed bank of all species was estimated annually by extracting soil cores and documenting seedling emergence. All Japanese stiltgrass management treatments significantly reduced Japanese stiltgrass cover and seed bank over time compared to no management. However, recruitment and reestablishment of native plants and overall species richness were greater with selective Japanese stiltgrass management treatments including both hand-removal and fenoxaprop-P. Relative cover of other exotic plants decreased 2% to 49% after 3 yr with all Japanese stiltgrass management treatments except season-long hand-removal, which increased relative cover of other exotic plants 51%. Nomenclature: Japanese stiltgrass, Microstegium vimineum (Trin.) A. Camus MCGVM.

Control of Silvery-Thread Moss (Bryum argenteum Hedw.) in Creeping Bentgrass (Agrostis palustris Huds.) Putting Greens1

Field experiments were conducted to evaluate chemicals for silvery-thread moss control and bentgrass turfgrass quality. Treatments included iron (Fe)-containing products, nitrogen fertilizers, Ultra Dawn dishwashing detergent (UD) at 3% (v/v), and oxadiazon. In general, greater silvery-thread moss control was achieved with Fe-containing products. Ferrous sulfate at 40 kg Fe/ha plus ammonium sulfate at 30 kg N/ha, a combined product of ferrous oxide, ferrous sulfate, and iron humates (FEOSH) at 125 kg Fe/ha, and a combined product of iron disulfide and ferrous sulfate (FEDS) at 112 kg Fe/ha reduced silvery-thread moss populations 87, 81, and 69%, respectively, 6 wk after initial treatment (WAIT). UD reduced silvery-thread moss populations 57% 6 WAIT. The addition of oxadiazon to Fe-containing treatments did not improve silvery-thread moss population reduction. Other experiments evaluated two formulations of chlorothalonil, each applied at two rates, chlorothalonil with zinc at 9.5 and 17.4 kg ai/ha and chlorothalonil without zinc at 9.1 and 18.2 kg/ ha, and two spray volumes (2,038 and 4,076 L/ha). Greater silvery-thread moss population reduction was observed at Jefferson Landing in 1999 compared with Elk River in 1999 and 2000. Rainfall events at Elk River in 1999 and 2000 within 24 h after application and no rain at Jefferson Landing may account for variation in performance of products between sites. However, no difference in chlorothalonil formulation, rate, or spray volume was observed in any location or year. These data indicate that Fe-containing fertilizers or chlorothalonil can be used to reduce silvery-thread moss populations in creeping bentgrass putting greens. Nomenclature: Chlorothalonil, tetrachloroisophthalonitrile; oxadiazon; silvery-thread moss, Bryum argenteum Hedw.; creeping bentgrass, Agrostis palustris Huds. ‘Penncross’. Additional index words: Bryology, moss control, turfgrass injury. Abbreviations: BM, Black Mountain Golf Club; ER, Elk River Country Club; JL, Jefferson Landing Golf Club; MNP, micronutrient package; NPK, 20:20:20 nitrogen–phosphorus–potassium; UD, Ultra Dawn dishwashing detergent; WAIT, weeks after initial treatment.

Light, Temperature, Seed Burial, and Mulch Effects on Mulberry Weed (Fatoua villosa) Seed Germination'

Fatoua villosa (mulberry weed) is a new and invasive weed of container nurseries and landscapes in the southeastern United States. Studies were conducted to determine the effects of light, planting depth, mulch depth, and temperature on mulberry weed seed germination and seedling emergence. Light stimulated mulberry weed seed germination, with less than 5% of seeds germinating in the dark compared with 48 to 60% germinating in the light. In all emergence studies, the highest number of seedlings emerged when seeds were placed on the soil surface, with emergence decreasing as planting or mulch depth increased. Planting depths of ≥ 1.8 cm or mulch depths of ≥ 3.7 cm reduced mulberry weed emergence by ≥ 90%. These data suggest that mulch would control mulberry weed effectively. To study the effects of temperature on germination, two seed batches collected locally in October 1998 and August 1999 were used. Maximum germination of seeds collected in 1998 occurred at 25 C, with germination decreasing at higher temperatures and no germination at lower than 15 C or over 40 C. For seeds collected in 1999, maximum germination occurred from 19 to 29 C, with germination decreasing with temperatures above 29 C or below 19 C. At temperatures of 15 and 42 C germination, percentages were 71 and 11%, respectively. Seedlings germinated at 15 C developed slowly but otherwise appeared normal. For both seed lots, seedlings were stunted and chlorotic at ≥ 38 C. That mulberry weed seed germinated over a wide range of temperatures suggests its potential to emerge throughout most of spring, summer, and autumn in the southeastern United States. Nomenclature: Mulberry weed, Fatoua villosa (Thunb.) Nakai. Additional index words: Germination, light, mulch, planting depth, temperature.

Stakeholder Vision of Future Direction and Strategies for Southeastern U.S. Nursery Pest Research and Extension Programming

Extension and research professionals worked with a focus group of 10 nursery owners and managers across a five-state region (Georgia, Kentucky, North Carolina, South Carolina, Tennessee) in the southeastern United States to prioritize diverse nursery pests and production issues that are related to container and field production. A second focus group meeting, focused on technology, was followed by a survey that asked nursery growers to prioritize potential inputs and uses of information technology and the features they most valued, for example, that might be included within a nursery-specific mobile device application. The resulting prioritization highlights common challenges faced by growers across the southeastern United States in managing major plant diseases, arthropod pests, and weeds; as well as documenting emerging critical issues of nonpest related production issues, regulatory constraints, and technological needs. The focus group and survey format effectively identified grower needs that will help inform nursery producers and guide university Extension and research professionals, university administrators, industry associations, and state and federal government officials toward efficient resource allocation. These prioritizations explain the current state-of-need across a diverse agricultural industry segment and will help further refine future strategic action plans for nursery integrated pest management (IPM) and emerging critical nursery crop pest issues.

Assessing the integrated pest management practices of southeastern US ornamental nursery operations

BACKGROUND The Southern Nursery Integrated Pest Management (SNIPM) working group surveyed ornamental nursery crop growers in the southeastern United States to determine their pest management practices. Respondents answered questions about monitoring practices for insects, diseases and weeds, prevention techniques, intervention decisions, concerns about IPM and educational opportunities. Survey respondents were categorized into three groups based on IPM knowledge and pest management practices adopted. RESULTS The three groups differed in the use of standardized sampling plans for scouting pests, in monitoring techniques, e.g. sticky cards, phenology and growing degree days, in record-keeping, in the use of spot-spraying and in the number of samples sent to a diagnostic clinic for identification and management recommendation. CONCLUSIONS Stronger emphasis is needed on deliberate scouting techniques and tools to monitor pest populations to provide earlier pest detection and greater flexibility of management options. Most respondents thought that IPM was effective and beneficial for both the environment and employees, but had concerns about the ability of natural enemies to control insect pests, and about the availability and effectiveness of alternatives to chemical controls. Research and field demonstration is needed for selecting appropriate natural enemies for augmentative biological control. Two groups utilized cooperative extension almost exclusively, which would be an avenue for educating those respondents.

On the Identity of the Weedy Bittercresses (Cardamine : Brassicaceae) in United States Nurseries: Evidence from Molecules and Morphology

Bittercress (Brassicaceae) is one of the most prolific and costly weeds of the container nursery industry. Bittercress accessions from container nurseries throughout the major production zones in the United States were examined and compared with herbarium specimens. The identity of these weedy bittercress species were further explored using sequences of the nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) region and the nrDNA region for the COP1-interacting protein 7 (CIP7). Four species of bittercress were detected in the nursery industry of the United States, including New Zealand bittercress, hairy bittercress, flexuous bittercress, and little bittercress. The taxon referred to here as Cardamine flexuosa With. (flexuous bittercress) likely contains two genotypes previously reported as European C. flexuosa and Asian C. flexuosa. Phylogenetic relationships between the four species we examined, particularly in relationship to flexuous bittercress, were not fully resolved by the molecular evidence generated for this study. New Zealand bittercress is nonnative and does not appear in current keys to the species for the United States. Flexuous bittercress is also an alien species, which appears in some U.S. keys but not in all. To aid nurserymen and botanists in identification of these four closely related bittercress species, a key was developed and is accompanied by detailed descriptions and illustrations. Nomenclature Flexuous bittercress, Cardamine flexuosa With. CARFL; hairy bittercress, Cardamine hirsuta L. CARHI; Japanese bittercress, Cardamine scutata Thunb. CARSC; little bittercress, Cardamine oligosperma Nutt. CAROL; New Zealand bittercress, Cardamine corymbosa Hook f.