Polygonum Pensylvanicum Research Articles

Effects of soil water on seed production and photosynthesis of pink smartweed (Polygonum pensylvanicum L.) in playa wetlands

Soil moisture is frequently manipulated by wetland managers to achieve a desired composition and production of plant species. Pink smartweed (Polygonum pensylvanicum) is a species valued by wetland managers because of its potential seed production and food base for migrating and wintering waterbirds. To improve ability to manage pink smartweed, we measured the influence of four growing-season soil moisture regimes (flooded, field capacity, prescribed moist-soil management, and continuously dry) in playa wetlands of the Southern High Plains of Texas. We used xylem water potential as an index of soil moisture available to the plants and compared vegetation and seed production among the four moisture treatments. Daily net photosynthesis was measured in each playa at 0900, 1200, and 1700 hours. The continuously-flooded wetland had the lowest absolute xylem water potential value (−0.294 MPa), followed by the playa at field capacity (−0.446 MPa), moist-soil managed playa (−0.758 MPa), and dry playa (−1.039 MPa). Vegetation biomass (F3,40 = 97.7, P < 0.001) and seed production (F3,40 = 54.3, P < 0.001) of pink smartweed differed among soil moisture treatments. Conducting moist-soil management (x = 6816 kg/ha) increased vegetation biomass by 44% over the dry treatment (x = 4706 kg/ha). As soil moisture increased to field capacity (x = 9010 kg/ha) vegetation increased by 32% above the moist-soil treatment. Maintaining standing water in a playa maximized vegetation production (x = 12497 kg/ha) of pink smartweed. Seed production was greatest when soil moisture was maintained at field capacity (x = 695 kg/ha). There was no difference in seed production between the moist-soil managed (x = 492 kg/ha) and flooded playas (x = 514 kg/ha), which was 28% lower than the field capacity treatment. Seed production in the dry treatment (x = 377 kg/ha) was 46% lower than the field capacity treatment and 25% below the flooded and moist-soil managed treatments. Net photosynthesis and xylem water potential decreased throughout the day in all treatments except continuously flooded, which corresponded to the increased vegetation production in this treatment. Slight increases in water stress relative to the continuously flooded treatment resulted in a redistribution of resources from vegetation to seed production. Managers should consider maintaining wetland soils at field capacity to increase seed production of pink smartweed.

Summer Weeds as Hosts for Frankliniella occidentalis and Frankliniella fusca (Thysanoptera: Thripidae) and as Reservoirs for Tomato Spotted Wilt Tospovirus in North Carolina

In North Carolina, Tomato spotted wilt tospovirus (family Bunyaviridae, genus Tospovirus, TSWV) is vectored primarily by the tobacco thrips, Frankliniella fusca (Hinds), and the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). TSWV overwinters in winter annual weeds from which it is spread to susceptible crops in spring. Because most susceptible crops are destroyed after harvest before winter weeds emerge in the fall, infected summer weeds are thought to be the principal source for spread of TSWV to winter annual weeds in fall. A survey of summer weeds associated with TSWV-susceptible crops in the coastal plain of North Carolina conducted between May and October revealed that relatively few species were commonly infected with TSWV and supported populations of F. fusca or F. occidentalis. F. occidentalis made up > 75% of vector species collected from 15 summer weed species during 2002. The number of F. occidentalis and F. fusca immatures collected from plant samples varied significantly among plant species. Ipomoea purpurea (L.) Roth, Mollugo verticillata L., Cassia obtusifolia L., and Amaranthus palmeri S. Wats supported the largest numbers of immature F. occidentalis. Richardia scabra L., M. verticillata, and Ipomoea hederacea (L.) supported the largest numbers of F. fusca immatures. TSWV was present at 16 of 17 locations, and naturally occurring infections were found in 14 of 29 weed species tested. Five of the TSWV-infected species have not previously been reported as hosts of TSWV (A. palmeri, Solidago altissima L., Ipomoea lacunosa L., I. purpurea, and Phytolacca americana L.). Estimated rates of infection were highest in I. purpurea (6.8%), M. verticillata (5.3%), and I. hederacea (1.9%). When both the incidence of infection by TSWV and the populations of F. occidentalis and F. fusca associated with each weed species are considered, the following summer weed species have the potential to act as significant sources for spread of TSWV to winter annual weeds in fall: I. purpurea, I. hederacea, M. verticillata, A. palmeri, C. obtusifolia, R. scabra, Ambrosia artemisiifolia L., Polygonum pensylvanicum L., and Chenopodium album L.

Evaluation of Corn (Zea mays L.) Yield-loss Estimations by WeedSOFT® in the North Central Region1

Field studies were conducted in 2000 and 2001 to evaluate corn yield-loss predictions generated by WeedSOFT, a computerized weed management decision aid. Conventional tillage practices were used to produce corn in 76-cm rows in Illinois, Indiana, Kansas, Michigan, Missouri, Nebraska, and Wisconsin. A total of 21 site-years from these seven states were evaluated in this study. At 4 wk after planting, weed densities and size, crop-growth stage, estimated weed-free yield, and environmental conditions at the time of application were entered into WeedSOFT to generate POST treatments ranked by percent maximum yield (PMY). POST treatments were chosen with yield losses ranging from 0 to 20%. Data were subjected to linear regression analysis by state and pooled over all states to determine the relationship between actual and predicted yield loss. A slope value equal to one implies perfect agreement between actual and predicted yield loss. Slope value estimates for Illinois and Missouri were equal to one. Actual yield losses were higher than the software predicted in Kansas and lower than predicted in Michigan, Nebraska, and Wisconsin. Slope value estimate from a data set containing all site years was equal to one. This research demonstrated that variability in yield-loss predictions occurred at sites that contained a high density of a single weed specie (>100/m2) regardless of its competitive index (CI); at sites with a predominant broadleaf weed with a CI greater than five, such as Palmer amaranth, giant ragweed, common sunflower, and common cocklebur; and at sites that experience moderate to severe drought stress.Nomenclature: common cocklebur, Xanthium strumarium L. #3 XANST; common lambsquarters, Chenopodium album L. # CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; common sunflower, Helianthus annuus L. # HELAN; common waterhemp, Amaranthus rudis Sauer. # AMATA; corn, Zea mays L. # ZEAMX; eastern black nightshade, Solanum ptycanthum Dun. # SOLPT; green foxtail, Setaria viridis (L.) Beauv. # SETVI; giant foxtail, Setaria faberi Herrm. # SETFA; giant ragweed, Ambrosia trifida L. # AMBTR; fall panicum, Panicum dichotomiflorum Michx. # PANDI; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; morningglory spp., Ipomoea spp. # IPOSS; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; Pennsylvania smartweed, Polygonum pensylvanicum L. # POLPY; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; redroot pigweed, Amaranthus retroflexus L. # AMARE; velvetleaf, Abutilon theophrasti Medicus # ABUTH; Venice mallow, Hibiscus trionum L. # HIBTR.Additional index words: Bioeconomic model, decision support system, herbicide decision aid.Abbreviations: CI, competitive index; DSS, decision support system; HPMY, highest percent maximum yield; PMY, percent maximum yield; TCL, total competitive load.

Incorporating Foramsulfuron into Annual Weed Control Systems for Corn1

Field studies were conducted in 2000, 2001, and 2002 at Brownstown, DeKalb, Perry, and Urbana, IL, to evaluate weed control and corn tolerance from postemergence (POST) applications of foramsulfuron in sequential and total-POST herbicide programs. Foramsulfuron applied alone controlled giant foxtail, fall panicum, and redroot pigweed 88, 99, and 99%, respectively, 28 d after treatment (DAT), which was comparable with the standard treatment of nicosulfuron. However, control of common cocklebur, velvetleaf, and common lambsquarters was significantly higher with foramsulfuron compared with nicosulfuron. Sequential herbicide programs of atrazine, S-metolachlor, or isoxaflutole applied preemergence (PRE) followed by a POST application of foramsulfuron provided greater than 85% control of giant foxtail, fall panicum, common cocklebur, velvetleaf, common waterhemp, and redroot pigweed. Of the sequential herbicide treatments, atrazine applied PRE followed by a POST application of foramsulfuron provided the greatest Pennsylvania smartweed control. A PRE application of either atrazine or isoxaflutole was needed before a POST application of foramsulfuron to control common lambsquarters. POST tank mixtures of foramsulfuron with atrazine, dicamba, and dicamba plus diflufenzopyr improved control of Pennsylvania smartweed, common cocklebur, velvetleaf, common lambsquarters, and common waterhemp when compared with foramsulfuron applied alone. The tank mixture of foramsulfuron with mesotrione improved control of all species, except Pennsylvania smartweed, common lambsquarters, and common cocklebur. Foramsulfuron tank mixtures with carfentrazone did not improve control of any weed species to commercial acceptance. Adjuvant selection was important for POST tank mixtures. Control of giant foxtail and fall panicum was reduced when atrazine was tank mixed with foramsulfuron and crop oil concentrate (COC). However, when methylated seed oil (MSO) was added to the atrazine–foramsulfuron tank mixture instead of COC, giant foxtail and fall panicum control were similar to foramsulfuron applied alone.Nomenclature: Atrazine; carfentrazone; dicamba; diflufenzopyr, 2-[1-[[[(3,5-difluorophenyl)amino]carbonyl]hydrazono]ethyl]-3-pyridinecarboxylic acid; foramsulfuron, 2-[[[[(4,6-dimethoxy-2-pyrimidiny)amino]carbonyl]amino]sulfonyl]-4-(formylamino)-N,N-dimethylbenzamide; isoxaflutole; mesotrione; S-metolachlor; common cocklebur, Xanthium strumarium L. #3 XANST; common lambsquarters, Chenopodium album L. # CHEAL; common waterhemp, Amaranthus rudis Sauer. # AMATA; fall panicum, Panicum dichotomiflorum Michx. # PANDI; giant foxtail, Setaria faberi Herm. # SETFA; Pennsylvania smartweed, Polygonum pennsylvanicum L. # POLPY; redroot pigweed, Amaranthus retroflexus L. # AMARE; velvetleaf, Abutilon theophrasti Medicus # ABUTH; corn, Zea mays L.Additional index words: Antagonism, tank mixture, total-POST.Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); COC, crop oil concentrate; DAT, days after treatment; MSO, methylated seed oil; NIS, nonionic surfactant; POST, postemergence; PRE, preemergence; UAN, urea ammonium nitrate.

Survey of Winter Wheat (Triticum aestivum) Stubble Fields Sprayed with Herbicides in 1998: Cultural Practices1

A survey of 174 fields was conducted during August and September of 1998 to investigate effects of cultural and herbicide practices on postharvest weed control in winter wheat stubble fields across western and southern Nebraska. Seventy-four percent of the fields were seeded at rates of 67 to 100 kg/ha, with 60% of the wheat seeded in rows spaced 25 cm apart. Wheat seeded in east–west rows contained 98% more stinkgrass and 82% more tumble pigweed than wheat seeded in north–south rows. Sixty-nine percent of winter wheat stubble fields were rated excellent for weed control. Postharvest weed control with herbicides was not affected by row spacing. In western Nebraska, density of tumble pigweed and Russian thistle was greater when wheat seeding rate was 50 kg/ha than at higher seeding rates. Short-stature winter wheat cultivars had greater densities of Pennsylvania smartweed and toothed spurge than taller cultivars. The most common winter wheat cultivars were ‘Arapahoe’ (34%) and ‘Alliance’ (17%). Weed control was positively correlated with number of winter wheat stems per square meter (r = 0.22**). Density of several weed species was greater in fields seeded with a disk than with a hoe drill. The most common crop rotations sampled were winter wheat–corn–fallow (50%), winter wheat–fallow (18%), and winter wheat–corn–soybean (13%). Winter wheat yields and wheat stem densities were greater and weed density was less when winter wheat was seeded after an 11- to 14-mo fallow period rather than a 0- to 5-mo period.Nomenclature: Green foxtail, Setaria viridis (L.) Beauv. #3 SETVI; kochia, Kochia scoparia (L.) Schrad. # KCHSC; Pennsylvania smartweed, Polygoncum pensylvanicum P. # POLPY; Russian thistle, Salsola iberica Sennen & Pau # SASKR; stinkgrass, Eragrostis cilianensis (All.) E. Mosher # ERACN; toothed spurge, Euphorbia dentata Michx. # EPHDE; tumble pigweed, Amaranthus albus L. # AMAAL; corn, Zea mays L.; soybean, Glycine max (L.) Merr.; winter wheat, Triticum aestivum L.Additional index words: Atrazine, crop rotations, ecofallow, ecofarming, glyphosate, no-till, weed management.Abbreviations: W–C or Sor, winter wheat–corn or sorghum; W–C–F, winter wheat–corn–fallow; W–C–Soy, winter wheat–corn–soybean; W–C–Spgr, winter wheat–corn–spring grains; W–F, winter wheat–fallow; W–W, winter wheat–winter wheat.

The effect of flooding regimes on decomposition of Polygonum pensylvanicum in playa wetlands (Southern Great Plains, USA)

Plants in playa wetlands are hypothesized to have high decomposition rates due to rapidly fluctuating water levels. Therefore, Polygonum pensylvanicum (a dominant playa species) decomposition rates were studied in relation to four water regimes (F1 (flooded 30% of 321 days), F2 (41%), F3 (58%), or F4 (100%)) in playa wetlands of the Southern Great Plains of Texas, 1996–1997. Decomposition rates of stems, leaves, and seeds were generally lowest ( P<0.001) in the F3 and F4 treatments and highest in the F1 and F2 treatments. The highest rates of decomposition for all plant parts occurred within 56 days of placement in the field ( P<0.001), and gradually declined until the conclusion of the study (321 days). Crude protein levels were initially highest in leaves (21.9%) and lowest in stems (3.9%), whereas cellulose and hemicellulose levels were highest in stems (51.4 and 33.3%, respectively) and lowest in leaves (24.3 and 17.7%, respectively); seeds had moderate levels (protein (9.8%); cellulose (46.8%); hemicellulose (30.4%)). However, decomposition rates of seeds were lower ( P<0.001) than decomposition rates of stems and leaves. The natural wet–dry cycles in playas enhance decomposition and productivity of playa wetlands.

Pennsylvania smartweed interference and achene production in cotton

Studies were conducted to determine the effect of interference between Pennsylvania smartweed and cotton on plant growth and productivity. Pennsylvania smartweed remained shorter than cotton until at least 80 d after cotton planting. However, Pennsylvania smartweed produced considerable dry biomass by cotton harvest. Pennsylvania smartweed biomass per plant was not affected by weed density when grown with cotton. When grown alone, Pennsylvania smartweed produced 1,640 and 2,060 g dry biomass plant−1 depending on the year. This biomass was over four times greater than the biomass produced by plants grown with cotton. Cotton lint yield decreased between 1.3 and 1.1 kg ha−1 with each gram increase in weed dry biomass per meter of row. The relationship between Pennsylvania smartweed density and cotton percent yield loss was described by the hyperbolic function. The estimated coefficients a (maximum yield loss as density approaches infinity) and i (yield loss per unit density as density approaches zero) were 102 ± 23 and 51 ± 12, respectively, in 1998 and 53 ± 1 and 98 ± 5, respectively, in 2000. Pennsylvania smartweed achene production was also described by the hyperbolic function. Estimated achene production at 1 plant m−1 cotton row was 18,000 and 26,000 achenes m−2 in 1998 and 2000, respectively.

Effects of soil depth and aggregate size on weed seed distribution and viability in a silt loam soil

The position of weed seeds within the soil matrix plays an important role in seedling emergence and seed survival. The relationship of weed seeds with soil aggregates and soil depth was evaluated in a Waukegon silt loam soil that had been under a long-term, conventional tillage, annual crop management system. Soil aggregates were separated and classified into eight size classes from ≤5 to >12 mm and weed seeds were extracted from the aggregates. Amaranthus spp., Chenopodium album L. (common lambsquarters), Polygonum pensylvanicum L. (Pennsylvania smartweed), Setaria faberi Herrm. (giant foxtail), and Solanum ptycanthum Dun. (eastern black nightshade) accounted for the majority of seeds recovered. In general, seed viability declined from April to June, but increased in October following seed deposition. Seeds of individual species were most abundant in the aggregate size class most closely matching its seed size. However, seeds were commonly found associated with aggregates larger than 9 mm. Highest seed viability was found in the aggregate fraction closest to the seed size, however, S. faberi viability was also high in the >12 mm aggregate size class. Regardless of aggregate size, seed numbers were generally greatest in the upper 5 cm of soil. The results of this research were species-dependent and variable and demonstrated the complexity of weed seed/soil aggregate associations. However, they did show that seed placement within the soil matrix may play an important role in weed population dynamics.

Nutritional Consequences of Gastrolith Ingestion in Blue-Winged Teal: A Test of the Hard-Seed-for-Grit Hypothesis

One benefit attributed to retention of mineral grit in avian gizzards is enhanced digestive efficiency, which may be realized through higher metabolizable energy of hard seed diets. The hard-seed-for-grit hypothesis also suggests that hard seeds can substitute for grit in the gizzard as an aid to mechanical digestion. However, neither of these presumed nutritional benefits of gastrolith ingestion have been quantified. We maintained captive blue-winged teal (Anas discors) on 4 experimental dietary supplements (none, grit, milo, and both grit and milo), and conducted true metabolizable energy (TME) feeding trials to demonstrate the nutritional consequences of gastrolith consumption. We measured TME of 3 test diets: millet (Echinochloa crus-galli), milo, and smartweed (Polygonum pensylvanicum), Mean TME did not differ among treatments for any of the test diets, suggesting that pretrial gastrolith ingestion did not appreciably increase metabolizability of these foods. There was little evidence that birds retained either pretrial seed supplements or the experimental diets in the gizzard, suggesting that seed substitution did not occur. Birds frequently regurgitated the test diet. Although we corrected food intake for regurgitated food mass, a significant positive relationship between net intake and TME occurred for smartweed. However, variation in net intake and occurrence of regurgitation did not appear to alter the effects of gastroliths on TME. This study does not provide support for either presumed nutritional benefit of gastrolith ingestion. These results may reflect the lack of energetic constraints on food acquisition in captive birds. A similar study of Canada geese (Branta canadensis) showed a significant effect of grit on TME of some foods, suggesting that digestive responses may vary across a gradient in body size.

Reduced rates of sulfentrazone plus chlorimuron and glyphosate in no-till, narrow-row, glyphosate-resistantGlycine max

Abstract Field studies were conducted in 1998 and 1999 to evaluate crop response, weed control, Glycine max yield, and economic returns of labeled (1×) and one-half labeled (½×) rates of early preplant (EPP) sulfentrazone plus chlorimuron and postemergence glyphosate, compared to glyphosate-alone systems in no-till, narrow-row, glyphosate-resistant G. max. Treatments containing a 1× or ½× rate of EPP sulfentrazone plus chlorimuron with glyphosate followed by (fb) a postemergence treatment of glyphosate provided 80 to 100% control of Xanthium strumarium, Ambrosia artemisiifolia, and Polygonum pensylvanicum and 82 to 100% control of Setaria faberi and Amaranthus rudis if glyphosate was applied mid-postemergence (MPOST) or late postemergence (LPOST). Glyphosate alone EPP fb glyphosate postemergence or sequential postemergence treatments of glyphosate provided 77 to 100% control of S. faberi, A. artemisiifolia, and P. pensylvanicum. Glycine max yield did not significantly differ between treatments that contai...

Use of preplant sulfentrazone in no-till, narrow-row, glyphosate-resistantGlycine max

Abstract Field studies were conducted in 1998 and 1999 to evaluate crop response, weed control, Glycine max yield, and economic returns with sulfentrazone alone and tank-mixed with glyphosate, cloransulam, or chlorimuron at two preplant application timings in no-till, narrow-row, glyphosate-resistant G. max. No significant crop injury was observed. Setaria faberi and Polygonum pensylvanicum control 5 wk after planting (WAP) was generally greater with sulfentrazone applied early preplant (EPP) than with sulfentrazone applied at planting (AP). When applied AP, glyphosate plus sulfentrazone provided greater S. faberi control than sulfentrazone alone. Control of Amaranthus rudis, Ambrosia artemisiifolia, and Ipomoea hederacea was greater in 1998 than in 1999 because of more timely early-season precipitation. Sulfentrazone-based programs provided 80 to 100% control of A. rudis in 1998, but control in 1999 ranged from 72 to 95% at Columbia and 46 to 83% at Novelty. Cloransulam alone, at either application timin...

DIET OF MALLARDS WINTERING IN GREENTREE RESERVOIRS IN SOUTHEASTERN ARKANSAS

Loss of wetlands to agriculture and development negatively impacts waterfowl. Greentree reservoirs are forested tracts that are purposefully flooded to increase hunting opportunities for sportsman and to provide shelter for waterfowl such as Mallards (Anas platyrhynchos). These human-made wetlands can also make natural foods such as acorns and invertebrates available to Mallards. Food habits analysis conducted in 1959 indicated acorns composed 24% of the volume of diets of Mallards collected from a variety of habitats including agricultural fields, naturally flooded bottomland forests, and greentree reservoirs in Arkansas. However, changes that may have occurred in food use by Mallards in bottomland hardwood habitats in Arkansas since last examined are unclear. We examined foods used by Mallards in greentree reservoirs from November 1990 to February 1991 in southeastern Arkansas. Seventeen species of plants and 21 families/orders of animals occurred in the diet of Mallards. Mallards consumed 65% plant matter, primarily seeds of narrowleaf foresteria (Foresteria angustifolia), Nuttall oak (Quercus nuttallii), Pennsylvania smartweed (Polygonum pensylvanicum), and rice (Oryza sativa). Invertebrate taxa, constituting 6% or more of the sample by both volume and mass, included the orders Coleoptera, Diptera, and Isopoda. Diets of Mallards present in greentree reservoirs in our study indicate Mallards still use natural foods, though agricultural seeds were in close proximity to natural foods.

Rotary Hoeing Substitutes for Two-Thirds Rate of Soil-Applied Herbicide1

Dose–response curves for acetochlor with and without timely rotary hoeing (two passes) were derived for corn (Zea mays) fields over 2 yr. The fields were dominated by green foxtail (Setaria viridis), which constituted 73 to 86% of the weed vegetation, but also contained minor populations of common lambsquarters (Chenopodium album), Pennsylvania smartweed (Polygonum pensylvanicum), and redroot pigweed (Amaranthus retroflexus). In the absence of herbicide, rotary hoeing achieved about 50% weed control. In the absence of rotary hoeing, weed control averaged > 90% at the full label rate of acetochlor (3 kg ai/ha on clay loam soil). With two timely rotary hoeings, however, this same level of control was achieved with only 1 kg/ha acetochlor. Given the suite of weed species present in these experiments, timely rotary hoeing substituted for 67% of the label rate of acetochlor. Timeliness of rotary hoeing operations also provided consistency of results from one year to the next.Nomenclature: Acetochlor, 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide; common lambsquarters, Chenopodium album L. #3 CHEAL; green foxtail, Setaria viridis (L.) Beauv. # SETVI; Pennsylvania smartweed, Polygonum pensylvanicum (L.) # POLPY; redroot pigweed, Amaranthus retroflexus L.; corn, Zea mays L.Additional index words: Integrated weed management, interrow cultivation, preemergence herbicide, seedling emergence, timeliness.

The vegetation of wet meadows in relation to their land-use

Wetland biomonitoring approaches are needed to determine when changes in response to stressors are occurring and to predict the consequences of proposed land-use changes. These approaches require an understanding of shifts in biota that occur in response to land-use, data that are lacking for most kinds of wetlands. Changes in floristic composition corresponding to land-use differences at multiple scales (site to 2500 m radius) were characterized for 40 wet meadows associated with prairie glacial marshes in Minnesota (U.S.A.). In general, guild was more useful than species composition for indicating land-use impacts. Site impacts (stormwater, cultivation) and landscape disturbance (agriculture and urbanization, combined), coincide with a reduction in native graminoid and herbaceous perennial abundance (e.g., Carex lasiocarpa, Calamagrostis canadensis, Spartina pectinata). This vegetation is replaced with annuals (e.g, Bidens cernua, Polygonum pensylvanicum) in recently cultivated sites or introduced perennials (e.g., Phalaris arundinacea, Typha angustifolia) and floating aquatics (lemnids) in stormwater impacted wetlands. Ditches also reduce native perennial importance and increase perennials, but only when they are in highly impacted landscapes.

BIOMASS ALLOCATION IN PLANTS: ONTOGENY OR OPTIMALITY? A TEST ALONG THREE RESOURCE GRADIENTS

We examined biomass allocation patterns throughout the entire vegetative growth phase for three species of annual plants along three separate gradients of resource availability to determine whether observed patterns of allocational plasticity are consistent with optimal partitioning theory. Individuals of the annual plant species Abutilon theophrasti, Chenopodium album, and Polygonum pensylvanicum were grown from locally field-gathered seed in controlled greenhouse conditions across gradients of light, nutrients, and water. Frequent harvests were used to determine the growth and allocation (root vs. shoot, and leaf area vs. biomass) responses of these plants over a 57-d period. Growth analysis revealed that each species displayed significant plasticity in growth rates and substantial amounts of ontogenetic drift in root:shoot biomass ratios and ratios of leaf area to biomass across each of the three resource gradients. Ontogenetically controlled comparisons of root:shoot and leaf area ratios across light ...

Preemergence Weed Control in Conventional-Till Corn (Zea mays) with RPA 201772

Field studies were conducted at Dekalb, Urbana, and Brownstown, IL, in 1996 and 1997 to evaluate corn (Zea mays) injury and weed control from preemergence applications of RPA 201772 alone and tank-mixed with metolachlor, atrazine, or both. No significant corn injury from RPA 201772 was observed at any time for all experiments. Giant foxtail (Setaria faberi) control at 60 days after treatment (DAT) was variable and ranged from 47 to 93% for RPA 201772 applied alone at 105 g ai/ ha. Giant foxtail control of at least 90% was observed by applying metolachlor at 1,120 g ai/ha with 105 g/ha RPA 201772. The addition of atrazine at either 1,120 or 1,680 g ai/ha improved control of giant foxtail compared with RPA 201772 applied alone at 105 g/ha in two of the six studies. RPA 201772 applied at 105 g/ha controlled at least 88% of velvetleaf (Abutilon theophrasti), Pennsylvania smartweed (Polygonum pensylvanicum), and smooth pigweed (Amaranthus hybridus). RPA 201772 controlled 88% or less of common waterhemp (Amaranthus rudis), common ragweed (Ambrosia artemisiifolia), and common cocklebur (Xanthium strumarium). Control of these three species was 92% or greater with RPA 201772 plus atrazine. Control of common lambsquarters (Chenopodium album) was at least 96% with RPA 201772 applied alone at any rate in four of the six studies. However, common lambsquarters control was 68 and 77% for RPA 201772 applied alone at 105 g/ha at Urbana and Brownstown in 1997, respectively, where high common lambsquarters densities were prevalent. Under these conditions, the addition of atrazine to RPA 201772 at 105 g/ha improved control of common lambsquarters. RPA 201772 has excellent potential to provide consistent control of velvetleaf compared with atrazine. In contrast, these studies indicate RPA 201772 may provide inconsistent control of certain weed species in different environments. In order to achieve consistent control of a broad spectrum of weed species, RPA 201772 must be combined with other herbicides.

Broadleaf Weed Control with Sulfentrazone and Flumioxazin in No-Tillage Soybean (Glycine max)

Field trials were conducted at two sites in 1996 and 1997 to evaluate weed control and crop response to herbicide programs in no-till soybean that include flumioxazin or sulfentrazone alone and each herbicide tank-mixed with either chlorimuron or imazaquin. A prepackaged mixture of metribuzin plus chlorimuron also was included for comparison. Cool, wet conditions after herbicide application in both years were conducive to soybean injury up to 21% at 3 wk after planting (WAP). Flumioxazin and sulfentrazone alone provided ≥ 89% control of velvetleaf, Pennsylvania smartweed, and common cocklebur. Sulfentrazone alone provided greater control of common waterhemp, common cocklebur, and ivyleaf and pitted morningglories than flumioxazin. Flumioxazin provided greater control of common ragweed than sulfentrazone. The addition of chlorimuron to flumioxazin or sulfentrazone provided greater control of velvetleaf than flumioxazin or sulfentrazone alone. The addition of imazaquin or chlorimuron to flumioxazin provided greater control of common cocklebur than flumioxazin alone. The addition of imazaquin or chlorimuron to sulfentrazone provided greater control of common ragweed than sulfentrazone alone. The addition of chlorimuron or imazaquin to sulfentrazone or flumioxazin provided little or no additional control of pitted morningglory, common waterhemp, or Pennsylvania smartweed. Metribuzin plus chlorimuron provided control of velvetleaf, Pennsylvania smartweed, common ragweed, and common cocklebur that was equal to or better than the control provided by sulfentrazone or flumioxazin plus chlorimuron or imazaquin.

True Metabolizable Energy Estimates of Canada Goose Foods

We determined true metabolizable energy (TME) and digestibility of 8 foods commonly available to Canada geese (Branta canadensis) in order to provide managers with a better understanding of the nutritional value of these foods. True metabolizable energy estimates were highest for chufa tubers (Cyperus esculentus ; 16.86 kJ/g), corn (Zea mays; 16.32 kJ/g), and milo (Sorghum vulgare; 15.72 kJ/g), while estimates for soybeans (Glycine max; 14.85 kJ/g), wild millet (Echinochloa crusgalli; 13.77 kJ/g), and rice (Oryza sativa; 11.76 kJ/g) were intermediate in value. Winter wheat foliage (Triticum aestivum; 10.04 kJ/g) and largeseed smartweed seeds (Polygonum pensylvanicum; 6.65 kJ/g) provided the least TME of foods tested. Crude fiber accounted for 76% of the variation in TME. Digestibility values of the 8 foods ranged from 35.1 to 88.5%, with digestibility varying widely among both agricultural and natural foods. To supply Canada geese with a balanced diet and foods high in metabolizable energy (ME), managers should provide a variety of agricultural and natural foods that are low in fiber content.

Vanicosides C-F, new phenylpropanoid glycosides from Polygonum pensylvanicum.

The isolation of the protein kinase C inhibitors, vanicoside A (1) and vanicoside B (2), from Polygonum pensylvanicum prompted continued interest in the active principles of this plant. A new, more efficient isolation procedure has been developed to facilitate separation of homologues of vanicosides A and B from the complex extract. Several new phenylpropanoid glycosides have since been isolated. The structures of these principles were determined to be 2'-O-acetylhydropiperoside (4), 6'-O-p-coumarylhydropiperoside (5), 4'-O-acetylvanicoside A (6), and 3'-O-acetylvanicoside B (7) using negative ion FABMS, 1H NMR, and 2D NMR techniques.

Can plants track changes in nutrient availability via changes in biomass partitioning

Can old-field annuals exposed to temporally varying nutrient regimes adjust biomass partitioning programs in order to maximize growth? We grew three species of old-field annuals, Abutilon theophrasti, Chenopodium album, and Polygonum pensylvanicum, at low or high nutrient levels, and switched a subset of plants to the alternate nutrient regime after one or two weeks of growth. If plants were able to partition biomass in an optimal fashion, it would be predicted that changes in growth would be accompanied by changes in biomass partitioning programs. We found that when nutrient availability changes (e.g., from low to high) early in ontogeny, growth and partitioning to leaf area development are adjusted to be indistinguishable from those of plants grown at constant nutrient availabilities (e.g., always high). Root shoot partitioning, however, was developmentally fixed in two of the three species such that nutrient environment had no effect on root/shoot partitioning. Thus, although fluctuations in nutrient availability altered plant growth, the observed changes in growth occurred without concomitant adjustments to the root/ shoot partitioning program. These results imply that adjustments in allocation of biomass resources, at least between roots and shoots, are not necessary to effect alterations in plant growth in variable environments.