Prevention programs are often assumed to be the most cost-effective method for managing invasive plants. However, there is very little information available about economic and biological factors that determine the forage benefits resulting from prevention programs. We developed an easy to use economic model to assess potential savings in livestock forage that might result from implementing prevention programs. The model can be used to determine potential loss in forage production caused by invasive plants and to estimate potential income savings by preventing invasive plant infestations. The model compares a prediction of populations with and without a prevention program using a logistic growth function. Animal unit month (AUM) price and interest rates are the primary economic input variables. The primary biological input variables are amount of invasive plant utilization, size of the initial infestation, and the spread rate with and without prevention. Our model suggests that as the AUM price increases and/or the interest rate decreases, the total savings increases for each AUM that was protected through a prevention program. The model also shows savings per AUM increases as the size of the initial infestation decreases, suggesting that prevention should focus on eliminating seed sources and seed production early in the program. Using our model inputs, the savings per AUM was about $9.20 for each percent reduction in spread rate over 100 yr.

Numerous studies have quantified the developmental responses of wheat to vernalization, but its response compared to a weedy relative, jointed goatgrass, remains relatively unknown. Six paired jointed goatgrass collections gathered from Washington and Oregon fields, and winter and spring wheat, were grown in field studies to quantify yield and germination in response to vernalization. Monthly planting dates initiated in October and concluded in March were used to vary the vernalization durations for plants sown at three Oregon locations (Corvallis, Moro, and Pendleton) over two growing seasons. Minimum vernalization requirements to produce reproductive spikes were similar among plants of six jointed goatgrass collections. Jointed goatgrass collections grown at Corvallis required a minimum of 89 and 78 vernalization days (January 17, 2003 and January 22, 2004 sowing, respectively) to produce reproductive spikes, and plants grown at Moro required 60 vernalization days (March 3 and February 23) in both years, and 48 and 44 vernalization days (March 3 and February 24) were required by plants to produce spikes at Pendleton. Jointed goatgrass spikelet and winter wheat seed yield were positively influenced by vernalization days, experiment location, and year. The strength of the interactions among these main effects differed among jointed goatgrass collections and winter wheat. The effects of vernalization on jointed goatgrass yields and seed quality were more pronounced at Pendleton, OR, a location where jointed goatgrass has adapted, compared to Corvallis, OR, where it has not adapted. The minimum vernalization days required to produce germinable seed differed among jointed goatgrass collections, winter and spring wheat. There was not a selection of spring-adapted jointed goatgrass populations in the populations tested. Yet if spring temperatures are cool, minimum conditions for vernalization may be satisfied, and the benefits of planting spring crops to control jointed goatgrass would be reduced.

The control of grasses and broadleaf weeds in sunflowers (Helianthus annuus L. ‘Peredovik’) generally was as good with one or two cultivations during the 3-year period as with chemicals applied alone or in sequence with cultivation. Plant injury was not evident from mechanical treatments or from α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). However, plant injury occurred when plots were treated with 2-chloro-2′6-diethyl-N-(methoxymethyl) acetanilide (alachlor) plus 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) as a preemergence application in 1 year and from postemergence applications of 2-tertiobutyl-4-(2,4-dichloro-5-isopropyloxyphenyl)-5-oxo-1,3,4-oxodiazoline (RP 17623) and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) in 2 years. Seed yields from plots cultivated once were as good as yields from plots that received multiple cultivation or herbicide treatments. Other agronomic characteristics were favorable from plots that received one cultivation.

The translocation of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and 2,4-D [(2,4-dichlorophenoxy) acetic acid] in bean (Phaseolus vulgaris L. ‘Stringless Greenpod’) seedlings was studied. 14C-labeled herbicides in amounts of 0.75 to μg were injected into the center of the stem at the cotyledonary node with a 1-μL syringe pipette. The effects of time and duration of treatment, herbicide concentration, and herbicide interaction on acropetal and basipetal translocation subsequent to treatment were determined. There was considerable basipetal as well as acropetal translocation of herbicide from the site of injection. Acropetal translocation of 2,4,5-T to primary leaves was very rapid until 2 hr after treatment, and during the following hours of treatment the 14C disappeared from the primary leaves. Acropetal translocation of 2,4,5-T to the young shoots was slow but continuous up to 6 hr after treatment, did not decrease during the latter hours of treatment, and was enhanced by high 2,4,5-T treatment levels. Translocation of 2,4,5-T to the nutrient solution continued for at least 72 hr after treatment while the roots accumulated maximum amounts in 6 to 12 hr. High treatment levels of 2,4,5-T enhanced the translocation of 2,4-D in the young shoots. However, 2,4-D did not promote the translocation of 2,4,5-T. Considerable variation occurred in the total translocation of 2,4,5-T when treatments were made at various times during the day. Translocation rates to the nutrient solution were at a maximum at about 12 A.M. and 12 P.M. each day regardless of the time of application of the 2,4,5-T.

Putting green turf containing perennial ryegrass (Lolium perenne L. ‘Medalist IV’) overseeded on a bermudagrass [Cynodon dactylon (L.) Pers. ‘Tifway’] was treated with single and sequential herbicide treatments during the spring and transition period from cool to warm season grass. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] at 2.2 or 4.4 kg/ha and butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] at 3.4 or 6.7 kg/ha reduced the quality of putting green turf immediately after treatment in early spring. Turf injury was greater with oxadiazon than with butralin. Two applications of MSMA (monosodium methanearsonate) at 2.2 or 3.4 kg/ha resulted in a lower quality turf with less ryegrass when compared with the untreated check. Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] at 1.1 kg/ha severely injured ryegrass and resulted in a lower turf quality.

Seedling growth of soybean [Glycine max (L.) Merr. ‘Forrest’], common cocklebur (Xanthium strumarium L. # XANST), and tall morningglory [Ipomoea purpurea (L.) Roth. # PHBPU] was compared in field studies. Root growth was determined by measuring roots restricted to the inside of a permeable membrane that contained no soil. Leaf area duration and net assimilation rate between 4 and 9 weeks were greatest for common cocklebur compared to the other species. At 9 weeks, shoot and root dry weight and leaf area were greatest for common cocklebur compared to soybean and tall morningglory. Relative growth rate of common cocklebur roots was greater than the other species between 4 and 9 weeks. Tall morningglory had greater shoot length or height at 4 and 9 weeks and greater shoot or height elongation rate between 2 and 4 weeks, and 4 and 9 weeks than the other species.

Soybeans treated preemergence with carboxyl-labeled C14 amiben (3-amino-2,5-dichlorobenzoic acid) were harvested at 7-day intervals. The C14 activity per gram of dry plant matter decreased with later harvest dates but the activity per plant increased over the period. The cotyledons had considerable radioactivity. Both rates contained the same amount of C14 amiben but the soybeans exposed to 6 lb/A contained a significantly higher C14 count than did those exposed to 3 lb/A. All of the identifiable C14 components were amiben.

Most of the activity in soybeans from seed imbibed with C14 amiben remained in the cotyledons. That which did translocate was evenly distributed. Most (98.1%) of the radioactivity in plants grown in treated nutrient solution remained in the roots. Translocated C14 amiben appeared about 8 days after exposure and was evenly distributed in the top of the plant. Plant-respired CO2 had no radioactivity present.

Herbicide solutions of known concentration were applied to honey mesquite (Prosopis glandulosa Torr. # PROJG) with a tractor-mounted carpeted roller. The volume of solution applied was measured, and average height and density of the honey mesquite stands were also determined. The volume of solution applied ranged from about 3 to 20 L/ha and was positively correlated with stand density (r2 = 0.71). Height of the stand had no influence on volume of solution applied. Amounts of herbicide applied at concentrations of 30, 60, and 120 g/L averaged about 0.2, 0.6, and 1.25 kg ae/ha, respectively. Calculated amounts of active ingredient of herbicide applied to individual plants (dosage) ranged from 0.3 to more than 3 g/shrub and decreased curvilinearly with increasing stand density, suggesting that the carpeted roller is most efficient in treating sparse stands.

Three resistant (R) rigid ryegrass (Lolium rigidum Gaudin) populations from southern Australia (EP162, 375-14, and 198-15) with cross-resistance to thiocarbamate, chloroacetamide, and sulfonylisoxazoline herbicides displayed reduced sensitivity to the isoxazolidinone herbicides bixlozone and clomazone. Each of these R populations was exposed to two cycles of recurrent selection (RS) in which plants were treated with the field rate of bixlozone, survivors were bulk crossed, and seed was collected. After the first cycle of recurrent selection (RS1), the LD50 to bixlozone in population 198-15 increased to 17.5-fold compared with the S population and increased further to 26.9-fold after a second cycle of recurrent selection (RS2). The recurrent selection process also increased the level of resistance to bixlozone in populations EP162 and 375-14 (7.8- to 18.4-fold) compared with the S population. Phorate antagonized bixlozone and clomazone in SLR4 (34.6- and 28.1-fold increase in LD50) and both herbicides in populations EP162 (36.5- to 46.6-fold), 375-14 (71.4- to 73.9-fold), and 198-15 (86.4- to 91.5-fold) compared with the absence of phorate. The increase in LD50 of all L. rigidum RS populations when treated with phorate suggests a lack of herbicide activation is not the likely resistance mechanism to these herbicides. This research highlights the elevated risk of thiocarbamate-resistant L. rigidum populations to rapidly evolve resistance to the isoxazolidinone herbicides bixlozone and clomazone.

Birdsfoot trefoil, timothy, and sterile pea plants treated with 4-(2,4-dichlorophenoxy) butyric acid [4-(2,4-DB)], formed 2,4-dichlorophenoxyacetic acid (2,4-D) to about the same extent. Apparently the enzymatic ability for beta oxidation can reside in the plant as well as in microorganisms.

Immediate posttreatment irrigation has been proposed as a method to reduce hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] phytotoxicity from topramezone. Immediate irrigation is impractical, because it would take a turfgrass sprayer 10 to 15 min to cover an average golf course fairway or athletic field. There is also insufficient evidence regarding how posttreatment irrigation, immediate or otherwise, influences mature goosegrass [Eleusine indica (L.) Gaertn.] control from topramezone or low-dose topramezone plus metribuzin programs. We sought to investigate bermudagrass and E. indica response to immediate, 15-min, and 30-min posttreatment irrigation compared with no irrigation following topramezone at 12.3 g ae ha−1, the lowest labeled rate, or topramezone at 6.1 g ha−1 plus metribuzin at 210 g ai ha−1. We also evaluated placement of each herbicide and their combination on soil, foliage, and soil plus foliage to help elucidate the mechanisms involved in differential responses between species and herbicide mixtures. Responses were largely dependent on trial due to bermudagrass injury from high-dose topramezone being nearly eliminated by immediate irrigation in one trial and only slightly affected in another. When posttreatment irrigation was postponed for 15 or 30 min, topramezone alone injured bermudagrass unacceptably in both trials. Bermudagrass was injured less by low-dose topramezone plus metribuzin than by high-dose topramezone. All posttreatment irrigation timings reduced E. indica control compared with no posttreatment irrigation. The herbicide placement study suggested that topramezone control of E. indica is highly dependent on foliar uptake and that phytotoxicity of both bermudagrass and E. indica is greater from topramezone than metribuzin. Thus, posttreatment irrigation likely reduces topramezone rate load with a concomitant effect on plant phytotoxicity of both species. Metribuzin reduced 21-d cumulative clipping weight and tiller production of plants, and this may be a mechanism by which it reduces foliar white discoloration from topramezone.

Herbicides which contain primary or secondary amino groups may be detected on thin layers of silica gel G or silica gel H with 1% tert-butyl hypochlorite, followed with an aqueous solution of 1% KI and 1% soluble starch. Detection limits range from approximately 1 μg to less than 0.05 μg, depending upon the herbicide in question. The technique also appears to be effective for aromatic or aliphatic iodides.

Tall buttercup, a native of central and northern Europe, has become naturalized in the United States and Canada, and in South Africa, Tasmania and New Zealand. In Canada and New Zealand it has become an economically significant weed in cattle-grazed pastures. In this study we develop a CLIMEX model for tall buttercup and use it to project the weed's potential distribution under current and future climates and in the presence and absence of irrigation. There was close concordance between the model's projection of suitable climate and recorded observations of the species. The projection was highly sensitive to irrigation; the area of potentially suitable land globally increasing by 30% (from 34 to 45 million km2) under current climate when a “top-up” irrigation regime (rainfall topped up 4 mm d−1 on irrigable land), was included in the model. Most of the area that becomes suitable under irrigation is located in central Asia and central North America. By contrast, climate change is projected to have the opposite effect; the potential global distribution diminishing by 18% (from 34 to 28 million km2). This range contraction was the net result of a northward expansion in the northern limit for the species in Canada and the Russian Federation, and a relatively larger increase in the land area becoming unsuitable mainly in central Asia and south eastern United States.

Environmental and physical factors influencing the effectiveness of preemergence applications (4 lb/A) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) were evaluated under field conditions for 10 Hawaiian sugar cane (Saccharum officinarum L.) plantations. Rainfall, soil pH, organic composition, time lapse between field harvest and herbicide application, and maximum temperature had a significant effect on the resultant period of weed control. The data from 295 field tests conducted over a 10-year period then were subjected to multiple regression analysis. The prediction equation derived via these calculations was sufficiently accurate to justify its application to the Hawaiian sugar cane regions. The single most important factor adversely influencing the preemergence activity of diuron was the lapse of time between harvest and application, a factor within the control of the plantation personnel.

The anatomy of the first internodes of three different lengths of giant foxtail (Setaria faberii Herrm.) was studied in the seedling stage. Epidermis was non-cutinized throughout the entire length. Least cortical breakdown occurred in an area 1 cm below the coleoptilar node, regardless of the length of internode. Endodermis and pericycle were present throughout the internode length, but identity was lost at the coleoptilar node and above. The number of metaxylem and protoxylem elements decreased basipetally from the coleoptilar node. Adventitious root primordia, found in all first internodes, originated from the pericycle. The total number of primordia, at the growth stage studied, appears to be proportional to the length of the internode, with fewer primordia in the 1-cm sections below the coleoptilar node. The implications of root and shoot uptake are discussed in terms of the anatomy of the first internode.

The method was based on the minimum dosage of 2,4–dichlorophenoxyacetic acid (2,4–D) that would produce strapping or cupping of cotton leaves. Dilutions of an unknown were applied to cotton cotyledons. The minimum dosage required to produce strapped or cupped leaves two weeks later was approximately 0.05 μg/plant. The results of this bioassay were comparable to tracer methods, but the latter can detect smaller quantities of 2,4–D.

A Streptomyces, apparently S. viridochromogenes, was isolated from Louisiana crop areas where seven chlorinated herbicides had been used in weed control. It liberated no chloride when grown in a liquid medium containing 100 ppm of any of these seven herbicides. With a cucumber root bioassay, detoxification of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4,5-trichlorophenoxy)propionic acid (silvex), 2,3,6-trichlorophenylacetic acid (fenac), 2,2-dichloropropionic acid (dalapon) was observed, but little detoxification was shown with 2-chloro-N,N-diallylacetamide (CDAA), isopropyl N-(3-chlorophenyl)carbamate (CIPC), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Manometric studies with 2,4-D, 2,4,5-T, and silvex showed the streptomycete was capable of adapting to the compounds after a short period, but not to 2,4-dichlorophenol, a proposed intermediate of 2,4-D metabolism. The organism did not alter the ring structure of the aromatic herbicides, and 2,4-D and 2,4-dichlorophenol showed identical absorption curves with the spectrophotometer used.

Golf putting greens were sprayed with N-(2-mercaptoethyl) benzenesulfonamide S-(O,O-diisopropyl phosphorodithioate) (bensulide). Creeping bentgrass (Agrostis palustris Huds.) and annual bluegrass (Poa annua L.) were observed for injury. Preemergence and postemergence treatments of 5-bromo-3-sec-butyl-6-methyluracil (bromacil), 5-chloro-3-tert-butyl-6-methyluracil (terbacil), and 5-bromo-3-tert-butyl-6-methyluracil (hereinafter referred to as DP 733) were applied to a prepared seedbed planted with Kentucky bluegrasses (Poa pratensis L., var. Merion and var. Newport) and annual bluegrass.

Thirty lb/A of bensulide produced leaf discoloration and root length reduction of established annual bluegrass plants without injuring creeping bentgrass. Terbacil at 0.2 lb/A and bromacil at 0.4 lb/A gave highly selective control of annual bluegrass in Merion and Newport Kentucky bluegrasses when applied preemergence to the three grasses. Postemergence applications of these compounds produced moderate selective control of annual bluegrass.

Metabolites of the fungus Fusarium solani (Sud 96) inhibited Striga hermonthica germination induced by the germination stimulant GR24. The active principles were identified as trichothecenes acuminatin, neosolaniol, 8-acetylneosolaniol, and tetraacetoxy T-2 tetraol (neosolaniol diacetate) on the basis of their chromatographic behavior and nuclear magnetic resonance and mass spectra. Inhibitory activity of the four trichothecenes against Striga germination increased with acetylation of the hydroxyl moieties. The most abundant inhibitor produced by the fungus, 8-acetylneosolaniol, completely inhibited Striga germination at 24 μM. The fungal toxin did not affect the germination of sorghum, a host crop, but retarded root and shoot elongation of the seedlings by 60 and 30%, respectively, at the same concentration.

Laboratory and greenhouse experiments were conducted to determine the allelopathic potential of centipedegrass. Germination and growth of indicator species were evaluated in soil leachates, leaf debris, and aqueous leaf extracts of centipedegrass. Centipedegrass soil leachates did not inhibit annual bluegrass, goosegrass, henbit, large crabgrass, or perennial ryegrass germination compared with the nonfertilized control. Incorporated centipedegrass leaf debris did not reduce lettuce germination, shoot weight, or root weight compared with the control. However, shoot and root dry weights of radish were reduced with increasing rates of centipedegrass leaf debris. Six and 9 mg debris g−1 soil reduced radish shoot weight by 49 and 64%, respectively, compared with the control. Aqueous leaf extracts of centipedegrass reduced lettuce germination; however, radicle and hypocotyl length were similar to the control. These data do not conclusively suggest centipedegrass has widespread allelopathic activity; however, significant reductions in shoot and root weight of radish with increasing centipedegrass leaf debris demonstrate a pattern of inhibition of one species against another, which fulfills a requirement of allelopathic interactions.