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Downy brome (Bromus tectorum L. #3 BROTE) has developed into a severe weed in several agricultural production systems throughout North America, particularly on rangeland and in winter wheat (Triticum aestivum L.). Several million hectares of winter wheat, pastureland, alfalfa (Medicago sativa L.), grass seed fields, and overgrazed rangeland, as well as other crops, have been invaded by this annual grass since its introduction into this hemisphere. Downy brome is most abundant in the Great Basin and Columbia Basin areas of the western United States, but is found throughout the continental United States and parts of Canada and Mexico. In some cases, the vegetation on overgrazed rangeland consists totally of downy...
The influence of soil moisture stress, temperature, and bulk density on the germination and seedling emergence of downy brome (Bromus tectorum L.) was investigated in the laboratory. Reductions in soil matric potential from -2 to -16 bars markedly reduced the percentage and rate of emergence. Seedling emergence was better at constant than at alternating temperatures. At high matric potentials, the rate of emergence was accelerated by warmer soil temperature (20 C), while at very low matric potentials, the percentage and rate of seedling emergence were least restricted at cooler temperatures (10 and 15 C). Soil matric potential did not influence the percentage or rate of emergence of seedlings grown from seed lots...
To evaluate relationships among populations, phenotypic variation of morphological characters in one Gutierrezia microcephala and eight Gutierrezia sarothrae populations from New Mexico was quantified and compared with variation expressed when these same populations were grown in a common garden. During flowering, plants were randomly collected from each population across New Mexico during two growing seasons. A common garden of stem cuttings from these same populations was established in Las Cruces. Vegetative and reproductive characters were measured for each population at original and common sites. Vegetative characters did not differ between G. sarothrae and G. microcephala collected from the same location;...
Establishment of seedlings of big sagebrush subsequent to range weed control treatments limits the economic feasibility of such treatments for increased forage production. This study investigated the dynamics of seed production by this species as one step in understanding seedling establishment. Studies were conducted on five different ecological sites along the arid extremity of big sagebrush distribution in western Nevada. Demography, physical dimensional parameters, biomass, and community structure were determined for each site and related to seed production over a 4-yr period. In addition, seeds harvested from each site were used to grow plants that were transplanted to establish reciprocal gardens at all sites....
In three replacement series experiments, winter wheat (Triticum aestivum L.), jointed goatgrass (Aegilops cylindrica Host. # AEGCY), and downy brome (Bromus tectorum L. # BROTE) were paired in all possible combinations to determine competitive relationships during vegetative growth. Under growth chamber conditions of ample fertility and soil moisture and day/night temperatures of 18/10 C, relative yield totals for the three species were similar, indicating that they compete for the same resources. Both winter wheat and jointed goatgrass had greater plant growth and higher relative crowding coefficients than downy brome, which indicated a hierarchy of relative competitiveness of winter wheat > jointed goatgrass >>...
Seedling vernalization was more effective than seed vernalization in promoting flowering of downy brome (Bromus tectorum L. # BROTE). Vernalizing imbibed downy brome caryopses at 3 C for 0 to 30 days did not induce rapid flowering when the caryopses were planted. Downy brome seedlings were exposed for 30 days to six photoperiod/temperature treatments. After subsequent transfer to long days, plants from the short-day/3 C treatment flowered within 30 days. Flowering was delayed or was absent in treatments with higher temperatures or long days. The shoot apex increased in volume during the short-day/3 C vernalization period. Two days following vernalization, floral initiation had occurred. By day 5, lateral organs...
Downy brome (Bromus tectorum L. #3 BROTE) may be a troublesome weed in winter small grains, perennial legumes, perennial grasses grown for seed, and orchards. In Nebraska, winter wheat (Triticum aestivum L.) yields have been depressed 30% by downy brome populations of 11 to 22 plants/mi2 (8). In Oregon, downy brome densities of 108 to 160 and 538 plants/m2 reduced yields by 40 and 92%, respectively (22, 23). In Idaho, wheat yields were depressed 20 to 40% with 55 to 110 plants/m2 (18). Downy brome has also been shown to lower yields and quality of hay from infested fields of alfalfa (Medicago sativa L.) (29). In perennial grass seed fields, downy brome may cause a serious seed quality problem (16). Some grass seed...
Downy brome seed production was measured in the field following the establishment of different moisture levels using a line source sprinkler irrigation system. Results indicated that seed production was strongly affected by different moisture levels, with a curvilinear decrease in seed number from higher to lower moisture. In a hydroponic study with water deficits induced by PEG-8000, no seeds were produced when plants were severely stressed (-1.1 MPa) for a 7-day period during culm elongation or anthesis. Number of seeds/panicle was reduced under severe water stress during seed fill, under moderate stress (-0.5 MPa) during anthesis or seed fill, and under mild stress (-0.1 MPa) during anthesis. Water stress also...
Downy brome is an introduced Mediterranean annual grass that now dominates millions of hectares of western U.S. rangelands. The presence of this grass has eliminated many native species and accelerated wildfire cycles. The objective of this study was to identify soil additives that allowed germination but inhibited emergence of downy brome, while not affecting germination or emergence of the native perennial grass Hilaria jamesii. On the basis of data from previous studies, we focused on additives that altered the availability of soil nitrogen (N), phosphorus (P), and potassium (K). Most water-soluble treatments inhibited downy brome germination and emergence. We attribute the inhibitory effects of these treatments...
Invasive plants impose threats to both natural and managed ecosystems. Downy brome is among the most aggressive invasive weeds that has infested the shrub-steppe ecoregion of eastern Washington. Hyperspectral remote sensing has potential for early detection and for monitoring the spread of downy brome?information that is essential for developing effective management strategies. Two airborne hyperspectral Advanced Visible Infrared Imaging Spectrometer (AVIRIS) images (electromagnetic spectrum ranging from 400 to 2,500 nm) were acquired at a nominal 4-m ground resolution over a study area in south-central Washington on July 27, 2000 and May 5, 2003. We used a mixture-tuned matched filtering (MTMF) algorithm to classify...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: MTMF,
Weed Science,
hyperspectral imaging,
invasive species mapping,
remote sensing
A downy brome population in a winter wheat field at , Spain, survived use rates of chlortoluron () over 2 consecutive yr, where wheat monoculture and multiple annual chlortoluron applications had been carried out. The resistant (CR) biotype showed a higher ED50 value (; the concentration required for 50% reduction of fresh weight) than the susceptible (S) control (), with a 3.4-fold increase in chlortoluron tolerance. Chlortoluron resistance in the CR downy brome biotype was not caused by altered absorption, translocation, or modification of the herbicide target site but by enhanced detoxification. The inhibition of both the recovery of photosynthetic electron transport and chlortoluron metabolism in the CR biotype...
Enhanced herbicide metabolism is less common than target site-based herbicide resistance in weeds and often confers resistance to chemically dissimilar herbicides. In a previous study, the mechanism of acetolactate synthase (ALS)-inhibitor resistance in a downy brome biotype was determined to be metabolism. Our research was aimed at determining the multiple resistance pattern in the downy brome biotype, establishing its physiological basis, and investigating its fitness. Dose-response experiments showed that the resistant biotype was also moderately resistant to ethofumesate, clethodim, fluazifop, diuron, and terbacil and highly resistant to the triazine herbicides, atrazine and metribuzin. DNA sequence analysis...
Downy brome (Bromus tectorum L. #3 BROTE), also known as cheatgrass, downy chess, broncograss, Mormon oats, and junegrass, was introduced into the United States from Europe, apparently during the middle of the nineteenth century (11, 21). According to Mack (23), downy brome entered British Columbia, Washington, and Utah around 1890; and by 1928 it had reached its present range, occupying much of the perennial grassland in Washington, Idaho, Oregon, Nevada, Utah, and British Columbia. Today, downy brome is a widespread weed throughout most of Canada, Mexico, and the United States, except for the southeastern United States (5, 17). Some consider downy brome to be an important forage because it provides most of the...
Densities up to 100 downy brome m� were established in winter wheat in southeastern Wyoming and west-central Kansas to quantify wheat yield loss from downy brome interference and to approximate economic threshold levels. A quadratic equation best described wheat yield loss as a function of weed density when downy brome emerged within 14 days after wheat emergence. Densities of 24, 40, and 65 downy brome m� reduced wheat yield by 10, 15, and 20%, respectively. Wheat yield was not reduced when downy brome emerged 21 or more days later than wheat. Economic thresholds varied with changes in downy brome density, cost of control, wheat price, and potential wheat yield. In a greenhouse experiment, dry weight of 72-day-old...
Field spectroradiometric plant canopy measurements showed that broom snakeweed [Gutierrezia sarothrae (Pursh.) Britt. and Rusby # GUESA] and spiny aster (Aster spinosus Benth. # ASTSN) had lower near-infrared (0.85-μm) reflectance than did other associated rangeland shrubs and herbaceous vegetation. The low near-infrared reflectances of both species were attributed to their erectophile (erect leaf/stem) canopy structures. These low near-infrared reflectance values caused broom snakeweed to have a dark-brown to black image on color-infrared aerial photos (0.50- to 0.90-μm), whereas spiny aster had a dark reddish-brown to black image. Other rangeland plant species had light-brown, red, or magenta images....
Foliar absorption of picloram by broom snakeweed, a rangeland shrub, was investigated. Picloram uptake into leaf, axillary bud, and stem tissues was similar. In addition, picloram uptake by leaf tissue from greenhouse- and field-grown broom snakeweed did not differ. Picloram accumulated rapidly and absorption saturated between 15 min and 1 h of application; no further absorption occurred through 72 h with maximum uptake ca. 15% of applied picloram. Picloram content increased linearly with increasing external picloram concentration, implying that movement of the herbicide across the cuticle is via diffusion. Absorption was dependent on relative humidity and temperature with the greatest uptake at 94% relative humidity...
Foliar and root absorption and translocation of metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one) by downy brome (Bromus tectorum L. # BROTE) and winter wheat (Triticum aestivum L.) was determined. After a 48-h absorption period, roots of three-week-old downy brome plants had absorbed two times more metribuzin on a total plant fresh weight basis than had roots of winter wheat. Root-absorbed metribuzin was translocated similarly regardless of species with 80% of absorbed �?C accumulating in leaf blades, 10% in the leaf sheaths, and 10% in the roots. After 24 h, leaves of downy brome and winter wheat had absorbed, respectively, 26 and 36% of foliar-applied metribuzin, and absorption...
As an agrestal weed, downy brome (Bromus tectorum L. #3 BROTE) is most troublesome in winter wheat (Triticum aestivum L. # TRIAE) and alfalfa (Medicago sativa L. # MEDSA) because of the ability of downy brome to reproduce prior to crop harvesting (70, 76). Geographically, downy brome is most common in the western half of the United States where annual rainfall totals 15 to 55 cm and autumn rainfall ranges from 5 to 12 cm (10, 11, 86, 98). In contrast, cheat (Bromus secalinus L. # BROSE) is more common in the eastern portion of the hard red winter wheat producing regions and in the more humid soft red winter wheat region. Behrendt and Hanf (12) state that cheat has been more common on acid sandy or loamy soils while...
Picloram (4-amino-3,5,6-trichloro-2-pyridine-carboxylic acid) and metsulfuron {2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoic acid} were applied to broom snakeweed (Gutierrezia sarothrae [Pursh.] Britt. and Rusby # GUESA) on two spring dates and three fall dates from October 1983 to 1985. Applications of picloram and metsulfuron in the fall more effectively controlled broom snakeweed than applications in the spring. Lower herbicide rates were necessary for 90% or greater control on a sandy loam than on a silty clay loam. Grass yield increased significantly the first, second, and third growing seasons when a majority of the broom snakeweed were killed by either herbicide, but was...
Broom snakeweed achene dispersal was monitored by placing surface-level traps outwards in the cardinal directions from 12 plants and collecting the achenes weekly or bi-weekly from September 1993 until seeds were no longer retained by the plants after 42 wk. About 50% of the achenes dispersed between October and December. Especially high numbers of achenes were dislodged during periods of intense winter winds and rains, with 78% of the seed placed into the east tray and 86% falling within 50 cm of the parent plant. Achene production averaged 3,928 (� 1,146) per plant in 1993 and 2,036 (� 987) per plant in 1994. Achenes collected over time directly from the inflorescence and achenes stored in nylon packets on the...
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