A replacement series study was conducted in a greenhouse in 1998 and 1999 to evaluate the interference interactions among two rice cultivars and two red rice ecotypes. Plants were established in proportions of 3:0, 2:1, 1:2, and 0:3 (rice–red rice) plants/pot. Relative yield of Kaybonnet based on the shoot dry weight was lower than that of KatyRR or LA3, whereas PI 312777 was comparable to that of KatyRR and LA3. These results indicate that Kaybonnet was less competitive than PI 312777 when contrasted with KatyRR and LA3 red rice ecotypes. Kaybonnet (commercial rice cultivar) was dominated by both KatyRR (suspected rice × red rice cross) and LA3 (tall red rice ecotype) in tiller production, whereas PI 312777 (weed-suppressive cultivar) was comparable to either KatyRR or LA3. Both KatyRR and LA3 considerably reduced the leaf area of Kaybonnet. In contrast, PI 312777 reduced the growth of KatyRR, and its leaf area was comparable to that of LA3. The data suggest that high tillering capacity, as demonstrated by PI 312777, should be considered when breeding for rice cultivars that are competitive against weeds. This agronomic characteristic of rice may improve the success of reduced herbicide rate application programs.

“Pesta” is a granular, extruded product made from a cereal grain flour and any biological control agent. A strain of Pseudomonas fluorescens, BRG100, which is a pathogen of green foxtail, has been formulated into a Pesta product. P. fluorescens BRG100 survived processing best in oat flour, and the addition of 20% (wt/wt) maltose extended the shelf life of the product to more than 32 wk. Field studies of 8-wk duration showed that a Pesta product containing BRG100 suppressed green foxtail emergence by as much as 90%. An optimally formulated and processed Pesta product has potential for the biocontrol of green foxtail.

Field experiments were conducted in 1999 and 2000 to determine the influence of mesotrione postemergence application rate, application timing, and addition of atrazine on corn injury, weed control, and corn grain yield. Corn injury in the form of leaf bleaching ranged from 0 to 15% at 7 d after treatment (DAT). In general, most of the bleaching injury rapidly dissipated with slight (≤ 8%) to no corn injury observed at 28 DAT. Control of common cocklebur with mesotrione at 14 DAT ranged from 79 to 98% for all treatments over both years. Applying mesotrione at 140 g/ha, at the early postemergence (EPOST) timing, or in combination with atrazine provided the greatest control of common cocklebur at 14 DAT. Application rate of mesotrione was the only factor that was significant in both years for control of common cocklebur later in the season at 56 DAT. Control of ivyleaf morningglory with mesostrione at 14 DAT ranged from 60 to 90% for all treatments in both years. Control of ivyleaf morningglory at 14 DAT was enhanced by the addition of atrazine to mesotrione. Control of ivyleaf morningglory at 56 DAT was greater with mid-postemergence and late postemergence than with EPOST applications, and was generally enhanced by the addition of atrazine. Yellow nutsedge control with mesotrione was inconsistent, ranging from 40 to 87% at 14 DAT for all treatments over both years. The addition of atrazine to mesotrione increased yellow nutsedge control from 47 to 87% at 14 DAT in 2000. Increasing the rate of mesotrione from 70 to 140 g/ha, as well as the addition of atrazine, improved control of yellow nutsedge at 56 DAT. Corn grain yield was not affected by corn injury or weed control as there were no significant differences in grain yield between herbicide-treated plots and handweeded plots.

Field studies were conducted in 1999 and 2000 at Simcoe, Ridgetown, and Exeter, Ontario, to evaluate the tolerance of nine sweet corn cultivars to mesotrione, applied preemergence (PRE) at 140 and 280 g ai/ha and postemergence (POST) at 100 and 200 g ai/ha. Urea ammonium nitrate fertilizer (28%) at 2.5% (v/v) and crop oil concentrate at 1% (v/v) were added to POST applications of mesotrione only. All cultivars were tolerant to mesotrione applied PRE. There was no injury, or reductions in plant height or yield with PRE applications of mesotrione at any location in either year. POST applications of mesotrione, particularly at 200 g/ha, caused significant phytotoxicity to ‘Calico Belle’ and ‘Del Monte 2038’. Other cultivars also showed phytotoxic symptoms; however, this injury was much reduced and did not occur at all locations each year. Sweet corn injury by mesotrione increased as rate increased. Del Monte 2038 also had significantly reduced plant height and yields. Other cultivars had no plant height or yield reductions because of POST applications of mesotrione.

Failure to detect noxious weeds with current survey methods prevents their control and has contributed to their ability to establish and spread in remote range and forest sites. Techniques used in remote sensing can classify plant occurrence on maps, offering a method for surveying invasive species in remote locations and across extensive areas. An imaging hyperspectral spectrometer recorded images on July 19, 1998 in Farragut State Park near Bayview, ID, in the reflected solar region of the electromagnetic spectrum ranging from 440 to 2,543 nm to detect spotted knapweed. The sensor records 128 spectral bands in 12- to 16-nm intervals at a spatial resolution of 5 m. A spectral angle mapper (SAM) algorithm was used to classify the data. Infestations in Idaho with 70 to 100% spotted knapweed cover that were 0.1 ha were detected regardless of the classification angle. However, narrow angles (2 to 8°) did not completely define the extent of the infestation, and the widest angle tested (20°) falsely classified some areas as infested. The overall image error for all classes was lowest (3%) when SAM angles ranged from 10 to 11°. Specific errors for the spotted knapweed class for the 10 to 11° angles showed that omissional and commissional errors were less than 3%. Areas with as little as 1 to 40% spotted knapweed cover were detected with an omissional error of 1% and a commissional error of 6%. Further verification sites were established on August 11, 1998 near Bozeman, MT, using the algorithms developed for Idaho. The omissional error for the Montana sites was 0%, and the commissional error was 10%. The hyperspectral sensor, Probe 1, proved an effective detection tool with the ability to detect spotted knapweed infestations.

The presence of volunteer canola is becoming a significant agro-ecological concern, given the large-scale use of herbicide-tolerant varieties in some areas. Our goal was to estimate the frequency and persistence of volunteer canola in Québec cropping systems by surveying fields that included a single canola crop since 1995. A survey was conducted in 131 fields in the main canola-growing areas of Québec: in the Saguenay-Lac Saint-Jean region and the Québec City–La Pocatière area. Volunteer canola plants were counted in 0.25-m2 quadrats every 10 m along a W pattern, and every 15 m along the margins of 88 fields. Volunteer canola plants were found in 90% of the fields surveyed and in a wide range of crops, including cereal, corn, and soybean. Average densities of 4.9 and 3.9 plants/m2 were found 1 yr after canola production in fields and field margins, respectively. Volunteer canola densities decreased significantly over time. However, volunteer plants were still present at low densities 4 and 5 yr after production. Dense stands of volunteer canola were found before postemergence herbicide application in no-till fields (9.8 ± 4.1 plants/m2), suggesting that, contrary to what was suggested in the literature, seeds could become dormant in no-till as well as in tilled systems. A small proportion of the volunteer canola plants observed in no-till fields near Québec City and Ottawa included plants that had overwintered, either originating from fall-germinated seedlings, harvested adult plants that had grown new leaves before the onset of winter, or spring regrowth from the base of unharvested adult plants from experimental plots. The presence and persistence of low densities of volunteer canola may not have been a cause of concern until now. However, producers should be made more aware of the potential short-and long-term problems associated with potential gene flow between different herbicide-tolerant canola (HT canola) varieties and also between HT canola and related weed species.

Midwest growers rely heavily on agrichemical retailers and crop consultants for making pest management decisions. A survey was mailed to 793 fertilizer and agricultural chemical dealers in Illinois to help understand their basis for pesticide recommendations, sources of information, and water quality concerns. Survey response rate was approximately 55%, and results indicated that agrichemical retailers use several sources of information, including manufacturers, universities, and company training programs. Newsletters and fact sheets were recognized as the most useful types of university resources, whereas videos were deemed the least useful. Product effectiveness was identified by 85% of the respondents as being the most important factor affecting pesticide selection. Soil erosion was listed as the greatest threat to water quality. Filter strips and best management practices were suggested as being the most likely to succeed in protecting water quality.

The sugarcane varieties ‘LCP 85-384’, ‘HoCP 85-845’, and ‘LCP 82-089’ were treated in the plant cane crop (first production year) with various combinations of azafeniden preemergence (PRE) at 0.56 or 0.84 kg ai/ha after planting in September/October, postemergence (POST) at 0.56 kg/ha in spring (March), and semidirected at 0.42 kg/ha after the final cultivation at layby in May. In the first ratoon crop (second production year) azafeniden was reapplied in spring and at layby. Herbicide programs were compared with the standard program of atrazine plus pendimethalin PRE after planting, POST applications of diuron plus pendimethalin in spring, and atrazine plus pendimethalin semidirected at layby. Crop injury was negligible for all herbicide treatments applied after planting. Azafeniden injured sugarcane 30 to 33% when applied POST in spring, and injury was most severe in plant cane and first ratoon HoCP 85-845 when they were considerably taller and had more foliage at application compared with the other varieties. Injury from azafeniden following layby application ranged from 9 to 19% in plant cane and first ratoon crops. Multiple applications of azafeniden during the plant cane and first ratoon years did not reduce stalk height, population, sugarcane yield, or sugar yield for any of the varieties when compared with the standard herbicide program.

Purple starthistle is one of the numerous species of Centaurea that have been accidentally introduced to western North America where most have become pernicious noxious weeds. Purple starthistle is not nearly as widely distributed as its close relative, yellow starthistle, but it is more undesirable because of its growth characteristics and the number, length, and persistence of its spines. Purple starthistle reproduces only by seeds. Knowledge of the seed and seedbed ecology of weeds is important in all suppression strategies and especially for purple starthistle, which has potential biological control agents that suppress seed production. Our purpose was to determine the germination of purple starthistle seeds at a wide range of constant or alternating incubation temperatures from 0 through 40 C. The maximum observed germination ranged from 94 to 100%. Some germination occurred at least 75% or above of the 55 temperature regimes tested. Optimum germination, defined as not less than the maximum observed minus one-half of the confidence interval at the 0.01 level of probability, averaged 88 to 96%. Only one accession of purple starthistle had germination at what we classify as very cold seedbed temperatures. All accessions had near 50% germination at cold seedbed temperatures. Germination was highest at moderate seedbed temperatures and declined at warmer temperatures. The only constant incubation temperature that supported optimum germination was 20 C, and that was for only one accession. The only temperature regime that always supported optimum germination was 15/25 C (15 C for 16 h and 25 C for 8 h in each 24-h period).

Our objective was to maximize Canada thistle control and plant community diversity in a waterfowl production area administered by the U.S. Fish and Wildlife Service. We tested three rates (1.5, 3.0, and 4.5 ai/ha) of glyphosate applied during spring, summer, or fall using two application methods. The lowest rate of glyphosate decreased the Canada thistle density by about 30% relative to the control. Glyphosate applied in the fall decreased Canada thistle density below that of the control more consistently than when applied in spring or summer. Wick application generally resulted in less Canada thistle biomass than did broadcast application. Species richness was generally higher when glyphosate was wick applied, and all rates of this application method increased species richness when compared with the control. We recommend fall wick application of glyphosate at 1.5 kg ai/ha to control Canada thistle near the riparian areas. This application provided optimum Canada thistle control, while maintaining species richness important for waterfowl.

Repeated application of acetyl-coA carboxylase–inhibiting herbicides, such as sethoxydim, may select for resistant (R) weed populations, making a rapid and reliable seedling bioassay a useful tool. Such a bioassay was developed to determine shoot and root responses of giant foxtail seedlings to sethoxydim. Root and shoot elongation of susceptible (S) and R giant foxtail seedlings was measured at 3 and 6 d after exposure to 0.1 to 100 mg/L sethoxydim. A bioassay concentration of 10 mg/L sethoxydim easily discriminated between S and R biotypes of giant foxtail at 6 d after exposure, with R:S shoot and root growth ratios of 3 and 10, respectively.

“All the herbe, his branches, leaves, and sede, do cleave and sticke fast to every thing that it toucheth: it is so sharp, that being drawen along the tongue, it wil make it to bleede.”

A Neiwe Herball, or Historie of Plantes, D. Rembert Dodoens, 1578

Catchweed bedstraw, Galium aparine L., is a winter or summer annual herb native to Eurasia and North America. The weed is more commonly known as “cleavers” in most of the English-speaking world outside the United States. Both names refer to the small hook-like bristles that cover the plant causing it to cling to almost anything that it touches. The plant is present on all of the world's continents in temperate zones, in warmer arctic zones, and at higher elevations in the tropics (Barkley 1986; Holm et al. 1991b). Catchweed bedstraw has numerous medicinal properties, has been used for animal feed and food processing, is a persistent weed in small grains and other crops, and is above all an accomplished world traveler and “hitch-hiker,” as we shall see.