Dry peas (pea) usually require early and effective weed management for optimum yields. However, it is not always possible to control all weeds with a single herbicide application. In experiments at Lacombe and Lethbridge, Alberta, Canada, we determined the relative importance of controlling redstem filaree or wild oat, or both species. Bentazon, sethoxydim, or a imazethapyr/imazamox mixture was applied to control redstem filaree, wild oat, or both weeds, respectively. None of the herbicides caused visually detectable crop injury. Time of weed removal effects on pea yield were inconsistent. In addition, applying half or full herbicide rates did not usually influence weed biomass, pea yield, or pea seed weight. Averaged across all variables except herbicide, pea yield losses due to competition from redstem filaree, wild oat, or both species averaged 31, 47, or 53%, respectively. When redstem filaree and wild oat were controlled with imazethapyr/imazamox, pea yields were the same as weed-free check plots in three of four location-years (89% of weed-free yields for all four location-years). Optimal pea yields in weed communities with redstem filaree and wild oat as dominant species were more dependent upon selecting an herbicide that controlled both species than a specific time of weed removal or herbicide rate.

Control of common lambsquarters with glyphosate in Michigan soybean fields has been inconsistent. Stem-boring insects and evidence of insect tunneling were found inside the stems of common lambsquarters plants not controlled with glyphosate. In 2004 and 2005, field surveys and studies were conducted to identify and evaluate the prevalence of stem-boring insects in common lambsquarters in Michigan and Indiana soybean fields to determine whether tunneling by insects occurred before or following POST glyphosate applications and to evaluate the effect of glyphosate rate, application timing, and insect tunneling on the control of common lambsquarters with glyphosate. Two insect species, the beet petiole borer (Cosmobaris americana) from the Curculionidae family and an unidentified leafminer fly larvae from the Agromyzidae family were found inside common lambsquarters stems. Leafminer larvae were present in Michigan soybean fields in mid- to late-June, when most POST glyphosate applications are made in Michigan and Indiana; however, beet petiole borer larvae were not found in common lambsquarters stems until mid-July and would only be present in common lambsquarters plants if glyphosate applications occurred at that time. Results from three field experiments in East Lansing, MI, demonstrated the variability in common lambsquarters control. Control ranged from 79 to 98%, 75 to 99%, and 49 to 97% from glyphosate applied at 0.84 kgae/ha to 10-, 25-, and 46-cm common lambsquarters, respectively. In general, applying glyphosate to common lambsquarters plants 10 cm or less, or increasing the glyphosate rate beyond 0.84 kgae/ha, improved common lambsquarters control. Insect tunneling by leafminer and beet petiole borer larvae did not contribute to reduced common lambsquarters control with glyphosate applied to 10- and 25-cm common lambsquarters.

Base temperature (Tb) for leaf appearance and the thermal time interval between appearance of successive leaves (phyllochron) were determined for six common weed species from a series of growth chamber experiments. Mean leaf appearance Tb values for giant ragweed, velvetleaf, redroot pigweed, large crabgrass, woolly cupgrass, and wild-proso millet were 1.3, 8.0, 8.5, 4.5, 2.2, and 5.1 C, respectively, and mean phyllochron values were 37.2, 34.4, 17.3, 42.2, 65.2, and 34.2 growing degree-days per leaf, respectively. Phyllochron values increased slightly with mean temperature for each weed species. To our knowledge, these are the first reported leaf appearance Tb and phyllochron values for giant ragweed, woolly cupgrass, and wild-proso millet. The results confirm leaf appearance Tb and phyllochron values reported previously for velvetleaf and redroot pigweed. However, large crabgrass leaf appearance Tb and phyllochron values in our study varied somewhat from those reported previously. The results provide information needed for parameterization of plant growth models that predict leaf development based on thermal time.

Considerable discussion has occurred among the weed science community regarding the potential benefits and limitations of integrated approaches to crop and pest management. This discussion also needs to occur in our weed science classrooms, where students from a wide range of academic disciplines are trained in the fundamentals of weed ecology and management. Although the inherent complexity of integrated crop and pest management can make this adaptation to our weed science courses challenging, the use of experiential learning techniques provides an effective means to promote understanding and retention of these concepts. This paper outlines several classroom activities based on the experiential learning approaches that have been implemented by the authors. The activities focus on (1) weed identification and natural history, (2) weed population processes, and (3) integrated management systems. For each activity, we offer our rationale for the exercise, an example of its implementation in the classroom setting, potential pitfalls, and student feedback regarding their perceptions of the activity's educational value. With this paper, we hope to provide examples that may be useful to other weed science educators wishing to incorporate more experiential learning activities into their courses and to initiate a dialogue between educators that can help our community improve and enliven weed science education.

Eradication is often stated as an essential element of weed management. Assessing the costs and benefits of eradication programs is often difficult because doing so requires speculation about the impacts and spread of weeds if eradication measures were not undertaken. The objective of this article is to describe and assess the Montana Dyer's Woad Cooperative Project, a program aimed at eradicating dyer's woad from Montana. The Project comprises four key components: early detection, treatment technologies, repeated site visits with monitoring, and education. To evaluate the success of the Montana Dyer's Woad Cooperative Project, we used monitoring data to observe the change in the number of counties where dyer's woad is present, plotted the trend in population size over time, and evaluated change in infestation size. We also predicted population spread based on the 1999 population size and demographic characteristics of dyer's woad. Dyer's woad has been eradicated from 9 of 13 infested counties in Montana, and infestation sizes have decreased in the remaining infested counties. In some counties, a containment effort was needed in conjunction with repeated inventories and treatment applications to prevent spread while depleting the seedbank to the point where eradication is possible. If not for the Project, our analysis suggests that some dyer's woad populations might consist of millions of plants, potentially covering 39,021 ha in Montana and costing $1.9 million/yr to manage. In comparison, the Project has reduced the total area infested in Montana to 2.6 ha and cost the state only $142,000 for the past 7 yr of management. In Montana, dyer's woad eradication from individual counties has been successful because of persistence and ongoing cooperative efforts.

In November 2004, a 29-question survey was mailed to Delaware soybean growers to determine grower perceptions of glyphosate-resistant (GR) horseweed and if glyphosate applications, GR soybean usage, and management practices had been altered in lieu of the presence of resistance. A total of 213 valid responses were received. Ninety-eight percent of respondents reported planting GR soybean at some point in the last 5 yr, with 90% reporting having planted GR soybean 3 or more years. The presence of GR horseweed on-farm was reported by 38% of the respondents and 95% of those growers with GR horseweed on-farm reported implementing one or more changes in GR soybean management. The most frequent change (66% of growers) due to resistant horseweed was the application of another herbicide with a different mode of action before planting. Forty-eight percent of growers with resistance on-farm reported a $5 to $17/ha increase to manage for GR horseweed, with 28% reporting a greater than $17/ha increase. Regardless of experience with GR horseweed, approximately 80% responded that it was worthwhile to incur additional costs now to preserve glyphosate for future use. Soybean grower reliance on glyphosate has not decreased in light of GR horseweed in Delaware. Misconceptions of timing for the selection of GR horseweed biotypes and the future availability of new herbicides with different modes of action exist within the farming community.

Jointed goatgrass is a prominent weed infesting winter wheat in the western United States. Individual control tactics often are ineffective and inconsistent, but management systems comprised of several tactics designed to disrupt population dynamics of jointed goatgrass can reduce infestation levels in winter wheat. Tactics are planned to favor decline of seedbank density, reduce seedling emergence in winter wheat, and minimize seed production of plants established in winter wheat. We describe a visual guide that will help producers plan management systems for jointed goatgrass with a diversity of cultural tactics. The guide organizes cultural tactics by decision times of producers during the winter wheat production cycle. Scientists are effectively managing jointed goatgrass in a diversity of production systems by integrating cultural tactics across decision times.

Although many of us fondly associate parsnips with a rustic, home-cooked meal, there is also a wild variety that is increasingly causing problems as a weed in North America. The cultivated variety is a subspecies of Pastinaca sativa (Pastinaca sativa ssp. sativa) and contains lower amounts of the problematic furanocoumarins than the wild version. Wild parsnip (Pastinaca sativa L. PAVSA) is an introduced facultative biennial from Eurasia. It has spread throughout the United States and southern Canada and is now colonizing old fields, railroad embankments, roadsides, and waste areas. Wild parsnip contains furanocoumarins, which deter herbivores from eating its foliage. These compounds can also cause phytophotodermatitis in humans and livestock, a condition that results in patches of redness and blisters on the skin when they come into contact with the sap or ingest parts of the plant in the presence of sunlight. Few people, including medical professionals, recognize the plant or associate it with the burns it causes. Recently, wild parsnip has received increasing attention as expanding populations have resulted in more frequent human and livestock contact with the plant. This article reviews important aspects of the etymology, distribution, history, biology, and management of wild parsnip. A key objective of this review is to raise awareness of the potential health problems caused by wild parsnip and to stimulate research that will lead to effective management of this increasingly problematic species.