Experiments were conducted in 2000 and 2001 to evaluate efficacy of AE F130060 03 plus AE F107892 applied postemergence for the control of Italian ryegrass in barley. AE F130060 03 plus AE F107892 controlled Italian ryegrass when applied at two application rates and at three timings. Barley successfully recovered from initial injury caused by early-postemergence (EP) and middle-postemergence (MP) application timings. The late-postemergence (LP) timing resulted in lower yield than the EP or MP application timings. AE F130060 03 plus AE F107892 applied EP controlled Italian ryegrass similar to flufenacet plus metribuzin applied delayed preemergence (DPRE) when rainfall was received. Barley yields were also similar. However, with insufficient rainfall, AE F130060 03 plus AE F107892 provided superior Italian ryegrass control. EP treatments of AE F130060 03 plus AE F107892 after a DPRE application of flufenacet plus metribuzin or chlorsulfuron plus metsulfuron completely controlled Italian ryegrass and resulted in excellent yields.

Soybean producers of South Carolina were surveyed in 2000 through mail and on-farm visits to determine which production practices limit seed yields the most. Production systems have direct implications on weed management practices, difficulties, and future problems. When asked to describe two extension and research focus areas that would improve current soybean production, the number one response was improved weed control strategies. Fifty-seven percent of the respondents indicated that weeds were the pest that most limited soybean yield. Sicklepod, Palmer amaranth, morningglory species, common cocklebur, yellow nutsedge, and Texas panicum were considered the most problematic weeds. More than half the producers (68%) used glyphosate-resistant soybean, with one-half of these farmers producing soybean in row widths > 51 cm. Of the farmers who grew conventional soybean, 10% used narrow rows (≤ 51 cm), whereas 22% used wide rows (> 51 cm). Only 27% of the farmers who planted glyphosate-resistant soybean used a soil-applied herbicide. Forty-three percent of farmers based the need for a postemergence herbicide on weed size, 21% used no repeatable method, 21% relied on days after soybean emergence, 11% depended on soybean size or groundcover, and only 4% used a combination of weed density and size. Thirty-five percent of the farmers did not rotate soybean with another crop. In fields where soybean parasitic nematodes reduced soybean growth or caused plant death, late-season weed infestations were often exacerbated, especially in the absence of nonresidual herbicides. Specific reasons for difficulty in managing weeds in soybean may include a diverse weed spectrum, which is difficult to control with a single herbicide, the use of wide-row soybean, the lack of crop rotation, the prevalence of nematodes that directly affect crop development and, in turn, weed management, the lack of an appropriate criterion for timing postemergence herbicide applications, and the greater attention paid to production of more valuable crops. Educational efforts addressing weed management problems and association of such problems with other production practices are needed if weed management is to be improved and weed-induced yield losses minimized.

Crop–weed interactions is an important topic for introductory weed science courses. The effect of the timing of weed emergence and the duration of weed competition on crop yield are two topics usually covered when discussing competition. Students generally gain a better knowledge of these concepts through observation in addition to discussion of the underlying concepts. An additive removal and plant-back experiment was used, in the undergraduate weed science laboratory at Iowa State University, to demonstrate critical period for weed control concepts for cultivated radish. In one series of treatments, weeds were sown at the time of radish planting and removed at 2, 3, and 4 wk after planting. In another series, weeds were sown at 1, 2, and 4 wk after radish planting and allowed to grow in the flats until completion of the experiment. Two controls, one weed free and one unweeded, were also included. The results from four semesters suggested that the critical period for weed control began immediately after planting and lasted 3 wk. The timing and duration of the critical period was consistent across the four semesters evaluated. This activity was successful in demonstrating the critical period for weed control in radish.

Row crop weed management decisions can be complex due to the number of available herbicide treatment options, the multispecies nature of weed infestations within fields, and the effect of soil characteristics and soil-moisture conditions on herbicide efficacy. To assist weed managers in evaluating alternative strategies and tactics, three computer programs have been developed for corn, cotton, peanut, and soybean. The programs, called HADSS (Herbicide Application Decision Support System), Pocket HERB, and WebHADSS, utilize field-specific information to estimate yield loss that may occur if no control methods are used, to eliminate herbicide treatments that are inappropriate for the specified conditions, and to calculate expected yield loss after treatment and expected net return for each available herbicide treatment. Each program has a unique interactive interface that provides recommendations to three distinct kinds of usage: desktop usage (HADSS), internet usage (WebHADSS), and on-site usage (Pocket HERB). Using WeedEd, an editing program, cooperators in several southern U.S. states have created different versions of HADSS, WebHADSS, and Pocket HERB that are tailored to conditions and weed management systems in their locations.

Over a decade ago, the Weed Science Society of America sponsored a symposium on the then emerging technology of herbicide-tolerant crops (HTCs). The symposium and subsequent proceedings addressed potential benefits and concerns about that new technology to control weeds. Technological, biological, and ethical questions were addressed that were likely to emerge from the widespread adoption of HTCs. It was suggested at that time that if such questions were answered, HTC development would proceed on a more solid foundation, whereas continued uncertainty and criticism would probably result if the questions were not answered. We now review developments in HTC technology. Questions and concerns posed one decade ago are still pertinent, but current knowledge is still insufficient to address them. Adoption of HTC has risen dramatically since their commercial introduction, but there is still no evidence of associated production cost reductions or enhanced yields

Field studies were conducted in 2001 and 2002 to determine the effect of clethodim, sethoxydim, and halosulfuron on centipedegrass seedhead suppression, seed yield, and seed germination. Clethodim (0.28 kg/ha), sethoxydim (0.31 kg/ha), and halosulfuron (0.06 kg/ha) applications were made at −2, 0, 2, 4, and 6 wk after mowing stopped (WAMS) in each year. Seedhead suppression varied in severity between 2001 and 2002, with increased suppression in 2001. Clethodim reduced seedhead emergence 50 and 33% when applied at 2 and 4 WAMS, respectively, in 2001. Sethoxydim reduced seedhead emergence by 21 and 18% when applied at 2 and 4 WAMS, respectively, in 2001. Halosulfuron had no effect on seedhead emergence in either year and did not reduce seed yield at any application timing. Clethodim reduced seed yield between 22 and 44% at all application timings. The pattern of yield reduction from sethoxydim was similar to that caused by clethodim; however, yield reduction with sethoxydim ranged between 7 and 48% for all application timings. The greatest reduction in seed yield occurred when clethodim and sethoxydim were applied 4 WAMS. Seed germination was not affected by halosulfuron or sethoxydim at any application timing. Clethodim, when applied at 4 and 6 WAMS, decreased seed germination by 17 and 20%, respectively.

There, fed by Food they love, to rankest size, Around the Dwellings Docks and Wormwood rise;

Here the strong Mallow strikes her slimy Root, Here the dull Nightshade hangs her deadly Fruit;

The Borough, Rev. George Crabbe, 1810.

The black nightshade (Solanum nigrum L.) complex consists of a group of plants in the section Solanum of the genus Solanum. Black nightshade is the type for the genus Solanum and the most well-known as a noxious weed species. Black nightshade also has been used around the world as a pot-herb, and the berries are used to bake pies despite its reputation as a poisonous plant (Edmonds and Chweya 1997; Mabberley 1997). The black nightshades form a complex group of mainly herbaceous or shrubby plants that are still not completely resolved taxonomically. Most weed references to black nightshade predating the 1980s simply refer to S. nigrum L. as the species. However, taxonomists now recognize many weedy species within this complex (D'Arcy 1991; Edmonds 1977; Edmonds and Chweya 1997; Mabberley 1997; Schilling 1981). This article will mainly cover the history of black nightshade as recorded in the literature. Current species names will be clarified or identified within the Solanum section where information is available.

Effect of weed interference duration and weed-free period on glufosinate-resistant rice was evaluated in 1998 and 1999. Weed interference for more than 2 wk reduced plant height 12 wk after emergence compared with the season-long weed-free treatment. Grain yield loss of 1,090 to 4,880 kg/ha was observed when weeds were allowed to interfere with rice from 2 wk to season-long. The weed-free period study indicated that early control of weeds could sustain rice growth and yield potential. This research suggests that effective weed control from 1 to 6 wk after rice emergence is important in fields with high weed densities for maximizing yield potential of glufosinate-resistant rice.

Soft red winter wheat tolerance and Italian ryegrass control with AE F130060 00 plus AE F115008 00 at 12.5 plus 2.5 g ai/ha applied alone and mixed with dicamba, 2,4-D, or thifensulfuron plus tribenuron were examined in separate field experiments. AE F130060 00 plus AE F115008 00 applied alone in December injured wheat 12% or less, whereas mixtures with thifensulfuron plus tribenuron injured wheat 15% or less. AE F130060 00 plus AE F115008 00 applied alone in February or mixed with dicamba, 2,4-D, or thifensulfuron plus tribenuron injured wheat 3% or less. No treatment affected yield of weed-free wheat. AE F130060 00 plus AE F115008 00 applied in December controlled Italian ryegrass 86 to 99% in May and increased wheat yield 142 to 254%. At two of four locations, Italian ryegrass control was greater with the December application of AE F130060 00 plus AE F115008 as compared with the February application. Dicamba or 2,4-D mixed with AE F130060 00 plus AE F115008 00 reduced Italian ryegrass control in May approximately 10% in half the trials but did not affect wheat yield compared with AE F130060 00 plus AE F115008 00 applied alone. Thifensulfuron plus tribenuron mixed with AE F130060 00 plus AE F115008 00 did not affect Italian ryegrass control or wheat yield. Under greenhouse conditions, the rate of AE F130060 00 plus AE F115008 00 needed for 80% Italian ryegrass visible control and 80% shoot fresh weight reduction was increased 60 to 68% in mixtures with 2,4-D. Dicamba increased the rate needed for 80% visible control and shoot fresh weight reduction 132 to 139%.

Wild garlic (Allium vineale L.), also called crow garlic in many English-speaking countries, is a perennial weed with a particularly noxious reputation. Although a native of Eurasia, it has found an especially suitable home in the eastern United States, among other places. Wild garlic has little redeeming value despite its similarity to cultivated garlic (Allium sativum L.). The property of wild garlic of passing its excessively strong flavor to food is infamous among dairymen and wheat (Triticum aestivum L.) growers, for whom contamination by the weed causes a serious reduction in product quality (Anonymous 1975; Holm et al. 1991; Iltis 1949).