A field study was conducted to determine the effect of increasing seed rates of spring wheat (Triticum aestivum) on redstem filaree (Erodium cicutarium) biomass and seed production and on wheat yield in a zero-tillage cropping system. Wheat was sown at 50, 100, 150, 200, and 300 kg/ha in an experiment four consecutive years to determine annual and accumulated effects over time. Redstem filaree was most competitive with wheat when it emerged before or with wheat and when rainfall was plentiful during May and June. Redstem filaree biomass and seed production were markedly inhibited by drought conditions. An increase in wheat seed rate from 50 to 300 kg/ha reduced redstem filaree biomass and seed production by 53 to 95% over the years. There was little yield benefit to increasing the seed rate of weed-free wheat above 50 kg/ha. However, in the presence of redstem filaree, an increase in wheat seed rate from 50 to 300 kg/ha resulted in wheat yield being increased by 56 to 498%. Over four consecutive years, an increase in wheat seed rate from 50 to 300 kg/ha reduced redstem filaree in the soil seedbank by 79%. Higher seed rates of wheat can be an effective component of an improved program for redstem filaree management in conservation tillage cropping systems.

Reports of resistance to grass-selective herbicides, including johnsongrass (Sorghum halepense) resistant to fluazifop-P, have become quite common. Experiments were conducted to determine if fluazifop-P resistance could be transferred from johnsongrass to crop sorghum (Sorghum bicolor) and to identify the heritability of resistance in the progeny. A population of male sterile, fluazifop-P–sensitive sorghum, AKS-82, was interplanted with fluazifop-P–resistant johnsongrass and progeny treated with 0.105 kg ai/ha fluazifop-P postemergence (POST). Surviving seedlings were backcrossed to fluazifop-P–resistant johnsongrass. Viable plants from this successful cross were then testcrossed to another sensitive sorghum, TX622. These testcross progeny were then screened for herbicide resistance by again applying fluazifop-P POST at 0.105 kg /ha. Chi-square analysis revealed that resistance to fluazifop-P was inherited by a single, dominant gene. Natural hybridization of johnsongrass and sorghum is possible, and transfer of herbicide resistance between species can occur.

Field studies were conducted in 1996 and 1997 to evaluate response of eight peanut cultivars to diclosulam applied preplant incorporated at 36 g ai/ha in a weed-free environment. Peanut cultivars evaluated included ‘NC 12C’, ‘NC 7’, ‘VAC 92R’, ‘NC-V 11’, ‘NC 10C’, ‘AT VC 1’,‘NC 9’, and the experimental breeding line N90010E. Visible injury 3 wk after planting was less than 5% regardless of cultivar. No injury was observed at 21 d after planting. Diclosulam did not influence the incidence of early leaf spot, late leaf spot, southern stem rot, cylindrocladium black rot, or tomato spotted wilt virus. Diclosulam did not affect percentage of extra large kernels, sound mature kernels, other kernels, and yield.

The effect of seeding depth on emergence of red rice (Oryza sativa) ecotypes from Arkansas (AR), Louisiana (LA), and Mississippi (MS) was determined under dry-seeded rice production in clay and silt loam soils in Arkansas. By 21 d after planting (DAP), all red rice ecotypes had emerged from planting depths of 1.3, 2.5, 5.0, and 7.5 cm in both clay and silt loam soils. In silt loam soil, seedling emergence from 2.5 cm 7 DAP tended to be greater than from 1.3 cm in an early (normal temperature) planting. Also in this situation, the LA ecotype emerged more vigorously than the other ecotypes at all seeding depths and emerged from 7.5 cm at levels 1.5 times those of the other ecotypes at the same depth. In the clay soil, seedling emergence from 7.5 cm at 21 DAP was greater for the LA and MS ecotypes than for the AR ecotype in an early planting, but these differences were not observed for a late (elevated temperature) planting. Seedling emergence was earlier and greater in silt loam than in clay. The LA ecotype generally produced the greatest aboveground dry matter, especially at the early planting. The MS ecotype averaged 30% less dry matter production than the AR ecotype for the late planting in both soils. The ability of the LA and MS ecotypes to emerge from greater depths than the AR ecotype under certain soil and temperature conditions suggests that they could be more difficult to control with cultural practices used in dry-seeded rice culture.

Field studies were conducted in 19-cm-row soybean during 1997 and 1998 to evaluate the rate and timing of glyphosate applications applied alone at 0.42 and 0.63 kg ae/ha and with other herbicides to glyphosate-resistant soybean in terms of weed control, soybean yield, and net return. Weed species included barnyardgrass, hemp sesbania, pitted morningglory, and prickly sida. Among glyphosate-alone weed control programs, sequential applications generally provided the highest and most consistent control of all species evaluated (above 90% for broadleaf species). Glyphosate applied in combination with selective postemergence (POST) herbicides or following soil-applied herbicides controlled most species comparable to sequential glyphosate applications. Most herbicide programs, except for single glyphosate applications, were comparable to sequential glyphosate applications in terms of soybean yield and net return and ranged from 2,221 to 2,827 kg/ha and $410.28 to $549.60/ha. Depending on the year, either one or two glyphosate applications were needed for adequate weed control in programs with a soil-applied herbicide. Glyphosate rate affected neither weed control, yield, nor net return. Depending on a producer's management style and weed spectrum, weed control programs with glyphosate alone, in combination with another POST herbicide, or following soil-applied herbicides are all viable options in drilled glyphosate-resistant soybean.

To manage jointed goatgrass (Aegilops cylindrica), growers need an action threshold decision aid to assist them in deciding when to rotate to a spring crop instead of growing winter wheat (Triticum aestivum). A study was conducted in Washington from 1992 to 1995 to predict winter wheat yield loss based on a jointed goatgrass population in the previous year's winter wheat crop. To describe the relationship between jointed goatgrass density in year 1 and the resulting winter wheat yield loss in year 2, data were fitted to a rectangular hyperbolic model. First year jointed goatgrass densities in winter wheat of 1 to 5 plants/m2 led to a second year winter wheat yield loss of 3 to 30%. Yield loss was greater in a dry year than in a normal to wet year. To initiate an action threshold for jointed goatgrass successfully, growers need to incorporate data from this study with their knowledge of yield potential, price dockage of the subsequent winter wheat crop, and profitability of alternative spring crop rotations.

Diagnosing herbicide-resistant weeds as a first step in resistance management and monitoring their nature, distribution, and abundance demands efficient and effective screening tests. This review summarizes and recommends appropriate seed sampling techniques, protocols for screening weeds for resistance to herbicides of different sites of action, interpretation of results, and information given to the grower. Elements common to all screening procedures are reviewed. Choosing appropriate discriminating doses to distinguish between resistant and susceptible weed biotypes is the most important factor in achieving accurate and consistent results. Interpretation of results is also critical because resistant weeds may comprise a small portion of the population in suspected accessions or biotypes.

Straight-backed sentinels in high crowned busbies
rise in crowded companies
from river bank and marsh.
Grown old and fluffed with a thousand florets
gone to seed, the heads make fine torches
for skaters on the pond.
(“Cattails,” Prentice and Sargent 1973)

Until recent times, Typha was the sole genus of Typhaceae, the cattail family. Now the family has been extended to include Sparganium, the burreeds. The 15 species of Typha are prevalent and bothersome emergent aquatic weeds with a worldwide distribution (Heywood 1993; Hickman 1993). The genus Typha was erected in 1753 by Carolus Linnaeus in his Genera Plantarum.