Velvetleaf control and sugarbeet response to POST triflusulfuron applied alone and in combination with desmedipham plus phenmedipham, nonionic surfactant, and urea ammonium nitrate (50:50) were evaluated in the greenhouse (velvetleaf only) and field. In a second field study, the effect of POST applications of triflusulfuron, desmedipham plus phenmedipham, ethofumesate, endothall, or combinations of these herbicides on sugarbeet root yield and quality was determined in the absence of weeds. Triflusulfuron controlled velvetleaf only when nonionic surfactant (NIS) was added to the spray solution. Desmedipham plus phenmedipham plus triflusulfuron gave greater velvetleaf control than triflusulfuron in the absence of NIS in the field. However, adding desmedipham plus phenmedipham to triflusulfuron plus NIS decreased velvetleaf control in the greenhouse. Adding desmedipham plus phenmedipham to triflusulfuron plus NIS increased visible sugarbeet response compared to triflusulfuron plus nonionic surfactant or desmedipham plus phenmedipham 14 d after the last POST application in 1994. In the absence of weeds, POST herbicide applications that included triflusulfuron did not reduce sugarbeet root yield more than other POST herbicides.

Greenhouse studies showed that the mixed function oxidase inhibitor, piperonyl butoxide (PBO), tank-mixed with the sulfonylurea herbicides, nicosulfuron, primisulfuron, and thifensulfuron, in the absence of effective adjuvants enhanced herbicide activity on both broadleaf and grass weed species. Effective adjuvants for nicosulfuron were K-3000 for common lambsquarters, Sylgard® 309 Surfactant for velvetleaf, K-2000 for barnyardgrass, and K-2000, K-3000, and Scoil® methylated seed oil for giant foxtail control. K-3000 and Sylgard 309 enhanced velvetleaf control with primisulfuron and thifensulfuron. The 28% urea and ammonium nitrate (UAN) was more effective as an adjuvant with thifensulfuron for velvetleaf than for common lambsquarters control. The enhancement of sulfonylurea herbicide activity with PBO was most apparent when other adjuvants were least effective.

Field studies were conducted over 3 yr to evaluate rhizome johnsongrass control with asulam applied POST at 3.7 kg ai/ha 3 d before fertilization (DBF) or 0, 3, 7, 10, or 14 d after fertilization (DAF). Liquid fertilizer (18-6-12) was applied with injector knives at 0, 112, or 224 kg N/ha 5 cm on each side of a 60-cm line of rhizome johnsongrass present on 1.8-m-wide conventional sugarcane beds. Johnsongrass response to timing of asulam application after fertilization varied among years but was not affected by fertilizer rate. Johnsongrass control with asulam applied 3 DBF was greater than applications made 0, 3, or 7 DAF. With one exception, differences in johnsongrass control following fertilization and asulam application times were also reflected in the biomass of treated johnsongrass and its regrowth harvested 6 and 10 wk after asulam application, respectively. Reduced johnsongrass control associated with asulam application following fertilization was related to stress from root/rhizome injury during fertilizer placement rather than the quantity of fertilizer applied.

Field studies were conducted on a Black Belt region clay soil to evaluate pyrithiobac injury to cotton and potential carryover to grain sorghum, soybean, and wheat. Pyrithiobac was applied PPI, PRE, POST at pinhead square, or POST at first bloom at rates of 70, 140, or 280 g ai/ha to cotton. Cotton injury was 7% or less at all rates and application timings. Cotton yield was not reduced by any treatment. The PRE application to cotton, averaged over rates, reduced yield of wheat planted in the fall compared to the POST pinhead square application or the nontreated check. Pyrithiobac at 140 g/ha applied PPI to cotton the previous year reduced soybean yield; at all other rates and timings no soybean yield reduction occurred compared to the nontreated check. Pyrithiobac at all rates applied PPI to cotton caused grain sorghum injury the following year. The 280 g/ha PPI application delayed grain sorghum maturity; however, this did not translate into a yield reduction.

Field experiments conducted at four locations in Georgia and two locations in Florida during 1992 and 1993 evaluated AC 263,222 application rates and timings, systems, and mixtures for weed control, peanut injury, and yield. All rates of AC 263,222 applied early POST (EPOST) or POST controlled Ipomoea morningglories and smallflower morningglory at least 90%, and purple and yellow nutsedge at least 81%. Florida beggarweed and sicklepod control generally was highest when metolachlor was applied PPI followed by AC 263,222 applied EPOST at 71 g/ha, AC 263,222 at 27 or 36 g/ha plus bentazon plus paraquat applied POST, or with bentazon plus paraquat applied EPOST followed by AC 263,222 applied POST at 36 or 53 g/ha. Acifluorfen and acifluorfen plus bentazon reduced Florida beggarweed and sicklepod control at several locations when applied in mixture with AC 263,222. Common ragweed and hairy indigo control were 85 to 95% with bentazon plus paraquat applied EPOST followed by AC 263,222 applied POST at 36 or 53 g/ha. Highest peanut yields were obtained with treatments providing high levels of weed control.

Water use by weeds is one type of loss that contributes to the cost of weeds to agriculture. Water use efficiency provides a mechanism by which water use by weeds can be estimated. Uncontrolled weed growth could result in estimated irrigation costs exceeding $50.00/ha. Weeds like barnyardgrass at threshold densities in irrigated crops like sugarbeet or tomato are estimated to increase production costs by about $20.00/ha depending on water cost.

The current state of registration requirements for mobility assessments of pesticides is described and the various uses for mobility estimates are outlined. A survey of recent literature on mobility assessments is presented along with a suggestion for a refocus on Kd rather than KF. A proposal for a different, yet standard, more efficient approach as a replacement for the current requirements is outlined. The suggested approach could fit well within a registration package or a limited research budget as well as provide more information for model input.

Characterization of pesticide degradation in soil is an important component in determining the environmental impact of agriculturally-applied pesticides. Several techniques currently are being used to generate these data, but small-scale laboratory studies remain one of the most effective, cost-efficient mechanisms of evaluating pesticide behavior in soil. With small-scale studies, many different environmental factors can be incorporated into the experimental design, and with the use of 14C-labeled material, these studies (often referred to as soil degradation or soil metabolism studies) provide information on test substance persistence, degradation, volatilization, and mineralization. Care must be exercised, however, in selecting the experimental parameters to be used because of the potential adverse or artificial effects on the soil system.

Surface and subsurface soils are complex biological, chemical, and physical environments and to understand the fate of pesticides in the soil environment is a formidable task. To determine the environmental fate of pesticides requires a diverse array of techniques and procedures. Microbiological approaches range from applied to basic, laboratory to field, qualitative to quantitative, and from low to high technology. In the arena of biodegradation, teams of scientists are needed to develop predictive models for the behavior of pesticides in the soil environment. From our perspectives, we have documented the existing status of the microbiology of environmental fate studies with pesticides. Verification of data from laboratory studies to the field environment is needed. On the other hand, efforts to design better field studies to assess microbial processes are essential to advance our understanding of environmental fate studies with pesticides.

Herbicides may be exposed to a broad range of anaerobic conditions in the environment. This range can extend from weakly reducing conditions within typically aerobic compartments to stable, strongly reducing conditions in sites well removed from oxidative conditions. Currently, Federal Insecticide Fungicide and Rodenticide Act (FIFRA) regulatory guidelines specify the design criteria for guideline studies that frequently result in highly stable, strongly reducing test systems. These test systems do not simulate environments where herbicides are likely to occur. Design criteria for anaerobic aquatic test systems can influence the nature of the results of anaerobic aquatic metabolism studies as well as the relevance of these results to natural environmental processes. Design criteria which should be considered are the effects of sediment to water ratio, establishment of an anaerobic system, monitoring the reducing potential (Eh) of the system and the system Eh-pH relationship. These criteria influence how results are interpreted and the extrapolation of data to field environments where herbicides are likely to occur.

A brief review is presented for the use of soil lysimeters in studying transpiration, evapotranspiration, moisture, and nutrient movement in earlier times and pesticide dissipation and movement, and mass-balance of pesticide dissipation in more recent times. The important factors needed to understand research findings and to model pesticide dissipation such as key soil and site characteristics, climatic conditions, and the methods involved are discussed. Several case studies carried out by Ciba and North Carolina State University are discussed and current developments in soil column field lysimeters are presented.

Various samplers have been developed for taking intact soil cores. Very often, the sampler was used once or twice to take only a few soil cores then it became either obsolete or a burden for maintenance and storage. An economic portable hand-operated soil core sampler was developed to obtain large soil cores with a diameter of 19 cm and a length of 120 cm. The quality of large soil cores was evaluated and compared with that obtained from short cores from each soil horizon. In addition, the large intact column was used to evaluate atrazine transport under the saturated condition. Results showed that the hydraulic conductivity of the large cores were of the same magnitude as that of short cores, except for the A horizon; the hydraulic conductivity of the large cores was about 10 times greater than the short cores. Even though the sampling procedure is labor intensive, the soil sampler has the flexibility to collect different size soil cores and can be constructed at a very low cost (less than $200 including labor). Lastly, the sampler is maintenance free and can be stored easily in a limited space.

Literature on the effectiveness of grazing animals (especially cattle, goats, and sheep) in controlling weeds is reviewed. Availability of animals and the ability to fence them onto or off weed infestations are essential. Weeds of pastures are the most suitable subjects for control, although weeds of arable crops, forestry, and waste places are sometimes amenable to control by grazing animals. Although grazing animals themselves often cause weed problems in pasture, adjusting grazing timing or intensity or both can sometimes redress the balance. Increasing sheep or cattle stocking rates prevents animals from grazing selectively and can help control some weeds. Adjusting grazing pressure can also improve the growth of desirable pasture species so that these are more competitive and able to resist invasion of annual or biennial weeds. Introducing a different class of stock, like sheep into a cattle system or goats into a sheep system can control many weeds. Goats are capable of browsing on and controlling spiny or poisonous brush weeds, including gorse and poison ivy, without suffering adverse effects. Examples are given of the use of grazing animals for weed control in crops and forestry.

Four of the world's worst weeds are in the genus Cyperus. These are smallflower umbrella sedge (C. difformis L.), yellow nutsedge (C. esculentus L.), riceflatsedge (C. iria L.), and the world's worst weed, purple nutsedge (C. rotundus L.) (7). Fourteen additional Cyperus species are listed in the Composite List of Weeds1. Cyperus is in the sedge family (Cyperaceae) which consists of about 600 species found mostly in tropical to warm-temperate regions around the world (9). Cyperus entrerianus Böckeler is an aggressive, robust, fast growing, tenacious pest that produces large numbers of seeds (4). Apparently, it was introduced into the southeastern United States from temperate South America or Mexico (2). Presently, it is found in the southeastern United States from southeastern Texas to southern Georgia (4). The senior author has observed severe infestations of this weed in ditches, pastures, and fallow fields in southwestern Louisiana and southeastern Texas. Our objectives are to alert weed scientists, agronomists, and others concerned to the potential of this species and to discuss its biology, distribution, ecology, and taxonomy.

“Wither'd hogs … on ragweed nags, They skim the muirs [moors].” Address to the Diel, 1785, Scottish poet Robert Burns (1759–1796).