Data on the spread of invasive weeds into arid western lands are used to evaluate the environmental and economic importance of controlling invasive weed infestations early. Variable rate and constant rate infestation expansion paths are estimated. The implications of variable vs. constant infestation growth rates for projecting both biophysical and economic effects are illustrated. The projections derived from both constant and variable growth rate expansion paths support the contention that it is expedient to control new infestations early.

Nonindigenous invasive weed species can have substantial negative impacts on the quantity and quality of outdoor recreational activities such as fishing, hunting, hiking, wildlife viewing, and water-based recreation. Despite the significance of impacts on recreation, very little research has been performed to estimate the corresponding economic losses at spatial scales such as regions, states, and watersheds. This is true primarily because in most jurisdictions the data necessary to estimate recreational impacts are scarce and incomplete. Because of the challenges involved in measuring recreational losses precisely, we illustrate a method that can provide indications of the ranges in which the true economic losses likely lie. To reflect underlying uncertainty in parameters such as the number of acres infested in a jurisdiction and the rate at which wildlife-related recreation decreases as a function of increasing weed infestation, we developed a range of estimates using lower, medium, and higher scenario combinations of parameter and variable values. Our case study jurisdiction is a western state (Nevada) in which nonindigenous weed infestations on public lands have expanded rapidly in recent years. Under conservative assumptions, the negative economic impacts stemming from the adverse influence of nonindigenous weeds on wildlife-related recreation in Nevada likely range from $6 million to $12 million per year. Using the most conservative findings for annual recreation losses, the predicted discounted stream of negative economic impacts over a future time horizon of 5 yr ranges from about $30 million to $40 million in Nevada, depending on actual future expansion rates of weeds.

Perennial pepperweed, found throughout the western United States, reduces biodiversity and causes economic losses in the form of control costs as well as decreased quantity and quality of agricultural yields. The future stream of net benefits of weed management and the future point in time at which they will have accumulated enough to equal total management costs were estimated under different land-use and expansion rate scenarios. Benefits and costs were calculated in present value terms by applying a rate of discount to future values. On land used solely for grazing, the total economic returns from management did not equal total costs until 15 yr after initial treatment. However, on land used for grazing plus hay harvest, cumulative benefits equaled and began to exceed cumulative costs after 4 to 5 yr. The costs and benefits of management efforts were also estimated for a landowner, who controls an adjacent infestation before it spreads. This landowner benefited economically from weed management in as little as 5 to 6 yr, highlighting the importance of cooperative efforts to control nearby weed infestations.

Eurasian watermilfoil, an aquatic invasive weed, has been identified recently at a number of sites in western Nevada and northeastern California, including Lake Tahoe. Because Eurasian watermilfoil is easily spread by fragments, transport on boats and boating equipment plays a key role in contaminating new water bodies. This is an important means of the potential spread of this weed throughout key recreational and agricultural areas surrounding Lake Tahoe. Unless the weed is controlled, significant alterations of aquatic ecosystems, with associated degradation of natural resources and economic damages to human uses of those resources, may occur. This research uses the economic valuation approach known as benefits transfer to estimate the value of a portion of the recreational service flows that society currently enjoys in the Truckee River watershed below Lake Tahoe. The lower-bound estimates of baseline water-based recreation value at a subset of sites in the watershed range from $30 to $45 million/yr. Impacts from the continued spread of Eurasian watermilfoil in the watershed could be significant; for example, even a 1% decrease in recreation values would correspond to roughly $500,000/yr as a lower bound.

Field studies were conducted at 35 sites throughout the north-central United States in 1998 and 1999 to determine the effect of postemergence glyphosate application timing on weed control and grain yield in glyphosate-resistant corn. Glyphosate was applied at various timings based on the height of the most dominant weed species. Weed control and corn grain yields were considerably more variable when glyphosate was applied only once. The most effective and consistent season-long annual grass and broadleaf weed control occurred when a single glyphosate application was delayed until weeds were 15 cm or taller. Two glyphosate applications provided more consistent weed control when weeds were 10 cm tall or less and higher corn grain yields when weeds were 5 cm tall or less, compared with a single application. Weed control averaged at least 94 and 97% across all sites in 1998 and 1999, respectively, with two glyphosate applications but was occasionally less than 70% because of late emergence of annual grass and Amaranthus spp. or reduced control of Ipomoea spp. With a single application of glyphosate, corn grain yield was most often reduced when the application was delayed until weeds were 23 cm or taller. Averaged across all sites in 1998 and 1999, corn grain yields from a single glyphosate application at the 5-, 10-, 15-, 23-, and 30-cm timings were 93, 94, 93, 91, and 79% of the weed-free control, respectively. There was a significant effect of herbicide treatment on corn grain yield in 23 of the 35 sites when weed reinfestation was prevented with a second glyphosate application. When weed reinfestation was prevented, corn grain yield at the 5-, 10-, and 15-cm application timings was 101, 97, and 93% of the weed-free control, respectively, averaged across all sites. Results of this study suggested that the optimum timing for initial glyphosate application to avoid corn grain yield loss was when weeds were less than 10 cm in height, no more than 23 d after corn planting, and when corn growth was not more advanced than the V4 stage.

We have designed, constructed, and are operating a unique capability for the production of highly controlled homophase and heterophase interfaces: an ultrahigh vacuum diffusion bonding machine. This machine is based on a previous design which is operating at the Max Planck Institut für Metallforschung, Institut für Werkstoffwissenschaft, Stuttgart, FRG. In this method, flat-polished single or polycrystals of materials with controlled surface topography can be heat treated up to 1500°C in ultrahigh vacuum. Surfaces of annealed samples can be sputter cleaned and characterized prior to bonding. Samples can then be precisely aligned crystallographically to obtain desired grain boundary misorientations. Material couples can then be bonded at temperatures up to 1500°C and pressures up to 10 MPa. Results are presented from our initial work on Mo grain boundaries and Cu/Al2O3 interfaces.