Barnyardgrass, large crabgrass, and Texas panicum were evaluated in field experiments over 3 yr to measure their duration of interference and density on grain sorghum yield. When grain yield data were converted to a percentage of the weed-free control, linear regression predicted a 3.6% yield loss for each week of weed interference regardless of year or grass species. Grain sorghum grown in a narrow (61-cm) row spacing was affected little by full-season interference; however, in wide (91-cm) rows, interference increased as grass density increased. Data from the wide-row spacing were described by linear regression following conversion of grain yield to percentages and weed density to log10. A separate nonlinear model also was derived which could predict the effect of weed density on grain sorghum yield.

Seed capsules of field-grown jimsonweed were harvested 2, 4, 6, and 10 weeks after anthesis. Degree day accumulation from anthesis and weeks after anthesis were equal in predicting the time required for nondormant jimsonweed seed production and seed dry weight. Seed germination increased as capsule age increased from 2 to 6 weeks. No additional increase in germination was observed in seed from capsules collected 10 weeks after anthesis. Maximum seed weight was obtained from capsules 6 and 10 weeks old in 1986 and 1987, respectively. Germination was correlated highly with seed weight.

Field experiments were conducted in 1985 and 1986 under eight environments to evaluate the population dynamics of a range of silverleaf nightshade densities and to measure the effects of those populations on cotton lint yield. Dry weed weights of silverleaf nightshade stands were influenced by growing conditions among years, but were positively related to initial densities as long as 2 yr after establishment. Stem numbers increased as initial densities and stand age increased. A negative linear relationship existed between cotton lint yield and weed biomass and between cotton lint yield and stem number from both 1- and 2-yr-old weed stands. For each 1 kg/10 m of row increase in dry weed weight from 1- and 2-yr-old stands, a 9 and 21% lint yield loss/ha was predicted, respectively. For each stem/10 m of row, a 0.35 and 0.31% yield loss was predicted, respectively. Late-planted cotton was less vulnerable to yield reductions by silverleaf nightshade; however, its yield potential was also less.

Field experiments were conducted to evaluate the critical period for velvetleaf interference with cotton and to assess the reliability of using weed growth variables as predictors of cotton lint yield losses. An inverse linear relationship existed between velvetleaf dry weight and cotton lint yield. The relationship between the number of velvetleaf main-stem nodes or velvetleaf height with cotton lint yield was best described by quadratic regression equations. Weed dry weight appeared to be the most accurate predictor followed by weed height and by number of velvetleaf main-stem nodes. A nonlinear equation best described percent lint yield loss as a function of critical-period interference intervals.

Weed prevention is recognized as one of the most cost-effective management strategies for invasive plants. In the field of invasive plant management increasing emphasis is being directed toward proactive management. However, land managers are still somewhat reluctant to aggressively employ prevention programs. Part of this reluctance could be due to lack of understanding of what a comprehensive prevention program entails. The purpose of this paper is to improve strategic decision-making for site-specific prevention programs, such as those on ranches or in watersheds. Our interest is in advancing prevention planning for land managers—the people who are faced with the constant pressure of potential invasive species infestations on a day-to-day basis. To facilitate more widespread use of prevention programs we are proposing definitions for key terminology to standardize and facilitate communication about prevention programs. Additionally, we present a flow model with the steps necessary to successfully implement such programs. The model has three categories from which specific prevention planning occurs: (1) education, (2) early detection and eradication, and (3) interruption of movement. The flow model directs users through a series of interlinked steps. Finally, we provide a case study in which a ranch manager implemented a prevention program using this framework. By using this model, managers are poised to conduct more strategic planning. This model also has applications in outreach and education programs to assist land managers in prevention planning.

Producers facing infestations of invasive annual grasses regularly voice the need for practical revegetation strategies that can be applied across broad landscapes. Our objective was to determine the potential for scaling up the single-entry approach for revegetating medusahead-infested rangeland to broader, more heterogeneous landscape-scale revegetation of winter annual grass–infested rangeland. We hypothesized, when applied on a highly variable landscape scale, the combination of imazapic and seeding would provide highest abundance of perennial grasses and lowest amount of annual grasses. Treatments included a control, seeding of crested wheatgrass (‘Hycrest’) and Sandberg's bluegrass, spraying (60 g ai ha−1 imazapic), and a simultaneously applied combination of spraying and seeding. The HyCrest and Sandberg's bluegrass seeding rates were 19 and 3.4 kg ha−1, respectively. The treatments were applied to large plots (1.4 to 8 ha) and replicated five times, with each replication located in different watersheds throughout southeastern Oregon. This study shows that the single-entry approach can be scaled up to larger landscapes, but variation within establishment areas will likely be high. This procedure should reduce the costs over multientry treatment applications and make revegetating annual grass–infested rangeland across landscapes more affordable.

Prevention programs are often assumed to be the most cost-effective method for managing invasive plants. However, there is very little information available about economic and biological factors that determine the forage benefits resulting from prevention programs. We developed an easy to use economic model to assess potential savings in livestock forage that might result from implementing prevention programs. The model can be used to determine potential loss in forage production caused by invasive plants and to estimate potential income savings by preventing invasive plant infestations. The model compares a prediction of populations with and without a prevention program using a logistic growth function. Animal unit month (AUM) price and interest rates are the primary economic input variables. The primary biological input variables are amount of invasive plant utilization, size of the initial infestation, and the spread rate with and without prevention. Our model suggests that as the AUM price increases and/or the interest rate decreases, the total savings increases for each AUM that was protected through a prevention program. The model also shows savings per AUM increases as the size of the initial infestation decreases, suggesting that prevention should focus on eliminating seed sources and seed production early in the program. Using our model inputs, the savings per AUM was about $9.20 for each percent reduction in spread rate over 100 yr.

Land managers have long identified a critical need for a practical and effective framework for designing restoration strategies, especially where invasive plants dominate. A holistic, ecologically based, invasive plant management (EBIPM) framework that integrates ecosystem health assessment, knowledge of ecological processes, and adaptive management into a successional management model has recently been proposed. However, well-defined principles that link ecological processes that need to be repaired to tools and strategies available to managers have been slow to emerge, thus greatly limiting the ability of managers to easily apply EBIPM across a range of restoration scenarios. The broad objective of this article is to synthesize current knowledge of the mechanisms and processes that drive plant community succession into ecological principles for EBIPM. Using the core concepts of successional management that identify site availability, species availability, and species performance as three general drivers of plant community change, we detail key principles that link management tools used in EBIPM to the ecological processes predicted to influence the three general causes of succession. Although we acknowledge that identification of principles in ecology has greatly lagged behind other fields and recognize that identification of ecological principles and the conditions in which they hold are still being developed, we demonstrate how current knowledge and future advances can be used to structure a holistic EBIPM framework that can be applied across a range of restoration scenarios.