Hand thinning is a necessary and costly management practice in peach (Prunus persica) production. Stone fruit producers are finding it increasingly difficult to find a workforce to manually thin fruit crops, and the cost of farm labor is increasing. A new “hybrid” string thinner prototype designed to adjust crop load in vase or angled tree canopies was evaluated in processing and fresh fruit plantings in varying production systems in four U.S. growing regions in 2009. Data were uniformly collected across regions to determine blossom removal rate, fruit set, labor required for follow-up green fruit hand thinning, fruit size distribution at harvest, yield, and economic impact. String thinner trials with the variable tree forms demonstrated reduced labor costs compared with hand-thinned controls and increased crop value due to a larger distribution of fruit in marketable and higher market value sizes. Blossom removal ranged from 17% to 56%, hand thinning requirement was reduced by 19% to 100%, and fruit yield and size distribution improved in at least one string-thinning treatment per experiment. Net economic impact at optimum tractor and spindle speeds was $462 to $1490 and $264 to $934 per acre for processing and fresh market peaches, respectively. Case study interviews of growers who thinned a total of 154 acres indicated that commercial adoption of string-thinning technology would likely have positive impacts on the work place environment.

A range of risk assessment systems has been applied to the field of weed management globally to address the ever-growing problem of plant invasions. Here, we review the development of risk assessment and management systems across the spectrum of weed management, spanning pre-border (quarantine), post-border (generally aimed at eradication and containment) and the protection of environmental assets. These systems have been developed using broader risk management frameworks, enabling consistency with a range of other agreements and strategies (e.g. pre-border with international phytosanitary measures). While a weed risk assessment system (pre-border) has been developed and widely tested/adopted, post-border systems, especially for established weed species, have been more varied in their nature and application. For example, a triage system has been outlined only recently for managing the current risks of established or widespread weeds to native species. This review also highlights a range of other weed management areas in which risk assessment systems have been applied (e.g. invasion pathways) and where further progress is needed in the current systems to make them more robust. By assessing risk across the spectrum of weed management, we have demonstrated the role of each system and how they link together to address the majority of the spectrum. The application of risk assessment procedures has helped to create systems that aim to prevent, eradicate, contain and protect assets from the effects of weed invasions, the legacy of which will be long lasting, globally.

No abstract

Predicting the influence of climate change on the potential distribution of naturalised alien plant species is an important and challenging task. While prioritisation of management actions for alien plants under current climatic conditions has been widely adopted, very few systems explicitly incorporate the potential of future changes in climate conditions to influence the distribution of alien plant species. Here, we develop an Australia-wide screening tool to assess the potential of naturalised alien plants to establish and spread under both current and future climatic conditions. The screening tool developed uses five spatially explicit criteria to establish the likelihood of alien plant population establishment and expansion under baseline climate conditions and future climates for the decades 2035 and 2065. Alien plants are then given a threat rating according to current and future threat to enable natural resource managers to focus on those species that pose the largest potential threat now and in the future. To demonstrate the screening tool, we present results for a representative sample of approximately 10% (n = 292) of Australia's known, naturalised alien plant species. Overall, most alien plant species showed decreases in area of habitat suitability under future conditions compared to current conditions and therefore the threat rating of most alien plant species declined between current and future conditions. Use of the screening tool is intended to assist natural resource managers in assessing the threat of alien plant establishment and spread under current and future conditions and thus prioritise detailed weed risk assessments for those species that pose the greatest threat. The screening tool is associated with a searchable database for all 292 alien plant species across a range of spatial scales, available through an interactive web-based portal at http://weedfutures.net/.

A number of policies, strategies and tools are available for the management of invasive alien plants. This review considers these and their suitability in the light of developing theory and practical experience. Policies range from quarantine and eradication to containment and asset protection. While there is scope for modelling the potential spread and impact of invasive plants, these factors are invariably species-specific and a land manager is typically faced with the problem of dealing with several species simultaneously. Weed risk management systems have been developed to prioritize species management actions. These systems will be improved by further efforts to encompass uncertainty. Most management actions require long time-frames, and institutional commitment, as well as stakeholder involvement for successful outcomes.