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THE NEED FOR WEED RISK ASSESSMENT

THE NEED FOR WEED RISK ASSESSMENT. Ricardo Labrada. 320.000 Species. Examples of major weeds introduced in different regions. Magnitude of the problem. There are 260 000 plant species worldwide 10 000 are weeds

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THE NEED FOR WEED RISK ASSESSMENT

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  1. THE NEED FOR WEED RISK ASSESSMENT Ricardo Labrada

  2. 320.000 Species

  3. Examples of major weeds introduced in different regions

  4. Magnitude of the problem • There are 260 000 plant species worldwide • 10 000 are weeds • 4 000 species have been exchanged among the continents (introduced as exotic weeds) • One can assume that there are still 6 000 species waiting for their exchange (plants without any history as weeds out of their known natural habitat).

  5. What is weed risk assessment? • Weed risk assessment (WRA) is the use of standard technical criteria to determine the relative weed threats posed by plant species (Virtue and Panetta, 2002). • Such a risk assessment is normally based on pest risk analysis (PRA) prepared and accepted by the IPPC, which consists of three stages: • initiating the process for analyzing risk • assessing pest risk • managing pest risk

  6. How to conduct weed risk assessment? Persons Pathways Weed Risk Assessment Habitats Plants

  7. Weed Risk Assessment is only one technical part of the pre-entry decision-making process Potential economic benefits Potential weed risks Risk & benefits assessed “Political Input” Accept the risk Reject the risk Decision

  8. Pre-Entry Risk Assessment

  9. Content of the procedures • The procedures for weed risk assessment are concerned primarily with preventing the entry and initial spread of plant species that are likely to become pests within a country, or which are there and ought to be considered pests. • They describe the responsibilities of all participants in the process of plant importation required to halt the spread of weeds. • The procedures are based primarily on the experience of Australia and New Zealand, two countries that have effective quarantine protocols for preventing the introduction of and spread of unwanted plant species.

  10. Pathways of entry Plants may be introduced into countries via 3 main pathways that will vary between countries according to their economies and the flow of trade goods and people: Introductions made intentionally • Plant imports for urban and/or commercial horticulture, or forestry. In several countries these purposeful introductions have been responsible for more than half the exotic weed flora. Introductions made unintentionally • Via contaminated goods and products, such as seeds for sowing or consumption by humans or livestock. This pathway is the easiest to monitor because much attention is already paid to such products owing to their potential to spread diseases. • Strictly accidental introduction of plants not included in either of the above pathways e.g., attached to clothing. It is actually the least important. Authorities need to determine the relative risk of these pathways in each country.

  11. The process of weed-risk assessment • The most effective legislative framework to prevent the entry of new weeds is the concept of a Permitted List of plant species (or defined taxa). • If a taxon with the potential to be a pest in an area is not on a list of taxa permitted to be in that area, then it will be prohibited until it has been determined whether it is potential quarantine pest. • A formal weed-risk assessment is part of that process. All plants not present in the country i.e., exotic, are deemed to be prohibited until they have undergone assessment. • By systematically undertaking weed-risk assessments, countries will develop lists of species that are either permitted entry and those that are prohibited.

  12. Scoring for Weed Risk Factors (critical score = 6) Aquatic plant ? Y=3 Other members of the genus are weeds ? Y=2 Propagules likely to be dispersed intentionally or unintentionally by human activity? Y=2 Produces spines, thorns or burrs? Y=1 Parasitic? Y=1 Unpalatable or toxic to grazing animals? Y=1 Host for recognised pests and pathogens? Y=1 Causes allergies or otherwise toxic to humans? Y=1 Climbing or smothering growth habit? Y=1 Produces viable seed? Y=1 Seed persists for > 1 year? Y=1 Reproduction by vegetative propagation? Y=1 Tolerates or benefits from mutilation, cultivation, or fire? Y=1 NB Where the status of a risk factor is unknown, it should be scored as a ‘yes’.

  13. Post-entry risk management

  14. When Should Risk Assessment be conducted? A species can be assessed: Pre-entry 1. When it is out of the area of interest area. 2. When it is arriving or entering the new territory. Quarantine Post-entry management 3. When it is established. 4. When it is spreading.

  15. The procedure on Post-border Weed Risk Management • It has a systematic process of six steps: Step 1 is establishing the weed risk management context: overall goal/s, stakeholders, existing legislation and resources to undertake the WRM. Step 2 is identifying the weed risk candidates. Plant species for WRA are determined from collating existing weed lists, surveillance to detect new species and/or review of likely incursions. Step 3 is analysing and evaluating weed risks. Comparative weed risks are scored and categorised using a WRA system that incorporates the three key criteria of Invasiveness, Impacts and Potential Distribution.

  16. Invasiveness • Invasivenessis a relative index of the rate of spread of a weed, and encompasses the factors of establishment, reproduction and dispersal. • Direct measurement of rate of spread is difficult, and requires sequential data over many years. There are three key factors for Invasiveness: • weed's ability to establish amongst existing vegetation. • weed's reproductive ability (germination process, reproduction by seeds or other propagules). • weed's dispersal ability (intervening factors, wind, water, flying and ground animals, human dispersal, vehicles, and produce or by-products contaminant).

  17. The Impacts • The procedure focuses on the effects of naturalised plants, and consider six factors, i.e. the degrees of weed to reduce, restrict or affect: • Establishment of desired plants • The biomass/yield of desired plants • The quality of products or services • Physical movement • Human and/or animal health • Ecosystem processes

  18. Potential Distribution • Potential distribution is the total area at risk if a weed were to spread uncontrolled. • It is best predicted using maps in a GIS framework. • Predictions should be conservative and only include areas where the weed is likely to have significant impacts. • The steps in determining Potential Distribution are: • World distribution data for the weed • Climate modelling • Soil tolerances • Land uses at risk

  19. 4-6 Steps • Step 4 is for analysing and evaluating feasibility of coordinated control.Comparative feasibility of coordinated control programs are scored and categorised using a system that incorporates the three key criteria of Current Distribution, Control Costs and Duration. • Step 5 is for determining weed management priorities.Such actions include preventing entry, eradication, containment and improving targeted control techniques. • Step 6 is for implementing weed management actions,based on the priorities determined above. This is the transition from the strategic planning stage of WRM to operational, on-ground programs.

  20. Stage 5 – Determine Weed Management Priorities

  21. Post –border Weed Risk System Southern Australia Invasiveness (0-10)  Impacts (0-10)  Potential Distribution (0-10) Comparative weed risk = ControlCosts (0-10)  Real Distribution (0-10)  Persistence(0-10) Containment Feasibility =

  22. WEED RISK CONTAINMENT FEASIBILITY No significative >13 Low>56 Medium >31 High >14 Very High <14 No significative >13 NO ACTION NO ACTION NO ACTION NO ACTION MONITORING Low <39 NO ACTION NO ACTION NO ACTION MONITORING PROTECT THE SITES Medium <101 MANAGE THE SITES MANAGE THE SITES MANAGE THE SITES PROTECT THE SITES EXPANSION CONTAINMENT High <192 MANAGE WEED MANAGE WEED PROTECT THE SITES EXPANSION CONTAINMENT DESTROY INFESTATIONS Very High >192 MANAGE WEED PROTECT THE SITES & MANAGE WEED EXPANSION CONTAINMENT DESTROY THE INFESTATIONS ERADICATE IN THE REGION Post –border Weed Risk System Southern Australia

  23. Any of these procedures can be modified and improved either locally or at a regional level once the countries use them and see their limitations. • Countries should have access to available international literature on weeds and also to internet related web pages in order to get the required information for the assessment. • Weed risk assessment will for sure improve the work of plant quarantine bodies in the country, making possible to focus on really exotic dangerous weeds.

  24. Importance of WRA to avoid new problems of invasive weeds • Many of invasive plants have been introduced in several countries without any regulation. • Mesquite or Prosopis is an example, introduced in several countries to help reduce the problems of drought, where years later it became a terrible weed. • There are many other examples. Prevention is the first way to combat weed spread, and WRA procedures are excellent tools to this end.

  25. Thank you

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