Weed Risk Assessment for Rumex United States sagittatus Thunb. (Polygonaceae) – Department of Agriculture Climbing dock Animal and Plant Health Inspection Service June 4, 2013 Version 1 Left: An infestation of fruiting Rumex sagittatus plants in Wanganui, New Zealand (photographer: Colin C. Ogle; NZ PCN, 2013; Ogle, 2013). Right: Infructescence in species’ native range in Zimbabwe (photographer: Bart Wursten; Hyde, 2013). Agency Contact: Plant Epidemiology and Risk Analysis Laboratory Center for Plant Health Science and Technology Plant Protection and Quarantine Animal and Plant Health Inspection Service United States Department of Agriculture 1730 Varsity Drive, Suite 300 Raleigh, NC 27606 Weed Risk Assessment for Rumex sagittatus Introduction Plant Protection and Quarantine (PPQ) regulates noxious weeds under the authority of the Plant Protection Act (7 U.S.C. § 7701-7786, 2000) and the Federal Seed Act (7 U.S.C. § 1581-1610, 1939). A noxious weed is defined as “any plant or plant product that can directly or indirectly injure or cause damage to crops (including nursery stock or plant products), livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment” (7 U.S.C. § 7701-7786, 2000). We use weed risk assessment (WRA)—specifically, the PPQ WRA model (Koop et al., 2012)—to evaluate the risk potential of plants, including those newly detected in the United States, those proposed for import, and those emerging as weeds elsewhere in the world. Because the PPQ WRA model is geographically and climatically neutral, it can be used to evaluate the baseline invasive/weed potential of any plant species for the entire United States or for any area within it. As part of this analysis, we use a stochastic simulation to evaluate how much the uncertainty associated with the analysis affects the model outcomes. We also use GIS overlays to evaluate those areas of the United States that may be suitable for the establishment of the plant. For more information on the PPQ WRA process, please refer to the document, Background information on the PPQ Weed Risk Assessment, which is available upon request. Rumex sagittatus Thunb. – Climbing dock Species Family: Polygonaceae Information Synonyms: Acetosa sagittata (Thunb.) L. A. S. Johnson & B. G. Briggs; Rumex scandens Burch. [Löve and Kapoor, 1967; NGRP, 2013; The Plant List, 2013]. Initiation: On November 25, 2011, Al Tasker (PPQ, National Weeds Program Coordinator) asked the PERAL Weed Team to evaluate Rumex sagittatus for potential listing as a Federal Noxious Weed (Tasker, 2011). This species has been listed under APHIS’ Not Authorized Pending Pest Risk Analysis (NAPPRA) regulations as a pest plant (APHIS, 2013). Foreign distribution: Native to Botswana, Lesotho, Namibia, Malawi, Mozambique, South Africa, Swaziland, Zambia, and Zimbabwe (APD, 2013; Hyde et al., 2013a; Hyde et al., 2013b; NGRP, 2013). This species is widely naturalized in subcoastal regions of Australia from southern Queensland through southeastern South Australia, and is present in Perth and Tasmania (The University of Queensland, 2013). U.S. distribution and status: We have found no evidence that this species is naturalized or currently cultivated in the United States (e.g., Backyard Gardener, 2013; Bailey and Bailey, 1930; Dave's Garden, 2013; Page and Olds, 2001). A report on Mediterranean invasive plant species reached a similar conclusion for California (Cal-IPC, 2008). One report exists of a donation of plant material to the Michigan Department of Agriculture in 1878 (p. 146, Baird, 1878), but it is unclear if this species is still present in the United States. WRA area1: Entire United States, including territories. 1 “WRA area” is the area in relation to which the weed risk assessment is conducted [definition modified from that for “PRA area” (IPPC, 2012). Ver. 1 June 4, 2013 1 Weed Risk Assessment for Rumex sagittatus 1. Rumex sagittatus analysis Establishment/Spread Rumex sagittatus is a scrambling, vine-like perennial that is naturalized in Australia Potential and New Zealand and is spreading (Heyligers and Adams, 2004; Williams et al., 1998). It has a rapid growth rate (Weedbusters, 2013) and can likely produce a new generation within two to three years after germination (see ES-13 in Appendix A). It produces an abundance of seeds (Williams et al., 1998) that are dispersed by wind and water (The University of Queensland, 2013; Weedbusters, 2013). Underground storage tubers greatly increase its resilience to drought, fire, and management (Heyligers and Adams, 2004; Reidy et al., 2005; Thomson and Leishman, 2005; Weedbusters, 2013) and contribute to unintentional dispersal through soil movement and vegetation dumping (The University of Queensland, 2013; Weber, 2003; Weedbusters, 2013). We had an average amount of uncertainty with this risk element. Risk score = 12 Uncertainty index = 0.20 Impact Potential Rumex sagittatus appears to be primarily a weed of natural areas, where it smothers herbs and shrubs, reduces native species richness, and prevents regeneration (Reidy et al., 2005; Weber, 2003; Weedbusters, 2013), particularly after disturbance (Heyligers and Adams, 2004). Rumex sagittatus forms a vine “blanket” that alters plant community structure (The University of Queensland, 2013). In New South Wales, it threatens endangered taxa (Coutts-Smith and Downey, 2006; The University of Queensland, 2013) and could do so in the United States as well. Rumex sagittatus is subject to control in natural systems (Smith and Patterson, 1978; Timmins and Braithwaite, 2002; Timmins and Mackenzie, 1995). It is a weed of wastelands and gardens (APD, 2013; Auld and Medd, 1987; The University of Queensland, 2013), but it is not clear if it is being actively managed in production systems, or urban/suburban settings. It is a weed of production systems in southern Africa because of potential toxicity to livestock (Wells et al., 1986). In an Australian model prioritizing 340 invasive weeds for management, this species ranked 22nd, posing a very high threat to biodiversity (Downey et al., 2010). This contrasts with observations from New Zealand that this species has not yet had a major impact (Williams et al., 1998), but that may be because it is a relatively new weed that is still spreading in New Zealand (Williams et al., 1998). We had an average amount of uncertainty with this risk element. Risk score = 2.5 Uncertainty index = 0.19 Geographic Potential Based on three climatic variables, we estimate that about 20 percent of the United States is suitable for the establishment of R. sagittatus (Fig. 1). This predicted distribution is based on the species’ known distribution elsewhere in the world and includes point-referenced localities and areas of reported occurrence. The map for R. sagittatus represents the joint distribution of Plant Hardiness Zones 8-11, areas with 10-70 inches of annual precipitation, and the following Köppen-Geiger climate classes: steppe, Mediterranean, humid subtropical, and marine west coast. In southern Africa there were a couple of point-sourced occurrences (GBIF, 2013) in dry (0-10 inches), desert-like conditions. However, because these appeared to be inconsistent with the rest of the species’ distribution and general morphological traits, we considered these occurrences doubtful and did not include them in our predictive mapping. The area estimated likely represents a conservative estimate as it only uses three Ver. 1 June 4, 2013 2 Weed Risk Assessment for Rumex sagittatus climatic variables. Other environmental variables, such as soil and habitat type, may further limit the areas in which this species is likely to establish. Rumex sagittatus occurs in a broad range of habitats: coastal bluffs, dry forests, dunes, forests, grasslands, riparian areas, river valleys, and stony hills (APD, 2013; The University of Queensland, 2013; Weber, 2003; Williams et al., 1998). Entry Potential Rumex sagittatus is likely to be introduced to the United States intentionally because it is positively valued elsewhere. In Africa, it is used in traditional medicine and thus may be of interest to western medicine (Brown, 1921; Jäger et al., 1996). Categorized as a garden escape (Coutts-Smith and Downey, 2006), it was likely introduced into Australia for horticulture, probably because of the bright display of pink infructescences. Although currently out of stock, one South African retailer offers R. sagittatus seeds for sale on the internet (Anonymous, 2013). We found no evidence suggesting it is likely to enter the United States as a hitchhiker or trade contaminant. Risk score = 0.5 Uncertainty index = 0.11 Figure 1. Predicted distribution of Rumex sagittatus in the United States. Map insets for Alaska, Hawaii, and Puerto Rico are not to scale. 2. Results and Conclusion Model Probabilities: P(Major Invader) = 54.9% P(Minor Invader) = 42.7% P(Non-Invader) = 2.4% Risk Result = High Risk Secondary Screening = Not Applicable Ver. 1 June 4, 2013 3 Weed Risk Assessment for Rumex sagittatus Figure 2. Rumex sagittatus risk score (black box) relative to the risk scores of species used to develop and validate the PPQ WRA model (other symbols). See Appendix A for the complete assessment. Figure 3. Monte Carlo simulation results (N=5,000) for uncertainty around the risk scores for Rumex sagittatusa. a The blue “+” symbol represents the medians of the simulated outcomes. The smallest box contains 50 percent of the outcomes, the second 95 percent, and the largest 99 percent. Ver. 1 June 4, 2013 4 Weed Risk Assessment for Rumex sagittatus 3. Discussion The result of the weed risk assessment for R. sagittatus is High Risk (Fig. 2). Our analysis indicates that this species has a high likelihood of naturalizing and becoming invasive if it is introduced to the United States. Limited biological information and conflicting information in existing evidence contributed to our uncertainty. Despite that, we are confident in our conclusion of High Risk because of the preponderance of High Risk outcomes in the uncertainty analysis (Fig.