Weed Risk Assessment for Pistacia United States chinensis Bunge (Anacardiaceae) – Department of Agriculture Chinese pistache Animal and Plant Health Inspection Service November 27, 2012 Version 1 Pistacia chinensis (source: D. Boufford, efloras.com) 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 Pistacia chinensis 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. Pistacia chinensis Bunge – Chinese pistache Species Family: Anacardiaceae Information Initiation: On January 5, 2012, the Exotic Pest Information Collection and Analysis group reported that Pistacia chinensis had naturalized in North Carolina (Krings, 2011). For that reason, the PERAL Weed Team initiated this assessment. Foreign distribution: Native to China (Min and Barford, 2008), P. chinensis is distributed in Japan, Taiwan, Australia, and Ethiopia (Csurhes and Edwards, 1998; GBIF, 2012; Mulvaney, 1991; University of Queensland, 2011). U.S. distribution and status: This species is naturalized in Alabama, California, Georgia, and Texas (NRCS, 2012), and is naturalized and spreading in North Carolina (Krings, 2011). It is also grown ornamentally in Arizona, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, Virginia, and West Virginia (Dave's Garden, 2012). Although this plant has been promoted by the nursery industry for at least 30 years, a new cultivar (male, seedless) is now being promoted as an alternative to female trees (Dave's Garden, 2012). WRA area1: Entire United States, including territories 1. Pistacia chinensis analysis Establishment/Spread Pistacia chinensis is a deciduous large shrub or small tree that reproduces primarily Potential by seed (Gilman and Watson, 1994). The species is dioecious (requiring both male and female trees to produce seed) (Smith et al., 2000) and wind pollinated (Yu and Lu, 2011). The fruits are drupes, dispersed by multiple species of birds (Smith et al., 2000) and possibly other animals, such as squirrels (Copeland, 1955). The trait 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 November 27, 2012 1 Weed Risk Assessment for Pistacia chinensis contributing most to the score for this risk element is its invasiveness elsewhere; it has naturalized and is spreading in Australia (Smith et al., 2000) and has naturalized in a number of U.S. states. Although trees may first flower at 6-10 years of age, wild trees appear to reach reproductive maturity more slowly, with one generation taking approximately 25 years (Smith et al., 2000). Uncertainty was low for this risk element. Risk score = 1 Uncertainty index = 0.13 Impact Potential Pistacia chinensis may displace native trees (change community composition) in Texas (Dave's Garden, 2012), and is under control in Australian urban areas (Smith et al., 2000). It sends out horizontal roots that lift sidewalks and curbs, and handling it may cause skin irritation or allergic reaction (Dave's Garden, 2012). It is sometimes used as understock (rootstock) for the pistachio nut, P. vera L. (Dirr, 1998). Uncertainty was high for this risk element because much of the information came from comments on an online gardening site. Risk score = 1.7 Uncertainty index = 0.33 Geographic Potential Based on three climatic variables, we estimate that about 45 percent of the United States is suitable for the establishment of P. chinensis (Fig. 1). This predicted distribution is based on the species’ known distribution elsewhere in the world and includes point-referenced localities and areas of occurrence. The map for P. chinensis represents the joint distribution of Plant Hardiness Zones 6-11, areas with 10-90 inches of annual precipitation, and the following Köppen-Geiger climate classes: steppe, mediterranean, humid subtropical, marine west coast, and humid continental warm summer. The area estimated is likely conservative (i.e., expansive) because it is based on only three climatic variables. Other environmental variables, such as soil and habitat type, may further limit the areas in which this species is likely to establish. Entry Potential We did not assess the entry potential for P. chinensis because it is already present in the United States (Dave's Garden, 2012; Krings, 2011; NRCS, 2012). Ver. 1 November 27, 2012 2 Weed Risk Assessment for Pistacia chinensis Figure 1. Predicted distribution of Pistacia chinensis 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) = 0.053 P(Minor Invader) = 0.597 P(Non-Invader) = 0.349 Risk Result = Evaluate Further Secondary Screening = High Risk Ver. 1 November 27, 2012 3 Weed Risk Assessment for Pistacia chinensis Figure 2. Pistacia chinensis 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 Pistacia chinensisa. 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 November 27, 2012 4 Weed Risk Assessment for Pistacia chinensis 3. Discussion Our model indicated a 60 percent probability of being a minor invader and a 35 percent probability of being a non-invader. The initial result of the weed risk assessment for P. chinensis was Evaluate Further, while the secondary screening resulted in a conclusion of High Risk. The most important traits leading to an evaluation of High Risk were having bird-dispersed fruit, its history of spread elsewhere, and potential impacts in urban areas. It is naturalizing in wooded and waste areas, similar to the habitats invaded by Ailanthus altissima (Krings, 2011), a widely distributed pest tree that is known to replace native plants and change community structure. Only one (anecdotal) source indicates that P. chinensis displaces native plants, however, and we found no reports that it changes community structure. Notably, based on threat and ability to impact biodiversity in New South Wales, a model ranked this species a low priority (323 out of 340 species) (Downey et al., 2010). Because this species is in the nursery trade and is a fairly popular landscape plant, encouraging purchases of the seedless cultivar may help minimize any negative impacts. 4. Literature Cited 7 U.S.C. § 1581-1610. 1939. The Federal Seed Act, Title 7 United States Code § 1581-1610. 7 U.S.C. § 7701-7786. 2000. Plant Protection Act, Title 7 United States Code § 7701-7786. Burrows, G. E., and R. J. Tyrl. 2001. Toxic Plants of North America (First). Iowa State University Press, Ames. 1342 pp. Copeland. 1955. The reproductive structures of Pistacia chinensis (Anacardiaceae). Phytomorphology 5:440-449. Csurhes, S., and R. Edwards. 1998. Potential environmental weeds in Australia: candidate species for preventative control. Canberra, Australia. Biodiversity Group, Environment Australia. 208 pp. Dave's Garden. 2012. Plant files database. El Segundo, CA. http://davesgarden.com/guides/pf/go/1764/. (Archived at PERAL). Dirr, M. A. 1998. Manual of Woody Landscape Plants: Their Identification, Ornamental Characteristics, Culture, Propagation and Uses (5th Edition). Stipes Publishing LLC, Champaign, Illinois. 1187 pp. Downey, P. O., T. J. Scanlon, and J. R. Hosking. 2010. Prioritizing weed species based on their threat and ability to impact on biodiversity: A case study from New South Wales. Plant Protection Quarterly 25(3):111-126. Evans, E. n.d. Pistacia chinensis. Plant Fact Sheet. North Carolina Cooperative Extension, Horticultural Science, North Carolina State University, Raleigh, NC. GBIF. 2012. Global Biodiversity Information Facility (GBIF), Online Database. http://data.gbif.org/welcome.htm. (Archived at PERAL). Gilman, E. F., and D. G. Watson. 1994. Pistacia chinensis. Fact Sheet ST-482. United States Department of Agriculture, Forest Service (USFS), Washington, D.C. 3 pp. Heap, I. 2012. The International Survey of Herbicide Resistant Weeds. www.weedscience.com. (Archived at PERAL). HEAR. 2011. Hawaiian Ecosystems at Risk (HEAR). Online database. University Ver. 1 November 27, 2012 5 Weed Risk Assessment for Pistacia chinensis of Hawaii, Honolulu, HI. (Available at http://www.hear.org/gcw/). (Archived at PERAL). Heide-Jorgensen, H. S. 2008. Parasitic Flowering Plants. Koninklijke Brill NV, Leiden, The Netherlands.