Spotted lanternfly (Lycorma delicatula). Photo by Surendra Dara
The spotted lanternfly (SLF) [Lycorma delicatula (Hemiptera: Fulgoridae)] is an invasive planthopper, which causes a significant damage to apples, grapes, stone fruit, trees used for timber, and other hosts (Dara et al. 2015). Native to China, SLF was first reported in 2014 in Pennsylvania and has been rapidly spreading in the eastern United States and moving westward. California has 22 cultivated and about 70 wild hosts of SLF and include several high value crops such as apples, cherries, grapes, and plums. The tree-of-heaven, an invasive species, is a favorite host of SLF and is widely distributed in California. SLF is also a nuisance pest with 100s or 1000s of individuals infesting landscape trees and hosts in residential areas. This pest deposits eggs on inanimate objects such as vehicles, furniture, stones, and packages and thus spread to other areas through the movement of these objects. Awareness of the pest and its damage potential, ability of Californians to recognize and report the pest if found, and the knowledge of control practices will help prevent accidental transportation of eggs or other life stages from the infested areas to California and prepare the citizens to take appropriate actions. Outreach efforts have been made in California since 2014 through extension articles, presentations at extension meetings, videos, social media posts, and personal communication (Dara, 2014).
Wakie et al. (2020) modeled the establishment risk of SLF in the United States and around the world and indicated that many coastal regions and the Central Valley of California are among the high-risk areas. Considering the risk to several high-value commodities and the presence of several wild hosts that are distributed all over California, mapping of the risk-prone areas based on the cultivated hosts, their acreage and value in different counties, and the distribution of wild hosts was done to help both growers and other Californians to prepare for potential invasion of SLF.
Methodology
The list of SLF hosts is continuously evolving with host specificity studies in various places. Based on two published resources (Dara et al. 2015; Barringer and Ciafré 2020), 22 cultivated and 70 wild hosts appear to be present in California. Plant species that support some of the feeding life stages or all life stages were included in preparing these lists. The cultivated hosts include apples, apricots, basil, blueberries, butternut, cherries, cotton, grapes, hibiscus, hops, mock orange, nectarine, peaches, pears, persimmon, plums, pomegranates, roses, soybean, sponge gourd, tea, and walnuts; and the wild hosts include Acacia sp., American hazelnut, Amur corktree, American linden, American sycamore, arborvitae, Argentine cedar, Asian white birch, bee balm, big-toothed aspen, black gum, black hawk, black locust, black walnut, Bladder senna, boxelder, chestnut oak, chinaberry tree, Chinese boxwood, Chinese juniper, Chinese parasol tree, Chinese wingnut, devilwoods, dogwood, Eastern white pine, edible fig, false spiraea, fireweed, five-stamen tamarisk, flowering dogwood, Forsythia, Glossy privet, greater burdock, grey alder, hemp, hollyhocks, honeysuckle, hornbeam, Japanese angelica, Japanese boxwood, Japanese maple, Japanese snowball, Japanese zelkova, jujubes, Kobus magnolia, Northern spicebush, Norway maple, lacquer tree, perennial salvia, Persian silk tree, plane tree, Poinsettia, poplars, princess tree, red maple, sapphire dragon tree, sassafras , sawtooth, serviceberry, silver maple, slippery elm, snowbell, staghorn sumac, sugar maple, tree-of-heaven, tulip tree, Virginia creeper, white ash, wild grape, and willows.
The summary of county crop reports from the California Department of Food and Agriculture (CDFA 2018) was used to determine the value and acreages of the cultivated hosts. To determine the distribution of wild hosts various online resources were used. SLF risk levels were determined as very low, low, moderate, high, and very high for the number of hosts, acreage and value of each cultivated host, and other such parameters within each county. The highest risk value within each parameter was used to determine ‘very high' category and 4/5, 3/5, 2/5, and 1/5 were used for high, moderate, low, and very low categories, respectively. In other words, 0-20% risk was considered very low, 21-40% as low, 41-60% as moderate, 61-80% as high, and 81-100% as very high for each measured parameter. Data were entered into a spreadsheet and maps were generated using QGIS open-source cross-platform geographic information system application.
Risk-prone areas in California
The following maps show areas in California that are prone to SLF risk based on the distribution of cultivated and wild hosts, and the acreage and value of important cultivated crops.
Based on these maps, the entire state of California is at some level of risk. In addition to the commercially produced crops, several backyard or landscape plant species such as roses, grapes, peaches, plums, and others are present throughout the state and can harbor SLF. Such host plants in residential and urban landscapes can serve as SLF sources for commercial crops. The tree-of-heaven is present throughout California and several such uncultivated hosts can serve as sources of undetected infestations. While researchers are working on appropriate biocontrol solutions such as releasing natural enemies, other control options such as synthetic and microbial pesticide applications, sticky traps, removal of egg masses and wild hosts, and other strategies can help manage SLF. In the meantime, Californians will benefit by knowing about this pest and its potential risk to the state. The ability to identify, destroy or capture, and report the pest to county and state departments or University of California Cooperative Extension offices will help prevent or delay SLF invasion and spread in California.
Conclusion
California is at the risk of SLF invasion and spread. Depending on the number of cultivated crops, their acreage, value, and the distribution of wild hosts, the risk level varies in various counties throughout the state. Outreach efforts are helping to alert Californians about SLF and its damage to cultivated crops and nuisance in urban and residential areas.
Additional resources
Refer to https://ucanr.edu/spottedlanternfly for additional information about the pest. If you happen to see this pest in California, please contact your local Agricultural Commissioner, California Department of Food and Agriculture, or UC Cooperative Extension office to report.
Acknowledgments
Thanks to the California Department of Food and Agriculture for funding this study.
References
Barringer, L. and Ciafré, C. M. 2020. Worldwide feeding host plants of spotted lanternfly, with significant additions from North America. Environ. Entomol. 49: 999-1011.
CDFA (California Department of Food and Agriculture). 2018. California County Agricultural Commissioners' Report Crop Year 2016-2017 (https://www.cdfa.ca.gov/statistics/pdfs/2017cropyearcactb00.pdf).
Dara, S. K. 2014. Spotted lanternfly (Lycorma delicatula) is a new invasive pest in the United States. UCANR eJournal Pest News (https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=15861).
Dara, S. K. 2018. An update on the invasive spotted lanternfly, Lycorma delicatula: current distribution, pest detection efforts, and management strategies. UCANR eJournal Pest News (https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26349).
Dara, S. K., Barringer, L. and Arthurs, S. P. 2015. Lycorma delicatula (Hemiptera: Fulgoridae): a new invasive pest in the United States. J. Integr. Pest Manag. 6: 20.
Wakie, T. T., Nevin, L. G., Yee, W. L. and Lu, Z. 2020. The establishment risk of Lycorma delicatula (Hemiptera: Fulgoridae) in the United States and globally. J. Econ. Entomol. 113: 306-314.
