MONDAY, JANUARY 11, 2021. BY EDWARD SOUTHWICK, CDFA.
Statewide activities for Pest Detection/Emergency Projects Branch in 2020 included a visual survey of host plants near high-risk target locations as well as air cargo flight inspections.
Statewide Risk-Based Survey
Overview
To determine whether spotted lanternfly (SLF, Lycorma delicatula) could be present in California, a risk-based survey was developed and executed in the summer of 2020. No evidence of SLF infestation was found during the survey. This survey focused on areas of a high risk of introduction where the preferred host, tree of heaven (TOH, Ailanthus altissima), is found. The movement of eggs from infested areas of the eastern United States and from infested areas of Asia was considered. Because SLF is known to lay eggs on any object near its primary host, many of the pathways are similar to those of gypsy moth movement, including vehicles, outdoor articles, containers, and packing materials. The first US detection in Pennsylvania in 2014 is thought to have been through eggs on imported stone and associated packing material from China.
The potential high-risk locations targeted in the survey were major railyards receiving a high volume of railcars from the eastern United States (Roseville) and Asia (those receiving cargo from the ports of Los Angeles and Long Beach); sites receiving multiple shipments of goods directly from SLF-quarantined areas in the eastern United States since 2017 as determined by records of gypsy moth hold notices issued by the border protection stations (Form 008A); direct stone importers potentially receiving material from infested areas of Asia; and port areas receiving cargo, containers, and other potentially infested material such as dunnage from Asia where Asian defoliating moth traps are currently serviced. Regarding 008A receivers, sites likely to store received and potentially infested materials outdoors for longer periods were prioritized, such as PODS and similar containerized moving systems, trucking companies, and distributors with many trailers on site. Though SLF has been found during air cargo inspections, it was determined that this is a relatively low-risk pathway for California because such SLF are likely to have flown into these planes (prior to takeoff), and flying SLF are unlikely to be gravid (gravid females are poor fliers). In addition, SLF are unlikely to avoid desiccation and remain viable without host plants after several hours in an aircraft (see air cargo inspection section below for additional information). TOH was the target host of this survey, though grapevines, either wild or maintained, were surveyed when no TOH was present. While SLF has been recorded feeding on many hosts, literature and eyewitness accounts from infested areas suggest TOH is the preferred host, particularly for adults.
Inspectors were instructed to find one or more survey sites with hosts near each target location, working from the target location outward up to 1/2 mile. Satellite view maps of the target locations with 1/4 and 1/2-mile buffers were provided. At each site, inspectors spent 5 minutes visually scanning the tree(s) or grapevine(s) and surrounding vegetation for signs of SLF nymphs, adults, egg masses, feeding damage, and honeydew. Latitude and longitude of the host were recorded. If multiple TOH trees were present, the largest tree or stand of multiple trees was chosen, since SLF are thought to be visually attracted to larger host trees. The date, surveyor name, site name, host presence, host info (single or multiple trees; diameter at breast height (> or < 6″ diameter), lat/long of the host, # suspect adults/nymphs/egg masses, and any relevant comments were reported. On an accompanying target location map, inspectors marked with pen or sharpie the location(s) of the host site(s).
Survey guidelines were based on the CAPS-approved methods and were carried out when or after the SAFARIS PestCAST model predicted 1-50% adult emergence in a given survey area (https://safaris.cipm.info/safarispestmodel/StartupServlet?pestcast). The degree-day threshold was reached at different times throughout the state, and the survey took place in August and September. Other SLF hosts include apple, kiwi, stone fruit, pomegranate, walnut, maple, Virginia creeper, willow, birch, bee-bee (Tetradium daniellii), and Chinese mahogany (Toona spp.). However, due to SLF’s preference for TOH, especially in the adult stage, these other hosts were not surveyed at this time.
Survey Results
Following the survey guidelines during August and September 2020, a total of 24 counties were visited, ranging from Butte in the north to San Diego in the south. 68 high-risk target locations were visited, including nine ports, nine stone importers, four railyards, and 44 008A receivers. In addition, one site near a purported public sighting from 2019 in Davis, as well as one site at the Ontario Amazon cargo terminal, were also surveyed. In some cases, there were multiple sites surveyed near one high-risk target location when hosts were present such as for railyards, ports, and the “Stone City” area of Anaheim (which includes multiple stone importers).
A total of 141 site observations were made including 119 for sites with tree of heaven, 13 where tree of heaven was not present but grapevines were, and nine where neither tree of heaven nor grapevines were found. Of the 119 sites with tree of heaven present, inspectors noted the presence of multiple trees at 90 sites and single trees at 29 sites. Of the 132 sites surveyed where either tree of heaven or grapevine were present, 29 were at or near major deep-water ports, 12 at or near stone importers, 47 at or near railyards, 42 at or near 008A receivers, one at an airport, and one at a location of a purported public sighting from 2019. No evidence of spotted lanternfly infestation was found at any of the survey sites.
Air Cargo Inspections
During the summer when adult Japanese beetles (JB) are active, an intensive aircraft inspection program is implemented at multiple California airports where incoming cargo aircraft arrive from airports in JB-infested states. Starting in 2019, spotted lanternflies have also been found during these JB inspections of cargo planes originating in the eastern United States. Below is a summary of spotted lanternfly detections through this inspection program for 2020 as well as 2019 for comparison. CDFA will continue to implement JB inspections of aircraft, including visual inspection for SLF. The area surrounding both Sacramento and Ontario airports were surveyed for SLF and none were found.
Pest Detection Advisory No. PD17-2020
Spotted Lanternfly PD/EP Activity Summary 2020
originally shared on December 29, 2020 and republished on this blog with permission from author
If you have any questions regarding this advisory, please contact Edward Southwick by email at edward.southwick@cdfa.ca.gov or by phone at 916.403.6679.
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