|
|
Pest Survey Program field specialists, in collaboration with plant pathologists at the DATCP Plant Industry Bureau Laboratory in Madison, carried out several early detection surveys for high-risk insects and plant pathogens during the 2023 season. While some of the survey targets, including European spruce bark beetle and pine-tree lappet, have never been found or reported in the state, others such as spotted lanternfly and Phytophthora ramorum have been periodically intercepted and require ongoing survey and inspection efforts to prevent their introduction into Wisconsin.
In addition to these exotic pest detection projects, DATCP’s Spongy Moth Program completed its annual trapping survey to identify emerging populations and determine future treatment areas. Spongy moth survey projects began in Wisconsin in 1971, and a total of 1,060,124 traps have been set throughout the last 53 years. Even more remarkable is the cumulative total of 6,195,644 spongy moths seasonal trappers have counted in those traps!
This second end-of-year edition of Field Notes highlights the results of our 2023 forest and nursery pest surveys and provides an update on recent interceptions of spotted lanternfly in the state.
__________________________________
|
|
DATCP continued early detection efforts for spotted lanternfly (SLF) in 2023, conducting 48 visual surveys in 13 counties. Program staff walked a total of 66.7 miles in areas thought to pose a high risk of introduction, surveying trees, objects and structures for signs of SLF. Although no SLF life stages were found during these visits, surveyors documented 106 new records of SLF’s preferred host, Ailanthus altissima (tree-of-heaven).
Additionally, staff responded to a total of 36 suspected SLF sightings reported by the public to DATCP’s online site SLF.wi.gov. While most of these reports yielded no signs of SLF, two independent accounts from Dodge County contained valid photos of single, dead SLF adults. Follow-up surveys in the areas surrounding these reports found no evidence of SLF, leading DATCP staff to conclude these specimens likely hitchhiked from another state in freight shipments and were dead upon arrival to Wisconsin. The locations of these reports, in combination with an expanding map of known tree-of-heaven locations throughout the state, will inform survey plans for the 2024 season.
As of December 2023, living SLF have not yet been found in Wisconsin. After recent detections in neighboring Chicago, however, early survey efforts and public vigilance for this pest are more important than ever.
A map showing the current United States distribution of SLF is available at Cornell IPM SLF map. Any suspected finds of SLF in the state should be immediately reported via DATCP’s online form. A photo of the insect is needed to verify identification. |
|
 __________________________________
|
|
Early detection work conducted by DATCP in 2023 also included a survey for nine national priority insect pests that pose a threat to Wisconsin’s pine resource. Three defoliator moths (pine-tree lappet, Siberian silk moth, and nun moth) and six wood-boring beetles (large pine weevil, six-toothed bark beetle, European spruce bark beetle, black fir sawyer, black spruce beetle, and brown spruce longhorned beetle) were the selected targets. Surveyors set a total of 75 traps across 14 counties at 15 industrial sites thought to pose a high risk of exotic pest introduction. Laboratory screening of the 585 samples obtained from these traps yielded no positive suspects of the national priority pests targeted in this survey. Pest Survey Program entomologists plan to further screen the bycatch of these traps for additional non-native species of interest. |
|
__________________________________ |
|
The state total spongy moth catch surged to a 20-year high this season, following four consecutive years of population growth. The Wisconsin Spongy Moth Program recorded an annual catch of 397,415 male spongy moths in 9,733 traps in 2023, nearly double the 201,549 moths collected in 2022, quadruple the 2021 catch of 99,847 moths, and the third highest total in the 53-year history of spongy moth trapping in Wisconsin. This year’s state average count was 40.8 moths per trap. As indicated in the map below, the traps with highest catches were located in the generally infested central and eastern parts of the state where spongy moth has been well established for 25-35 years.
These patterns reflect an outbreak phase that has been building since an exceptionally low population was recorded in 2019. Such outbreaks occur approximately every 10 years in areas infested with spongy moth, and usually persist for 2-4 years before populations collapse.
This rapid population growth in the last four years has been driven by weather factors such as warm, dry summers and relatively mild winters, which have limited the impacts of larval diseases and winter egg mass mortality, respectively. As a result, more caterpillars have been hatching and surviving to adulthood each year. If past trends are an indicator, the multiyear spongy moth outbreak phase could begin to subside in some areas of the state in 2024, depending on weather patterns and other variables. |
|
 __________________________________
|
|
|
Plant viruses continue to be a serious problem for nursery production. Besides lowering the commercial value and productivity of ornamental plants, many viruses can also be transmitted to agricultural crops. The Plant Industry Bureau Laboratory, in cooperation with DATCP nursery inspectors, have conducted sampling and testing for viruses in the Wisconsin nurseries and greenhouses for the last 20 years.
This season, nursery inspectors collected 136 ornamental samples for virus testing at the lab. Tobacco rattle virus (TRV) was detected most often, with 62 positives (mainly in astilbe, bleeding heart, hosta, and peony). Potyviruses were confirmed in iris, rose, sedum, and wisteria, for a total of nine positive samples. In addition, hosta virus X was found in nine hosta samples, cucumber mosaic virus (CMV) was detected in astilbe, lobelia, and monkshood, and Ilarviruses were confirmed in five samples.
Other virus finds included impatiens necrotic spot virus in begonia; alfalfa mosaic virus in phlox; and tomato ringspot virus in lily. Several plants co-infected with two viruses were also observed: astilbe ‘Fanal’ with Ilarvirus and TRV; astilbe ‘Bridal Veil’ with Ilarvirus and TRV; Joe-Pye weed with Ilarvirus and TRV; and lobelia ‘Monet Moment’ with CMV and TRV. Laboratory test results are summarized in the table below.
   
|
|
 __________________________________
|
|
DATCP’s Plant Industry Bureau Lab and nursery inspectors thwarted another potential introduction of Phytophthora ramorum into the state this year. Phytophthora ramorum is a plant pathogen that causes the diseases known as Ramorum blight and sudden oak death, which have led to devastating tree mortality in the coastal forests of California and Oregon since the mid-1990s. It infects more than 100 plant species, including hardwood and conifer trees, shrubs, ferns, and common horticultural plants such as azalea, magnolia, and viburnum.
In June 2023, DATCP staff observed symptomatic rhododendrons during routine inspections that led to 15 confirmed detections of Phytophthora ramorum at a licensed Wisconsin nursery dealer. The infected plants had been imported from Oregon earlier in spring. These detections were discovered on 12 ‘Holden’ rhododendrons, one ‘Nova Zembla’, one ‘Purple Passion’, and one ‘Maxecat’ rhododendron. All interceptions of P. ramorum-infected plant material were properly contained, disposed of, and the nurseries were disinfected as required by USDA regulation.
To date, P. ramorum has never been detected on plants in the Wisconsin landscape. DATCP has enacted an external quarantine on items that could harbor and spread P. ramorum. An external quarantine means that items including nursery stock, unprocessed wood, soil, and other plants and plant parts (mulch, wreaths, garlands and greenery) cannot be brought into Wisconsin from areas where the pathogen is known to occur without an inspection and certificate from the exporting state. Early detection of this pathogen, along with rapid response when interceptions occur, are key to protecting Wisconsin green industries and forests from this pathogen. |
|
 __________________________________
|
|
|
The Plant Industry Bureau Lab conducted a survey of ornamental nursery stock for root-knot (Meloidogyne spp.) and root lesion (Pratylenchus spp.) nematodes this year. The plant-parasitic nematodes in these genera are known for their broad host-ranges and capacity to cause disease in hundreds of agricultural and horticultural plants worldwide.
Of the 94 samples screened for nematodes at the lab, eight astilbe samples were positive for root-knot nematodes and six plant samples were positive for root lesion nematodes. The ornamentals infested with root lesion nematodes were astilbe (3), barrenwort, (2), and bleeding heart (1).
Soil-borne root-knot and root lesion nematodes may be spread by contaminated tools and soil, natural movement through the soil, and by contaminated plant propagules. Although nematode infestation may not be directly lethal to the host plant, their feeding interferes with proper root function (i.e., water and nutrient movement), reduces plant vigor, and root lesions or damage can become an infection point for other plant pathogens. It is important for consumers and nursery industry workers to be aware of the prevalence of nematodes in the nursery trade and to monitor plants for signs and symptoms of nematode infestation.
__________________________________
|
|
|
|
|
