By Jeremy Jubenville and Heidi Lindberg et.al
The Michigan Department of Agriculture and Rural Development (MDARD) has updated a quarantine on boxwood shrubs (Buxus spp.) effective July 31, 2023. The initial quarantine implemented on April 1 was for all of Lenawee and Washtenaw counties and large sections of Jackson and Monroe. The updated quarantine expanded the quarantine to ten southeast and central Michigan counties: Clinton, Eaton, Ingham, Livingston, Oakland, Jackson, Washtenaw, Wayne, Lenawee, Monroe, Macomb and St. Clair (Figure 1). The purpose of the quarantine is to prevent the spread of the box tree moth (Cydalima perspectalis, Photos 1 and 2), a new invasive insect pest that has destroyed an estimated 75% of boxwoods in Europe. MDARD has issued this quarantine in response to the discovery of a box tree moth infestation in Lenawee County in early November 2022. The quarantine area was expanded because of increasing detection of box tree moth in the landscape.
Quarantine restriction overview
- Movement of regulated articles (Buxus plant material — live or dead — and box tree moths) within or through the regulated area is subject to restrictions, with a few conditions or exceptions.
- Movement of regulated articles from a location inside the regulated area to a location outside the regulated area is prohibited.
- Movement of regulated articles from inside the regulated area to another location inside the regulated area is prohibited unless accompanied by a written compliance agreement issued by the director of MDARD.
- Movement of Buxus yard waste from inside the regulated area to another location inside the regulated area is allowed, but only if:
- The destination site has no Buxus within 100 yards.
- The waste is enclosed in a sealable covering material (e.g., plastic, canvas, etc.), trailer body, or vehicle while being transported (March through October only).
- Seeds of Buxus species are exempt from the quarantine.
- Holiday greenery, such as wreaths, boughs and grave blankets, from all Buxus spp., will no longer be regulated under the quarantine if moved during the period of Oct. 15 through Jan. 1.
Transporting Buxus nursery stock through the restricted area is allowed if it originated from outside the regulated area. During the high-risk period (March through October), the following requirements also apply:
- The shipment cannot be off-loaded in the regulated area.
- No Buxus nursery stock is allowed to be added to the shipment while inside the regulated area.
- The shipment should be transported directly through the quarantine area without stopping (except for refueling and when traffic conditions call for it).
- Regulated articles that are transported through the quarantine area must be accompanied by documents that clearly identify the place of origin.
Note: When transporting Buxus species into, within or through the quarantine area during the high-risk period (March through October), the shipment must be enclosed inside a sealable covering material, trailer body or vehicle in a manner that prevents the unintentional introduction of the box tree moth. It’s important to recognize that significant segments of U.S. 12, U.S. 23 and I-94 pass through the regulated area.
Recordkeeping
The quarantine rules also specify that all paperwork related to the shipment of the regulated articles should be retained by the person receiving the shipment for 36 months. Note that this includes materials such as boxwood stems for cut flower arrangements and holiday boxwood wreaths.
A brief history of the box tree moth in Michigan
In May 2021, the USDA announced that it had confirmed the presence of box tree moth (Cydalima perspectalis) in the continental United States and was working to contain and eradicate the invasive pest. Six states received shipments of boxwood shrubs from a nursery that was found to have a box tree moth infestation. Box tree moths were detected at three locations in Michigan and were subsequently eradicated by MDARD and the USDA Animal and Plant Health Inspection Service (APHIS).
Michigan State University Extension partnered with MDARD and USDA APHIS to implement an early detection program for box tree moth. With the help of businesses and residents across the state, we placed special traps designed to detect the presence of the invasive box tree moth at over 45 sites throughout Michigan in 2021 and 2022. Fortunately, no box tree moths were found at any of these locations in the two seasons that these sites were active and inspected.
As the 2022 trapping season was wrapping up, however, a resident in southeast Michigan noticed significant damage to boxwoods on their property. After an investigation in early November 2022, USDA APHIS confirmed the detection of box tree moth at two residences in Lenawee County. It is still unclear whether the populations found in southeast Michigan are connected to the infested boxwood shipments of 2021 or if they found their way into the state through other means.
Looking ahead
The box tree moth is a looming menace of the boxwood industry in Michigan. The USDA, MDARD and MSU Extension are all asking Michigan residents to examine their boxwood plants closely for signs of an infestation. Early infestations can be difficult to detect because the young caterpillars are small and usually hidden among the leaves. For this reason, Michiganders are encouraged to look for damaged leaves and stems, which are often much more noticeable (Photo 3).
Report suspected infestations
If you suspect you have found an infestation, please take photographs and report it at www.Michigan.gov/ReportBTM. Please allow state or federal agriculture officials to inspect your boxwood before spraying or disposing of the suspected infestation. Once an infestation is confirmed, you will receive instructions on how to treat or dispose of the infested plant material.
Preventative management
Nursery growers and landscapers may want to consider a precautionary spray program for 2023. This could be especially helpful in localities within, and adjacent to, the quarantine area. When spraying preventatively for the box tree moth, MSU Extension recommends two seasonal applications of a labeled pyrethroid product (e.g., bifenthrin) — once in late July and once again in early September. Be sure that the product is labeled for application at that site.
Alternatively, growers and landscapers can also spray a Bacillus thuringiensis (Bt) product once every two weeks starting in late June. Bt is a bacterium that kills insects when ingested. Be sure to use the kurstaki strain, as this is the only one that specifically targets caterpillar larvae. Look for product labels that say Bacillus thuringiensis subsp. kurstaki (Btk).
Homeowners within the quarantine area may want to implement a precautionary management program as well. Please follow the recommendations for nursery growers and landscapers as described above.
Considerations for cut flower growers and florists
Boxwood stems and branches are sometimes used in bouquets, arrangements and holiday wreaths. It’s important for growers, florists and other floral artists within the quarantine area that buy, sell or transport Buxus plant parts to be mindful of the quarantine restrictions. Floral industry professionals that operate in the quarantine area are encouraged to advise their customers of the restrictions associated with the transport and disposal of boxwood plant parts.
Source : msu.edu