MELeaf: A Newsletter From the Horticulture Program, January 3, 2025

Maine Department of Agriculture, Conservation and Forestry sent this bulletin at 01/03/2025 10:00 AM EST

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Horticulture Program

MELeaf: A Newsletter From the Horticulture Program, January 3, 2025

In this Issue:

One Last Look at 2024 and Looking Ahead to 2025

As 2024 comes to a close here’s a look back at some of the things that kept the Horticulture Program busy this year and a look forward to what we anticipate working on in 2025.

Phytophthora ramorum Identified in Maine Garden Center

Phytophthora ramorum is a federally regulated disease that occurs on the west coast where it has been killing tanoak and coast live oak since the 1990s. P. ramorum has an extensive host range of more than 100 species including many common ornamental plants such as Rhododendron and Pieris. Nurseries in the quarantine areas of California and Oregon are required to follow best management practices to prevent the movement of this disease, however, latent infections where plants exhibit no, or few, symptoms regularly lead to the shipment of potentially infected plants to other states. This summer USDA notified us that one business in Maine had received plants potentially infected with P. ramorum. Sampling, testing and follow-up surveys at the business identified three rhododendron plants infected with P. ramorum. All plants testing positive plus all host plants surrounding the positive plants were destroyed.

Phytophora ramorum symptoms

P. ramorum symptoms on a rhododendron include brown leaf spots and brown leaf tips. Photo credit: USDA

Check Your Inventory for Invasive Plants

Inspectors continue to see plants for sale on Maine’s Invasive Plant Do Not Sell List. The most frequently encountered plants were Callery pear, creeping Charlie, wintercreeper and European mountain ash. Check your inventory before the sales season starts to ensure that you are not selling any varieties, cultivars or hybrids of the species on the Do Not Sell List. Also, be sure to post the required signs with any rugosa rose plants that you sell. Free signs and other invasive plant outreach materials are available to order on the invasive plant website

Opportunity to Improve Your Weed and Invasive Plant Management

Conducting a weed risk assessment can help assist businesses in improving their weed and invasive plant management programs. Risk assessment is the process of identifying critical control points and applying best management practices to control pests. Conducting a risk assessment documents what you already do to control weeds and invasive plants, suggests additional management techniques to improve control and organizes it all into a management plan. Thanks to a USDA grant the Horticulture Program currently has staff available to assist businesses in conducting a weed risk assessment, but work must be completed before April 1, 2025. If you are interested in this opportunity email horticulture@maine.gov or come see us on the tradeshow floor at the Grow Maine Green Expo on January 22.

Box Tree Moth Continues Territory Expansion

USDA continued to expand box tree moth quarantines in 2024 and infested areas now include parts of Michigan, New York, Ohio and Pennsylvania as well as the entire states of Delaware and Massachusetts. In Canada, the infested area now includes parts of Ontario, Quebec, Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland and Labrador. Box tree moth caterpillars quickly defoliate boxwood leading to rapid decline and death of the plants. Early detection of box tree moth is difficult as the eggs are small, caterpillars and overwintering structures easily blend in with foliage and adult moths are most active at night. Box tree moth can easily move undetected in nursery stock. We have not yet found box tree moth in Maine and we encourage all nurseries to become familiar with this pest and report any suspected box tree moth damage to horticulture@maine.gov.

box tree moth life stages and damage

photo 1 (Ian Redding): Box tree moth adult – light morph; photo 2 (Juergen Kottmann): adult – dark morph; photo 3 (Mujezinovic Osman, Faculty of Forestry, bugwood.org): mature caterpillar and your caterpillar feeding damage (“peeling”); photo 4 (Ferenc Lakatos, University of Sopron, bugwood.org): heavy defoliation showing midribs of leaves left behind.

Tomato Brown Rugose Fruit Virus Survey Conducted

Horticulture inspectors assisted University of Maine Cooperative Extension, Plant Diagnostic Lab with a survey looking for Tomato Brown Rugose Fruit Virus (TOBRFV), a disease of regulatory concern that is not known to occur in Maine. Samples of tomato, pepper and other solanaceous crops exhibiting viral symptoms were collected and submitted to UMCE for testing. No TOBRFV was identified.

Symptoms of tomato brown rugose fruit virus

Shipping Plants Out of State? You Need a Compliance Agreement for That

Anyone shipping plant material out of state must have a signed compliance agreement on file with the Horticulture Program. Starting in 2025, the fee for these agreements will be $60 for shippers that have a nursery license or $106 for shippers that send plant products that do not require nursery licensing. The fees collected will help cover the costs of creating and maintaining the agreements. Compliance agreements are specific to a business, require an inspection of the business, allow the shipment of plant products using a Maine Nursery Stock Certificate (or other approved certification), provided the conditions in the agreement are met, and must be reviewed and renewed annually. In some instances, a phytosanitary certificate (PC) is required for a shipment of plant material. PCs are specific to a particular shipment, require an inspection of the plant material in that shipment, and may include specific statements on pests of regulatory concern to the destination. PC fees remain unchanged: $60/certificate for non-commercial shipments (shipments valued under $1250) or $106/certificate for commercial shipments (shipments valued over $1250). Shipments to international destinations requiring a PC are subject to an additional $6/certificate federal fee.

Beech Leaf Disease

Beech leaf disease (BLD) continues to expand its presence in Maine with some towns seeing significant symptoms and tree decline in 2024. BLD is caused by a nematode. Look for dark banding between leaf veins and deformed or shriveled leaves especially on trees with a thinning canopy. There are few treatment options for BLD and nurseries and garden centers in infested areas may need to make difficult decisions about whether they want to continue to sell trees that will require continued maintenance to survive in the landscape.

Beech leaf disease symptoms

Left: Dark interveinal bands indicating BLD infection as seen looking up into the canopy from the understory; Right: Upper leaf surface symptoms from undersized leathery leaves to banding to asymptomatic leaves, all on the same branch Photo Credit: Maine Forest Service

Nursery Survey in 2025

The Cooperative Agriculture Pest Survey Program (CAPS), has requested funding to conduct a nursery survey to monitor for a variety of invasive pests that are not known to occur in Maine and/or the United States. Visual inspections for target pests will occur during routine nursery inspections, but we will also be looking to place traps at some nurseries. These types of surveys assist in preventing agricultural and environmental damage by detecting harmful species when populations may be low and before they become problematic.

Winter is for Learning

In person

  • January 14-16, 2025: Maine Agricultural Trades Show, hosted by the Maine Department of Agriculture, Conservation and Forestry (DACF) at the Augusta Civic Center
  • January 22, 2025: Grow Maine Green Expo, hosted by the Maine Landscape and Nursery Association (MELNA) at the Augusta Civic Center
  • January 25, 2025: Winter Tree Talks – Patten hosted by the Maine Forest Service and National Park Service at the Lumbermen’s Museum, 61 Shin Pond Road, Patten, ME
  • Greenhouse Best Practices Workshop, hosted by DACF, Horticulture and IPM Programs. Details TBD, stay tuned!

Online

On-demand