MELeaf: A Newsletter From the Horticulture Program, November 7, 2022
In this issue:
The holiday season is fast approaching and many nurseries, greenhouses and garden centers will soon be receiving and selling wreaths, trees and other live holiday decorations. Plant pests can be lurking in holiday greenery and other plant material. Follow these tips to help prevent moving pests this holiday season.
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Choose Maine grown plant material. Purchase wreaths, trees, greenery and other live holiday decorations from local sources. Plants grown locally are less likely to move a new pest to a new area.
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Look for pests. Inspect incoming live decorations including greenery, twigs, cones, fruits, nuts and berries for signs of insects and diseases. Boxwood blight has been found in wreaths in recent years. Aphids, mites and scales are all common on holiday greenery. Also, take the time to look for insect egg masses like those laid by spotted lanternfly and spongy moth and for tunneling and exit holes left behind by wood borers.
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Beware of invasive plants! Asian bittersweet and multiflora rose have pretty, decorative berries, but both are invasive and illegal to sell in Maine. Better plant choices with colorful berries include winterberry and holly.
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How about the yulelog? Firewood can harbor pests and should be sourced locally or heat treated to kill any hitchhiking pests. Maine’s emerald ash borer quarantine requires any hardwood firewood leaving the quarantine areas be heat treated and all out-of-state firewood must be heat treated before entering Maine.
If you send wreaths and trees out-of-state you must follow plant health regulations of the destination state to prevent the spread of plant pests, avoid unnecessary delays and the destruction of plant material upon arrival at its destination.
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Import regulations vary from state to state. Check destination state regulations before sending plant material. A summary of plant health regulations for Maine grown holiday decorations is on the Horticulture Program website.
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Shipping internationally? Always contact the Horticulture Program before sending any plant material internationally. Many countries prohibit most types of plant material included in holiday decorations. Some countries, like Canada, may allow some holiday decorations with the proper certification.
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Look for pests. Carefully inspect plant material before packaging to ensure that there are no insects, egg masses or other pest damage. Look for evidence of pests that are commonly found on greens used in holiday decorations such as scales and balsam gall midge.
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Clearly label packages. Begin with the statement "Grown in Maine" followed by the county of origin and the name and address of the shipper. Labels should also indicate the different types of greenery, nuts, fruits and cones used to decorate wreaths.
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Don’t forget about spongy moth! Spongy moth (Lymantria dispar, formerly known as gypsy moth) certification is required when sending plant material outside the spongy moth quarantine area. Christmas tree shippers must have a compliance agreement with USDA-Plant Protection and Quarantine (USDA-PPQ) and inspect their trees for egg masses before shipment. Wreaths and other holiday decorations assembled with branches that are less than ½ inch in diameter may not require a compliance agreement but do need to be inspected. Contact the Maine USDA-PPQ office at 207-848-0000 for more information.
 This wreath contains plant material that may need certification to move to another state.
The Horticultural Research Institute (HRI), the National Plant Board (NPB) and USDA recently announced the launch of a new pest risk assessment tool that can help nursery and greenhouse growers improve plant production processes and grow healthier, pest-free plants. The tool helps growers identify areas in the growing process where plants can become contaminated with plant pests (the “hazards”), the time or place in the growing process when a control can be implemented to mitigate the hazards (the “critical control point” or CCP) and the measure to be taken to reduce or eliminate the hazards (the “best management practice” or BMP). A grower can use the pest risk assessment tool to help identify improvements or additional BMPs that can be implemented to manage pests or to organize and document the practices that are already in place.
The pest risk assessment tool was developed to simplify the risk assessment process required for nurseries and greenhouses that participate in the Systems Approach to Nursery Certification (SANC) program. SANC is a voluntary, state-verified plant health certification program that integrates best practices throughout a growing operation to address pest risk and satisfy applicable state and federal plant health shipping regulations. The pest risk assessment tool is available at no cost to any nursery or greenhouse seeking to improve their processes, whether they choose to pursue SANC certification or not. Growers may request free user access to begin a facility risk assessment by visiting the Risk Assessment website.
There’s a new slug in town. And by town, I mean just over the border in Canada. How is this slug different from all the others we see under rocks and sticks near our veggie and flower gardens? According to USDA experts, this new slug, Arion vulgaris, is considered the worst slug pest known in Europe. It has been documented destroying different types of vegetables, especially brassicas, potatoes, and tomatoes, as well as ornamental plants, like Rhododendrons. Although native to Europe, and for reasons not well understood, A. vulgaris started spreading in the 1950s from northeast France to virtually every European country. In 2018, it was found in a suburb of Toronto, and this year in Quebec City. Experts think that its sudden, rapid spread could be in part due to successful mating with other Arion species in the same complex. These other Arion species, Arion rufus and Arion ater are both established in the US; Arion ater is found in Maine on Vinalhaven. Hybrid Arion vulgaris may establish easier in new environments and spread its pestiferous ways.
Like many exotic plant pests, long-distance spread can happen with the movement of plants, plant parts, containers, or soil. Mollusk eggs are difficult to notice as they are very small and often translucent, but if you notice any or other life stages of an unusual snail or slug, please make sure they don’t travel off-site. And please contact us at bugwatch@maine.gov if you come across an Arion species. You can’t miss ‘em as they are large (5-6”) and come in a variety of reds, browns, and blacks.
 
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