MELeaf: A Newsletter From the Horticulture Program, March 13, 2024
In this issue:
The Horticulture Program has assembled invasive plant outreach materials that can help educate you, your staff, and your customers. Request copies of outreach materials
-
Rosa rugosa signage: The Maine invasive plant rule requires that signs (or labels) be posted with Rosa rugosa plants offered for sale. These signs are printed on weather resistant paper and meet all requirements in the rule.
-
Rosa rugosa factsheet: This factsheet describes habitats where Rosa rugosa should not be planted and includes a list of alternative plants.
-
Invasive Plant Guide for Maine Horticultural Businesses: A comprehensive manual that covers all the information Maine plant sellers need to comply with the invasive plant rule including:
- Copies of the invasive plant rule,
- The full list of plants on the Do Not Sell List, including synonyms and common cultivars,
- List of alternative plant suggestions for invasive plants,
- An identification guide for invasive plants,
- And more!
-
Do Not Sell List Factsheet: Full page, 2-sided factsheet that includes invasive plant quick facts and the full list of plants on the Do Not Sell List.
-
Plant This, Not That! Bookmarks: Now with designs featuring 8 of the plants on the Do Not Sell List.
-
Hitchhiker Postcards: In two different designs, one featuring mile-a-minute vine and the other invasive stiltgrass. Both plants are known to move with nursery stock, are of limited distribution in Maine, and are plants we’d like to have reported to horticulture@maine.gov.
-
Why can’t I buy… Factsheets: Several designs featuring 5 of the in-demand invasive plants on the Do Not Sell List. These factsheets include information on why the featured plant is prohibited from sale and a list of potential alternatives. Great to have on hand for those customers that are still asking for ‘Crimson King’ Norway maples or burning bush!
Quick Facts About the Invasive Plant Rule
The invasive plant rule review completed in 2022 included a phase-in period, and the full rule went into effect on January 1, 2024. What do you need to know?
-
30 species added to the Do Not Sell List: Those 30 joined the existing 33 species on the Invasive Plant Do Not Sell List. Any remaining inventory of these plants cannot be offered for sale and must be removed from sales areas. The ban includes all hybrids, cultivars or varieties of the species on the list as well as all viable parts of the species including rootstocks.
-
Rosa rugosa signage or label required: The 2022 rule review added Rosa rugosa to a new category called Invasive Species of Special Concern. Species listed in this category may still be sold, but specific signage or labeling must be displayed that indicates the plant could be invasive under certain conditions.
-
29 species added to a Watch List: Species on the Watch List may still be sold, but may exhibit some invasive characteristics. These plants may be banned in future rule reviews.
More information on the invasive plant rule, the full lists of plants and how to order outreach materials
Our field season is just starting and we haven't conducted enough inspections yet to have any observations to share. Here are a few pests we'll be thinking about this season as we start inspections, and some tips on how you can help us keep an eye out for these pests.
Reportable Pests: These pests are not known to occur in Maine or are of very limited distribution. If you suspect any of these pests please note your location, take a picture and email it to horticulture@maine.gov.
-
Spotted lanternfly: Spotted lanternfly (SLF) continues to expand its range in the eastern US. SLF is an excellent hitchhiker. This spring check plants as they arrive for egg masses. SLF will lay their eggs on anything; it is also prudent to check shipments of other goods that may have been stored outdoors (like stone, statuary, lawn furniture etc.) for egg masses.
-
Mile-a-minute and stiltgrass: Mile-a-minute (MAM) was found for the first time in Maine in 2023. It is likely these MAM plants were introduced either on newly planted plants or with mulch and other soil amendments that were applied at the time of planting. All MAM plants have been eradicated and the sites will be monitored for any regrowth this summer. Another invasive plant, stiltgrass is known to move to new areas on nursery stock. There are a couple of known established populations of stiltgrass in Maine, but it is currently of very limited distribution and the property owners are actively working to eradicate these populations.
-
Thrips parvispinus: There were no official reports of Thrips parvispinus in Maine last growing season, but this newer thrips is likely much more widespread in North America than any official known distribution (It is currently known in Florida, Georgia, Ontario and perhaps a few other states). We covered this pest in a MELeaf article last spring and while we think our conclusions on the impacts of this pest in Maine are still sound, we would like to know if you suspect this thrips is in your greenhouse.
-
Box tree moth: We talked about box tree moth in the December 2023 and July 2023 issues of the MELeaf. Both articles are good introductions to this federally quarantined pest. Box tree moth hibernacula (overwintering structures) and small newly emerging caterpillars can be hard to spot, check incoming plants carefully for any signs of this pest. If you receive boxwood from an area near or infested with box tree moth, ask questions of your supplier to ensure that they are following quarantine requirements.
 Left to Right: An SLF egg mass (Richard Gardner, bugwood.org), mile-a-minute vine (Leslie Mehrhoff, University of Connecticut, bugwood.org), stiltgrass, Thrips parvispinus damage to pepper plant (LS Osborne, UF/IFAS-MREC) and a young box tree moth caterpillar in a hibernacula.
Non-reportable Pests: These pests are widespread in Maine, there is no need to report them if you find them, but we will be on the lookout for these during our growing season inspections.
-
Impatiens downy mildew: When newer varieties of impatiens that are resistant to impatiens down mildew (IDM) were released a couple of years ago, this disease fell off the radar of many growers. Last growing season there seemed to be an uptick in IDM reports throughout much of the US. Concerningly, the disease seemed to be infecting resistant as well as non-resistant varieties, although resistant varieties may have faired better with fewer disease symptoms. We did not observe any infected plants during greenhouse inspections in Maine last year, but we have heard anecdotally from several people that IDM was indeed here. Look under leaves for white to gray fuzzy growth.
-
Browntail moth: We anticipate impacts from browntail moth to continue this summer; be prepared to continue to deal with the itchy rash caused by this pest. Caterpillars will be emerging from their winter webs starting when the buds begin to break in April. If you are clipping winter webs as a management strategy, those activities should be completed by the end of this month.
Rosa rugosa Signage: If you sell Rosa rugosa we will be checking this year to be sure businesses are complying with Maine's invasive plant rules by posting the appropriate signage around Rosa rugosa plants that are offered for sale. We have a supply of signs printed on weather resistant paper that you can request using the "Request Outreach Materials" button above. If you prefer to create your own signs, or would rather tag individual plants you can find the specifications on the invasive plant website.
 Left to Right: A leaf infected with impatiens downy mildew (Laura Sanagorski, University of Florida), a browntail moth winter nest, an example of required signage for rugosa rose.
|
