View the Aquatic Plant Regulations spreadsheet.
Q: I’ve heard that since Mosquito Dunks contain BT (Bacillus thuringiensis), they will also work against China Mark Moths?
There are two different subspecies of BT that are used for different pests on aquatic plants. Bacillus thuringiensis subspecies israelensis (BTI) is the active ingredient in both Mosquito Dunks and Mosquito Bits. BTI is not effective against China Mark Moth. It is effective against a fly larvae commonly referred to as the Muck Midge. It is a tiny worm, clear in color to whitish and approximately ¼ in length and about the diameter of a straight pin. It chews a distinct random pattern on the leaves of Water Lilies (Nymphaea). The larvae hide themselves in a sheath of tissue at one end of the random line of destruction and make difficult to find. Most of the damage occurs in late summer and early fall. A heavy infestation can easily defoliate lilies in a short amount of time and severely weaken the plants if left untreated. The Mosquito Dunks are a better preventative treatment, but if an infestation occurs we find the Mosquito Bits are better for the quick kill. These naturally occurring bacteria will not harm anything else in the pond except mosquito larvae. Not a bad side effect. For large nurseries BTI can be purchased from Summit Chemical under the brand name of Aquabac in 40-pound bags. For more information, or for a dealer near you, contact them at 410-282-5200. Bacillus thuringiensis subspecies kurstaki (BTK) is the active ingredient in Dipel. BTK is very effective against the China Mark Moth Larvae. Sometimes referred to as Sandwich Man, the moth larvae chews off oblong pieces of Water Lily leaves, fastens them together and hides inside. This floatation device allows the larvae to float around the pond and eat off of the lily leaves. They are sometimes found attached under the leaves or they will bore a hole in the stem of the leaf for an inconspicuous hiding place Dipel is available as a dust or wettable powder. The dust can be applied in the evening when the sun is lower and should be rinsed off in the morning. Most of the chewing by the larvae is done at night. Applications may have to be repeated at 7-10 day intervals to get control. The wettable powder should be mixed according to the label directions and should also be applied in the evening at the same intervals as the dust. A spreader/sticker (Silwet) can be used to help the Dipel adhere to the leaf surfaces. Both products are easily available from Horticultural or Farm Supply Companies.
More recently a product called Conserve SC has become available that is excellent for the control of lepidopterous larvae (such as: cutworm, sod webworm, gypsy moth larvae, bagworm, fall webworm and others), sawflies, leaf feeding beetles, midges, thrips and leafminers). It has proven much more effective at controlling the China Mark Moth and Muck Midge larvae’s than either of the above. In addition to its effectiveness on Water Lily’s (Nymphaea) it works on Lotus (Nelumbo) leaf chewing larvae and Canna leaf rollers among other pests in the nursery. This also simplifies the process rather than using multiple treatments. It is available from most Horticultural Supply Companies. Conserve is not a consumer recommended product. Dipel and Conserve are not labeled for use in water, but the plants could be removed, treated and returned to the water. As always, take care to follow all label instructions on any pesticide or insecticide.Manual removal of the larvae is always the first reccomendation but take care to remove the insect pests from the pond area and place them in closed container for disposal. Otherwise they will climb back into the pond and require removal again.
Q: What is the best recommendation to my customers for the control of aphids?
We have tested Aquarium Pharmaceuticals Herbal Aphid control. It has proven extremely effective for for the treatment of aphids. It is a contact killer. If it hits them, it kills them. I have even used it on my roses at home. It is critical to rinse the plants after use to wash off residue and to remove the dead aphids. A few plants like Taro and Water Lettuce do not tolerate it well and will show some foliage burn. As always follow label directions carefully.
Q: I’ve been noticing some dense weeds growing in the aquatic plant pots in my display water gardens in my garden center. How can I control them without getting into the pond and manually pulling them out? Are there any safe products that will kill th
Weeds can surely be a problem in a water garden. Prevention is the best defense. When potting water plants, use topsoil that is free of plants debris that may contain weed seeds. Don’t use soil from a compost or soils containing uncomposted cow or horse manure. These soils can be full of weed seeds. Once potted, place the top of the pot at least 2 inches below the surface of the water. This depth should prevent the germination of terrestrial weeds. There are such weeds that do just fine in water as long as they are not covered with water. At the nursery, we have two kinds of weed grass that love to grow in pots that are just out of the water. One grass will literally consume the pot while the other will insinuate itself into the resident plant and become impossible to remove without removing everything and sorting one from the other.
Perhaps the worst weeds in the pond are waterweeds. There is no easy defense against these plants. In fact, one man’s attractive plant may be another man’s weed. Alisma for example, is very attractive in the pond but spreads everywhere via seeds. For this plant and others like it, cut the seed heads off before they mature.
Underwater weeds, e.g., hydrilla and sago can be particularly tenacious. For these, chemicals herbicides may be your only defense. The chart associated with this article prescribes various herbicides, many of which may not be available to the home gardener. We have tried a combination of diquate and cutrine to good effect against underwater weeds but found it difficult to guage the dosage rate. In our case, the weeds died and so did many of the fish. The water lilies were unaffected. Probably, for most backyard ponds, hand removal of underwater weeds and a thorough cleaning of the pond once a year is best.
Q: I’ve been having problems with a native horsetail growing around my display ponds. I assumed that they needed to be in a constantly wet media, but it’s thriving in my mulch and terrestrial plantings. How can I get rid of it? It has spread dramatic
Equisetum – Horsetail has been around since the dinosaur days and doesn’t give up easily. I have seen it growing along rivers 8-10 feet above water level in nothing but sand as well as 6 feet under water covering a pond bottom. I have seen it grow under heavily driven gravel roads and pavement to prosper on the other side. It is not terribly particular about what conditions are present. Full sun or full shade has little or no effect on the aggressive growth habit. The best control is to never give it access to the garden, not even through the drain hole in the bottom of a pot. All of the horsetails can be grown in containers for extended periods with little care. I have an 18” wide 24” tall decorative planter in my garden with E. hyemale ‘Robustum’ that is 2 years old and a good 4 feet tall. It is a beautiful specimen, standing taller than myself.
We carry four varieties of horsetail, all of which offer ornamental appeal. Bear in mind that Equisetum has excellent properties when confined. The E. hyemale - up to 3’ tall and E. hyemale ‘Robustum’ – up to 6’ have a strong cylindrical habit. The ‘Robustum’ develops side shoots on the upper joints in the second and third year that give it a slightly fern-like appearance. Equisetum scirpoides is a dwarf variety that is dark green and wiry growing only 6-8” tall. E. diffusum 6” has soft sweeping stems giving it an almost fern-like appearance as well and it is the only deciduous one we have. In a lined pond a container without holes is not critical. They will grow out of the drain holes in the bottom but not with the aggressive habit they display in the garden.
We have had many customers tell us what doesn’t work to eradicate horsetail but never one to tell us what did.
Wyman’s Encyclopedia notes – Horses have been poisoned from eating this plant, usually cut with hay in moist ground. Another species E. arvense or the Field Horsetail is frequently found as a weed in gardens and must be vigorously dug out.
Botanica, R G Turner, Jr. - They rarely exceed 10 ft tall and grow from vigorous creeping rhizomes. Although quite ornamental, their use in gardens is limited because they become invasive and are difficult to eradicate. Horsetails have been used since Roman times to scour pots and medically as a general tonic and astringent.
Hortus Third – The siliceous stems are sometimes used in polishing. Occasionally used as an ornamental in moist places including pool margins. Easily propagated by division.
Aquacide Company in Great Bear Lake, MN told me their recommendation is persistent physical removal and that a product they have called Eagre may work. Glyphosate is the active ingredient. To make contact 651-429-6742.
According to Weeds of the US & Their Control by Harri Lorenzi and Larry Jeffery, Equisetum spreads by spores and rhizome borne tubers. It is cultivated (plowed) regularly to remove nutrient and moisture. Young seedlings can be treated with 24D or MCPA, adult growth would be treated with an herbicide called Bromacil.
Agriliance Don Klein told me Dow Chemical 717-792-4470
Anita Nelson fron Nelson Water Gardens in Texas said the best way to get rid of Horsetail is to move!!!
Q: I’m getting more and more frustrated by uncertain and conflicting information about invasive plants. It seems that governments, both Federal and State, are starting to crack down on individual businesses. However often there is only incomplete inform
You’re right, frequently there is conflicting, incomplete, or out-dated information. Even worse, there is no single source for accurate listings. Since our industry definitely needs this kind of resource, I was motivated to compile something that would be helpful and accurate. It wasn’t long before I realized that creating a master list for publication was definitely a bigger challenge than I had ever imagined. Uncertainties and obstacles arouse almost immediately.
Let’s start with the Federal level. The Federal Noxious Weed List (FNWL) was last updated in September 2000 and can be easily found at www.aphis.usda.gov/ppq/permits/noxiousweed_list.html under the Plant Protection and Quarantine page. This seems simple enough, except that the FNWL found at http://plants.usda.gov/plants/cgi_bin/federal_noxious.cgi is an invalid list last updated in 1999. Go figure … it pays to be careful when checking sources since some sites have invalid or outdated lists.
Most State lists also include the Federally prohibited plants while some States use only the Federal list. Other States have not officially adopted the FNWL but require a permit from the USDA before plants on the list can be moved into their State. Plants listed on the FNWL are not State regulated or enforced unless also included on the State list.
Obtaining complete and accurate State Lists was, on the other hand, a more difficult task for many reasons.
The formal chain of command for State legislation as it applies to noxious weeds is as follows:
1. The State Government determines a plant to be prohibited from sale or have restrictions on import, distribution, or possession (except by permit) within their boundaries, sighting it as a noxious weed.
2. The updated plant list for that state is to be forwarded to the National Plant Board (NPB) for posting on their website www.aphis.usda.gov/npb/statenw.html. (This is the responsibility of the individual States.)
3. The NPB site is supposed to be THE authoritative source for ALL State Nursery Inspectors across the country.
Unfortunately, that’s not always what happens. For example, Alabama has prohibited the sale of Myriophyllum aquaticum in their state since August 2000. Check the NPB site and it is not listed as prohibited even though the NPB updated in December 2000. Alabama’s own web site does not have an available list of noxious weeds. They are not alone; many of the State sites do not post a list.
Remember, ignorance of the law is not a valid excuse. Our State of Maryland Inspector did say he would go to bat for us in the event we did ship Myriophyllum aquaticum to Alabama unknowingly and that we would more than likely win the battle.
But … Washington State added new plants to their prohibited list, effective January 2001, that are still not posted to NPB site. Since they are posted on Washington’s site, we would be liable for shipping prohibited plants to Washington because the information has been made available to the public. (What exactly constitutes “made available”?)
And … Florida publishes a list of Most Wanted ‘Outlaw’ invasive aquatic and wetland plants. The unsuspecting consumer, retailer, or grower (myself included) might be led to believe that they are on Florida’s prohibited list. In fact some are and some aren’t. Florida is not alone; other States publish similar plant pest/weed lists. Pay careful attention to the wording of information when researching.
The most difficult part of this seemingly never ending project was weeding out the inaccurate information. Wyoming shed some light on another reason for confusion. Their own web site (as well as many others) produces different lists from different queries. The reason is some plants have restrictions by county and/or by State. The list will also vary depending on whether the restriction is a ruling, statute, or law, and which branch of government it falls under. Additionally it may depend upon whether the noxious weed restriction is for the plant or the seed.
Even more problems are created because noxious weed lists are not always maintained by the States’ Department of Agriculture. Sometimes they fall under the Department of Wildlife and Fisheries, the Department of the Environment, the Department of Natural Resources, or another branch of government.
More conflicts arose from ‘comprehensive’ sites that seemed to have everything in one place. The noxious weed list on Maryland’s web site is a link to the INVADERS Database System posted by the Agricultural Research System and the USDA. I was sure I had a great find since I could search every State from a single site. So I printed a few for comparison and found that most of the lists did not match or even come close to the list faxed to me by that State. (Could that be because the ruling, statute, law, seed, or plant “thing” generated mixed information for the queries?)
To get around all these ambiguous situations I faxed a request to the States without current information available on their web site. My request to them was to provide a confirmed list of aquatic plants they regulate as noxious weeds. The replies I received provided the core of my “Regulated Noxious Aquatic Weeds” list. When clarification was needed, I chose the faxed information as the official version.
A complete accounting of the researched information has been compiled into two lists. The first is the “State & Federal Contacts for Invasive Aquatic Plant Information.” The second is a list of “Regulated Noxious Aquatic Weeds” and their restrictions by State. I cannot assure absolute accuracy, but I am confident this is a far better accounting than previously available. Both lists can be found in PONDKEEPER Magazine’s Annual Buyers’ Guide and PONDKEEPER has generously offered to post a perpetual work in progress list on their website, www.pondkeeper.com.
This raises some interesting questions to the industry as a whole:
How often is the USDA and National Plant Board site updated?
If the industry makes every effort to regulate itself, how much effort will be placed on each company that ships interstate? Will each have to come up with a complete and accurate accounting of prohibited or restricted plants to individual states if the formal chain of command is not followed in a timely manner?
Can we rely on industry volunteerism to be the source of current information for new plant restrictions in various states?
Could a corner of Pondkeeper magazine be dedicated to announcing new additions to the list/s?
Editor’s note: Yes, consider it done. As information is faxed or emailed to us, it will be published.
Should the same information be published in other trade magazines and/or journals?
Would the publicity of prohibited and restricted plants have an impact on their sales in states where they are not prohibited? How could it effect the industry’s reputation?
How involved in the process does the industry want to become?
Now I seem to have raised more questions than I answered. Any feedback out there????
Maryland Aquatic Nurseries, Inc.
Special Thanks to:
Maryland Department of Agriculture
Q: Many floating aquatic plants are prohibited in our state, like water hyacinth (Eichhornia) and water lettuce (Pistia). What non-invasive substitutes do you suggest we recommend and sell to our customers?
The numbers of prohibited plants, not just floaters, are increasing at a rapid rate. (See the January/February issue of Pondkeeper and the associated Buyer’s Guide.) We find that these two plants in particular are a favorite of customers to accomplish two things. First, to add them to a natural or biological filtration system for the purpose of clearing water. Second, to provide quick surface coverage in the pond.
Water hyacinth and lettuce are not the only two plants that can accomplish either of the above. While it is true that they are effective we are uncertain how the myth among consumers began. As water gardening becomes more popular the demand for both of these tropical plants comes earlier and earlier. A warm week in February or March will send the phone a flutter with retail customers in search of both. We are still trying to figure that out.
As a general rule the worst times of year for pea soup algae blooms are in the early spring before the plants in the pond are active and in the late summer when the plants are resting from the extreme heat and are transitioning to the fall season. Since both water hyacinths and lettuce require warm temperatures to start growing, they are not effective at removing accumulated nutrients from the pond in the early spring. We strongly suggest you recommend that your customers purchase some plants that prefer colder temperatures to do the job early before the algae gets the upper hand.
Iris pseudacorus (Yellow Flag Iris) and Iris versicolor (Blue Flag Iris) are an excellent choice that can be added to the biological or natural filter either potted or bare root. Both of these varieties are more clump-habited than some of the Louisiana hybrids. If either is added as a bare root plant it needs to be anchored to keep it from floating toward the overflow area. It may lay sideways for a few days but it will find up. It will soon form a dense root mat that will keep it in position and help trap sediment. Simply lift and rinse periodically as you would your biological filter media. I. pseud.
Prohibited to VT.
Oenanthe javanica (Water Celery) and Oenanthe javanica ‘Flamingo’ (Variegated Water Celery) both thrive in cool weather and in southern climates are evergreen, performing best during the late Winter and early spring. They will grow well potted or floating if in moving water. Both plants are on the racy side but are not listed as prohibited.
In areas where hyacinth and lettuce are not prohibited they are an excellent addition to the filter, when the water gets warm, to help combat the late summer algae bloom and to the pond to provide shade and cover for fish. In your case try some plants like Aeschynomene fluitans (Giant Sensitive Fern) or Neptunia aquatica (Sensitive Plant). These plants, like Water Celery, benefit from being potted if not in moving water. They creep quickly across the water’s surface and can be pruned liberally to keep them in check. They have the added attraction of folding their leaves when touched. Yellow Sweet pea-like flowers add decoration to the foliage when it really gets warm.
Bacopa caroliniana (Lemon Bacopa), Bacopa lenagera “Variegata’ (Variegated Bacopa), and Bacopa ‘Monnieri’ (Moneywort Bacopa) are all great choices to serve both purposes. Each of these creepers has it’s own attributes. The Lemon Bacopa foliage has the distinct aroma of lemons when broken. The Variegated Bacopa has bright yellow veins on crisp green foliage and both have delicate blue flowers in summer. The Moneywort Bacopa tolerates cold temperatures better and has a continual display of delicate white blossoms all summer long.
Ludwigia peploides (Primrose Creeper) is another choice that will work. It has creeping shiny ovate foliage with bright yellow flowers throughout the summer months. It grows to a height of 2 feet with a much faster spread than the others listed and should be reserved for larger ponds.
It can be given a swift haircut as needed.
Lysimachia nummularia ‘Aurea’ (Creeping Jenny) will brighten up a shady area with its golden yellow flowers and even brighter yellow flowers. Creeping Jenny along with the Bacopa are the best choices for dense creeping foliage that will help conceal a filter or soften the hard look of a lot of stone around the pond.
There are also the old stand-bys Mentha aquatica (Water Mint) and Myriophyllum aquaticum (Parrot Feather) that work wonders in a pond to help filtrate and offer quick surface coverage. Mint is prohibited in ID, MT, NE & WY due to some risk associated with the huge Mint industry there and Parrot Feather is prohibited in AL, ME, NV, NH, VT & WA.
Educating consumers is an endless job, but giving them as much information and selection as possible will help maintain loyalty and keep them coming back.
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