Extension Communications
Extension 4-H Youth Building
Ames, Iowa 50011-3630
(515) 294-9915
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Extension Communications |
10/4/04
Contacts:
Betsy Matos, Entomology, (515) 294-1999, bmatos@iastate.edu
Del Marks, Continuing Education and Communication Services, (515) 294-9807,
delmarks@iastate.edu
Garden Column for the week of Oct. 8, 2004
Enemy In Our Garden - Purple Loosestrife
By Betsy Matos
Entomology Graduate Student
Iowa State University
Have you heard the saying, "It's like a wolf dressed in sheep's clothing."? This describes the beautiful plant of purple loosestrife.
Purple loosestrife (Lythrum salicaria) was introduced in the early 1800s by European immigrants for herbal and medicinal uses. The plant may grow up to seven feet tall and up to four feet wide. Its primary identification characteristic is the erect stalk of purple flowers, which bloom from late July to early August in Iowa. Beekeepers were told to plant purple loosestrife because it provides large quantities of nectar for honey production.
Its fast establishment and spread is thought to have occurred because no natural enemies were present in the introduced areas. This has resulted in a competitive advantage for purple loosestrife over plants such as cattail. Purple loosestrife can displace more than 50 percent of a wetland's biomass.
A few native insects feed on purple loosestrife, but not enough to cause suppression. In the 1980s, the U.S. began exploration in Europe for insects that would serve as biological control agents against purple loosestrife. After extensive tests, four species were released in purple loosestrife infested areas.
State of Iowa
In Iowa, purple loosestrife is found in wetland and prairie areas. Wetlands affect the environment and human health. Healthy wetlands improve and maintain good quality water, provide habitat for wildlife species and provide recreational landscapes. When purple loosestrife infests a wetland, it alters the wetland functions (e. g. acts as a filter by improving and maintaining good quality of water, serves as habitat for wildlife, etc.).
In 1994, Iowa initiated a biological control program by rearing and releasing Galerucella species in the northwest area, where purple loosestrife was very abundant. More than 800,000 Galerucella beetles have been released in different wetlands throughout Iowa. In 2001, Iowa passed legislation prohibiting the importation, selling, offering for sale or distribution of purple loosestrife. Twenty-eight other states have adopted similar laws.
It is not illegal to have purple loosestrife in your garden, but it works against efforts to suppress this pest. Horticultural varieties of purple loosestrife were thought to be sterile, but scientific studies have shown that these varieties can cross-pollinate with 'wild' purple loosestrife. Seeds may disperse into susceptible areas where these may germinate and eventually bloom to make the problem worse. In addition, cuttings from the plant may re-establish because they have the ability to grow roots from clippings.
Purple loosestrife is a beautiful plant, but it damages our environment.
There are many native plants that have similar color, structure, height and blooming that can be used as alternatives to purple loosestrife in the garden. Some examples are Gayfeather, Obedient Plant, Joe-Pye Weed, Marsh Milkweed, Blue Vervain, Fireweed, Ironweed, Bergamot, Great Blue Lobelia and Wild Blue Phlox (For more information on other native plants, see the Wisconsin Department of Natural Resources on the Web at http://www.dnr.state.wi.us/org/land/er/invasive/info/loose2.htm).
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ml: isugarden
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Editors: Two color photos, suitable for publication, are available at right. Click on each thumbnail photo to go to the fullsized photo. The top picture's fullsize photo is 376K and the bottom picture's fullsize photo is 288K. Caption: Purple loosestrife's primary identification characteristic is the erect stalk of purple flowers. It is a beautiful plant, but it damages our environment. |
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| Caption: More than 800,000 Galerucella beetles have been released in different wetlands throughout Iowa to provide biological control. |  |