MNWR Photo - USFWS
Purple loosestrife, the beautiful purple plant found throughout Montezuma National Wildlife Refuge and other wetlands and moist soil areas, is an exotic species of Eurasian origin and a threat to the viablity of North American wetland habitats. In Europe and Asia purple loosestrife is a minor component of wetland habitats and not the dominant species it tends to be in North American wetlands. The major difference involves the lack of the plant's natural enemies. When purple loosestrife arrived in North America during the early 1800's no natural enemies accompanied it. This, along with the plant's abitily to grow in a variety of soil types and in various depths of water, has given purple loosestrife a competitive edge over North America's native wetland plants.
Purple loosestrife typically infests areas where native wetland plant communities have been disturbed. This includes manmade disturbances such as digging or moving wetland soils with tractors and bulldozers as well as natural disturbances like droughts and floods. Purple loosestrife spreads primarily by seed germination in moist soil areas. A typical 3 year old plant can produce in excess of 1 million seeds.
The impact of this weed on North American wetlands has been disastrous. Native wetland plants have been crowded out by purple loosestrife. This in turn causes a reduction in suitable habitat for wildlife, particularly waterfowl and waterbirds like this Green Heron, and reduced productivity for those species which depend on aquatic ecosystems.
Green Heron
Photo by Les Maynard
For example, platform nesting species can not use the stiff stems for nest construction, nor are stems or rootstocks palatable to muskrats. Dense, closely-spaced clumps do not provide brood cover or foraging areas for waterfowl. These clumps are fairly resistant to decay and over several years the ground level surrounding these clumps is raised as organic litter is trapped in the root system. As a result, native plants such as cattails, smartweed, rushes and sedges are greatly reduced, or even eliminated.
Montezuma National Wildlife Refuge has been, and will remain, a key area for research on the management and control of purple loosestrife. In part, this is due to the fact that the refuge has suffered one of the nation's worst infestations of loosestrife over the past 45 years. In 1951, loosestrife was found only in sparse stands; by 1980, the plant occupied 1,500 acres (607 hectares) of the refuge's 3,200 acres (1295 hectares) of managed wetlands.
Past efforts to control purple loosestrife have provided a great deal of knowledge about the biology of the plant but there has been little or no success in its control, except where it occurs on small, localized stands and can be intensely managed. These control measures however, are costly, require long-term maintenance, and in the case of herbicides, are non-selective and environmentally degrading.
In the summer of 1996, the Biological Control of Non-Indigenous Plant Species Program at Cornell University began a biological control program on the Refuge using several of the plant's natural enemies to control purple loosestrife. The goal of this biological control program is to establish the competitive balance between native plant species and purple loosestrife. This is not an attempt to erradicate purple loosestrife but to reduce its abundance to an acceptable level and reduce the need for herbicide useage.
Since 1985 Cornell scientists, in cooperation with the U.S. Fish and Wildlife Service and the International Institute of Biological Control, have identified three species of weevils and two species of leaf-beetles that live and feed exclusively on purple loosestrife and are approved for introduction and release by the Animal and Plant Health Inspection Servive and the U.S. Fish and Wildlife Service.
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| Galerucella sp. (Beetle) | Hylobius sp. (Weevil) |
Ideally, the interaction of natural enemies and plant competition will provide a self-sustained balanced system in the future. Biological control will take time (5-10 years) but hopefully after a long battle, native wetland plant communities will reclaim their original habitats, restoring the quality of habitat provided in North America's wetlands.
The first phase of this project has been declared a success. Both the beetles and the weevils have survived the winters, and are reproducing and spreading. We are starting to see the effects on the loosestrife.
The following is excerpted from an article by Dan Carroll (a DEC Senior Wildlife Biologist) intended for publication in The Conservationist, a magazine published by the DEC.
Purple loosestrife began to appear at the Oak Orchard and Towanda Wildlife Management Areas in the 1960's and early '70s; by 1990 it was rapidly spreading. Early attempts to control by pulling, mowing, burning, flooding, discing, herbicides were ineffective, costly, and generally needed to be repeated frequently. By the late 1980's, it became apparent that biological control was the best approach to control in the least environmentally damaging way. Testing began in 1991 at Towanda Wildlife Management Area, using primarily the Gallerucella beetle species, which proved capable of surviving a New York winter. By 1999 all the loosestrife in the 50 acre test site was under control (reduced by 75-80%; surviving plants stunted, and native vegetation dominant).
Additional successful releases have taken place at Braddock Bay Fish and Wildlife Management Area, and at a site in Batavia. A nursery to produce Gallerucella beetles was established at Oak Orchard Wildlife Management Area; each year 250-350 purple loosestrife roots were dug, planted in plastic pots and fertilized; they were then placed in pools filled with water. After about a month, the pools were covered with screen and 300 adult beetles were placed in each tent to breed; after eggs were located on all the plants, they were distributed to the release sites, where each plant produced up to 400 late stage larvae or emerging adults. In 1999, pre breeding adults were moved to new locations to establish new populations. Hopefully this method will be successful and can be used to establish new populations of beetles in the future.
To date, the results of this biological control project in Western New York has been very impressive. However, we must remember that purple loosestrife has a 100-150 year head start on the bio-control insects. Therefore, there is an urgent need for additional releases all across New York State before a major impact will be seen statewide on purple loosestrife.