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Beetles on the loose
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A large infestation of purple loosestrife in Michigan. Photo by Linda Nelson |
Purple loosestrife (Lythrum salicaria), an invasive plant of European origin that was introduced to the U.S. in the early 19th century, is an attractive plant with showy flowers that has been cultivated for its medicinal value. It’s also considered a noxious weed in 33 states.
Purple loosestrife is able to survive in a variety of habitats, but it is considered a wetland perennial, and wetlands and waterways are the areas where it causes the most damage. According to the Weed Science Society of America, loosestrife can “displace native vegetation, disrupt wildlife habitats, clog irrigation ditches and negatively affect water quality.” It’s also considered a “serious threat” to wetlands and waterways, particularly in the Midwestern U.S.
It’s been nearly impossible to control the plant, partly because a single purple loosestrife plant boasts an annual production of 100,000 to 2.5 million seeds that are small, lightweight and easily disbursed.
Scientists and managers from the University of Minnesota, the Minnesota Department of Agriculture, the Minnesota Department of Natural Resources, local park lands, Cornell University and CABI Bioscience of Delémont, Switzerland, worked together to develop a biological control program involving loosestrife beetles (Galerucella calmariensis and G. pusilla). Within two years of the beetles’ release in the early 1990s, purple loosestrife biomass and seed production were significantly reduced, and within five years, the beetles had dramatically reduced loosestrife stands.
The beetles feed on the plants and delay flowering by stripping away the canopy. This delay reduces the number of seeds produced each year, decreasing the population as well as slowing its spread. The plants attacked by the beetles are also stunted and therefore less able to compete with the native vegetation.
As a result of the success in Minnesota, beetles were released in 13 Midwestern and Northeastern states. In order to be effective, the beetles must be released in large numbers. In Minnesota, more than 8 million beetles have been released, and in Nebraska 500,000 have been released annually since 1997.
Although reducing purple loosestrife through beetle infestation is a slow process, the Nebraska program, for one, has been considered a success. Dennis Daum, a U.S. Army Corps of Engineers park ranger, who took part in both rearing and releasing beetles in the state, says, “We’ve been able to reduce purple loosestrife infestations by about two-thirds in just eight years.”
Advan LLC has expanded its product line with the introduction of Proplant turf and ornamental fungicide, which the company says makes it the first alternative supplier of the active ingredient propamocarb hydrochloride. Advan says Proplant prevents and cures many Pythium diseases, including damping off, cottony blight, grease spot and root rot on turfgrass and ornamentals. A systemic fungicide, Proplant is quickly absorbed and translocated through the grass and features a multisite mode of action to help prevent resistance, the company says. It can be applied post-germination or to established turf and can be used during all stages of ornamental production to prevent root rot and damping off. For more information, contact Advan LLC, www.advanllc.com. |
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