ANNANDALE-ON-HUDSON, N.Y. – Purple loosestrife is reviled as a public enemy, a purple plague that chokes out native species, a scourge so severe beetles have been enlisted to chomp it into submission.

But is it really such a bad seed?

Erik Kiviat says people might be too quick to judge. To illustrate his point, the veteran field biologist points out a streamside stand of purple loosestrife topped with cones of purple flowers. The head-high plants growing by the Hudson River buzz with life: A honeybee hovers by bright petals and a beetle feeds on a leaf near a ladybug, which likely is looking for some aphids to eat.

“It’s hard for me to imagine that purple loosestrife is doing harm here,” Kiviat said, “It’s probably feeding a lot of native insects.”

Kiviat, executive director for the research institute Hudsonia, argues that the plant is not always the bane it’s cracked up to be. Yes, he says, it can be a problem, but it also can be beneficial and should be studied more before wildlife managers try to control it with loosestrife-eating beetles.

This is not a popular view. Beetles have been unleashed on the plants in 35 states and warnings about its behavior have been issued by institutions from the Nature Conservancy to the U.S. Fish and Wildlife Service.

In Maine, beetles have been used experimentally in some areas to defoliate purple loosestrife. It could lead to widespread use of the beetles in other areas of Maine where the plant has begun to take hold.

“Over 20 states have declared loosestrife a noxious weed, so I think most people would not agree with what he is saying,” said Bernd Blossey, an assistant professor of natural resources at Cornell University.

Purple loosestrife can be hard to miss in New York state in late summer, a time when purple flowers grow atop stems that can stretch taller than a grown man. It grows in thick-looking stands almost any place with enough sun and moist soil, from old farmland to roadside ditches.

The plant is considered an invasive species because it came to this country from Europe 200 years ago. Biologists think the seeds came over accidentally in ship ballast or imported wool. Since loosestrife is a folk remedy for ulcers and other ailments, it also might have been brought over intentionally. Or it could have been a combination of all three.

The plant has spread to almost every state, often with help from loosestrife-liking beekeepers and gardeners. Problems occur when the seeds spread beyond isolated gardens to protected areas. Naturalists worry about it crowding out native plants, such as cattails. The Invasive Plant Council of New York State, for instance, places purple loosestrife in the company of garlic mustard and Eurasian water milfoil on its list of Top 20 Invasive Plants.

Kiviat said purple loosestrife often proliferates in areas damaged by road runoff or other factors, making it a symptom of a problem rather than a problem in itself. And he disputes the “myth” that it is always a biological bully that dominates wherever it takes root. In the 30 years he has kept an eye on purple loosestrife at a nearby freshwater tidal marsh, he said its coverage actually has declined.

“I don’t want you to think it’s never a pest,” he said on a walk by Hudsonia’s Bard College Field Station. “It depends on the situation.”

Richard S. Mitchell challenged readers of Wildflower magazine in 1999 to come up with a documented case of purple loosestrife invading a wetland and replacing a federally listed or state endangered plant.

None could.

Mitchell, the state botanist at the New York State Museum, notes that species compete with each other all the time, but people get more alarmed if one of the competitors is introduced from elsewhere.

Common plant-control methods such as burning and mowing have failed to slow the spread of purple loosestrife. But wildlife managers have had some success since the ’90s introducing a combination of beetles that separately concentrate on eating the plant’s leaves, roots and flowers.