Dan Molloy is a research scientist with the State University of New York at Albany. In previous work with the New York State Museum, he developed the biological agent Zequanox, which kills zebra mussels in confined areas, such as power-plant water intake pipes.
The non-native mussels are believed to have arrived in North America in ship ballast water. They filter up to a liter of water daily, competing with native fish for plankton.
This summer, the federal government approved Zequanox for lake applications, and Molloy is in Minnesota this week helping to oversee its use in Christmas Lake in the west metro. Juvenile zebra mussels were discovered recently in Christmas Lake near the public boat access.
That area has since been sealed off from lake bottom to surface using heavy plastic, and Zequanox, in powdered form mixed with lake water, will be distributed in the containment zone.
Molloy was flown to Minnesota by the Christmas Lake Homeowners Association, in part to assess whether the lake’s zebra mussel infestation has spread beyond the access area. Molloy found no evidence of additional mussels in an inspection Sunday.
In the following interview, Molloy discusses possible uses of Zequanox (which has since been licensed to a California company) in the fight against zebra mussels, and other strategies intended to stop, or slow, their spread.
Q What is your primary area of expertise?
A The biological control of zebra mussels. Most of my publications are on natural diseases that kill zebra mussels.
Q Are there such diseases?
A Yes. And I and others are trying to figure out how to use them for biological control. So far, the fight against zebra mussels has been concentrated on slowing their spread. This gives people like me time to find answers. This isn’t something that will happen in a year or two or three, but over decades.
Q How long did it take to develop Zequanox?
A About 20 years. But I have been studying the biological control of aquatic pests for much longer, about four decades. Years ago, I had a major success as part of an international team developing a bacterium that is still used by your Metropolitan Mosquito Control District, among others, to control black flies and mosquitoes. It’s effective, and incredibly safe. After that, the Department of Environmental Conservation in New York came to me with the zebra mussel problem. That was in 1990, and in 2010 my employer, the New York State Museum, licensed it as Zequanox.
Q But its primary use has been in pipes, correct?
A Yes. Now the question is whether it will succeed in open water. But keep in mind: We’re talking limited areas of lakes, not entire lakes. And even in this application there are unknowns. To my knowledge, the Christmas Lake application will be the first that attempts to solve a problem in open water.
Q Can zebra mussels someday be eradicated entirely?
A I don’t think so. You can fight them. But you can’t truly beat them. To do that, you would have to totally eradicate them from a lake. I’m not sure that’s possible. It would be so expensive, and I’m not sure every zebra mussel in every crevice throughout a lake would be killed. That’s why, at Christmas Lake, it’s so important that there are no zebra mussels outside the containment area. Then we’ll see if the Zequanox can kill all the zebra mussels in that area.
Q So there’s no hope of total eradication?
A There’s always hope. It’s difficult to find an elm tree these days, for example, because there is a specific disease that kills them. The same is true for American chestnut trees. So it’s possible. But probably not in the near term.
Q In Europe where zebra mussels have been established for many decades, do native fish thrive?
A In ancient native ranges, zebra mussels are not as abundant as they are in new areas. That’s because natural enemies have developed over eons to keep them in check. Whereas here in North America, they’re having a field day. Interestingly, a very recent study in the Hudson River found that zebra mussels are being suppressed by a new natural enemy, the blue crab. Fish population numbers aren’t necessarily rebounding, but increased growth rates have been found. So to one extent fisheries can perhaps recover from the presence of zebra mussels. But it can take decades.
Q Until more effective methods are developed to combat zebra mussels, what’s the best strategy to keep them in check?
A It’s very valuable to slow their spread as much as possible. Boat traffic is the key. All this talk about turtles or waterfowl spreading them is wrong. It’s boat traffic. And worst of all is a trailer or boat dangling a piece of milfoil, on which hundreds of juvenile zebra mussels can be attached. Postponing the year that zebra mussels infest a broader number of lakes gives people like me time to find cheap control methods that are highly specific.