NEW HAVEN, Conn. (AP) - There is a savage biological war going on across Connecticut’s fields, forests, lakes and ponds.

It’s an unseen conflict pitting foreign fighters recruited from around the world against a host of destructive invaders.

Environmental scientists are using carefully selected predatory wasps, beetles, flies, fungi and fish in hopes of controlling an increasing number of invasive species threatening Connecticut’s natural landscape. The tricky part is finding creatures that will only go after the “targeted” invaders and leave our native plants and animals alone.

Tens of thousands of wasps from China have been released to help control the Emerald ash borer. A Japanese fungus is being used to attack gypsy moths. European parasitic techinid flies have been launched against a new threat from winter moths. And Asian grass carp are mowing down invasive watermilfoil in places like Candlewood Lake and Ball Pond in New Milford.

More than six other non-native species are being employed to halt, or at least retard, the spread of invasive creatures and plants like the “mile-a-minute” vine, winter moths, lily leaf beetles and purple loosestrife, according to state officials.

Some of these biological control agents have been used with success in other states, but finding out whether they will work in Connecticut almost always takes years of patient monitoring and research.

“It’s a long process,” said Claire Rutledge, an assistant agricultural scientist at the Connecticut Agricultural Research Station in New Haven, “but when it does succeed, it’s permanent.

Rutledge is working on ways to deal with the damage the emerald ash borer is doing to Connecticut forests. The borer, from Asia, has already killed tens of millions of ash trees since it was detected in Michigan in 2002, and its arrival in Connecticut in 2012 sent shivers down the spines of forestry experts.

Rutledge said it’s likely to be 10 to 15 years before researchers can definitely determine whether the two types of Chinese wasps involved will be able to keep the ash tree-killing beetles in check.

Scientists aren’t even attempting to eradicate the borers, a task that appears impossible once the creatures have established themselves in a forest.

“Probably most adult ash trees will die,” Rutledge said. “The EAB kill all these trees so very, very rapidly.”

Once the adult ash trees are dead, the beetle’s population crashes. The hope is that the two wasps now being released (close to 20,000 were loosed in various borer-infested locations around Connecticut last year), will be able to contain the pest “so that the … population can’t build up to that catastrophic level again,” Rutledge said. That could allow young ash trees, which the beetles don’t attack, to mature and survive.

One of the wasps being released lays its parasitic eggs inside the emerald ash borer’s larva, while the other attacks the beetle’s eggs directly.

The two species of Chinese wasps had to undergo years of screening and testing to make certain they would only attack the emerald ash borer and not start slaughtering native North American insects. The wasps are harmless as far as humans are concerned.

Kirby Stafford, the state entomologist, said ensuring that alien predators like the wasps “don’t end up attacking something else” is a major responsibility of environmental researchers looking to stop invasive species.

In the past, there have been some spectacular misfires in bringing in one alien creature to control another.

One of the most infamous examples involved Australia’s cane toad experiment. The poisonous toad was introduced from the Americas in 1935 to counter beetle infestations in sugar cane fields. The toxic amphibians now number in the millions, have killed off various native Australian reptiles and are considered a major pest.

Stafford said long-standing fears about the unintended consequences that can happen when a foreign species is released into the environment “certainly has created more extensive screening” procedures for biocontrol efforts.

In the U.S., it can take more than five years of testing in isolation labs before a new species is released to attack an invasive species.

Purple loosestrife, an attractive flowering invasive introduced in North America from Europe, has been crowding out native species for something like two centuries. It wasn’t until 1986 that scientists in Europe began using the Galerucella leaf-eating beetle as a way to control purple loosestrife, and it took another seven years before the beetle was allowed to be released in the U.S.

In Connecticut, environmentalists began unleashing the Galerucella beetle in 1996, according to Donna Ellis, a senior extension educator with the University of Connecticut’s Department of Plant Science and Landscape Architecture, and co-chairwoman of the Connecticut Invasive Plant Council.

“We’ve been very pleased with its success,” Ellis said of the beetle’s efforts.

When the program was launched, purple loosestrife was flourishing “in hundreds of locations” around the state, Ellis said. Today, “it’s been reduced in population . it’s not as healthy, and it shows a lot of damage.”

“One of the best things is that, wherever you find purple loosestrife, now you also find the beetles,” she said. That means more native plants have a better chance of competing against the intruder.

The long-running campaign to control the gypsy moth is another apparent bio-control success story.

Gypsy moths were deliberately introduced into the U.S. in 1869 by a bumbling amateur French scientist named Etienne Leopold Truvelot who thought he was going to create a silk worm industry here. Gypsy moths come from Japan, didn’t work out as silk producers, and have been spreading through the Northeast ever since. They reached Connecticut by 1905.

One of the worst outbreaks occurred in 1981, when an estimated 1.5 million acres of Connecticut woodlands were defoliated by gypsy moths.

Melody Keena, a research entomologist with a U.S. Forest Service laboratory in Ansonia, said there was an early effort to bring in an “entomopathogenic” Japanese fungus known to prey on gypsy moths. The fungus was released here in the early 1900s, but at first didn’t seem to do much to control the moths.

Then in 1989, Connecticut researchers realized the fungus was actually killing gypsy moths, and it’s been the primary control over the pest ever since.

There also appears to be similar hopes for long-term control over the hemlock woolly adelgid, the tiny aphid-like insect that was accidentally released into the U.S. in 1924 and has been ravaging hemlock trees ever since. The adelgid is native to China and Japan and is parthenogenetic, which means all individuals are female and offspring develop from unfertilized eggs.

In Connecticut, the main biological control agent to date has been a beetle imported from Japan that is the woolly adelgid’s natural predator. The agricultural experiment station’s Valley Laboratory in Windsor raised more than 175,000 of the predatory insect and they have been released across the state.

Keena said there “is a brand-new kid on the block” that’s being used to attack the hemlock killers. A type of silver fly from the hemlock forests of the West Coast of the U.S. turns out to love eating woolly adelgids. According to Keena, it’s now being tested in Connecticut and could be ready for release soon.

Not every attempt at using natural predators to control invasive species works.

Candlewood Lake in western Connecticut has been plagued by the Eurasian watermilfoil for decades. The fast-spreading water plant was first found in Connecticut in 1979, and experts consider it “one of the most serious invasive plant threats in the U.S,” according to one legislative study.

Native plants can’t complete with it, water quality can be changed because of decreased oxygen levels and higher temperatures it creates, boat engines get clogged by it and swimmers hate getting tangled up in the plant.

Larry Marsicano is executive director of the Candlewood Lake Authority, the organization made up of the five towns that border the more than 5,400-acre lake. He said the Eurasian milfoil started becoming really troublesome in the early 1980s, and the authority considered all sorts of methods to combat it.

One that worked fairly well for a while was lowering the lake’s water level in the winter to allow sub-zero temperatures to kill the plants. But the utility responsible for releasing more water from the lake eventually decided that it was too costly to continue, and the milfoil rebounded.

So the lake authority decided to bring in an aquatic beetle known as the milfoil weevil, an insect native to the U.S. that has had some success elsewhere in going after the Eurasian milfoil. Unfortunately, explained Marsicano, “We weren’t successful with that.”

The weevil had some impact, weakening the water plants, Marsicano said, “but we weren’t seeing any reduction in terms of the intensity of the weeds.”

Last month, the authority brought in a new milfoil assault force: about 3,870 grass carp that act like an underwater lawn mower on the weeds. In Connecticut, only sterilized grass carp are permitted for use in ponds and lakes, and they can only be used in bodies of water where there is no chance they will escape into other streams or rivers.

Sterile grass carp have been used with success against milfoil in New Fairfield’s Ball Pond and in various private ponds around Connecticut. The story is somewhat different in other parts of the U.S., where grass carp have been able to reproduce and spread.

Grass carp, from East Asia, were first introduced in the U.S. in the 1960s to combat water weeds, but many of those weren’t sterile and escaped. Today, grass carp have been recorded in at least 45 states.

Meanwhile, invasions by alien invaders continue and so do the efforts by researchers to use natural enemies to control them.

There are new battles being waged against the lily leaf beetle (parasitic wasps released in 2012), and the winter moth (techinid flies let loose just last year).

Now, if only scientists can come up with something to take down the brown marmorated stink bug that’s moved into Connecticut from the south.

“We have about 50 native stink bugs in Connecticut,” Stafford warned. “Finding a predator that attacks only the brown marmorated will be a real challenge.”

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Information from: Hartford Courant, https://www.courant.com

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