Disadvantages of natural pest controls

For years governments and private labs have been testing and releasing "beneficials," predators and parasitoids attacking pest bugs and mites. We have been assured that these introduced aliens are not hazzards in the general natural environment. Is this really true?

I "borrowed" the following from another website with some editing:

"Study Shows Perils of Importing Non-Native Species"

WASHINGTON (Reuters) - Documenting the ecological perils of
introducing non-native species to control pests, researchers said on Thursday parasitic wasps brought to Hawaii as part of sugar cane farming had become the dominant
players in a native ecosystem.

In research appearing in the journal Science, ecologists Jane Memmott and M. Laurie Henneman of the University of Bristol in Britain sought to determine the degree to which alien species imported as so-called biological control agents had infiltrated a local ecosystem.

They found that parasitic wasps transplanted from Texas and China into Hawaii more than half a century ago to prey on pests that devour sugar cane have emerged as commanding figures in the complex food web of a boggy forest on Kauai island, many miles away from where they were introduced.

``It's not just that they're in low numbers in a few habitats near agricultural fields. They're there in high numbers and they're there in places that are really remote from agricultural areas,'' Memmott said in an interview.

The research examines the consequences of using non-native species as ``biocontrol'' agents.

Some agricultural experts, foresters and conservationists have preferred this method over using chemical pesticides to combat bugs or weeds. Many have considered this method to be environmentally friendly. But now there is mounting concern that alien species can do more harm than the very pest or weed they are intended to eliminated.

``It does have some environmental risks attached,'' Memmott said.

The use of parasitic wasps that kill other insects by laying eggs inside the victim's body is a common way to combat pests. Many of these wasps have been used in Hawaii.

STUDY LOOKED AT SWAMPY ECOSYSTEM

Memmott and Henneman examined what was happening in Kauai's Alakai Swamp, where wetter, cooler and higher-elevation conditions differed from the lowland sugar cane fields.

The researchers constructed food webs of Hawaiian plants, butterflies and moths, as well as the wasps. From two plots in the forest, they retrieved 2,112 moth caterpillars and documented the 52 types of plants they were chomping.

The researchers waited in the laboratory to see evidence that the parasitic wasps had laid eggs inside the caterpillars and whether the young wasps would emerge from their victims' bodies. They found that about 20 percent of the caterpillars had contained wasp eggs.

Of these wasps, only 3 percent were native to Hawaii. Fourteen percent of the wasp species had been accidentally
introduced to the state over the years. But three wasps that had been introduced as biocontrol agents accounted for an overwhelming 83 percent of the attacks.

That provided strong evidence that these biocontrol agents had seized a dominant role in an ecosystem far removed from the agricultural sites where they had been released, they said.

The findings represented a mixed bag, Memmott said.

The research definitely showed the biocontrol agents had turned to attacking native species in a natural ecosystem. But the species of wasps implicated all had been released prior to 1945, suggesting more recent biocontrol efforts may be having a smaller adverse effect, she said.

``We've really tightened up a lot of the safety of biocontrol. My interpretation is that it does seem to be getting safer,'' Memmott added.

In an article accompanying the study in Science, Robert Pemberton of the U.S. Department of Agriculture's Invasive Plant Research Laboratory in Fort Lauderdale, Florida, said the study represents a call for safer practices in the use of biocontrol agents, and emphasizes the need for using insects or other biocontrol agents that narrowly target only pests.

Memmott agreed, saying, ``We just need to think a little more about the risks. And we also have to be careful to release just very specialized things.''