Hormone proves
effective in fighting fly

Scientists hope to stem the
swarms of midges in Maui wetlands

WAILUKU >> A synthetic hormone appears to be effective in controlling the growing cycle of a fly that sometimes swarms residents and visitors during the winter in south Maui.

Scientist Martin Berg, a professor at Loyola University Chicago, said in tests of the synthetic hormone methoprene in plots at the Kealia Pond National Wildlife Refuge, researchers found a 90 percent reduction in the number of midges reaching adulthood for 18 days.

Berg said the application needs to be tested on a larger scale at the pond to determine its effectiveness.

"If there is an nuisance emergency, we'll be ready to apply the treatment to see if it's successful," he said.

In the winter of 2000-01, millions of midges rose out of the 200-acre pond in plumes described by some as "small tornadoes" and became a major nuisance in residential and visitor areas at wildlife refuge.

The insects landed in swimming pools, splattered on car windshields and appeared like tiny black flakes of drifting soot as their bodies collected along sidewalks.

Federal research money of $60,000 annually has been provided to find a way of controlling the occasional swarming of midges.

Berg said that in mid-December, the research will be into its fourth and final year. He said researchers not applied the methoprene to control midges for the past two years, because the midges have not been swarming in large numbers.

Berg said he does not know what causes the midges to appear in large numbers in certain years but it might be tied to the pond's water level.

He said in the year there was swarming, the pond level was low.

Berg said in the last two years, the pond level has been relatively high. "It appears this species doesn't like deep water," he said.

Under the control plan, pellets of methoprene would be dropped into select areas of the pond and sink to the bottom where there were eggs dropped by midges.

Berg said the methoprene has the effect of keeping the midges at the juvenile stage and unable to fly. He said the use of the synthetic hormone will have no impact on the rare Hawaiian birds that frequent the pond and eat the midges.

Wildlife manager Glynnis Nakai said even if the research project is completed in 2003-04, federal wildlife officials still have enough methoprene in stock to use if the swarming occurs later.

The midges, known as Polypedilum nubifer and found in Australia and some Pacific islands, have bodies about a half-inch long and wingspans about a quarter-inch wide.

Scientists say they don't know when these alien midges appeared in Hawaii but sightings of the midges were reported on Oahu in 1945.

A Bishop Museum entomologist estimated the number of mature midge maggots at 150 million to 200 million at Kealia in 1998 and estimated that 50 million midges emerged in the first week of December 1997.


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