While weevil projects are successful in some places (like Australia), the consensus is they are not working to control the giant salvinia on Lake Bistineau.
"Our climate is different than in Australia," said Jeff Sibley, LDWF biologist and director for Region 1. "In Australia, year round, the water temperature falls within the range where the weevils can successfully reproduce. Here, we are below that during the winter. There's only a portion of the year where we are in that range."
"In the fall, their numbers begin to decline. The larvae follows the same trend. What you see is during the summer, yes, we possibly exceed the population rates; as the temperatures rise in the spring, the number of larvae increase. But as soon as we approach fall and winter, reproduction tends to drop off, and our adult numbers soon follow behind."
And this is a problem, since numbers need to remain high to be a viable control method; in fact, 680,000 adult weevils are needed to control one acre of land (one acre is approximately 18.75 tons of salvinia, according to a recent field sampling).
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