DULUTH  (AP) -- Agricultural officials are preparing their largest air war ever to protect the forests of northeastern Minnesota and northwestern Wisconsin against gypsy moths.

In the wake of infestations found in the region last year, including in Duluth, experts in both states are expanding aerial spraying to keep the leaf-eating, tree-killing gypsy moth caterpillars in check.

In June, planes will spray a natural soil bacterium that kills the caterpillars.

In July, they'll drop synthetic hormone flakes to confuse male moths so they can't mate.

The invaders have been on a century-long march westward across North America.

Lucia Hunt, gypsy moth expert for the Minnesota Department of Agriculture, says there's little hope of ultimate victory, but any delay may help as scientists look for a more permanent solution.

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