Pine-killing bee­tles may be even dead­lier in north­ern forests

The Washington Times Daily - - NATION - BY MARY ESCH

AL­BANY, N.Y. | A bee­tle that has killed mil­lions of acres of pines in south­ern forests is munch­ing its way north, and new re­search sug­gests its tree-killing prow­ess could be mag­ni­fied in cooler climes.

Once un­heard-of north of Delaware, south­ern pine bee­tles have been steadily ex­pand­ing their range as the cli­mate warms. Ef­forts are un­der­way to quell a large out­break in Long Is­land’s pine bar­rens and mon­i­tor­ing traps have caught bee­tles as far north as New Eng­land.

The in­sect could reach Nova Sco­tia by 2020 and cover forests from the up­per Mid­west to Maine by 2080, ac­cord­ing to a Columbia Univer­sity study pub­lished in the jour­nal Na­ture Cli­mate Change in Au­gust.

Now there’s more bad news in a new study from Dart­mouth Col­lege: Cooler fall and win­ter tem­per­a­tures in this new range in­crease the bee­tle’s de­struc­tive po­ten­tial.

That’s be­cause lar­vae de­vel­op­ing in the fall are put on hold as pu­pae when the tem­per­a­ture drops be­low 50 de­grees Fahren­heit to emerge as adults for a mass killing spree in spring­time.

The re­searchers found that in warmer re­gions, bee­tles ma­ture at var­i­ous times rather than all at once.

“The way they kill trees is by at­tack­ing in large num­bers, like a pack of wolves killing a moose,” said Matthew Ayres, co-au­thor of the study pub­lished last month in the jour­nal Oe­colo­gia. “When they all at­tack at once, they draw down the tree’s de­fenses — bleed it out — and the tree is toast.”

The rice-size black bee­tles chew wind­ing tun­nels un­der the bark that dis­rupt the flow of nu­tri­ents and kill the tree in a few months. Pines fend off in­sect as­saults by ooz­ing toxic resin.

But pine pitch is no match for thou­sands of bee­tles bur­row­ing at once.

South­ern pine bee­tles nor­mally pool their ef­forts by us­ing chem­i­cal at­trac­tants called pheromones to sum­mon each other to tar­get trees. The syn­chro­nized de­vel­op­ment brought about by cooler win­ters gives an­other means of mas­sive at­tack.

“The power of num­bers from syn­chronously emerg­ing bee­tles can spell dis­as­ter for pine trees,” said lead au­thor Jef­frey Lom­bardo.

The bee­tles are in the genus Den­droc­tonus, or “tree killer” in Greek. The genus in­cludes moun­tain pine bee­tles, which have killed trees across mil­lions of acres in the Rocky Moun­tains.

An out­break of south­ern pine bee­tles in the south­east­ern United States be­tween 1999 and 2002 caused more than $1 bil­lion in losses for the tim­ber in­dus­try, ac­cord­ing to the U.S. For­est Ser­vice.

“Mil­lions of acres of pines get killed in the south­east,” Mr. Ayres said. “It’s the bee­tle’s nat­u­ral bi­ol­ogy to have huge pop­u­la­tion fluc­tu­a­tions and when they’re abun­dant to kill large num­bers of trees, you can eas­ily see it from outer space.”

Such wide-scale dam­age is un­likely in the Adiron­dacks and New Eng­land forests be­cause white pines are the pre­dom­i­nant pine species there, said Jeff Gar­nas, a for­est ecol­o­gist at the Univer­sity of New Hamp­shire who’s not as­so­ci­ated with the Dart­mouth study. The south­ern pine bee­tle’s pri­mary tar­gets are pitch pines, red pines and jack pines.

Mr. Gar­nas said it’s pos­si­ble the ben­e­fit of syn­chro­nized emer­gence in spring could be out­weighed by the North’s shorter warm sea­son, which lim­its over­all pop­u­la­tion growth, and sub­zero cold snaps that kill over­win­ter­ing bee­tles.

Ar­eas most at risk of south­ern pine bee­tle in­fes­ta­tion are pitch pine bar­rens, which are scat­tered around the North­east in­clud­ing Long Is­land and Al­bany in New York and Cape Cod in Mas­sachusetts. New York’s De­part­ment of En­vi­ron­men­tal Con­ser­va­tion has cut 18,000 trees in Long Is­land’s cen­tral pine bar­rens since an in­fes­ta­tion was found there four years ago.

Mr. Ayres, who pre­vi­ously worked for the U.S. For­est Ser­vice in Louisiana, said early de­tec­tion, sup­pres­sion by re­mov­ing in­fested trees and thin­ning to im­prove for­est health are the keys to quelling out­breaks.

AS­SO­CI­ATED PRESS

The south­ern pine has killed mil­lions of acres of pines in south­ern forests is munch­ing its way north. Its prow­ess could be mag­ni­fied in cooler climes.

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