Winter Mortalities of the Mountain Pine Beetle Andrew HabigWinter Ecology

Spring 2009

Mountain Research Station, University of Colorado, Boulder

Question

How does winter affect populations of the Mountain Pine Beetle (MPB)?

Outline

• MPB life cycle.• MPB winter survival strategy.

– Variable freeze resistance• Blue Stain fungi winter survival.• Conclusion• Climate change implications

Beetle Life cycle• Adults attack live trees in late summer.• Lay eggs in tree’s phloem.• Larvae survive the

winter in tree phloem.

MPB Winter Survival Strategies

• Bark of host provides very little protection• MPB’s are Freeze resistance.• Use of glycerol primarily as a cryoprotectant.• Level of freeze resistance changes over life

stages and temperature changes.

Variation in Freeze Resistance due to life cycle

• MPB have different levels of freeze resistance during each stage of their lives.

• Egg and pupa stage, which occur in fall and spring, respectively are least freeze resistant.

• MPB populations subject to high mortalities in cold falls and springs.

Temperature Induced Variation in Freeze Resistance

• MPB will change level of freeze resistance in response to changes in temperature.

• Warmer temperatures cause beetles to begin to loose their antifreeze.

• Sudden drops in temperature will cause beetle deaths.

Blue Stain Fungi Winter Survival

• Three strains of fungi:– Grosmannia clavigera, Ophiostoma montium and

Leptographium longiclavatum• Different cold tolerance for each strain• G. clavigera and L. Leptographium adapted to

cold winters.• O. montium adapted to warm summers.

MPB Winter Mortalities• Mortality from all sources must add up to 97-

98% in order to see significant population decline.

• 70-80% wintertime mortality is common in most MPB populations.• Decline in beetle populations due to cold

usually only occurs when winter mortalities are above 80%.

Implications of Warmer Winters.

• Milder springs and falls would allow MPB to survive and spread at higher latitudes and elevations.

• Climate change could allow MBP population to grow to large numbers because of fewer winter mortalities.

Conclusion• MPB populations are severely limited by

winter mortalities.• In spite of high winter population loss,

population size can still increase because of the high number of offspring per reproduction. (r selected)

• Could not find data that MPB were limited by blue-stain fungi winter mortalities.

• Climate change could cause further spread of the MPB.

Works CitedModeling cold tolerance in the mountain pine beetle, Dendroctonus ponderosae. Régnière, Jacques;

Bentz,Barbara. J.Insect Physiol., 2007, 53, 6, 559-572

Mountain pine beetle-associated blue-stain fungi are differentially adapted to boreal temperaturesRice,A.V.; Thormann,M.N.; Langor,D.W. For.Pathol., 2008, 38, 2, 113-123

Mountain Pine Beetle and Climate Change. Jacques Régnière and Barbara Bentz. USDA Research Forum on Invasive Species

Ecology of the Mountain Pine Beetle (Coleoptera: Scolytidae) Cold Hardening in the Intermountain West. BJ Bentz; DE Mullins. Environ. Entomol., 1999, 28, 4, 577-587

Mountain Pine Beetle. D.A. Leatherman, I. Aguayo, and T.M. Mehall. CSU Extension. No 5.528.

Natural Recourses Canada, 2007 <http://cfs.nrcan.gc.ca/subsite/mpb/mpb-mortality>