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Douglas-fir tussock moth- and Douglas-fir beetle-caused mortality in a ponderosa pine/Douglas-fir forest in the Colorado Front Range, USA

Formally Refereed
Authors: Jose F. Negron, Ann M. Lynch, Willis C. Jr..Schaupp, Vladimir Bocharnikov
Year: 2014
Type: Scientific Journal (JRNL)
Station: Rocky Mountain Research Station
DOI: https://doi.org/10.3390/f5123131
Source: Forests. 5: 3131-3146.

Abstract

An outbreak of the Douglas-fir tussock moth, Orgyia pseudotsugata McDunnough, occurred in the South Platte River drainage on the Pike-San Isabel National Forest in the Colorado Front Range attacking Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. Stocking levels, species composition, and tree size in heavily and lightly defoliated stands were similar. Douglas-fir tussock moth defoliation resulted in significant Douglas-fir mortality in the heavily defoliated stands, leading to a change in dominance to ponderosa pine, Pinus ponderosa Lawson. Douglas-fir beetle, Dendroctonus pseudotsuqae Hopkins, populations increased following the defoliation event but caused less mortality, and did not differ between heavily and lightly defoliated stands. Douglas-fir tussock moth-related mortality was greatest in trees less than 15 cm dbh (diameter at 1.4 m above the ground) that grew in suppressed and intermediate canopy positions. Douglas-fir beetle-related mortality was greatest in trees larger than 15 cm dbh that grew in the dominant and co-dominant crown positions. Although both insects utilize Douglas-fir as its primary host, stand response to infestation is different. The extensive outbreak of the Douglas-fir tussock moth followed by Douglas-fir beetle activity may be associated with a legacy of increased host type growing in overstocked conditions as a result of fire exclusion.

Keywords

Orgyia pseudotsugata, Dendroctonus pseudotsugae, douglas-fir tussock moth, douglas-fir beetle, forest insects, defoliators, bark beetles

Citation

Negron, Jose F.; Lynch, Ann M.; Schaupp, Willis C., Jr.; Mercado, Javier E. 2014. Douglas-fir tussock moth- and Douglas-fir beetle-caused mortality in a ponderosa pine/Douglas-fir forest in the Colorado Front Range, USA. Forests. 5: 3131-3146.
Citations
https://www.fs.usda.gov/research/treesearch/47918