Tree Mortality and Increased Fuels Following Severe
Defoliation by Pine Butterfly in Oregon:
Assessing the Aftermath of the 2008-2012 Epidemic
Ari DeMarco M.S. Candidate, Forest Entomology, Oregon State University, Corvallis, OR. 707-540-5030. ari.demarco@oregonstate.edu
David Shaw Dept. of Forest Engineering, Resources, and Management, OSU, Corvallis, OR. 541-737-2845. dave.shaw@oregonstate.edu
Robbie Flowers Forest Health Section, Oregon Department of Forestry, Salem, OR. 503-945-7396. rflowers@odf.state.or.us
Introduction
Methods
• The pine butterfly (Neophasia menapia) is a native insect that is commonly
observed at endemic levels in forests of the Pacific Northwest. Pine butterfly
epidemics appear to occur at widely-spaced, irregular intervals with each lasting
approximately 3-5 years.
• Within areas designated by ADS as having moderate-to-heavy
defoliation by pine butterfly, stands were delineated using GIS
data from the Malheur National Forest.
• During outbreaks in pine-dominated forests, large areas can be completely
defoliated for several consecutive years, and variable tree mortality can result in
association with attacks by pine bark beetles, drought, or other factors. The most
recent outbreak in eastern Oregon, which occurred from 2008-2012, has affected
over 179,000 hectares and is the largest ever documented in the State.
• As previous outbreaks have not been well-described, a cooperative research
effort is underway to examine infestation characteristics and assess the effects
of severe defoliation within the Malheur National Forest.
• In 2012-2013, 25 stands were randomly selected and 75 transect
plots (10 x 40 m) were installed and assessed.
• Standard plot measures were taken as well as heights and
percent defoliation of all ponderosa pine >5 cm DBH. Over 500
trees were tagged for continued evaluation.
Stand Structure
(Ponderosa pine)
No. Stands
Evaluated
Mean Defoliation (%)
and 95% CI
Even Aged
9
71.2 (69.9, 72.5)
Mixed / Neither
7
62.2 (58.7, 65.7)
Uneven Aged
9
66.1 (64.8, 67.4)
Mean defoliation by N. menapia was not significantly different by stand structure (shown above), or by density,
crown class, or canopy position. The majority of foliage was consumed throughout these single-host stands.
• Initial data were analyzed using linear mixed effects models.
Photo: Ari DeMarco
Photo: Ari DeMarco
Photo: Dave Shaw
Parasitic wasp attacking N. menapia pupae.
N. menapia adults nectaring.
Photo: Dave Shaw
Heavily defoliated ponderosa pine on the Malheur National Forest.
Hemipteran predators feeding on N. menapia pupae
Future Research and Products
• Quantify the radial growth loss of ponderosa pine due to the outbreak.
Photo: Dave Shaw
• Examine the natural enemy complex of pine butterfly and historic
occurrences of outbreaks relative to environmental conditions.
N. menapia eggs are laid along needles.
• Evaluate the contributions of the cumulative tree mortality that has/will
occur following this outbreak to forest fuels conditions.
Map: Rob Flowers
Pine butterfly study area on the Malheur National Forest. ADS results indicated the peak of the outbreak
occurred in 2011, followed by a decline in 2012. The outbreak ended in 2013, with no visible defoliation.
• Products include a M.S. thesis by the lead author in 2014 and a peerreviewed publication following additional data collection from 2014-2016.
Initial Results and Implications
Photo: Ari DeMarco
Aggregation of N. menapia larvae; pupae are also present.
Photo: Rob Flowers
Severe defoliation of ponderosa pine by N. menapia.
Objectives
• Quantify the extent and causes of tree mortality in ponderosa pine stands heavily
defoliated during the 2008-2012 pine butterfly outbreak.
• Develop stand management guidelines to assist forest managers in areas that
have recently experienced or are susceptible to pine butterfly outbreaks.
• Provide feedback to inform aerial detection surveys (ADS) of affected areas.
• Initial findings indicate very low occurrence of tree mortality.
Where it did occur, pine bark beetles (Dendroctonus spp.) were
the most commonly observed cause.
• Mean defoliation was not significantly different by stand density,
structure, crown class, or position within the canopy.
References
Scott, Donald. 2011. Chronology of Pine Butterfly, Neophasia menapia (Felder & Felder),
Infestations in Western North America, U.S. Forest Service - Forest Health Protection, Blue
Mountains Pest Management Service Center. Report No. BMPMSC-10-01
Flowers, R. et al. 2013. Forest Health Highlights in Oregon - 2012. ODF and USDA-FS FHP. 25 pp.
http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5426969.pdf
Acknowledgements
• Natural enemies (esp. insect predators and parasites) and larval
starvation appeared to contribute to the collapse of the outbreak
and a return to endemic levels in 2013.
• Generally recommended silvicultural techniques for pine including
thinning to increase tree vigor and maintaining proper densities
for the site should be sufficient for managing pine butterfly.
• Cooperators: Don Scott, Lia Spiegel, and Robert Schroeter (USDA-FS R6 Forest Health
Protection); Jon Laine (Oregon Dept. of Forestry); Paul Oester and Bob Parker (Oregon State
University Forestry Extension); Robert Progar (USDA-FS PNW Research Station); USDA-FS
Malheur National Forest; USDOI BLM; Private landowners
• FHP Sponsor: Lia Spiegel, USDA-FS R6 Forest Health Protection,
Center (541-962-6574, lspiegel@fs.fed.us)
Blue Mountains Service
• Funding was provided by the USDA-Forest Service, Forest Health Monitoring, Evaluation
Monitoring Program: WC-EM-F-12-01.