Observed and anticipated impacts of drought on forest insects and diseases in the United StatesAuthor(s): Thomas E. Kolb; Chris Fettig; Matthew P. Ayres; Barbara J. Bentz; Jeffrey A. Hicke; Robert Mathiasen; Jane E. Stewart; Aaron S. Weed
Source: Forest Ecology and Management. 380: 321-334.
Publication Series: Scientific Journal (JRNL)
Station: Pacific Southwest Research Station
Download Publication (862.0 KB)
Future anthropogenic-induced changes to the earth’s climate will likely include increases in temperature and changes in precipitation that will increase the frequency and severity of droughts. Insects and fungal diseases are important disturbances in forests, yet understanding of the role of drought in outbreaks of these agents is limited. Current knowledge concerning the effects of drought on herbivorous insect and pathogen outbreaks in U.S. forests is reviewed, and compared between the relatively mesic and structurally diverse forests of the eastern U.S. and the more xeric forests of the western U.S. Theory and limited evidence suggests a non-linear relationship between drought intensity and outbreaks of aggressive bark beetle species (i.e., those capable of causing extensive levels of tree mortality), where moderate droughts reduce bark beetle population performance and subsequent tree mortality, whereas intense droughts, which frequently occur in the western U.S., increase bark beetle performance and tree mortality. There is little evidence for a role of drought in outbreaks of the southern pine beetle (Dendroctonus frontalis), the only bark beetle species that causes large amounts of tree mortality in the eastern U.S. Defoliators do not show consistent responses to drought. The response of sapfeeders to drought appears non-linear, with the greatest performance and impacts at intermediate drought intensity or when drought is alleviated by wetter periods. Interactions between tree pathogens and drought are poorly understood, but available evidence suggests reduced pathogen performance and host impacts in response to drought for primary pathogens and pathogens whose lifecycle depends directly on moisture (humidity). In these cases, rates of reproduction, spread, and infection tend to be greater when conditions are moist. In contrast, secondary fungal pathogens (i.e., those that depend on stressed hosts for colonization) are anticipated to respond to drought with greater performance and host impacts. In the western U.S., drought increases stress on trees severely infected by mistletoes thereby predisposing mistletoe-infected trees to attack by insects, particularly bark beetles and wood borers. Research needed to advance understanding of drought impacts on forest insects and diseases, and the role of forest management in mitigation of infestations during drought are discussed.
- You may send email to firstname.lastname@example.org to request a hard copy of this publication.
- (Please specify exactly which publication you are requesting and your mailing address.)
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
Kolb, Thomas E.; Fettig, Christopher J.; Ayres, Matthew P.; Bentz, Barbara J.; Hicke, Jeffrey A.; Mathiasen, Robert; Stewart, Jane E.; Weed, Aaron S. 2016. Observed and anticipated impacts of drought on forest insects and diseases in the United States. Forest Ecology and Management. 380: 321-334.
Keywordsclimate change, drought, forest pathogens, forest health, forest insects, herbivory
- Historical and current roles of insects and pathogens in eastern Oregon and Washington forested landscapes.
- Bark beetles and dwarf mistletoe interact to alter downed woody material, canopy structure, and stand characteristics in northern Colorado ponderosa pine
- Tree mortality after synchronized forest insect outbreaks: effects of tree species, bole diameter, and cutting history
XML: View XML