Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/23/2010
Publication Date: 8/8/2010
Citation: Clement, S.L., Huseby, D.S., Eigenbrode, S.D. 2010. Ecological Factors Influencing Pea Aphid Outbreaks in the U.S. Pacific Northwest. Book Chapter. Interpretive Summary: Insects as cold blooded creatures are dependent on temperature for life-history processes (development, reproduction, dispersal). Therefore, the prospect of global climate change in the form of rising temperatures could affect insect development, survival, abundance and dispersal patterns. These changes could possibly lead to increases in pest abundance and, by extension, more crop losses. Aphids are sensitive indicators of temperature change and are thus ideal subjects for studying the impacts of climate change on insects. In this regard, the pea aphid, a major pest of grain legumes in the U.S. Pacific Northwest (PNW), is an excellent candidate to study because ambient temperature is widely thought to be the most significant exogenous factor influencing the earliness of population increases that lead to spring and summer outbreaks on grain legume crops in this region. Therefore, the prospect of warmer winter temperatures could lead to higher pea aphid infestations and thus more crop losses. To examine a possible link between warming temperatures and pea aphid outbreaks in the PNW, a USDA-ARS Research Entomologist and two entomologists at the University of Idaho examined 26 years of pea aphid density and temperature data in this region and summarized their findings in an invited chapter for a book on global warming and aphid biodiversity. Their main conclusion is that the onset of mild winters is not the sole determinant of pea aphid outbreaks and subsequent crop loses. An equally important finding of this long-term research is that myriad biological factors, both biotic and abiotic, interact with temperature to influence the life-history processes of the pea aphid.
Technical Abstract: A long term data set involving 26 years of ambient temperature data and pea aphid population cycles in grain legumes in the U.S. Pacific Northwest (PNW), and presented in an invited chaper for a book on global warming and aphid biodiversity, shows that outbreaks of this aphid and subsequent crop losses in this region are not consistently associated with mild winters. Demonstrating that mild winter temperatures alone are not sufficient to account for spring and summer pea aphid outbreaks and crop losses is important because mild winters have historically been linked to these outbreaks in the PNW. Specifically, four outbreaks occurred at 6-9 year intervals during this long-term study, showing that outbreak years are the exception rather than the norm. A moderation in winter temperatures over a number of years bridging the 20th and 21st centuries has not resulted in changes in the frequency and severity of pea aphid outbreaks in this region. This important finding is discussed in relation to the importance of a other factors, both abiotic and biotic, that could potentially interact with increasing temperatures to affect pea aphid population cycles in the Pacific Northwest.