Influence of El Niño southern oscillation on historical outbreaks of the southern pine beetle, Dendroctonus frontalis Zimmermann, in the southern United States

The southern pine beetle (SPB), Dendroctonus frontalis Zimmermann is a major destructive pest of pines in the southern United States. It attacks and kills a broad range of pine species with preference for loblolly pine (Pinus taeda), and few other pine species. Pine mortality may range from a single tree to several hundred acres. The objective of this study was to examine the relationship between the El Niño Southern Oscillation (ENSO) and the historical outbreaks of SPB in the southern United States. Data from the United State Department of Agriculture, Forest Service, on SPB outbreaks between 1960 and 2004 in counties from 12 states were examined. Outbreaks record and the corresponding ENSO classification of each year based on the Niño 3.4 SST Index by the Climate Prediction Center, National Oceanic and Atmospheric Administration were analyzed. Results showed that the number of counties with an incidence of SPB spots was significantly higher in years with La Nina spring season than in years with El Niño or Neutral spring season. Similar patterns were observed in years preceded by a La Niña fall or winter season. Typically, during a moderate to strong La Niña, the January to March weather conditions over a large portion of the southern forests are drier and warmer than normal, thereby providing favorable conditions for developments and increase in populations of SPB in the region. Understanding the influence of El Niño Southern Oscillation on outbreaks of SPB could be useful in long-term management efforts.