Photo credits below
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Many of us in central and western Pennsylvania may not be giving this a second thought as it is out of sight and out of mind. The insect is isolated to the southeast portion of the state, and there is an enormous effort to keep it that way. The Pennsylvania Department of Agriculture has imposed a quarantine as one of the approaches to prevent the spread throughout the rest of the commonwealth.
Quarantines are used to restrict movement of material that could carry a troublesome organism from one area to another. But do they work? And will it be effective in preventing the spread of SLF to all corners of Pennsylvania? To answer these questions, it might be helpful to look at two recent quarantine efforts in Pennsylvania; plum pox virus and the emerald ash borer.
Back in 1999, a peach grower in Adams County noticed some odd patterns on ripening peaches. Farmers, researchers, and government officials had never seen this before and it took a little detective work to determine it was a new disease to the North American continent. Plum Pox Virus originated over in Europe and somehow made its way to our shores. While not killing trees, it greatly reduces yield and quality of the stone fruits (peaches, plums, cherries, etc.). Go to Plum Pox Virusfor additional information on this issue.
A quarantine was put into place where surveys determined the virus’ presence to prevent the spread to other fruit growing regions. This program prohibited the movement of stone fruit trees and grafting wood out of the regulated areas. Once the containment area was set up, then an effort was employed to remove and destroy infected trees and nursery stock.
Most Pennsylvanians have never heard of the Plum Pox Virus, probably because the quarantine and subsequent eradication effort was so successful (Figure 1). After millions of dollars and the destruction of 1,846 acres, the virus is no longer a concern to the Pennsylvania industry.
But as successful as the Plum Pox story went, it was a completely different ending for the emerald ash borer (EAB). This insect was thought to be introduced into North American in the 1990’s from packing material originating in Asia. It wasn’t until 2002 that the insect was fingered for extensive ash mortality in southeast Michigan. For those that need additional information on EAB, The Emerald Ash Borer Information Network is a wealth of material.
Just by looking at the early quarantine maps to the most updated version illustrates the difficulty in preventing the spread of EAB. From a few quarantined counties in southeastern Michigan (Figure 2), EAB has spread like wildfire to an area that covers 31 states (Figure 3).
At a more local level, Pennsylvania did take a stab at preventing the spread of EAB by quarantining several counties in western Pennsylvania back in 2007 (Figure 4). Figure 5 shows how rapidly the insect moved eastward over the next decade, despite the best intentions and efforts to slow and stop it.
It will be interesting to see how the quarantine effort works with SLF. It will take a lot of money, labor, and science (and a little bit of luck) to have this insect follow the path of the Plum Pox Virus rather than EAB.
Figure 1. A quarantine was in place for several townships in southeastern PA to prevent the spread of Plum Pox Virus. The effort was successful and the quarantine was lifted in 2009. Map courtesy of Pennsylvania Department of Agriculture.
Figure 2. 2004 EAB quarantine map showing Michigan quarantined counties. Note, EAB was not found in any other area of the US at the time. Map courtesy of Michigan Tech University
Figure 3. From 13 counties in Michigan in 2004, the EAB quarantine now encompasses numerous states. Map courtesy of USDA
Figure 4. An adult emerald ash borer was collected on a green ash tree in a non-residential landscape in Butler County, Cranberry Township, Pennsylvania. On June 27, 2007, the Pennsylvania Department of Agriculture issued a quarantine for Allegheny, Beaver, Butler, and Lawrence Counties in western Pennsylvania.
Figure 5. A color-coded map shows the spread of EAB from the western edge of Pennsylvania to the eastern edges over a matter of several years.
Lead photo credits: Top Left photo: Biologische Bundesanstalt für Land- und Forstwirtschaft, bugwood.org, Fruit symptoms of plum pox potyvirus infection on plum.
Right photo: Leah Bauer, bugwood.org, Emerald ash borer adult feeding on ash leaf
Bottom left photo: Lawrence Barringer, Pennsylvania Department of Agriculture, bugwood.org, spotted lanternfly adult