Invasive species often spread rapidly, and they are likely to be more damaging in their new environment than in their original location. One such invasive insect species that is considered North America’s most destructive insect is the emerald ash borer, a beetle thought to have entered this continent from Asia in wooden pallets from China. In less than a decade, the emerald ash borer has killed tens of millions of ash trees and threatens to eliminate all North American ash species. The efforts to identify and control this invasive insect are detailed in a New York Times piece, http://www.nytimes.com/2011/09/13/science/13beetle.html. Often, invasive species have their populations held in check in their native environment by pests, pathogens, or competing species. Without these limiting factors, the populations of an invasive species may explode across its new range. That seems to be happening with the emerald ash borer following its discovery near Detroit in 2002. To follow the spread of the beetles, now in 15 states and adjacent Canadian provinces, the Forest Service developed a purple-colored, scented beetle trap to locate the invasive insects. Control of the beetles using insecticides is considered too costly for North America’s more than seven billion ash trees. While biological controls are being investigated, a control strategy using “sink trees” is being used. A few ash trees are intentionally killed and used to attract emerald beetles. These trees are then cut in the winter killing the beetle larvae. In today’s photo, rows of green ash and oak trees stretch for sunlight above annual grasses in Peace Farm’s Wetland Reforestation Project. The trees will protect a tributary of the Mississippi River from erosion.
The spread of emerald ash borers has occurred at the same time as small hive beetles spread through bee yards across the states. Effective methods of control of the rapidly spreading small hive beetle will rely upon cultural, biological, and mechanical methods. It is too dangerous to the bees to use insecticides inside bee hives.--Richard