Japanese Beetle Eradication

Additional Information

The UDAF Invasive Insect Program has one of the most robust JB detection programs in the country. All of Utah’s 29 counties are annually surveyed for this invasive pest via trapping. Traps placed as a method of early detection are part of the standard detection survey. Standard detection traps are placed at a density of approximately two traps per square mile in areas of the state that have host material that is suitable for JB survival. Therefore, in years where not even a single JB is detected, there will be roughly 1,800 traps placed just as a precaution! However, when a JB is detected, trappers will set up a “delimiting grid,” which usually involves placing 100 traps, about 75-150 meters (250-500 feet) apart in a square block centered around the capture site. These traps are checked on a bimonthly basis. If no other beetles are found in this delimiting grid for two subsequent years, it can be assumed that JB did not establish in the area.  It is not uncommon for the program to find a couple of beetles in a given vicinity, heavily trap the area and find no beetles in succeeding years. While there are many explanations as to why this may happen, the most likely scenario is that a handful of beetles were artificially transported within the state, however there were not enough individuals to create a stable population.

Nonetheless, there are instances where a beetle is found, a delimiting grid is set and more beetles are found later. In this case, the delimiting grid will be enlarged and it will expand in the direction of the capture. For instance, if a JB is found on the northwest corner of a grid, then additional traps will be placed surrounding the existing grid in that direction. However, if additional beetles are found in the same trap that originally caught the target pest, there is no need to enlarge the grid. This is because the entire purpose the delimiting grid is to determine the extent of an infestation; there is no reason to expand the trapping because it is already known where the beetles are located. Delimiting grids are especially helpful in determining if and where interventions are needed to eradicate a target pest. As mentioned, Utah’s JB standard detection survey is large and covers the entire state. Therefore there is a great degree of confidence in where this pest is present or not present.