By Kyoko Scanlon, Forest Pathologist, Kyoko.Scanlon@wisconsin.gov or 608-235-7532 and Elly Voigt, Forest Health Communications Specialist and Lab Technician, Eleanor.Voigt@wisconsin.gov

Oak wilt is a serious disease of oaks that spreads to new areas when insects carrying oak wilt fungal spores land on a fresh wound of a healthy oak tree. To prevent oak wilt infections, it is important to avoid pruning, wounding and harvesting of oaks when these insects are abundant.

Predicting when these insects emerge in spring can be difficult as their emergence is highly weather-dependent and spring weather varies significantly year to year. The good news is that a new online interface is now available to provide users with localized information about the emergence status of the two most important insects that transmit oak wilt in Wisconsin. Because the interface uses a degree-day model constructed from insect trapping data and actual weather data, it is useful to refine the beginning of the periods when pruning, wounding and harvesting of oaks should be avoided.

This interface runs on the UW Ag Weather website and is easy to use. You need to enter only two pieces of information on the homepage: the location and the date of interest. The DNR created a user guide and video tutorial for this interface, available both on the DNR’s oak wilt webpage and on the interface itself.

The homepage of the oak wilt vectors emergence user interface.

The DNR’s oak harvesting guidelines restrict oak harvesting and pruning from April 1 (southern Wisconsin) and April 15 (northern Wisconsin) to July 15, because there is a high risk for oak wilt infection during this time. These guidelines allow for flexibility when the landowner/property manager and other affected parties (foresters, loggers, etc.) all agree based on local weather information. When experiencing an unusually warm or cold spring, an adjustment to the beginning of the harvesting-restricted period may be considered, using a modification described in the guidelines. The DNR worked with partners to create the oak wilt vectors emergence user interface to help landowners and forest managers use the latest science to make localized decisions about adjusting their pruning and harvesting schedules.

Please note that this interface is intended to supplement, not replace, the calendar dates specified in the DNR’s oak harvesting guidelines. This interface provides degree-day-based information about the beginning of the oak wilt high-risk period, not the end of the high-risk period. At this point, the interface is not built to predict future growing degree-day information.

If you have any questions about this interface, please contact your Regional DNR Forest Health Specialist or Kyoko Scanlon at Kyoko.Scanlon@wisconsin.gov.