Fact Sheet No. 257 Prepared by David E. Yarborough, Extension Blueberry Specialist and Jennifer D’Appollonio, Assistant Scientist. The University of Maine, Orono, ME 04469. Revised January 2018. How weed resistance occurs Figure 1.  Fine-leaf sheep fescue (Festuca filiformis), an introduced perennial grass in Maine wild blueberry fields, was resistant to Velpar (group