The Effect of Warming Winter Temperatures on the Severity of Pierce's Disease in the Appalachian Mountains and Piedmont of the Southeastern United States

Fig. 4. Contour lines for Pierce’s disease risk zones based on number of days of minimum temperatures 1972-1997 (25-year average): (A) ≤: -12.2°C contour lines and (B, shown here) ≤ -9.4°C contour lines.



Image from Plant Health Progress article:
The Effect of Warming Winter Temperatures on the Severity of Pierce's Disease in the Appalachian Mountains and Piedmont of the Southeastern United States