Symptoms often resemble disease in early stages. Usually more devastating to young or tender plants. Sudden drops in temperature are more damaging than gradual decline. The worst scenario consists of warm winter temperatures then sudden cold spells, then back to warm. Not unlike the winters we've been having lately.
Winter drying is the most common cause of injury to pines.
Evergreens keep their needles and continue to transpire water. If the soil is dry or frozen, the plant cannot replace water lost and the result is scorching of the needles. Again, results are confusing, and can be confused with diseases. Call a professional if in doubt. Crabapples are very susceptible to apple scab.