Plant Disease Management Handbook

Step 1: Is it normal? Walnuts (right) typically break bud late in western Oregon while other plants such as cherry (left) have been growing for several weeks.

Step 2a: Look for patterns in the community. All the strawberries do not look the same in this picture. The circular areas have both Verticillium wilt and nematode problems.

Different plants in this community have the same problem along the edges of this nursery bed. Roots froze during a winter cold period.

Step 2b: Look for patterns on individual plants. This Christmas tree has lost many lower needles due to Lophodermium needle cast.

Step 2c: Look for patterns on plant parts. Ringspots and line patterns on these Kalmia leaves indicate necrotic ringspot virus infection.

Step 3: Investigate time development. These Port-Orford Cedar trees have root rot and over time have been progressively getting worse.

Time development can be seen on this Katsura tree shoot when you understand how plants grow. After bud break normal leaves were formed but then deformed leaves were made. The growing point did not die, the non-living problem stopped and new leaves formed were normal again.