Diagnose: Rhododendron Leaf Scorch

1. Brown runs in from the tip and margins while the midrib stays green
2. That pattern is scorch, and every cause on this page produces it. The dead area may be a narrow rim or half the blade, but it always starts at the edge and works inward, and there is a reasonably sharp line between dead tissue and live. Three other patterns are not scorch and belong somewhere else. Fine pale stippling spread evenly across the whole blade, with black varnish-like specks on the underside, is lace bug feeding rather than a water problem. Round or angular spots with defined borders, sitting anywhere on the blade including the middle, are a leaf spot fungus. Crescent notches chewed out of the edge, where tissue is missing rather than dead and the cut edge stays green, are adult black vine weevils. One branch whose leaves all roll, dull, and hang down together is a root or stem failure instead. Check the bark at the base of that branch and the roots below it before anything else, and start with rhododendron root rot if the soil there stays wet.

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