European Kalmia Society - Pests & Diseases

European Kalmia Society

Pests & Diseases

 
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Leafspot and leafblight on the foliage of a Kalmia latifolia-Hybrid.
photo: Dr. Karl-Heinz Hübbers

The following information is given for Mountain Laurel (Kalmia latifolia) and its cultivars.
Mountain laurels are remarkably free of trouble caused by pests and diseases compared with most other cultivated plants. In addition they are perfectly hardy.
Pests
In cultivation one cannot avoid that insects, mites and so on are coming from accompanying plants. Especially those that prefer Rhododendron and other Ericaceae should be mentioned.
You might find damages on Kalmia by Vine Weevil, Lacebug and Whitefly. Parts of the young shoots might be sometimes eaten away by caterpillars.
Normally deer avoid the poison foliage. Slugs keep away from the leathery leaves.
Diseases
Phytophthora root rot or wilt is a serious fungal disease. It is worst at high temperatures and in moist situations, especially if the drainage is poor.
Leafspot and leafblight are one of the most common diseases on Kalmia. They can be found particularly on plants that are crowded or shaded. Because under this conditions humidity is high and moisture is retained on the foliage for long periods. Symptoms generally appear as yellow, brown or reddish spots. Normally plants would not die but look very unattractive. Best thing to avoid leafspot is to hybridize resistant cultivars.
Miscellaneous Afflictions
Salt damage occurs on plants that are over fertilized. Leaf tips and edges turn brown. Leaching with water may be worthwhile.
Chlorotic symptoms can result from soil with a high pH rate or from a wrong type of fertilizer. When plants are growing in sunlight the colour of the foliage normally looks lighter green than grown in the shade.
Frost damages especially on young shoots can only occur under bad conditions.