Diseases of the Euonymous Shrub

Written by irum sarfaraz
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Euonymus is a large plant family of 60 different evergreen and deciduous shrubs, small-sized trees and vines. Some common euonymus varieties include the 4- to 6-foot tall deciduous shrub American euonymus (Euonymus americanus), also known as strawberry bush or hearts-a-busting; the deciduous, 30-foot high, spindle tree (Euonymus europaeus); and the 4- to 6-foot tall, evergreen ground cover wintercreeper euonymus (Euonymus fortune). Euonymus plants are susceptible to a number of diseases and pests.

Powdery Mildew

Powdery mildew is a serious fungal disease of euonymus caused by the fungus Oidium euonymi-japonici. The disease is not only very common in the plants, but is also the most difficult to bring under control. Earliest symptoms of the disease include a flat, white or grey growth on top of the foliage. You can rub powdery mildew off the leaves in its initial stages. As the disease progresses, it leads to yellowing and dropping of leaves. Younger plant shoots start to curl and become scarred. Preventive measures include pruning diseased plant parts and making sure plants receive full sun. Fungicidal remedies include myclobutanil, propiconazole and triadimefon.

Crown Gall

Crown gall is a bacterial disease of euonymus caused by the soil-borne bacteria Agrobacterium tumefaciens. The disease causes large, round, corklike galls with an irregular, rough surface on the plant base, roots and stems. As galls grow in number, the plants weaken, their growth stunted with yellowing leaves and branch dieback. Preventive measures include avoiding the use of dirty, unsterilised pruning tools. There is no fungicidal cure for crown gall, and plants may survive in their weakened state for several years.

Cercospora Leaf Spot

The fungal disease cercospora leaf spot in euonymus results from the fungi Cercospora detructiva and C. euonymi. The earliest symptom of the disease is the appearance of irregular, brown spots on foliage ranging in size from pinpoints to 1/2 inch in diameter. As spots grow, they merge and cover the entire leaf area, developing greyish-tan centres with black fruiting bodies. Although cercospora leaf spot is a common disease, it is not a serious threat to plant health. The best preventive measure is to remove and destroy all fallen leaves. Fungicidal control includes spraying infected plants with thiophanate-methyl.

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