12/26/2023 0 Comments Viburnum hedgePowdery mildew can be controlled with fungicides containing myclobutanil, propiconazole, thiophanate-methyl, or horticultural oil (see Table 1 for specific products). carlecephalum ‘Cayuga’, exhibit some resistance to powdery mildew. Additionally, some cultivars, such as Viburnum burkwoodii ‘Mohawk’ and V. Sanitation and measures discussed for fungal leaf spot control will aid in powdery mildew control. Prevention & Control: Since high relative humidity is an important factor favoring disease development, certain cultural practices can help prevent the disease or decrease its severity. Developing leaves may be deformed by severe infections. The disease typically appears in the summer and reaches its peak in late summer. The fungus is mostly found on the upper leaf surface but also may be found on the lower leaf surface. Affected plant tissues develop a powdery white to light gray growth of fungal mycelia. Powdery mildew of viburnum primarily affects young leaves and shoots. Powdery mildew is worse on plants in the shade. The occurrence and spread of this disease is favored by a combination of warm days, cool nights, and humid conditions but is inhibited by rain. Viburnum species may become diseased with powdery mildew caused by the fungus Erysiphe viburni. Apply when symptoms first appear and repeat every 10 to 14 days as needed. Algal leaf spot can be controlled with sprays of copper fungicides (see Table 1 for specific products). Monitor the plants for disease problems, practice good sanitation as stated with fungal leaf spot control, and treat any other landscape plants in the area that have algal leaf spots. Prevention & Control: Algal leaf spots are common on several ornamental shrubs and trees, including camellias, magnolias, azaleas, aucubas, gardenias, and rhododendrons. This pathogen will overwinter in leaf spots. These sporangia are spread to adjacent foliage by wind and splashing rain. When the spots become reddish-brown, they are producing their reproductive structures called sporangia. Often the spots appear raised and velvety with feathered edges. Leaf spots start as small, pale green circular spots and eventually become light brown or reddish-brown with age. Algal Leaf SpotĪlgal leaf spot, caused by Cephaleuros virescens, may occur especially during cool, moist conditions. If chemical control is needed, most fungal leaf spots and anthracnose can be controlled with fungicides containing chlorothalonil, thiophanate-methyl, myclobutanil, or mancozeb. The removal of this leaf material and then applying mulch will minimize the chances of the disease reoccurring the next season. Rake up and destroy infected fallen leaves, and then apply a fresh layer of mulch beneath plants. Hand remove spotted leaves on lightly diseased plants. Prune overhanging trees around diseased shrubs to reduce humidity levels and speed the drying of foliage. Avoid overhead irrigation and improve air circulation with adequate plant spacing and selective branch pruning. Prevention & Control: Many foliar problems can be prevented by keeping leaves as dry as possible. Leaf spots and anthracnose are fairly common on viburnum foliage, but these foliar diseases are not usually serious. The disease anthracnose (caused by Colletotrichum species) appears as black, sunken lesions. Fungal leaf spots typically occur during warm, moist summer months and initially will occur on older foliage. Spots may begin small but enlarge or merge and may be reddish to grayish brown. These fungal leaf spots on viburnum typically are angular to irregular-shaped, and the leaf tissue in the spots is sunken and dry. Fungal Leaf SpotsĪ variety of leaf spots are caused by the fungi Cercospora species, Phoma species, and Phyllosticta species. Occasionally, disease or insect pest problems do occur, and usually, during those times, the plants are under stress or growing in less than ideal conditions. In general, most viburnums are relatively pest-free.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |