Arborvitae Blight

Types of Blight

• Several types of blight, a fungal disease spread through spores, affect arborvitae: phomopsis tip blight, kabatina tip blight, cercospora blight and pestalotiopsis blight. Blight affects foliage and spreads through the plant, discoloring foliage and interrupting healthy growth. If left unchecked, especially in wet, airless conditions favorable to the fungi, blight severely disfigures the plant and eventually kills it.

Identification

• Different types of blight attack arborvitae in different ways. Phomopsis fungi attacks the new shoots in the spring, browning leaf and branch tips and causing dieback. Kabatina tip blight is very similar to phomopsis but only affects branch tips of older growth, not new growth. It attacks through wounds in the plant such as insect damage, pruning damage or weather damage. Cercospora fungi family has more than 1,200 species. It spreads in warm, wet weather, attacking new and older foliage near the bottom of the plant. It starts on the inside of the plant, turning green growth brown, then gray and fuzzy as it produces spores. Pestalotiopsis is a fungal disease that attacks the base of the plant, turning foliage yellow then black.

Control Methods

• Planting and growing resistant varieties, proper spacing of plants to promote access to sunshine and good air circulation, removing affected plant parts, pruning hygiene and providing winter protection all prevent blight conditions. Fungi spores can overwinter in plants, so close observation of plants that have been affected, looking for browning areas and watching for fuzzy growth that indicates spores, helps prevent spreading blight.

Cultivation

• Care in selecting arborvitae shrubs, proper spacing and planting, and winter protection contribute to healthy growth. Select shrubs with healthy, shiny green growth, no bare branches and no yellowing, brown or black foliage. Plant them in a well-drained area, and space them so they are not crowded against other landscape trees and shrubs and receive full sun. Fungus thrive in dark, damp conditions, so air circulation around arborvitae all year long is very important to avoid blight. Protect arborvitae from harsh, drying winds in the winter with burlap or shade cloth firmly staked around bushes. Avoid excess watering and fertilizing that encourages fungal growth