2 (1 = rare 5 = annual)

1.5 (1 = very little damage 5 = plants killed)

This fungal disease is usually considered to be minor. The fungi in this genus are considered most often to be oportunistic, meaning that they invade weakened or damaged plant tissue. However there are a few species that are weak pathogens. The genus attacks a wide range of plants around the world.

Tree

• Eastern Arborvitae, American Arborvitae (Thuja occidentalis)
• Western Arborvitae, Giant Arborvitae (Thuja plicata)

The fungus attacks foliage that has been injured or weakened by unfavorable weather or growing conditions. Usually, the killed foliage is near the base of the plant and where foliage is relatively dense. The disease usually starts at the tip of the foliage and progresses towards the leaf base. The color of the foliage goes from green to yellowish, then to a dark brown that can look almost black. The pathogen may kill the smaller twigs where the infected needles died.

Varies with the fungal species.

Control is to prune out killed foliage and, if necessary the twigs, as soon as possible in the spring. Reduce winter injury by minimizing dehydration. Do not allow snow to accumulate or remain up and around the base of the plant for any length of time - especially during melting. Avoid overcrowding the plants to allow sufficient sunlight and air circulation. During prolonged drought periods, be sure to correctly water the plant to reduce stress.

Home, Yard & Garden Pest Guide
The Home, Yard & Garden Pest Guide (C1391) provides is written for homeowners and other residents and provides nonchemical and current chemical recommendations for controlling pests associated with trees, shrubs, turf, flowers, groundcovers, vegetables, fruit, and houses. In addition, you'll find detailed information about integrated pest management, pesticide safety, and pesticide application and calibration techniques. This publication may be purchased at your local University of Illinois Extension Unit office, or by calling 800-345-6087, or by placing an order online (search for "C1391").
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Illinois Commercial Landscape and Turfgrass Pest Management Handbook
The Illinois Commercial Landscape and Turfgrass Pest Management Handbook (ICLT) is written for professional applicators and provides nonchemical and current chemical recommendations as well as application timing information for all major pests of turf, woody ornamentals and herbaceous ornamentals. This publication may be purchased at your local University of Illinois Extension Unit office, or by calling 800-345-6087, or by placing an order online (search for "ICLT").
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U of IL - Distance Diagnosis through Digital Imaging
A free plant, weed, insect and disease identification service available through your local University of Illinois Extension office. Center Educators or State Specialists review & respond to information and digital images submitted by local Extension office personnel. Some samples may require further examination or culture work (nominal fee involved) at the U of IL Plant Clinic.
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U of IL - Plant Clinic
Services include plant and insect identification, diagnosis of disease, insect, weed and chemical injury (chemical injury on field crops only), nematode assays, and help with nutrient related problems, as well as recommendations involving these diagnoses. Microscopic examinations, laboratory culturing, virus assays, and nematode assays are some of the techniques used in the clinic.
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