Spruce: Rhizosphaera needle cast

• Categories: Conifers Ornamentals Spruce Spruce Diseases
• Last review date: 2025-07-31 02:24

Biology

The first symptoms occur in late summer, when a yellow mottling develops on the current season’s needles. During the fall to early spring, the infected needles turn brown or purplish brown.

The needles are usually dropped later that spring or in the following summer. Tiny black fruiting bodies are formed in rows on the underside of the affected needles in the spring and occasionally at other times.

This disease can cause severe needle loss.

Management Options

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

Non-chemical Management

Select non-chemical management options as your first choice!

• Remove and destroy all fallen needles from in and under the tree. Do not compost diseased plant material.
• Avoid overhead irrigation.
• Provide good air circulation in plantings. Avoid shading or crowding trees.

Chemical Management

• Begin applying when new shoots are 1⁄2″ to 1 1⁄2″ long.
• Continue at 3- to 4-week intervals if weather remains very wet.
• Horticultural oils, soap-based products and some other products may cause discoloration of spruce needles, particularly on Colorado blue spruce.
• Read labels carefully and test on a small area before application.
• Homeowners should not make foliar applications to trees over 10 ft tall.
• Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.

• Bonide Fung-onil Multi-Purpose Fungicide Concentrate
  Active ingredient: chlorothalonil
  EPA registration number: 60063-9-4
• GardenTech Daconil Fungicide Concentrate
  Active ingredient: chlorothalonil
  EPA registration number: 67572-82-71004
• Ortho Max Garden Disease Control Concentrate
  Active ingredient: chlorothalonil
  EPA registration number: 239-2522
• This list may not include all products registered for this use.