Spruce: Rhizosphaera needle cast
categories: Conifers Ornamentals Spruce Spruce Diseases
revision date: 2023-02-07 12:00
Photo by: R.S. Byther
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
Use Integrated Pest Management (IPM) for successful plant problem management.
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
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- 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
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
Additional Image
Photo by: R.S. Byther