If the majority of needles are infected for 3 to 4 years in a row, the branch will die. Avoid wetting needles watering the lawn. Water in summer and fertilize in the spring to keep trees growing vigorously and prevent needle cast. If the tree is in a landscape with a sprinkler irrigation system, make sure that water is not spraying the needles. Needles are most commonly infected when they are young and still growing. Young seedlings and saplings are susceptible, as well as pure and crowded stands. Steve Nix is a natural resources consultant and a former forest resources analyst for the state of Alabama. White pines have fewer disease problems than Austrian or Scots pines. Trees planted on poor sites are more likely to be infected with Rhizosphaera needle cast due to stressful conditions. Prevention and Control of Common Conifer Tree Diseases, Needle Blight Tree Disease - Identification and Control, Diagnosing and Controlling Heart Rot in Trees, Common Hardwood Tree Diseases - Prevention and Control, Leaf Spot Tree Disease: Prevention and Control, Identifying and Controlling Powdery Mildew on Trees, Preventing and Controlling Sooty Mold Tree Disease, Use Needles to Identify Common North American Coniferous Trees, Leaf Scorch Tree Disease - Prevention and Control, B.S., Forest Resource Management, University of Georgia. Tiny black fruiting bodies (spore producing structures) form on the surface of the needles before or after the infected needles are shed. Make one application in spring or early summer when the new needles have grown to half their mature length. Chlorothalonil based fungicides may discolor spruce needles. Similarities and differences between the two diseases exist. Needle cast is a broad group of fungal diseases that cause conifers to shed needles. All rights reserved. Do not overcrowd plants. Infected needles, including those that are still attached to branches and those that have fallen to the ground, produce spores that can be blown or splashed to healthy needles. Inspect the depth of the mulch layer each year. Plant Norway (P. abies) or white spruce (P. glauca) as they are more resistant to Rhizosphaera needle cast. Discolored needles fall off in late summer to fall. In spring or early summer, new needles at the branch tips are green, and the older needles turn brown to purple. Extension is expanding its online education and resources to adapt to COVID-19 restrictions. Older needles can become infected if environmental conditions are highly favorable for disease. Rhizosphaera needle cast is a fungal disease of spruce trees that causes needles to turn brown and fall off. Consider treating affected trees with fungicides containing the active ingredient copper (e.g., Bordeaux mixture) or chlorothalonil. Apply a fungicide labeled for this disease, following label directions. Damage typically starts on the lower branches and moves up the tree. These plants are likely to be best adapted to the local conditions. Two needle cast diseases occur in North Dakota: Rhizosphaera needle cast and Stigmina needle cast. Rhizosphaera needle cast is a fungal disease of spruce trees that causes needles to turn brown and fall off. As a result some chlorothalonil-based fungicides are listed as phytotoxic to spruce trees. If control is desired for cosmetic reasons, protection of newly emerging needles through June with regular applications of an appropriate fungicide may be helpful. Norway spruce (P. abies) is relatively resistant but can become infected when grown under stressful conditions. However, Christmas tree growers must take some action against the disease. Needle cast diseases cause spruce trees to “cast off” their older needles and keep only the young needles at the tips of the branches. Add additional mulch only to maintain a 3 to 4 inch depth. In spring through early autumn, spores spread to new needles within the tree or in neighboring trees via splashing water. Watch for reinfection. Submit a sample to the UMN Plant Disease Clinic for testing. The symptoms of needle cast first appear on needles as light green to yellow spots, which eventually turn red or brown. White spruce (P. glauca, including Black Hills spruce) is somewhat resistant but can become infected when grown under stressful conditions. CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. These diagnostic tools will guide you step-by-step through diagnosing a plant problem or identifying a weed or insect. Treatments will not cure … Remember, the label is the law. This shedding of needles can be more serious to conifers than losing leaves is to deciduous hardwoods. The tree becomes unattractive and may look as though it is dying, but don’t despair. Other evergreen options include concolor (white) fir, Easter red cedars or other junipers, and yew. Do not shear spruce as shearing creates a dense, compact growth that stays wet longer. Needle infection occurs best during warm (77 F) wet weather. Regents of the University of Minnesota. We have much to learn about when these fungi attack a tree, how long the fungus must be in the tree before needles are shed, when is the best time to apply a fungicide, and which chemicals provide the best protection. Cynthia Ash Kanner and Michelle Grabowski, Extension educator. Repeat the spray every 14 to 21 days, as necessary. Needlecast diseases of evergreens are caused by several fungi. Maintain a 3 to 4 inch deep, even layer of wood chip mulch around your tree to prevent weed growth. Do not plant Colorado blue spruce (Picea pungens) or other spruce that are not well adapted to the environmental conditions in your area. At M&M Tree Care, we’ll treat the tree for the fungus over the course of two years. These are the spore producing structures of the Rhizosphaera fungi. Infected needles usually turn red to brown from their tips beginning in winter or early spring. Needle cast is a broad group of fungal diseases that cause conifers to shed needles. Growth of the fungal pathogen from the spots on the needle will cause the death of the entire needle.