The classic symptoms of needle cast include brownish purple discoloration and eventual death of older needles, while current-year needles show no symptoms (Figure 1). There are over 40 kinds of needle casts in North America. Do not shear spruce as shearing creates a dense, compact growth that stays wet longer. When setting out sprinklers, direct the water away from needles. Leave at least a 2 inch space between the mulch and the trunk to allow for air movement. Needlecast diseases of evergreens are caused by several fungi. Trees can be protected from Rhizosphaera needle cast with properly timed fungicide applications. These diagnostic tools will guide you step-by-step through diagnosing a plant problem or identifying a weed or insect. Do not mound the mulch around the trunk of the tree. Trees stressed from drought, poor planting practices or other factors are more likely to suffer from Rhizosphaera needle cast. Needles are most commonly infected when they are young and still growing. Avoid wetting needles watering the lawn. White spruce (P. glauca, including Black Hills spruce) is somewhat resistant but can become infected when grown under stressful conditions. The fungus survives winter on living and recently killed needles. Several other fungi cause symptoms very similar to Rhizosphaera and correct identification is important. Other evergreen options include concolor (white) fir, Easter red cedars or other junipers, and yew. Tiny black fruiting bodies (spore producing structures) form on the surface of the needles before or after the infected needles are shed. Needle infection occurs best during warm (77 F) wet weather. Another key characteristic of needl… Trees planted on poor sites are more likely to be infected with Rhizosphaera needle cast due to stressful conditions. In spring through early autumn, spores spread to new needles within the tree or in neighboring trees via splashing water. Treating Rhizosphaera Needle Cast should always be done by a professional arborist. Apply a fungicide labeled for this disease, following label directions. Rhizosphaera needle cast is caused by the fungus Rhizosphaera kalkhoffii. To control Needlecast on a tree that is already infected, prune severely infected branches. Damage typically starts on the lower branches and moves up the tree. Similarities and differences between the two diseases exist. Older needles can become infected if environmental conditions are highly favorable for disease. Young seedlings and saplings are susceptible, as well as pure and crowded stands. All rights reserved. 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. Keeping your tree healthy can minimize the harmful effects of this disease. Chlorothalonil based fungicides may discolor spruce needles. 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. Always follow the pesticide label directions attached to the pesticide container you are using. Rhizosphaera needle cast is a fungal disease of spruce trees that causes needles to turn brown and fall off. The tree becomes unattractive and may look as though it is dying, but don’t despair. Water in summer and fertilize in the spring to keep trees growing vigorously and prevent needle cast. Submit a sample to the UMN Plant Disease Clinic for testing. Fungicides with the active ingredient chlorothalonil, copper hydroxide or mancozeb will protect new spruce needles from infection by Rhizosphaera. Whenever possible plant spruce trees grown from local seed sources. Inspect the depth of the mulch layer each year. Rhizosphaera needle cast is a fungal disease of spruce trees that causes needles to turn brown and fall off. At M&M Tree Care, we’ll treat the tree for the fungus over the course of two years. Tiny black bumps can be seen arranged in neat rows on infected needles. Maintain a 3 to 4 inch deep, even layer of wood chip mulch around your tree to prevent weed growth. Several other fungi result in symptoms very similar to Rhizosphaera. As a result some chlorothalonil-based fungicides are listed as phytotoxic to spruce trees. Needle cast diseases cause spruce trees to “cast off” their older needles and keep only the young needles at the tips of the branches. Lab analysis is necessary to distinguish Rhizosphaera needle cast from other diseases of spruce trees. Regents of the University of Minnesota. Trees can be protected from Rhizosphaera needle cast with properly timed fungicide applications. He is a member of the Society of American Foresters. Cynthia Ash Kanner and Michelle Grabowski, Extension educator. Discolored needles fall off in late summer to fall. Growth of the fungal pathogen from the spots on the needle will cause the death of the entire needle. Control is unnecessary in most non-commercial situations. Extension is expanding its online education and resources to adapt to COVID-19 restrictions. Colorado Blue Spruces are very susceptible to Rhizosphaera needle cast, but other types of spruce are more resistant. If control is desired for cosmetic reasons, protection of newly emerging needles through June with regular applications of an appropriate fungicide may be helpful. The symptoms of needle cast first appear on needles as light green to yellow spots, which eventually turn red or brown. These plants are likely to be best adapted to the local conditions. Needle cast is a broad group of fungal diseases that cause conifers to shed needles. Steve Nix is a natural resources consultant and a former forest resources analyst for the state of Alabama. Infected trees have few needles near the trunk and look thin, or see-through. By mid to late spring the death of infected needles is well advanced giving diseased trees a red to brown "fire-scorched" appearance. Infected needles usually turn red to brown from their tips beginning in winter or early spring. In spring or early summer, new needles at the branch tips are green, and the older needles turn brown to purple. To enhance the effectiveness of the fungicide mix with Nature's Own Spray Helper. White pines have fewer disease problems than Austrian or Scots pines. Make one application in spring or early summer when the new needles have grown to half their mature length. © Use the mature size of the tree as a spacing guide when planting. Avoid planting trees on sites not suited for a particular species. 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