![]() ![]() Remember, the label is the law.IPM or Integrated Pest Management is a strategy of managing pests that is designed to meet an individual’s production goals in the most economically and environmentally sound manner possible using a combination of control tactics. Always follow the pesticide label directions attached to the pesticide container you are using. As a result some chlorothalonil-based fungicides are listed as phytotoxic to spruce trees.ĬAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Make a second application 3 to 4 weeks later.Ĭhlorothalonil based fungicides may discolor spruce needles. Make one application in spring or early summer when the new needles have grown to half their mature length. Before spraying fungicide, send a lab sample to the UMN plant disease clinic to confirm that Rhizosphaera is responsible for the damage.įungicides with the active ingredient chlorothalonil, copper hydroxide or mancozeb will protect new spruce needles from infection by Rhizosphaera. Several other fungi result in symptoms very similar to Rhizosphaera. When setting out sprinklers, direct the water away from needles. If the tree is in a landscape with a sprinkler irrigation system, make sure that water is not spraying the needles. Add additional mulch only to maintain a 3 to 4 inch depth. Inspect the depth of the mulch layer each year. Leave at least a 2 inch space between the mulch and the trunk to allow for air movement.ĭo not mound the mulch around the trunk of the tree Maintain a 3 to 4 inch deep, even layer of wood chip mulch around your tree to prevent weed growth. Remove the bottom most branches from the trunk to help increase circulation around the tree canopy.ĭo not shear spruce as shearing creates a dense, compact growth that stays wet longer. Use the mature size of the tree as a spacing guide when planting. Maintain good air circulation around treesĭo not overcrowd plants. These plants are likely to be best adapted to the local conditions. ![]() ![]() Whenever possible plant spruce trees grown from local seed sources. Trees planted on poor sites are more likely to be infected with Rhizosphaera needle cast due to stressful conditions. Plant spruce trees on sites with acidic, moist, well drained soils and full sun. glauca) as they are more resistant to Rhizosphaera needle cast. New needles remain green, while old needles turn brown on a spruce infected with Rhizosphaera needlecast Plant disease tolerant treesĭo not plant Colorado blue spruce ( Picea pungens) or other spruce that are not well adapted to the environmental conditions in your area. abies) is relatively resistant but can become infected when grown under stressful conditions. glauca, including Black Hills spruce) is somewhat resistant but can become infected when grown under stressful conditions. Trees affected by Rhizosphaera needle castĬolorado blue spruce ( Picea pungens) is highly susceptible and is commonly affected. Submit a sample to the UMN Plant Disease Clinic for testing. Lab analysis is necessary to distinguish Rhizosphaera needle cast from other diseases of spruce trees. If the majority of needles are infected for 3 to 4 years in a row, the branch will die. Infected trees have few needles near the trunk and look thin, or see-through.ĭamage typically starts on the lower branches and moves up the tree. These are the spore producing structures of the Rhizosphaera fungi.ĭiscolored needles fall off in late summer to fall. Tiny black bumps can be seen arranged in neat rows on infected needles. Use a magnifying glass to look closely at both green and discolored needles. In spring or early summer, new needles at the branch tips are green, and the older needles turn brown to purple. ![]() Young tree with a thin canopy due to Rhizosphaera needle cast ![]()
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