Type of Sample Needed for Diagnosis and Confirmation This disease is common in the spring but we receive samples anytime throughout the growing season. are during times of excess moisture and humidity. Disease cycle of Rhizosphaera needle cast Severely infected needles turn black due to the sheer number of pycnidia. Small black fruiting structures (pycnidia) can be seen under slight magnification on infected needles the spring after an infection. Trees that have been reinfected for multiple years may sparse hollow appearances as the needles die. Branches lower to the ground are more commonly affected with the disease traveling upwards and outwards in conditions are favorable. Needles can turn brown and then black as the fungus takes over the needle. Typically symptoms first appear on the lower branches of a tree and work from the inside of the tree out.įaint yellow bands can be seen on newly infected needles. This symptom gives the disease its name “needle cast”. Rhizosphaera needle cast is the most common disease on spruce trees that is received in the Plant and Insect Diagnostic Clinic. Rhizosphaera needle cast is caused by fungal pathogens within the genus Rhizosphaera. This genus also infects several conifer species including fir, cedar, spruce, and pine Symptoms of Rhizosphaera needle castĭisease symptoms include a browning or purpling of needles, which eventually drop from the tree leaving bare patches. In severe cases, fungicides can be used.Eventually new needles will replace the old, diseased needles. Manage by aiming to reduce spread to healthy tissues.Optimal conditions are during excess moisture and humidity.Symptoms include needles turning brown then black as fungus takes over needles.Can infect spruce, fir, cedar, and pine trees.
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