Infected needles with rows of fruiting bodies (pycnidia) protruding through the stomates. Rhizosphaera needle cast causes needles to turn brown, or in the case of the Colorado blue spruce, a purplish-brown, and fall from the tree prematurely (Figure 1). Blue spruce in Michigan suffers from a serious needle casting disease caused by the fungus Rhizosphaera. The symptoms of needle cast first appear on needles as light green to yellow spots, which eventually turn red or brown. How to treat or prevent Rhizosphaera needle cast. This is usually mid-to late May. Linda: Rhizosphaera needle cast is a fungal needle disease that causes needles to die and drop off the tree prematurely. Another needle disease with similar symptoms that we’re seeing quite a bit of this year is Stigmina needle cast. Rhizosphaera needle cast is a very significant disease of landscape, nursery and plantation conifers. It is caused by a group of fungi in the genus Rhizosphaera. It starts on the inner and lower growth and progresses upward through the tree. This disease is … Growth of the fungal pathogen from the spots on the needle will cause the death of the entire needle. A second spray should then be applied 3 to 4 weeks later. Rhizosphaera needle cast (Rhizosphaera kalkhoffii) is a foliar disease of spruce trees. It is most common in trees growing outside of their native range. Rhizosphaera needle cast is best managed using a combination of methods: Plant only disease-free plants. Sprays may need to be made for 2 or 3 consecutive years depending on disease severity. Needle cast is a broad group of fungal diseases that cause conifers to shed needles. Rhizosphaera needle cast disease can be diagnosed by looking at the discolored needles with a magnifying glass; the fungus pushes through the stomata of the affected needles … However, in some plantations needle casting symptoms still occur after sprays (Photos 1 and 2). Products containing chlorothalonil or other active ingredients listed for Rhizosphaera needle cast can be used for treatment. Well-timed sprays in the spring will normally suppress Rhizosphaera to non-detectable levels in the population of trees. It can take up to 15 months for the needles to show visible symptoms after the initial infection. Rhizosphaera needle cast is caused by several species in genus Rhizosphaera, and while the ecology and pathogenicity of these species are poorly understood, the disease is most often attributed to R. kalkhoffii.Research from the UMass Plant Diagnostic Laboratory has identified at least seven phylogenetic species in the northeast from six host genera (Picea, Abies, Tsuga, Pinus, Pseudotsuga … Before planting, check suspect needles for fruiting bodies by following the method outlined above.
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