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|Spruce, in particular, Colorado blue spruce, can be infected with a needlecast disease caused by the fungus Rhizosphaera kalkhoffii.
Learn more about the diseases that affect plants, ranging from garden flowers to food crops.
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Rhizosphaera Needlecast on SpruceSpruce, in particular, Colorado blue spruce, can be infected with a needlecast disease caused by the fungus Rhizosphaera kalkhoffii. Trees planted in nurseries, Christmas tree plantations, and landscapes can be infected. Trees are not usually killed by this disease; however, premature needlecast results in trees that are not marketable, or which are not acceptable in the landscape.
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Reference: Ohio State University Extension
Symptoms and Disease Cycle
Although needles on new growth become infected in May and June, symptoms are not visible until late fall or the following spring, when infected needles turn purple to brown and begin to drop (Figures 2, 3, and 4). Tiny fruiting bodies of the Rhizosphaera fungus protrude through the stomata of the infected needles. Under a hand lens, these stomata appear as fuzzy black spots instead of their usual healthy white color (Figure 5). During wet weather in late spring, spores are released from these fruiting bodies and are rain splashed onto newly developing needles where infection occurs and the disease cycle is repeated.
Use Healthy Stock
Maintain Tree Vigor
Prevent Spread by Shearing Tools
Chlorothalonil fungicides such as Bravo or Daconil 2787 and manganese/zinc such as Cleary's Protect T/O are labeled for control of this needlecast. Follow label directions for rate and frequency of application.
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|Data Source: Ohio State University Extension. Articles and resource may contain pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide and it is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used.|