Needle blight spruce trees1/22/2024 Tip blight is a potentially lethal urban tree disease, but it tends to kill shelterbelt trees planted close together in rural areas. The colour changes varied from tree to tree from pale yellow to bright yellow to orange to bright orange to rusty brown. This natural death process tends to coincide with the second wave of tip blight infection in late summer, producing a dramatic change in the colour of the needles. It surprises many people when I tell them that the interior needles of many spruce trees naturally die of old age in mature trees. When the disease shows up, it has a tendency to infect nearby needles and adjacent twigs located near the original source of infection. In Colorado blue spruce, this discolouration is often very dramatic - the blue needles turn bright green and then slightly discolour to a green-yellow. Later in the summer, the disease returns to change the needle colour at the ends of the twigs to a bright green-yellow. The needles turn a straw- or red-brown colour in the late spring before falling from the twigs. Infected twigs are denuded of their needles except, in some instances, on one side. The disease causes slightly or prominently curled ends of the twigs, starting in late May or June. Sirococcus tip blight disease normally affects the current growth of spruce twigs, resulting in the death of the needles and twig tips. Within the last five years, the Sirococcus tip blight fungal disease has leapfrogged into a significant concern - a threat not only to urban spruces but especially to shelterbelt trees on rural acreages and farms. I've written about the problems with spruce trees a number of times, but these issues keep returning and growing.
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