Whats Causing These Yellow and Brown Needles on Conifers?
By Krystal Tentinger Plant Health and Protection Student Iowa State University Extension When looking out at your conifer windbreak or observing the stately Scots pine across the street, you may notice something alarming. Yellow and brown needles on conifers–also known as evergreens–are a common sight during the spring in Iowa. This discoloration can be due to several factors, including winter injury, Rhizosphaera needle cast, bark beetle damage and pine wilt. Winter injury is common when winters are dry and mild. Last summer and fall, our conifers were under drought stress. Then the dry winter caused even further stress. During the winter, water can be lost from conifer needles when air temperatures rise above freezing and the tree is unable to replace the it in sufficient amounts. The mild, sunny, winter days cause such an effect. Common symptoms of winter injury are brown to red needles and loss of needles in the newest growth. Winter injury often is most severe on the south and w
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