Karen Rane, Plant Disease Diagnostician, Plant and Pest Diagnostic Lab,
Photos by: Jeff Burbrink
Every year in late summer and fall, the PPDL receives several calls about conifers that appear to be dying. Clients complain that the inner foliage of affected trees turns yellow then brown, followed by the affected needles falling from the branches. There is no cause for alarm, however – this is a condition called normal fall needle drop.
Evergreen foliage does not stay green forever. The foliage produced each year has a finite life-span, which can be 2 to 4 years depending on the host species and overall health of the tree. Each year, the oldest foliage will turn yellow or brown and die. With some species, this is a gradual change that occurs over several weeks or months. With others, such as white pine and arborvitae, this change occurs over a relatively short period of time, and is therefore quite noticeable. The environment may also play a role in how quickly this natural phenomenon occurs. Trees under stress from adverse environmental factors such as drought may lose more than one year’s foliage at a time, or the discoloration may occur more quickly than in healthy trees. However, as long as the youngest foliage (1 to 3 years’ worth, depending on the tree species) remains green, the tree will suffer no adverse affects from the loss of the oldest foliage.
Normal fall needle drop should not be confused with needle loss due to spider
mites. These arthropod pests often feed on interior foliage, and cause stippled
or speckled discoloration which eventually leads to brown needles. If spider
mites are responsible for interior needle loss, you should see the mites or
their eggs, webbing or cast skins when you examine the foliage with a hand lens.
For more information on spider mites, refer to E-42-W,
Spider Mites on Ornamentals PDF.
Click on the small image to view a larger image.
Fall Needle Drop of Pine
|Close-up View of Pine Tree|
Photos courtesy of Jeff Burbrink
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