P&PDL Picture of the Week for
October 16, 2006

Yikes, My Pines Are Dying! Otherwise known as Normal Fall Needle Drop

Gail Ruhl, Sr. Plant Disease Diagnostician, Dept. of Botany & Plant Pathology, Purdue University

About this time every year we receive a number of phone calls in the P&PDL regarding yellowing and dropping of inner needles on pines. The symptoms are very striking and tend to alarm people. Rest assured, this phenomenon is a natural one called Fall needle drop. It is normal for pines to drop their oldest (inner) needles at this time of year. Older arborvitae leaves turn a reddish brown. Natural needle discoloration may be more noticeable on trees that have experienced root stress due to less than optimal growing conditions. Extended dry periods during the summer months, as well as sites with poorly drained, heavy clay soils may accentuate root stress to pines. If the newest growth (this year's needles) is still green and healthy in appearance, you can rest assured that this yellowing phenomenon is natural.

To improve the growing conditions around your trees you may want to refer to HO-140 , Fertilizing Wood Plants (PDF 60K . In addition, deep-core aeration may help improve root growth by improving the soil structure and the percolation of water into the soil. To apply one inch of water a week (the minimum needed during drought periods) you may need to run a hose and sprinkler or soaker at full capacity for 1.5 hours under the branch spread (drip line area).

 

Click image to enlarge

Fall needle drop on white pine

White pine

Fall needle drop on ground

Close up of normal fall coloration on white pine

Fall needle drop on red pine

Red pine

Fall needle drop on arborvitae

Arborvitae

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service