The fall season brings cooler weather and the reds, oranges and yellows in leaf color of our deciduous trees. You may also notice the evergreens or conifers in your landscape changing color too.
The eastern white pine may look like they are dying as the three year old needles die and drop off. The older needles on the interior of the branches turn yellow and fall this time of year. This is a natural process, so do not be alarmed.
However, if you have noticed patches of brown needles in the canopy of the spruce trees in your yard or windbreak, this can be a sign of a problem. There are several diseases that can affect Colorado blue spruce, causing needles to turn brown and drop.
The two common diseases affecting blue spruce include rhizosphaera needle cast and cytospora canker. The symptoms for both diseases look similar. To differentiate these diseases, a branch sample can be submitted to the University of Illinois Plant Clinic in Champaign.
If the tree is diagnosed with cytospora canker, dead branches should be pruned and destroyed. Fall fertilization of the tree and mulching of the roots is recommended. Both of these techniques will help to improve the vigor of the tree, as there is no effective pesticide treatment option for this disease.
The disease rhizosphaera needle cast can be treated -- not now, but in the spring. So, this is a good time to diagnose your tree’s problem to prepare for the spring fungicide treatments.
I have recently seen several spruce trees with brown needles not caused by a disease. These trees were affected by the spruce spider mite. These mites attack spruce trees in the spring and again in the fall. So, if you noticed dying needles on your trees in the late spring and early summer, take a closer look at those trees right now.
Look on the branches for tiny webs on them; oftentimes you will notice dead needles dangling by a tiny thread of web. You can also shake suspected branches over a white sheet of paper. Some of the mites will fall onto the paper where they can be seen as greenish to grayish slow-moving dots that streak green when smashed. Faster-moving red or clear mites that streak red when smashed are predatory mites that feed on the spider mites. If predatory mites are common, they are likely to control the spider mites without the need for pesticides.
Spider mites are controlled with two or three miticide sprays applied at five to seven day intervals. Most miticides do not kill the eggs, so the repeated spray is important.
If you have questions about the health of spruce trees on your property, feel free to contact the Extension office in Charleston at 217-345-7034. You can also reach me in the Extension office in Arthur at 217-543-3755.