Sick Sioux Falls Trees: Recent case solved. “The brown spruce”

Brown needles on the new growth.

In the Sioux Falls area, I look at more spruce tree issues than any other tree. It’s not surprising, really, with all the issues that spruce can have within the area.

Why, you wonder, more than other trees? Its because spruce isn’t native to the prairie and as they age cannot handle the hot and humid summers, the heavy sometimes oversaturated soil, and the sometimes dry, windy, and extremely cold winters as they age. Colorado blue spruce especially is better suited to mountain climates where its not as humid and doesn’t have such extreme weather fluctuations.

This case for example was a tougher one for me to get a handle on because the tree was being attacked so severely that it threw me off as to what was actually causing the damage. But after some research and consulting with colleagues I determined that the tree in the pictures had been attacked by spider mites this spring.

Spider mites are small sucking insects that can cause the needles of spruce trees to turn bronze or brownish looking (all brown in this severe case) and under close examination have a dimpled or speckled look to the needles from where the insect suck out the juice from inside the needle cells. Feed on needles can also look a bit wilted and not have the same bright coloring as healthy needles.

The spring of 2015 started off very dry and warm, then quickly turned wet and cool. The rain was very welcomed, but it also made the perfect storm for some very bad infestations of some certain insects.

Spider mites are fairly common with spruce within the area, but usually at low enough levels in healthy trees were they are barely noticeable or only cause a little bit of harm. But in stressed trees, they can build up strong populations and cause some extensive damage. In this case, it is more unsightly than damaging as the tree seems to recover from what seems to be only spring feeding by the mites. But after this years damage it may cause more stress to the tree and open things up for other pathogens such as Stigmina needle cast, Rhyzospharea needle cast, or Ctospora canker.

The recommended treatment for this tree is to spray the needles this fall with a dormant oil and then again in the spring with a combination of dormant oil and a miticide. There were also a few needles with signs of Stigmina needle cast, but only a few, so one spring of fungicide control on the new needles should control the needle cast.

Prevention of such problems is sometimes impossible. But as with most tree health issues, if the trees are watered, planted, mulched, and cared for properly, these issue are far and few between.

Shriveled brown needles with no spots of fungal activity.

Healthy twig and buds, but shriveled needles.

Needle loss but the twig is healthy