COLORADO BLUE OR COLORADO GREEN SPRUCE TREES ALERT!
Many of you have Spruce trees on your properties. Most of our clients already have us treating their Spruce trees for the destructive Spruce Mites but now there is an additional concern. If you have one or more Spruce please read on to better understand what is going on with these trees.
For those of you who might be unsure which type of tree we are referring to, below is a photo of a healthy Spruce. If you haven’t paid much attention to area Spruce trees, we request that you do going forward. As you drive around different neighborhoods and up and down main thoroughfares, you will notice Spruce trees in different stages of distress. While Spruce Mites were the biggest enemy of Spruce during the last several years, these trees are now additionally being attacked by a fungus known as Rhizosphaera Needle Cast. Below are photos of Spruce under attack by ‘Rhizosphaera’.
What Brought This On?
There were negative effects created to tree root systems during the wet years of 2009, 2010 and 2011, two of which were the wettest on record. When the ground is wet for abnormally long periods of time, oxygen has trouble penetrating the wet ground and some of the roots suffocate causing different degrees of what’s referred to as ‘root rot’. Then in 2012 we had the worst drought in history. The four connected years of 2009 to 2012 were horrible years for trees and they are still paying the price today.
When those years occurred, the Department of Agriculture and the Morton Arboretum announced that many trees could die over the next 10 to 12 years due to the root damage sustained during that period of time due to the stressful conditions that existed back then. That means trees are potentially at risk until 2024.
Although root damage can put any tree at risk, trees such as Spruce have been most adversely affected by those years. When a tree is under stress, it is more prone to attack by insects, Mites and fungal disease.
So what’s going on now?
A couple years ago we started seeing minor Spruce tree damage from Rhizosphaera ‘Rhizo’ Needle Cast. We had first seen Rhizo about 40 years ago. Then we noticed it again about 28 years ago and then again 15 years ago and each time it was minimal and seemed to disappear before any substantial damage occurred to these trees. We hoped it would remain a minor annoyance and that it would not be much of an issue as it had in the past. We have to report that last year, and it appears this year, Rhizo has been accelerating, much worse than ever before. It is so widespread, and in so many areas, that we are guessing it’s not going to go away any time soon, if at all. As you saw in the photos this is a devastating disease which does severe damage and can, and has been, killing Spruce trees.
Under current conditions, we are forced to suggest a change to our treatment program for any Spruce trees important to your property.
We are suggesting two fungicide spray applications for Rhizosphaera in the late Spring and early Summer period about 3 to 4 weeks apart followed by a third application late Summer into Fall consisting of a fungicide/miticide mixture. We feel this will give the best protection from both Rhizo and Mites.
Most importantly folks, even if you have Spruce trees which appear to be ‘perfect specimens,’ and you were not spraying for Spruce Mites, you should really consider the recommended program to protect them. Since this fungus moves as an airborne spore traveling by wind or even on the feet of birds, and then spreads within the tree itself, it is important to be proactive, not reactive.
We have never treated for Rhizosphaera Needle Cast in the past. There are high quality products available but we have no track record with their use against Rhizo. We will say however that we do use some of these products on other fungal issues and they work tremendously well so we are ‘expecting’ them to work on Rhizo. Ordinarily we test products against insects or diseases for two to three years before we offer them to clients but the way the Rhizo has progressed we feel we need to offer this option ‘untested’. We hope to have some idea of how well they seem to be working by next year and a better idea two years from now.
Why two years? Because once the fungus infects a Spruce, it takes 12 to 15 months for the damage to start showing up on the tree. Therefore, if we start treating this year for you we will only be protecting branches not yet affected because fungicides work on a prevention basis, never an eradication basis once it is already present.
If you aren’t sure you want to protect against the Rhizo fungus we recommend at least sticking with your current Mite spray program as the Mites are everywhere and very damaging in their own rite.