Rhizosphaera Needle Cast Fungus and Mite

Last year we made you aware of a fungal condition which we refer to as ‘Rhizo’ that has been wreaking havoc especially to Colorado Green & Blue Spruce!

For many years, Spruce Mites were a Spruce tree’s main issue and most of our clients had us treating for them. While Mites are still an issue, we recommended that you consider changing over to an encouraging new program which controls Mites but also includes fungicidal products to control Rhizo as well.

As always, we were up front in telling everyone that we had no history treating for Rhizo and that we might not know how effective the treatments would be until the Summer of 2020 since we had only started this new program last year. We normally do not suggest treatments or products that we haven’t had a chance to test for ourselves but we just didn’t feel we could recommend waiting two years before we knew for sure the efficacy of these applications. The fungus is just too aggressive to have not offered the new program. Some clients started treating immediately and others opted to wait but as of now, we are pleased to report…










This particular tree was severely damaged from Rhizo. Initially we felt it might be too infected to survive but we needed to get an idea of what we could realistically expect from our product mix. We treated it last year and never imagined it would make the recovery it has in just one short year. We think it is very safe to say that this tree is improving and will look even better moving forward. By preventing the fungus from continuing to spread throughout the tree, we think you can see that it has allowed the tree to begin displaying new, healthy and unimpeded candle growth.









This Spruce was getting pretty scraggly but if you look closely you can tell that the decline has stopped and the tree is starting to fill in around the diseased areas. Some trees may recover more quickly than others as there are always additional factors at play. Clay soil is a huge detriment to these trees as are areas that hold water and don’t allow the root systems to dry out adequately. We always recommend Professional, High Pressure Root Fertilization for any prominent trees on your property. This keeps your valuable landscaping as healthy as possible so that they are better equipped at handling negative, environmental stressors as they pop up. Additionally, our rich mixture of minerals, nutrients and amino acids encourages new growth which helps cover up and hide previously diseased areas.

We could have included many more photos but these are a good representation of what we and our clients are seeing. Even if a treated tree simply appears to have remained in the same condition as it was last year and hasn’t declined further, that’s still an achievement. Stopping additional fungal and Mite damage is our goal. As mentioned, with time, the tree should continually put out new growth, enhancing its appearance year after year.

Folks, if you have Spruce trees that are only being treated for Spruce Mites, we would encourage you to change to this combination program. If you have Spruce that are not being treated at all, we really suggest you consider protecting them. This Rhizo fungus is a very aggressive disease. It travels by wind and on the feet of birds and squirrels. It is far better to stay ahead of the curve and prevent the fungus from taking hold through proactive treatment measures rather than waiting for limbs to start dying and trying to save the tree later.



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.

Full Disclosure

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.

Spruce Mites

Spruce Mites attack the interior of Colorado Blue Spruce, Green Spruce and Arborvitae shrubs. We are seeing a big increase in the Spruce Mite populations.

Many of our clients have us treat their Spruce and/or Arborvitae not only to control an active Mite problem, but also as a preventative treatment, which is the best approach.

Spruce Mites cause a ‘drab’ green or actual browning of the interior needles. They will not attack the new candle growth that first appeared this year so don’t be fooled by nice exterior color on the tree. Next year, beginning in the Spring, the new candle growth from this season will be attacked by the ‘overwintering’ mites. To see a video on how to test for Mites Click Here.

Although some of our clients have these trees and shrubs treated once a year, many have them sprayed twice; once in Spring and once in the Fall. We are finding that two applications, on a Spring and Fall time table, controls Mite damage more effectively.

If we are only treating your Spruce and Arborvitae in the Spring, and you would like to be included in the Fall application schedule, just call or email the office. The Fall price will be the same as the Spring application.

Mites are difficult to control as they multiply every 10 to 17 days. The more that show up, the more damage they do. On a treatment note, we need to rotate the products that we use so that they cannot build up a tolerance and immunity to any particular product, which they famously do.