Why Is My Blue Spruce Losing All Its Needles
Oftentimes asked questions almost bandbox decline.
What's wrong with the blue bandbox trees in my neighborhood?
Colorado blue spruce copse have long been among the most popular conifers for landscaping in Michigan and the upper Midwest. Bluish bandbox copse are widely planted due to their skilful growth rate, stately form and, of form, their blue foliage. Unfortunately, bluish spruce trees are discipline to a wide range of insect and disease problems that can impact their growth and aesthetic appeal.
The prevalence of diseases on blue spruce trees has intensified in recent years and trees are failing chop-chop in many areas (Photo 1). The central symptom of spruce decline is co-operative dieback, which progresses over two to 4 years and renders the plant'south advent unacceptable for virtually homeowners (Photo 2). The rapid decline of many spruce trees in Michigan and surrounding states appears to be related to an increase of canker diseases coupled with other disease and insect problems that plague the species.
What kind of diseases impact blueish spruce trees?
There are iii principle types of diseases that bear on blue spruce trees: needlecasts, tip blights and canker diseases. All of these diseases are caused by fungal pathogens and each produce specific symptoms that can be useful in diagnosing the trouble.
1. Needlecasts. As the name implies, trees with needlecast diseases shed needles. Needlecast fungi ofttimes infect needles on the electric current year'due south shoots. Every bit the disease progresses, the needles dice, usually the year following the infection. Equally a result, trees affected by needlecasts ofttimes have an outer "shell" of alive needles on current shoots and dead needles on older shoots (Photo 3). The two most common needlecasts we find in spruce are caused by the fungal pathogens Rhizosphaera and Stigmina/Mycosphaerella.
two. Tip blights. Tip blights are fungal diseases that typically crusade dieback to new, emerging shoots (Photo 4). Tip blights are most common on pines, particularly Austrian pines, simply can also occur on spruces.
3. Canker diseases. Herpes diseases are caused past fungi that infect branches or the main stem of trees. Typical symptoms of cankers are sunken areas along a stalk that may ooze resin (Photo v). Trees may produce ridges of wound tissue around older canker infections equally the tree attempts to restrict the fungus' growth. As cankers develop, they can interfere with the branch's power to transport water and nutrients, resulting in the death of individual branches often referred to as "flagging."
Photos three-5. Left, Needlecasts kill older (inner) needles, just leave newer needles unaffected. Centre, New shoot tips killed past Phomopsis tip bane. Right, Resin oozing from a branch canker caused by Cytospora. Photo credits: Left and middle photo, Dennis Fulbright, MSU; correct photo, Michael Kangas, NDSU, Bugwood.org.
What kinds of insects affect blue bandbox copse?
Numerous insect pests tin can affect spruces in Michigan'due south landscape, simply the ii nigh common are gall adelgids and spruce spider mites. In both cases, the insect pests are tiny and yous may demand a hand lens to run across them. Oft times, people are more probable to see the damage as opposed to the insect pests themselves.
1. Gall adelgids. Adelgids are modest insects that feed on shoots by sucking institute sap. Equally they practise so, they crusade the shoots to deform and produce galls that resemble cones (Photo 6). Impairment from gall adelgids is mainly aesthetic.
2. Bandbox spider mites. Spruce spider mites cause needle discoloration and somewhen kill needles, which can be mistaken for a needlecast disease (Photo 7). Technically, mites are not insects, but are related to spiders. This distinction is of import since not all insecticides will command mites.
Photos half dozen-7. Left, Gall caused by Cooley bandbox adelgid. Correct, Needle damage caused by mites. Photo credits: Jill O'Donnell, MSU
Why are we seeing increased decline in bluish spruce trees?
There are a number of factors contributing to the decline we see in blue spruce trees, including environmental changes, poor site conditions and new pathogens. Colorado bluish spruce is native to barren regions in the Rocky Mountains. Michigan's climate is more often than not more boiling, especially in the summer, which is ideal for fungal pathogens to thrive. In landscapes, Colorado blue spruces have been planted on some sites that are marginal for their success. Equally a result, they are stressed and more susceptible to fungal pathogens.
Finally, for decades the default diagnosis for almost problems with blue spruce has been Rhizosphaera needlecast or Cytospora co-operative canker. However, a recent survey by Michigan State University researchers suggests ii other fungal pathogens, Diplodia and Phomopsis, were much more commonly associated with co-operative decease and tree decline than Cytospora (Photos viii-ix). Diplodia and Phomopsis are both considered weak or secondary pathogens, then it is unclear at this betoken why they appear to cause major disease problems for spruce. As well, in many cases in that location may be more than one issue that is affecting your tree's health.
Photos 8-9. Left, Refuse symptoms moving upward. Right, Wood staining on branch with Phomopsis canker. Photo credits: Left photo, Christine McTavish, MSU; right photo, Dennis Fulbright, MSU .
Tin can I do annihilation about these spruce problems?
As with any tree health problem, the first step in dealing with failing spruce trees is to diagnose the problem and identify the cause. For big or important landscape trees, homeowners should contact a professional person arborist or tree care company.
For some affliction problems, such as needlecasts, fungicides may be effective in preventing or controlling the disease. It is important to note that fungicide treatments for needlecasts only protect new growth. For command to be fully successful, it may take 2 to three years of yearly fungicide applications. For herpes diseases, the effectiveness of fungicides is commonly limited. Removing affected branches is usually the best action to improve the tree'due south advent and slow the spread of disease within the tree.
For insect or mite problems, insecticides or miticides can exist effective, even so option of the proper production and timing are critical.
Should we keep to constitute blue spruce trees?
This is a hard question. Although spruce decline is widespread and appears to be increasing, it is non a certainty that all trees will be affected. In fact, it is not uncommon to come across salubrious, thriving spruce trees most or adjacent to trees that are in severe decline. Some other complicating cistron is that copse may be healthy for a number of years and so begin to refuse as they mature and are more difficult and costly to remove.
The likelihood of having success tin exist improved past planting bluish spruce trees on sites with conditions they favor. Key site factors for blue spruce trees are full sunlight, good air move and excellent soil drainage. Michigan Land University Extension recommends homeowners diversify their landscapes to help make their landscapes more resilient to pest and environmental changes, and seek to plant a variety of species wherever possible.
Additional resources
- Alternative conifers for Michigan landscapes for suggested alternatives to blue spruce trees from MSU Extension
- MSU Extension website for upward to engagement information on bandbox decline research
- Gardening in Michigan website for more than information on planting and caring for trees in the landscape
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Source: https://www.canr.msu.edu/news/what_is_spruce_decline_and_what_should_you_do_about_it