GoodSeed Farm > Spruce Decline

Spruce Decline

Colorado Blue Spruce decline has increased recently in southern Ohio

Do you have a Colorado Blue Spruce tree in your landscape? Do you wish you did? Colorado blue spruce trees are widely planted due to their good growth rate, stately form and, of course, their blue foliage. They are not native to Ohio, however blue spruce are available in Ohio nurseries, and are popular landscape trees in this area. Unfortunately, the success rate for blue spruce here in southern Ohio is not very good, and lately there has been an increase in the decline and death of Colorado blue spruce in this area.

Blue spruce decline can be due to environmental changes, poor site conditions and new pathogens. Colorado blue spruce is native to arid regions in the Rocky Mountains. Ohio’s climate is generally more humid, 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. As a result, they are stressed and more susceptible to fungal pathogens.

Blue spruce trees invite many insect and disease problems that can impact their growth and appearance. The key symptom of spruce decline is branch dieback, which progresses over two to four years and causes unsightly bare spots, or branches with very little foliage. The rapid decline of many spruce trees in the Midwest appears to be caused by disease and insect problems that plague blue spruce.

The three most common types of diseases that affect blue spruce trees are needlecasts, tip blights and canker diseases. All these diseases are caused by fungal pathogens, each of which has specific symptoms that help diagnose the problem.

1. Needlecasts. Shedding of needles points to needlecast diseases. Needlecast fungi often infect needles on the current year’s shoots. As the disease progresses, the needles die, usually the year following the infection. As a result, trees affected by needlecasts often have an outer “shell” of live needles on current shoots and dead needles on older shoots.

2. Tip blights. Tip blights are fungal diseases that typically cause dieback to new, emerging shoots. Tip blights are most common on pines, especially Austrian pines, but can also occur on spruces.

3. Canker diseases. Canker diseases are caused by fungi that infect branches or the main stem of trees. Typical symptoms of cankers are sunken areas along a stem that may ooze resin. As cankers develop, they can interfere with the branch’s ability to transport water and nutrients, resulting in the death of individual branches. Trees may produce ridges of wound tissue around older canker infections as the tree attempts to restrict the fungus’ growth.

Numerous insect pests can impact spruces, but the two most common are gall adelgids and spruce spider mites. In both cases, the insect pests are so tiny you may need a magnifying glass to see them. You are more likely to see the damage than the insect pests themselves.

1. Gall adelgids. Adelgids are small insects that feed on shoots by sucking plant sap, causing new shoots to deform and produce galls that resemble cones. 

2. Spruce spider mites. Spruce spider mites cause needle discoloration and eventually kill needles, which can be mistaken for a needlecast disease. Technically, mites are not insects, but are related to spiders. This distinction is important since not all insecticides will control mites.

As with any tree health problem, the first step in dealing with declining spruce trees is to diagnose the problem and identify the cause. For large or important landscape trees, homeowners should contact a professional arborist or tree care company. For insect or mite issues, insecticides or miticides can be effective, however selection of the proper product and timing are critical.

Success with blue spruce can be improved by planting blue spruce trees on sites with the right growing conditions, such as full sun, good air movement and excellent soil drainage. Over the years we’ve found that Norway spruce is more tolerant of southern Ohio’s heavy clay soils and humid, wet conditions than Colorado blue spruce.