SNEED, or Sudden Needle Drop, also called Spruce Needle Drop, is a fungal disease that, as its name suggests, causes the needles to drop from Spruces. It is known to affect Colorado Blue Spruce, White Spruce, and Norway Spruce. SNEED is a relatively uncommon disease that was identified in the Midwest and Canada in 1998. It is thought that SNEED is caused by a fungus called Setomelanomma holmii, but it has not been proven reliably, and it is not considered a true pathogen. This fungus can be found at the base of needles, on the woody portions the needles emerge from, on both affected and healthy trees. It appears as small black fruiting bodies on the small branches where needles emerge. Because the disease is uncommon and relatively new, the lifecycle of the pathogen is not well studied. There are also numerous other fungal pathogens that lead Spruce trees to drop their needles, so the exact pathogen causing needle drop should be confirmed with a diagnostic lab test. The most common fungal pathogen that causes Spruces to drop their needles prematurely is called Rhizosphaera Needle Cast, and you may be hard pressed to find a Colorado Spruce in our area not affected.
You may first notice the yellowing of older needles in late Spring. It may affect a number of branches scattered throughout the canopy. By the end of Fall, all of the older needles may drop from a branch, leaving behind just a tuft of the newest needles at the tip of a branch. This will eventually cause the whole canopy of a tree to thin, and may lead to the death of branches as well. Symptoms of SNEED tend to progress more quickly than Rhizosphaera Needle Cast, which is a clue to which pathogen you may be dealing with. SNEED will also affect certain branches in a more random pattern, while Rhizosphaera will begin in the bottommost branches of a tree and work its way up.
SNEED is considered a secondary pathogen of Spruce trees, which means that it usually affects trees that are already weakened by other stressors. Trees that struggle with poor or compacted soils, drought stress, root rot, construction damage, or transplant shock are much more susceptible to the effects of SNEED. That is why it is important to be practicing proper cultural practices to keep your Spruces healthy. Spruces need a lot of water and well-draining soil. Established trees should be getting 1 inch of water per week, or about 2 gallons of water per inch in diameter. Anytime we go several days with no rain during the growing season, your spruce or pine should be watered. Using slow soaking methods, such as soaker hoses, is the best practice for watering. Water up until the ground freezes or we get significant snowfall. Maintain a 2-3” layer of mulch over your tree’s root zone as well. Mulch helps the soil to maintain moisture and insulates the roots from temperature extremes. It is good practice to leave the tree’s needles as they fall. Fallen spruce needles are the perfect mulch for spruce trees.
If your Spruce is showing signs of needle cast, call Tree Health Management to have an ISA Certified Arborist inspect your tree. There are chemical controls that can help to slow or prevent the progression of SNEED. The same fungicide treatments that help with Rhizosphaera Needle Cast and other needle cast diseases are also effective against SNEED. A set of two fungicide sprays are applied in the late Spring when new foliage appears, and then again about two weeks later. Your Tree Health Management Consulting Arborist will put together the best treatment plan for your tree.