If you are a homeowner with evergreens or a windbreak tree planting on your property, perhaps you've asked yourself or a neighbor this question recently. And if you haven't, chances are you soon will!
Calls have been pouring in this spring about sick evergreen trees, especially Colorado blue spruces and Black Hills spruces. Most homeowners report severe needle death on the lower half to two-thirds of the tree, and on the interior portion of the tree. The needles turn purplish-brown in fall and winter, and then fall off. The only green parts left alive are out at the tips and up at the top.
These symptoms are characteristic of Spruce Needlecast disease, or more scientifically, Rhizosphaera, which is a fungus that is pervasive across the Midwest. This fungus spreads via moisture in raindrops, dew, fog, etc. As the raindrops splash downwards, they tend to collect more on the bottom of the tree and infect more needles there. Sometimes, the problem is worse on the north side of the tree where it takes longer to dry out in the shade, and it's especially bad in windbreaks where no wind or air can circulate.
T-R PHOTO BY MIKE?STEGMANN
District Forester Joe Herring discusses spruce tree health with a Marshalltown resident. He has received many calls this spring on the unhealthy Colorado Blue Spruces throughout Marshall County.
The problem is not so much the presence of the fungus here in the Midwest, but rather the misplacement of these foreign trees into a different environment than they're used to. The blue and Black Hills spruces are native to the Rocky Mountain region of the US, where the climate is much more arid than ours, and soils that are much more, well rocky. Transporting these trees 10 hours to the east and planting them in a clay soil with our humid Midwestern climate is akin to planting a palm tree in the Arctic Circle. (I can just picture the planting instructions: "Chip hole in ice. Backfill with tundra peat moss. Fertilize with 20-10-10 caribou scat. Cross fingers firmly!")
So what's a Midwesterner to do who already has one planted in their yard and is experiencing the disease? For starters, make sure that you get the problem accurately diagnosed. There's no point in spending good money on sprays or fertilizers if it's not called for, and oftentimes, it's not. The Iowa State University Plant Diagnostic Clinic can help with this (www.ent.iastate.edu/pidc/), or perhaps a local consulting arborist.
Secondly, pruning off all the dead branches will improve air circulation which will help the needles dry faster and lessen infection. Raking up dead needles underneath the trees will also help reduce the source of infection, as will removing any trees which are severely diseased. Mulching and watering the trees (when needed) can also improve health and help them better fight off the disease.
Third, fungicides can be applied to the fresh outer growth to prevent new needles from becoming infected. Timing is everything, as the spray must be applied when new growth is emerging in mid-May, and once again in mid-June when needles are fully elongated. (We've already missed the early spray period, but hitting the second one now may still help). Fungonil, Daconil, or Bordeaux are all products that can work. Usually you can find one of these three products at an Earl May, Theisens, or other garden or farm store. Keep in mind that what's dead is dead; these sprays only work by preventing the newest growth from becoming infected. It may take many years of repeated protection of new growth to fully conceal the diseased inner tree, and older trees often do not have this growth capacity and will never look "good" again. Follow all label instructions, as it is a violation of Federal law not to do so.
As with most maladies that affect humans, prevention is the best medicine of all. There are several alternatives to the blue spruce that are much more resistant to disease, including white pine, concolor fir, arborvitae, Norway spruce, and our native and very hardy Eastern red cedar. If you're planting multiple trees for a windbreak or grove, using more than just one or two species can lessen the impact of potential health problems.
If you still really want to plant a blue spruce or other exotic evergreen for their outstanding beauty, just understand their limitations - many may only live 20 years, just long enough to grow to a "mature" size before they run out of life. Blue spruces planted as a windbreak will almost always get diseased because of poor air circulation and tight spacing; they perform better when they're planted out in a yard in the wide open, where the sun & air will help dry them off after rains & nighttime dew. Also, clay soils and soggy bottoms just won't do. Nearly all ornamental evergreens require a well-drained, loamy (& even slightly sandy), black soil with low pH to really thrive.
More information on tree diseases and tree planting can be obtained from the County Extension office or online at www.iowatreeplanting.com.
The Izaak Walton League will be hosting two more classes of Hunter Safety this summer. The first class will be June 16 from 6 p.m. to 9 p.m. and June 18 from 8 a.m. to 4:00 p.m. The second class will be held Aug. 18 from 6 p.m. to 9 p.m. and Aug. 20 from 8 a.m. to 4 p.m. Both classes will be held at the Izaak Walton League grounds located 1 mile south of Iowa Ave on S 12th/Smith Ave. Completion of a hunter safety course is required for anyone who wishes to buy a hunting license born after Jan. 1, 1972. Must be 12 or older. Register for this free 10-hour class at www.iowadnr.gov/training.
A Mosaic Stepping Stones class will be held Thursday, June 23from 6:30 to 8:30 p.m. at the GrimesFarm & Conservation Center. Need a garden highlight or a county fair entry? Create a unique stepping stone using assorted decorative objects such as shells, flat marbles, keys, broken plates or tile, beads, etc. Bring your own decorations or use ours. Cost $5. Pre-register by June 17 by calling 752-5490. All ages welcome.
The DNR and MCCB staff will band Canada geese on either June 28 or 29 in the morning hours. Come help us round up birds or just watch. The morning of June 28 or 29 at Green Castle Recreation Area located one south of Ferguson. To sign up to help, call 641-752-5490 by June 24.
Joe Herring graduated from Iowa State University with a BS degree in Forestry and a Master in Water Resource Management. He is employed by Iowa Department of Natural Resources and if the District Forester for Marshall County and 10 other counties in central and north central Iowa. He can be reached at 752-3352