ISSUE 2 May 21, 2009
EVERGREEN PROBLEMS IN 2009
Among the woody ornamental evergreens, winter injury or other environmental stress was the most common diagnosis, followed by possible root or lower trunk injury (root girdling, mechanical injury, or improper cultural practice). Normal needle drop was evident for at least one spruce sample. A needle cast disease has been diagnosed on one spruce sample submitted to the lab this season. Many other factors can cause inner needles of spruce trees to turn brown prematurely, but given cool, moist conditions during spring in some parts of North Dakota, needle cast may be a possibility. Please refer to the article on spruce problems in this issue to aid in more accurately diagnosing needle cast diseases and to learn about the proper timing of fungicide applications to manage needle cast diseases.
LAWN PROBLEMS AND TIPS TO KEEP YOUR LAWN HEALTHY
Turf samples have also been common this spring. Both seeded and sodded lawns have shown problems, with large areas reportedly not ‘greening’ up. Death of portions of a lawn can be due to winter kill, prolonged soil saturation, excess salts (from de-icers, even those that are labeled as ‘safe’ for plants), disease, and other factors. This spring, few disease problems have been confirmed as a primary problem, even though in some cases where patchy death of grass has occurred, low levels of a root-rotting pathogen have been detected.
With turf, primary problems observed this spring appear to be winter kill, compaction, excess thatch, and peat-backed sod over clay (with no or little topsoil evident). The following sequence of events is typically recommended for remediating dead patches in a lawn: core aeration, over-seeding the dead areas, and raking the seed to help it make good contact with the soil. Watering about two to three times per week for a few weeks will help improve germination of the seed. After the stand is established, supplemental water can be reduced to normal levels.
Raising the mower height to at least 2.5 inches (preferably higher) can help improve the over-all health of the lawn, as can reducing water inputs to no more than once or twice per week. A typical, actively growing lawn uses about 1 inch of water week. If many mature trees are competing with the lawn for moisture, more water may be needed. In many parts of North Dakota, normal rain fall is sufficient for most lawns, but in dry periods, the lawn will benefit from a deep drink. Fungicide use is typically not warranted on home lawns, except possibly in rare instances where foliar diseases may be problematic. Fungicides are not recommended for managing patch diseases (root or crown rotting diseases) on home lawns.
SUBMITTING SAMPLES TO THE NDSU PLANT DIAGNOSTIC LAB
The NDSU Plant Diagnostic Lab examines samples on a ‘first-come-first-serve’ basis, except in certain situations where a rapid and accurate diagnosis is required (such as suspected high risk pests or pathogens, and samples where a timely diagnosis is required for appropriate treatment). A good sample usually includes plants or plant parts showing different stages of symptom, and the best sample includes an entire plant (with roots intact) that is just beginning to show symptoms. Completely dead plants or twigs by themselves seldom yield any useful information.
In general, wrap a sample in dry paper towels before placing the entire sample in a plastic bag. Place the bag in a sturdy shipping box to avoid damage to the sample. Images (photographs or digital images) are particularly helpful for tree or turf/lawn samples. Images of trees should show the entire planting (the ‘big picture’), the entire tree, the lower trunk, the ground area around the lower trunk, and close-up images of symptoms of interest.
Before submitting a sample to the NDSU Plant Diagnostic Lab, please first consider using your local county extension agent or other local expertise. A minimum fee of $15 for routine diagnoses that do not require special handling is applied for North Dakota residents ($25 for non-residents outside the Red River Valley).
For more information on how to submit samples to the NDSU Plant Diagnostic Lab, please see the following website, http://www.ag.ndsu.nodak.edu/diaglab/, where you can obtain a lab form and additional tips on submitting good quality samples.
NEW CONTACT INFORMATION
Please be sure your databases are updated with the new mailing and shipping addresses of the NDSU Plant Diagnostic Lab:
Mailing Address (USPS):
NDSU Plant Diagnostic Lab
NDSU Dept 7660; PO Box 6050
Fargo, ND 58108-6050
Shipping Address (carriers other than USPS):
NDSU Plant Diagnostic Lab
306 Walster Hall/206 Waldron Hall
Fargo, ND 58102
The general email address has also changed to NDSU.PDL@ndsu.edu.
Feel free to email the lab or call (701 231-7854) with any questions.
NDSU Plant Diagnostician
Department of Plant Pathology