By: Dave Scharfenberger, Board Certified Master Arborist WI-0131B
Predicting problems in the coming season by looking at past problems and weather conditions can be very helpful. We can watch specific trees at certain times to get on top of problems early. Drought impact from past years is still a big issue. Unfortunately, this can linger for many years. Affected larger trees will need more continued care. Small and medium trees may also. Expect borer problems, increased deadwood, dieback or root rots.
The good snow cover has set up rodent (vole) damage on thin bark trees and shrubs with some being girdled or even killed. In addition, rabbit damage is very common with low branches being chewed off.
- Dothistroma needle cast: is a foliar fungal disease of pine needles. This was very bad in 2007 and 2008. Watch for older needles browning.
- Sphaeropsis/Diplodia Tip Blight in Pine: was up again for the second year. This is tied to drought stress, which encourages many fungal stem canker diseases. Watch for dying tips. You need to continue or start treatment.
- Cytospora canker: on spruce is another stem canker that is up. Watch for lower branches dying.
- Spruce: Other problems with spruce have been growing over the last few years and we have talked about this a lot in past issues that involve needle diseases. Watch for needles turning brown or purple.
- Apple scab: Levels have been high the last few years. While this is mostly determined by spring moisture on leaves, there are many spores out there waiting for your crabapple. You need to continue treatments.
Good snow cover during the cold periods has helped to protect insects. So do not expect any help with insect control from our suffering through the cold this winter!
- Gypsy moth: The best indication for summer 2009 numbers is fall 2008 egg mass counts. By our observations and surveys carried out by the state in our area, numbers could be up slightly but should not be at bad defoliating levels. There is a chance of some pockets with high numbers that will need treatment, so you still need to watch for caterpillars and feeding in spring.
- Japanese Beetles: While these are only in some areas at this time, their numbers are building and spreading. First signs will be holes in leaves during early summer. See our Fall 2008 issue for more details.
- Bronze birch borer: Birch is another tree being heavily impacted by past dry conditions. Continue to water when dry and keep up with soil systemic insecticide protection from bronze birch borer. Watch for thinning or dieback in the top of your birch.
- Numbers of two-line chestnut borers and firewood borers in oaks have continued to run high. Continuing protection for valuable oaks will be critical.
- Emerald ash borer has been found in Wisconsin. Please see separate article in this issue.
Only time will tell if my predictions are correct. There is no doubt that this has been an unprecedented period of problems and increased stress on our urban trees. With multiple assaults on our big mature trees, be sure that you are doing all you can to protect the mature trees on your property. Wachtel Certified Arborists will work with you to solve your tree care problems.
© Copyright 2009 – Wachtel Tree Science & Service, Inc.