One of my Royal Raindrop crabapple trees only developed a few flowers last...

Asked September 13, 2015, 12:53 PM EDT

One of my Royal Raindrop crabapple trees only developed a few flowers last year, and almost none this year. Last year it had fewer than normal leaves, and this year it dropped all the few leaves it did develop. Before the leaves fell off the tree, they turned a copper orange. Now another Royal Raindrop crabapple tree next to it is developing some of these copper orange leaves, and is less leafy than the third one in the same vicinity. I have searched this site but cannot find a crabapple disease that looks like the one I have described above. Any idea of the problem causing this?

Stearns County Minnesota crabapple trees

4 Responses

Thank you for the question. Typically, crabapple trees are quite tough once established. They thrive best in rich, moist, slightly acidic loam type soil with good drainage and full sun exposure of 8 or more hours per day. Your variety is known to have good disease resistance to the most common afflictions of apple trees: fire blight, apple scab, apple rust, and powdery mildew but resistance is relative and doesn't mean the tree is immune to disease problems. Your trees are stressed as evidenced by their unhealthy appearance and can be due to many factors: under or over watering, too much shade, insect damage, disease, and physical damage from things like lawn mowers, weed whips, animals, and so forth.

It is difficult to diagnose your problem from limited information. If your trees are getting proper care, planted in appropriate locations and are not suffering from insects or physical damage as described above, the best guess I can make is they may have apple scab.

Apple scab is a fungal condition that occurs most often during moist conditions. Severely infected leaves turn yellow and drop prematurely, weakening the tree. Several years of early leaf loss can result in decreased growth, reduced bloom and increased susceptibility to winter injury. The healthy color of your tree leaves is deep purple. It's possible that this "base" color resulted in coppery leaves that dropped instead of the typical yellowing of affected leaves.

Control of scab involves raking up and disposing of all fallen leaves, making sure there is good air flow between trees by properly spacing them and pruning them. Sometimes fungicides are used but must be applied yearly early in the season to healthy leaves BEFORE any infection starts.

Learn more about this disease and control options here: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/managing-apple-scab/

Thank you for contacting Extension.

Thank you for the information. I am assuming from the information that my tree is not dead, but needs treatment. I will try the fungicide spraying treatment next year, and think I will treat all 3 of the trees that are in proximity to one another. I think all other factors you mentioned are OK-good site placement, plenty of room between trees, full sun, rich, well composted soil. I guess I'm not sure about slightly acidic, but I can test the soil. I do have garden beds around the trees filled with many tulips. When we made the beds we used a machine to remove the sod, but I don't think we damaged the trees or roots when we did it.

Before I found your website, I did get advice from a garden center to use Bayer Advanced Tree and Shrub 12 month Protect and Feed, which I just applied, and watered in very well. Will that hurt the tree that probably has a bad case of apple scab?

Connie

The product you purchased is a systemic insecticide combined with a long acting fertilizer. Apple scab is a fungus, not an insect, so the product you applied will have no effect if apple scab is the problem. Also, we don't recommend fertilizing trees in the fall or when they are stressed. Fertilizer promotes new growth which doesn't have time to harden off for the winter and the new growth uses up precious carbohydrate (food) reserves the plant stores to survive the winter.

The key to using any of these products is to make sure the disease or insect you want to treat is listed on the label as well as the plant you desire to treat. The label is very important.

What you can do now is continue to water well until the ground freezes, remove all fallen tree debris and discard it in the garbage and reevaluate in the spring. If you decide to use a fungicide in the spring, it needs to be applied to healthy leaves to be effective.
Please read the publication I included in my first response. It lists methods of control and products that can be used to control apple scab.


Hope the insecticide/fertilizer will not do too much harm the diseased tree. I will water well as you recommend, and hope for the best. The container said it could be applied any time before the ground freezes. Not very good directions, sounds like.

I read the publication you recommended and will follow its instructions next spring. Thank you again for your very good advice. Connie