Help for my Hopa crabapple (pics included)

[Steve Foss]

Hey all:

These images were taken today of my Hopa variety crabapple. It is an 8-foot tree with a trunk diameter of 1.5 inches. I planted it last spring, cut a 4-foot-diameter circle out of the sod and mulched it in, watering it well. It grew quite well all last summer. I did not fertilize it, because many fruit trees, including apples, should not be fertilized their first year. It was in a five-gallon container, not a bare-root tree, and it had leafed out already when I planted it. I drove t-posts and used rope (loosely around the trunk) to stabilize the tree, so none of heavy winds we had last summer or this spring have dislodged roots from the soil, which can happen if the base of a newly planted tree bends too hard in strong wind.

It leafed out beautifully this spring, but in the last two weeks has started to develop speckled leaves that yellow, then brown, then fall off. You'll see from the second image that new leaf growth is happening very nicely.

I fertilized it lightly late last fall after it went dormant so it would have a bit extra to draw from this spring.

I have planted and cared for hundreds of trees but I do not know a lot about tree diseases, though I'm a bit better on tree insect pests. This, however, looks like some type of fungal disease quite similar to black spot, which infects many types of hybrid tea roses. Cotoneaster, a few other shrub varieties and some trees, including apple varieties, are more susceptible to fungal diseases and scabs than other species.

Here is what the NDSU Extension Service said about similar sypmtoms: "Apple scab is common on Hopa crabs. Clean up fallen leaves this autumn; spray with lime sulfur next spring when dormant; spray with Bordeaux mixture at leaf out, and again 7-10 days later there after; Or, just live with it as you have."

While we have a lot of knowledge among us about gardening/trees/lawns, I highly recommend bookmarking the extension service Web site in your state. They know their onions. Uh, so to speak.

I'll be taking this advice because, while a mature tree often can absorb periodic infestations of fungus and some other diseases/insects, young trees need all the help they can get, and any measure that maintains the leaves and allows them to keep feeding the young roots through photosynthesis is worth taking.

[Powerstroke]

Hey catfish, I have to agree with the extension service. This is very typical Apple Scab disease. As you suspencted it is of the same type of spot diseases. This is probably the #1 complaint/service call I investigate. Everyone who has a crab will get aplle scab eventually, even nt he disease-resistant cultivars seem to find a way.

The fungal disorder thrives in the cool wet springs we have, especially if there is little air movement in the area of your tree and also if the tree is still pretty thick (leaf-wise).

There is nothing you can do for it this year. The leaves that were infected will continue to blacken, curl and fall off. It will look like your tree is in October during July and August. Expect to have very few leaves during the late summer and fall.

How to prevent it.....I agree that you should clean up the leaves as the spores will spread if you don't. The disease will come back because its still on the bark and twigs of the tree.

Next spring-I disagree with the whole "lime-sulpher/bordeaux" treatment. Thats a bit more complicated than I would recommend to anyone even if you have experience with herbicides.

Go to a nursery or lawn/garden store and ask for a fungicide to treat apple scab. Its very common and there are some great products. I would recommend Banner Maxx if they carry it. You spray once at 1/4-1/2 leaf expansion and then 2 more times at 7-10 day intervals. IN the future if you get good control of the disease, you can cut back to 2 treatments per season.

Timing is critical. You may still find sick leaves but your tree will stay 90+% green and leafy all the way till fall. In the cities, the company I used to work for would charge $50 per application for a small tree like yours. Its so easy to treat and the results are almost unbelievable after seeing what a tree will look like with the disease.

[Steve Foss]

Thanks, Powerstroke, for filling in a few gaps. I have extensive experience with herbicides and fungicides, but mostly the fungicides have been used on house plants and the herbicides on lawns. I've done some tree treatments, but those were mostly insecticide sprays.

[Big Roy]

I had the same thing with my Red Splender Crab. I got a product from Dege's on Century ave. in Maplewood, you spray it on 3 times in the early spring. I have done it for 3 years in a row and the tree is very healthy.