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Apple Trees Looking a Little Rusty
Apple Trees Looking a Little Rusty?
WD40 won't help you fight the dreaddisease they call Rust

Question. Every spring our ornamentalcrab apple tree is infested by a rust that ruins the leaves and causesthem to dry and shrivel in the summer. I am aware that these trees needto be sprayed with an oil-based solution immediately prior to budding,but this has not worked in the past.  I have also been told thatsuppository-like things can be drilled into the tree or put into theground during the fall to prevent the problem. Any other suggestionswould be appreciated.  The tree looks terrible most of the springand summer months.
                   ----Nancy in Media, PA

Answer. Yes, rust really does liketo go after apple trees—both fruit bearing and ornamental types likeyour flowering crab apple—big time. It generally shows up late in theSpring, in the form of pale yellow spots that gradually get bigger andtake on that familiar orangey color.

The answer you always hear is to remove any nearby cedartrees—especially Eastern red cedar—and, less frequently, other membersof the Juniper family (yes, cedars are junipers—plants have familiesevery bit as confused as yours). There are a number of different'species' of spore-borne fungal diseases grouped under the general name'rust'—another well-known one loves to attack roses—but this type needsto also grow on cedars (or other junipers) before it can infect appletrees (that's why its common name is 'cedar-applerust'). And it's far from the most complicated kind—one type ofrust has to 'jump' to five different types of plants in a season tocomplete its life cycle. Kind of like that bug the kids brought homefrom school for your Christmas present.
Anyway, the spores can overwinter in debris on the ground (which makesa good clean-up underneath the tree in the Fall essential), and/or theycan spend the off-season on cedars and junipers, which I'm now justgoing to pretend are two different things so I don't have to insertfamily tree explanations into the dialogue every time I mention thedang things. On cedar and junipers, the disease takes the shape oflarge, soft galls on the branches that, like teenagers, develop longcolorful horn-like structures when the weather warms up. Those hornsthen spit out disease spores that go looking for your floweringcrabapple—their hands-down favorite victim. (If you ever see thesekinds of structures on your cedars or junipers, prune them off andtrash them—even if you don't have apple trees; you might be ending therusty misery of an apple grower miles away!)  

If you've got an apple tree planted close to a cedar or juniper, it'llnever be happy till one or the other goes bye-bye. But rust may stillcome a callin' even if you do get rid of any cedars and junipers closeby. Those rusty spores can travel up to four miles on a windy day, andyou may never even see the playmate that's making your plant sick.

That's why you should make your apple trees as resistant to the problemas possible:

1)    Clean up EVERYTHING underneath the tree after theleaves drop in Fall. Really rake that ground hard, and throw all thedebris in the trash—don't compost it.


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