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White "residue" on the undersides of my red oak le
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Author:  dcluck [ Wed Jul 09, 2003 10:46 pm ]
Post subject:  White "residue" on the undersides of my red oak le

I've got two healthy looking (to my untrained eye at least) 40ft red oaks in my back yard. For the past year (bought the house last summer) I've noticed that the undersides of the leaves have always had a white residue - last year's growth and well as this year's. Is this normal? Today I noticed that the 12ft red oak I have in the front yard doesn't have any signs of this, nor have I seen it on any of the others trees or shrubs.

Is it an indicator that something might be wrong with them? I have no idea what the previous owner did in terms of fertilization or care, and I've done the usual organic fetilizers and amendments for the lawn since moving here. Any help would be appreciated.

~Dave Cluck

P.S. I'm calling these (texas) red oaks, but I was told that by a friend. How do you tell the difference between a shumard and a texas red?

Author:  Dirt Doctor [ Sat Jul 12, 2003 8:59 am ]
Post subject: 

White stuff under oak leaves can be cosmetic and no problem or the indicator of major stress in the trees. If the white material has little tent-shaped insects that jump when touched, leafhoppers or planthoppers are usually not very damaging. Blasting them away with compost tea or garlic pepper tea is all that's needed. If the insects are mealybugs and stay put when touched, they indicate that the trees are in stress. Make sure they are not too deep in the ground. Fix that situation if it's the problem. Too much or too little water can be the problem. Too much or the wrong kind of fertilizer can be the problem. Even though you are using the organic method now, a previous owner could have contaminated the soil. In that case detox with NORIT or zeolite.

Texas red oaks and shummard red oaks are very similar. Some people will argue that they are the same. What's normally called Texas red oak has smaller, more deeply cut leaves and is smaller overall than the trees called Shumard. That could be simply a result of where they were grown. Check out the photos and additional information in my book Texas Trees.

Author:  dcluck [ Sat Jul 12, 2003 9:50 am ]
Post subject: 

Thanks for the reply, Howard. Everything I've seen indicates that there aren't any insects present on the leaves. I'll try getting up into the tree to inspect things closer once the resident blue jays have calmed down or moved out (see my "Blue jays seeking retribution!" post in the pet care forum).

On the shumard vs. texas red issue, as long as there's no appreciable difference in care or disease issues I suppose it doesn't really matter. The pictures you have in your Plants for Texas book didn't help indentifying mine. I'll give Texas Tree a go. Thanks again.

~Dave Cluck

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