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Sunday - August 01, 2010

From: Lincoln, TX
Region: Southwest
Topic: Diseases and Disorders, Planting, Trees
Title: Brown spots on young redbuds in Lincoln TX
Answered by: Barbara Medford

QUESTION:

I have lined my driveway in Lee County Texas with Red bud trees purchased both in Dripping Springs and in College Station. The 14 trees are of varying ages and heights (planted during the fall and winter of 2009 and 2008). We nursed them through the past 2 years of drought, caged them from nibbling deer, etc. This spring some bloomed but not much (figured they were still young and coming off stressful first years). Some are only 3' tall while some top out at 8' or 9'. Some are in full sun and some get partial shade. Some are on clay but most in sand. This year the grasshoppers are a bit hard on them but not strippng them or anything too bad. My question is about brown spots the leaves get every year mid summer. I am not a gardener but the spots look rusty brown to me and not all the trees get this. Can you help me with this? THANKS!

ANSWER:

Whoa! Too much information! You have older trees and younger trees, trees purchased from different nurseries and planted at different times.  There are big trees and little trees, sun and shade, clay and sand. And they don't even all have the same symptoms. If we could say, yes, this is such and such a disease of redbud trees in your area, and all you have to do is go to your nearby nursery and purchase such and such a spray, spray all over everywhere, and your problem is solved, we would, honest.

But things are never that simple. Because we can't come and visit your trees individually (and wouldn't know what we were doing if we did) you are going to have to do some detective work. We will happily give you clues, but there is no way to know which problem we uncover is the right one, or even if there is only one.

All we can do is make some assumptions, like that your trees are all  Cercis canadensis var. texensis (Texas redbud), but some of them could be Cercis canadensis (eastern redbud) or even Cercis canadensis var. mexicana (Mexican redbud), all of which are considered native to Texas. They could be hybrids, they could  be selections for tallness or dwarfness or color, bred for certain characteristics. Taller ones may continue to be taller than the others, the shorter ones may be dwarf selections which will never get any bigger. So, we're going to look at some known causes of brown spots on redbuds. If it's too much fertilizer, or too little water, or soil they don't like, you'll have to decide which tree is suffering from which cause and do what you can about it. We realize that you probably want a nice uniform border along your driveway, but we hope you won't be too disappointed when we say it's probably not going to happen. 

Cercis canadensis var. texensis (Texas redbud)

10-20 ft. in ht., flowers appear before leaves in early April, prefers limestone soil, can tolerate dappled shade, but likes full sun Soil Description: Well-drained, calcareous, rocky, sandy, loamy, or clay soils, usually limestone-based.

Cercis canadensis (eastern redbud)

15-30 ft., Soil Description: Moist, fertile, well-drained soils.

Cercis canadensis var. mexicana (Mexican redbud)

Soil Description: Calcareous, limestone-based sands, loams, clays, often rocky. One of three Cercis canadensis varieties naturally occurring in Texas, the Mexican redbud is shorter and more compact in Texas than the others and is more likely to have multiple trunks. The leaves tend to be darker, smaller, and slightly ruffled along the margins.

Here are some articles to help you with your detective work:

treehelp.com Redbud Trees Notice especially this paragraph:

"Leaf Spots

Leaf spots can be a problem during wet weather. The spots appear as small brown or black spots on the top of leaves. Since the disease is rarely serious, no chemical controls are normally needed, however, in severe cases or to improve the look of the tree, spray the tree with Liquid Copper. The fungicide spray should be applied when the leaf spots are first noticed and again in about 14 to 20 days. The following spring, shortly after bud break, re-spray the tree with the Liquid Copper to ensure no over-wintering of the spot disease. Since the leaf spot fungus over winters in the fallen leaves and then re-infects the tree the following spring, it is important in the autumn to collect up and remove any leaves that have fallen to the ground."

University of Illinois Extension Fungal Leaf Spot Disease of Shade and Ornamental Trees in the Midwest.

eHow.com Redbud Tree Leaf Diseases

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