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Extension Agent: Death of a Live Oak

July 5, 2011 at 2:05 a.m.

By Brian D. Yanta, Goliad CEA-Ag

"Help, my Live Oak is looking more like a dead oak! It has no leaves. It has ball moss. There are scabby sections on the bark. There are little "balls" on the bottom of some of the leaves. We just built our house around these trees because they were so beautiful. It sure is dry for them now. There were millions of worms eating it last spring. Can you tell me what is killing my tree?" Yes I can . . . you just did.

Ordinarily it is not one thing that kills your tree. When an extension agent comes to your property and issues the death certificate for your tree, the landowner always wants to know what killed it. Nine times out of 10 we will not be able to pinpoint the exact cause because it is usually a combination of issues. More than likely, it is an environmental stress like a drought that can be the last nail in the coffin. It is often what we might describe as a condition called "Oak Decline."

These Live Oaks have been living through all of these problems for hundreds of years before we got here, and I imagine they will be doing the same for hundreds of years after we have gone.

Ball moss, Spanish moss, lichens and mistletoe are commonly found growing on shade trees in Texas. Of these, only mistletoe is classified as a parasitic plant on ornamental shade trees. Lichens, ball moss and Spanish moss, although found on trees, are not feeding on the tree, but only using the tree for support.

Stresses associated with construction are very common. Live Oaks, in general, are fairly tolerable of construction damage. If they are looking weak near a jobsite, time usually will alleviate the problem and they should come out of it by the next spring. However, if they are already stressed by the aforementioned problems, they may not.

Don't associate your fallen leaves with balls. These "balls" are galls. Gall formations have been observed in this area on red oak (cottony gall and apple gall), live oak (gouty oak gall), hackberry (nipple gall), pecan (phylloxera) and live oak (red "berry galls" on the bottom side of leaves). Spraying after you see galls won't make them disappear. They're part of the leaf, not the insect that causes them. Preventive spraying, repeated several times earlier in the year, possibly could have reduced the population of this tiny, wasp like insects that cause this growth. Despite their undesirable appearance, they don't kill trees.

Improvement in environmental conditions on a large scale (such as some rainy years) of infected trees growing in shallow or particularly sandy soils will increase the appearance of declining trees. There is not much more that we can do to assist our trees with their stresses. Unless they are around the house, most of the treatments and remedies that we sometimes recommend will be too cost prohibitive to utilize out on the landscape in the pastures.

Brian Yanta is the Goliad County Extension agent.



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