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Wednesday - December 26, 2012

From: San Antonio, TX
Region: Southwest
Topic: Diseases and Disorders, Shrubs
Title: Mountain Laurel slowly dying in San Antonio, TX
Answered by: Jimmy Mills

QUESTION:

My Texas Mountain Laurel seems to be dying in a slow unusual manner. Over the past two weeks the leaves have been turning yellow and falling off starting with the south facing side of my multi-trunk tree and moving to the north facing side. Leaves from all trunks seem to be falling off. About 1/3 to 1/2 of the tree has shed it's leaves. What's more unusual is the newest leaves that grew this past spring seem to be unaffected (so far). But since the tree was heavily attacked last spring by worms, there wasn't much new growth I could save by the time I treated the worms with two separate rounds of BT and Spinosad. Therefore each of the barren branches have only a few inches of green leaves still on them, right at the tips. This tree was transplanted 7 years ago and has done tremendously well (doubling in size to around 12 ft high) until last year when it was attacked by the caterpillars and one of it's trunks died for no apparent reason. It was planted by Millbergers nursery in a raised bed that is also on a slope of a hill so I truly don't believe drainage is an issue. It was on a drip system until the first trunk died and I removed it's emitters in fear that it might have been getting overwatered, while still taking care to make sure it was getting occasional water. No pesticides or roundup of any type has been used near it as well. I also lightly fertilized it this summer with Medina organic granular fertilizer. I can't find anything describing a Texas Mountain Laurel dying in this slow type manner from left to right while keeping (for now) it's newest growth. There are multiple Mountain Laurels in other yards all around me that are doing fine. Obviously the tree is in extreme stress, but my question is do you have any other ideas of what I can possibly do to save what's left of my beautiful tree? Thank you!

ANSWER:

Texas Mountain Laurel Sophora secundiflora (Texas mountain laurel) is often described as being relatively disease and pest free, however it can be attacked by the Genista caterpillar , sometimes referred to as Sophora worms. These two links describe the caterpillars and suggests management options.

Another common comment about Sophora is that it doesn’t transplant well. You apparently had a six foot sapling transplanted seven years ago, and has so far done well until last year. A question for you to consider is what changed in the plant’s environment at this time? One red flag is your mention of drip irrigation. Sophora is very particular about having its feet wet. Also, fertilizing plants in stress is something we recommend against.

Although the plant was transplanted seven years ago, the symptoms sort of sound like transplant shock. This link explains causes and remedies for this malady. This answer to a previous question about a similar situation also has some good advice. The directional nature of your plant’s demise might be explained by the the fact that the south-facing side of the plant is generally getting more intense sunlight during the day than the north-facing side.

From the Image Gallery

Texas mountain laurel
Sophora secundiflora