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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

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Tuesday - May 13, 2014

From: Austin, TX
Region: Southwest
Topic: Pests, Shrubs
Title: Webs on limbs of evergreen sumac from Austin
Answered by: Barbara Medford

QUESTION:

We have a mature Evergreen Sumac (Rhus virens) that has spider webs on the end of some limbs. The end of the those limbs have died although new growth is coming on further up the limb. We live in the west Austin west of Loop 360 in the hills. Do you know what this is and, if so, how to keep it from spreading the rest of the tree? Is it a natural reaction to the drought, possibly? Eddie Sutherland

ANSWER:

The first suspect in this scenario is the spider mite. See this article from the University of California Integrated Pest Management site on spider mites. Compare the pictures and descriptions with those on your plant.

Most frequently, when we hear of webs on plants, we think of webworms of several types. The webs are tents for various forms of caterpillars, frequently the larvae of a white moth. From Texas A&M AgriLife Extension, here is an article on webworms.

Various forms of control suggested included spraying with water or with soapy water. The most freqent tip was to keep the leaf litter beneath the affected plant cleared up year round to deny the moths and caterpillars shelter and breeding grounds.

There is always the possibility that drought-related stress can take a toll on plants and make them more vulnerable.

 

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