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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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Sunday - April 14, 2013

From: Aledo, TX
Region: Southwest
Topic: Pests, Seeds and Seeding, Cacti and Succulents
Title: Black bugs on yucca from Aledo TX
Answered by: Barbara Medford

QUESTION:

We have flowering yuccas that have thousands of small black bugs that seem to be hurting the plant. They are not on any other foliage in our beds. What do I use to get rid of them??

ANSWER:

When we answer a question about a plant, we always like to have a more specific species for an example. There are 28 yuccas native to North America and 18 native to Texas. According to this USDA Plant Profile Map Yucca pallida (Pale-leaf yucca) is native to Parker County. That may not be the precise yucca you have, but the bugs on it would probably be the same for all members of the Yucca genus.

We believe you might be seeing the larvae of Tegeticula yuccasella or yucca moth. At the Lady Bird Johnson Wildflower Center, we frequently clean the seeds that have been gathered of native plants in Texas, including the yucca. Sometimes when we have young people volunteering for this, we get a certain amount of squealing when a little black worm emerges out of the center of a stack of yucca seeds in their pod. Those seeds have to be abandoned and not saved for our seed bank, because the depredations of the moth larvae have destroyed the usefulness of the seeds. Please read this article on Yucca and Yucca Moths from the Chihuahuan Desert Center. The yucca and the moth are interdependant so destroying the moth is not a good practice.

If, however, you feel that it is something else that is damaging your plant, read this article from Arizona Cooperative Extension on Problems and Pests of Agave, Cactus and Yucca.  You will have to scroll down to Page 6 to find the section on Insects. If some of these match what you are seeing, the article gives some management suggestions.

 

From the Image Gallery


Pale-leaf yucca
Yucca pallida

Pale-leaf yucca
Yucca pallida

Pale-leaf yucca
Yucca pallida

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