En EspaŅol

Q. Who is Mr. Smarty Plants?

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.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

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

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Thursday - April 05, 2012

From: Fort Worth, TX
Region: Southwest
Topic: Pests, Cacti and Succulents
Title: Insects on yucca from Ft. Worth TX
Answered by: Barbara Medford

QUESTION:

I have a plant labeled Yucca Soft Leaf recurvifolia that I planted about 5 years ago,& was beautiful until last summer when it became infested with thousands of fast, tiny, dark insects. I sprayed with Whitney Farms Outdoor Insect Killer (pyrethins, mostly) and that seemed to kill most, but the plant is reinfested, and the leaves are either dead or pale, light green, & spotty. Can it be saved?

ANSWER:

Yucca recurvifolia does not appear in our Native Plant Database, but this article on the plant from the Master Gardeners of the University of Arizona Pima County Cooperative Extension can give you some information on it. It appears that the reason Yucca recurvifolia does not appear in our database is because it is a synonym for Yucca gloriosa (Moundlily yucca), according to the USDA Plant Profile. Both are native to North America and the southeastern states. Of course, Fort Worth is hardly in a southeastern state, but we can probably address your question by searching on pests and diseases of yuccas.

We should first mention that we are neither plant pathologists nor entomologists. Without that kind of training and without being able to see the plant, about all we can do is give you some references with pictures to help you. We also want to mention that most insects and diseases do not strike healthy plants, but plants that are weakened by improper care, watering or fertilizing.

The Horticultular Site Diseases of Sansevieria and Yuccas:

Arizona Cooperative Extension Problems and Pests of Agave, Aloe, Cactus and Yuccas

The more we read about the problems you are having with your plant, the more we are convinced that the little black bugs are not causing the problem, but that the problems with the yucca are attracting the bugs; that is to say, fungus gnats. Yuccas are desert plants, they need to be planted in a well draining soil, perhaps half of it  made up of decomposed granite. From the article from the Arizona Cooperative Extension Program, scroll down to Page 4 and read the articles under "Poorly-drained soils" and "Irrigation." At the bottom of the same page, read "Fungal diseases." On Page 5, you will find pictures of fungal lesions.

Your final question involved asking if your plant could be saved. Frankly, this is a decision only you can make. It sounds like you need to begin at Square One preparing a planting hole in full sun, amending your (probably) clay soil with a well draining cactus soil and decomposed granite, NOT sand. The gnats are not going to leave until the diseased material is gone, so removing the plant and disposing of it should discourage the gnats. Yuccas are survivors, and it could be that in your excavations, you will find some healthy root to plant a new yucca. From GardenGuides.com, here are instructions on How to Plant a Yucca Root. Just remember, good drainage, plenty of sun, no overhead watering (like a sprinkler system), no fertilizer, and minimal watering.

Pictures of Yucca recurvifolia

 

More Cacti and Succulents Questions

Monocarpic plants for Indiana
October 06, 2005 - We were in Hawaii this summer and became acquainted with the Silversword. This plant (according to what we were told) blooms only once in it's lifetime (of 50-70 years). Are you aware of any other pl...
view the full question and answer

Spanish Dagger plant interfering with walkway in Ingram TX
April 09, 2010 - I have a Spanish Dagger that is now 8 feet tall and about to fall over in a walkway. Due to the danger of these very sharp tips I need to either cut down the plant or try to root in and replant. If ...
view the full question and answer

Worms found in Agave used in tequila
February 06, 2008 - Hi, I am a writer and have been trying to find some referenced information regarding the moth larvae/'worms' associated with Agave and some mezcal beverages - specifically, Hypopta agavis, Aegiale ...
view the full question and answer

Trimming damaged leaves on agaves
February 05, 2009 - Some of the leaves on my agaves are damaged. Can I cut them off? If yes, how can I prevent the wound from becoming infected? Thanks.
view the full question and answer

Life span of the century plant (Agave spp.)
June 17, 2009 - I have a beautiful century plant that is blooming. what will happen once the bloom is done? What is the life span of the plant?
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP | STAFF
© 2015 Lady Bird Johnson Wildflower Center