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Sunday - June 08, 2008

From: Alpine, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Black growth on sotol plants
Answered by: Barbara Medford

QUESTION:

My mature sotol plants have a black-like growth on the leaves. Is there any thing I can do to treat what looks like a disease on these plants?

ANSWER:

There are three plants going by the common name sotol in our Native Plants Database. They are: Dasylirion wheeleri (common sotol), Dasylirion leiophyllum (green sotol, and Dasylirion texanum (Texas sotol) . It really doesn't matter which yours is, they are very similar in appearance and culture. One surprising fact; they are not members of any of the cacti or agave families, but of the Liliaceae, or Lily, Family. Furthermore, Alpine, Texas would seem to be an ideal environment for them to grow.

We found two good websites discussing these plants: Texas A&M Horticulture Desert Sotol and Greenbeam.com Dasylirion ssp. What we did NOT find was much of any suggestion of what would be causing the spots on your sotol leaves. However, we have had several inquiries about various succulents and desert plants being grown in gardens that involved similar spots. We have learned from various sources that there are fungi that will attack otherwise very healthy plants if the atmosphere is too humid, or the plants are too well fertilized and watered. The best therapy we can recommend is to cut out the involved leaves, and dispose of the cut leaves so there will be no opportunity to transmit the infection to anything else. Be sure that the drainage in your sotol bed is very good, that water never stands there, and that it is not watered from overhead, except by rain, which has been pretty rare this year. Especially cut out any leaves on the lower part of the plant that are affected, so they will not continue to transmit the problem upward from the soil. These plants are evolved, over millennia, to survive in very difficult circumstances-rocky soil, no shade and very little moisture. It appears that when things get a little too plush for these plants, the very opportunistic fungi will leap in to share the wealth.

Dasylirion wheeleri

Dasylirion leiophyllum