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

Friday - June 06, 2008

From: Austin, TX
Region: Southwest
Topic: Cacti and Succulents
Title: Leaves turning black on Agave americana
Answered by: Barbara Medford

QUESTION:

Dear Mr. Smarty Plants- We have a ~5-year-old agave americana that began to have leaves turn yellow (to black in some areas) just this past spring (2008). A neighbor's tree had started to overhang the plot it was in, putting it in substantial shade, so I cut away several large branches from the tree, thinking that lack of sun could be part of the problem. Is there anything else I can do?

ANSWER:

We really hate it when someone asks us about an obvious problem with a plant, and when we do research we are told this plant has "no serious pests and diseases," which is pretty much what we got on your Agave americana (American century plant) spots. One thing we did find out, from our own webpage (link above) is that the Agave can tolerate light shade, but really needs sun. But, we did find two websites that admitted there could be anthracnose, a fungal disease, in agaves that could cause those spots.

Michigan State University Extension Agave Disease Problems

Arizona Cooperative Extension Problems and Pests of Agave - This is a PDF document, and you will have to page down to Page 6, lower right hand column, for "Fungal Lesions." Anthracnose of agaves is discussed as a problem during moist conditions or occasionally when the garden is overhead irrigated, as in a sprinkler system or too much rain (hardly a problem right now in Austin). Unfortunately, a plant in too much shade will be more prone to fungal diseases because the sun would ordinarily retard the fungal production, drying out the moisture on the plant. The advice given for treatment is to remove the diseased leaves. And let us warn you, we have discovered that there can be severe and uncomfortable skin blistering from contact with the juices in the leaves when they are cut. Go prepared in long pants, long sleeves, heavy leather gloves, closed-toe shoes and maybe even protective goggles. Once a leaf has gone black, you can be pretty sure it is dead and needs to be removed and disposed in such a way as to prevent further spreading of the fungus to other succulents. This site did suggest one possible chemical treatment, but stated that its actual efficacy is not substantiated. We tried to find pictures of agaves with the anthracnose spots, so you could compare them to your plant, but were unsuccessful. In summary, more sun, less water, and cut out the affected leaves - VERY CAREFULLY!

 

More Cacti and Succulents Questions

Runaway Agave Americana from Pacific Palisades CA
April 29, 2013 - We live near open space on Santa Monica Mountain State Park. Our Association planted non-native, invasive Agave Americanas all over the adjacent slopes, and we are trying to get the exploding pups and...
view the full question and answer

Need plants to replace cedars on a 40 degree slope in Boerne, TX.
August 28, 2012 - My backyard is a roughly 40 degree slope that is covered with cedars. The slope is basically all rock, what can I grow here to replace the cedar which drink too much water. I would still like the area...
view the full question and answer

Is a yucca going to have a stalk from Sylvania OH
March 15, 2012 - Hi, I was wondering if the stalk on a yucca plant grows back every year after it is cut off? How to tell if it is going to have a stalk because some of my yucca's do not have one? Thank you for your ...
view the full question and answer

Cleaning up Adams Needle yucca in Vancouver Island BC
May 19, 2009 - We have Adam's needle yucca's in our the flower bed of our newly purchased home here on Vancouver Island BC. They thrive and produce impressive flowers. How do I clean them up in the spring time ...
view the full question and answer

Cactus failing to thrive in New York City
November 21, 2008 - My cactus seems to be either weak or dying. Its long stems are bending and softer than the rest. What is happening to it?
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