Plant Diseases/agave



leaf cose up
leaf cose up  
I'm attaching two photos, the entire plant and a closeup of a single leaf. I believe it's an agave but can't remember which one it is. It's in a large cactus/succulent bed, with specially made well draining cactus mix. All of the other plants, 20 or so are doing very well. This "spotting" started to show up about three weeks ago. The bed is never watered, we're in 9b,Orlando Fl., get a fair amount of rain but it's been unusually dry for the last several weeks. Would appreciate any help. Thanks

Dear John, First let me apologize for the delay in sending you an answer.  I have looked at your pictures and done a great deal of searching, but I can't be positive of what is wrong with your agave.  I believe I have it narrowed down to two different problems.  It doesn't look like any fungus that I've seen and these plants don't often get fungus unless they are being overwatered.  At least half of the known problems with these types of plants involve damage due to overwatering, lack of sunlight, overly rich soil, or a similar problem involving location or care.  It can also have problems due to hail or freeze damage, which is unlikely given your location.  One of these problems due to care issues is called agave edema, but it is usually caused by watering during the heat of the day.  Given that you never water this area, this isn't likely either.  That leaves the only real possibility, which is scale.  Scale is an insect which doesn't move in its adult phase, and it stays protected under a hard or waxy covering.  The covering protects the insect from most insecticides, so it must be smothered using a lightweight horticultural oil, which can be purchased at a gardening center.  Don't use vegetable oil or dormant oil.  Vegetable oil will sauté the plant, and dormant oil is far too heavy given your location.  You will need to spray the plant several times about a week apart to get rid of the condition.  However, I am concerned that these pictures don't definitively look like scale to me.  It is possible that there is some bug that has targeted this specific plant and is leaving these marks or you could have some fungus that is not listed in any common data base.  In that case you could spray with NEEM which is an organic ingredient and will kill insects, mites, and fungus.  You could actually add the NEEM to the horticultural oil and spray with the combination.  I would suggest that you do that, and whatever it is should start to look better within a few weeks.  There is one other solution, and it is a radical one, but since you have 20 other plants in this large bed that are all doing well, it might be prudent to simply eliminate this one plant and put another healthy one in its place.  Occasionally I run across plants that, despite my best efforts, remain sick, and once they are eliminated, the overall health of everything else improves.  I'm sorry for this belated response, and I regret the vagueness of this answer, but I hope this helps you somewhat.  Please feel free to ask me more questions.  Good luck, Melissa

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Melissa Johnston


Plant diseases, landscaping, tropical plants, roses, herbs, plant care, grafting, horticulture, plant identification, anything about plants I can likely answer.


35 years experience in various plant businesses, 1984 Certified Texas Master Gardener.

Master Gardener Association of Texas charter member

none as of yet, but I have a plant q&a book I am in process of submitting.

Magna cum laude graduate of Texas A&M, 1978

Awards and Honors
Plant growing awards, highest grade for Texas Master Gardener graduates.

Past/Present Clients
Past member of and was very highly rated. Owned landscape company in the past, Almost Paradise, and was very successful despite little equipment, no help, and no advertising. Lived well for two years until 9/11.

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