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Plant Diseases/unknown disease


QUESTION: I have some florida native toothache trees, I assume Zanthoxylum clava-herculis. Very slowly, only on one tree, some leaves on one branch turned brown, that branch died then another branch started turning brown. It is spreading to a nearby tree now. I only saw one small fluffy white scale-type insect, and giant swallowtail caterpillars love the trees. I included pictures of the tops of 4 leaves, and a branch on the tree which has totally succumbed to it, other branches have not fully died like this. On the bottom, you can see some small bumps throughout the leaf, best on the 2nd leaf, they seem to be in the leaf because I couldn't scratch them off.
Another expert I asked, said he did not have enough information, what else do you need? Should it go away if I cut off the bad parts. The plants are in pots so I can separate them.

ANSWER: Dear Shelly, I am not absolutely sure what exactly is plaguing your trees, however, I can still give you a very good solution to your problem.  It is very helpful that these plants are in pots, as this will make them very easy to spray.  I am not sure if you have a fungus, or perhaps you have a fungus in addition to something eating your trees.  It does look a bit like spider mite damage in the second picture.  What I would do is to combine a strong fungicide with NEEM and this will ensure that everything that may be affecting these trees will go away.  NEEM is very effective in getting rid of insects, spider mites, and fungus, however, when I have a severe fungus I prefer to get rid of it with a stronger fungicide.  Look for a product containing the active ingredient Proprioconozole.  There are other good fungicides if you can't find this one, but I prefer that or the ingredient Chlorothalonil.  Look for the ingredient, not the name brand in choosing garden chemicals.  Be sure not to chew the leaves (for toothache) for a few weeks after spraying, or until the condition improves.  You will probably have to spray about 3 or 4 times about 5-7 days apart to be sure the disease is gone.  In the meantime, make sure that the plants are evenly watered, but that NO WATER remains behind in any saucer under the plants.  Also make sure they have a reasonable amount of sunlight.  Be sure to discard any fallen leaves and do not compost.  This should clear up your problem, but write back if you have further problems.  I apologize for the lateness of this reply, but I didn't see it in my inbox.  Very sorry for the delay, and I hope that your trees get better soon.  Good luck, Melissa

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QUESTION: I appreciate that you gave a natural remedy with the Neem, I don't use chemicals. I was planning on doing a baking soda spray, but have not started it yet. Would it be effective if I did a combo neem and baking soda, or would that be counter effective? Maybe I could do one before the other, or just one at all. For Neem, would I put a teaspoon of neem oil in a spray bottle?

Dear Shelly, I applaud your efforts to stay organic.  Except for an occasional fungicide on an orchid, that's how I treat my garden as well.  In that case, I would strictly go with just the NEEM, being very careful to keep the garden clear of fallen bad leaves.  That should clear the tree up just fine.  I wouldn't go with the baking soda, because there is a possibility that you could burn the leaves from the base, or just leave a residue on the leaves.  For the NEEM, I would put a teaspoon or two in a spray bottle, or get a pump up sprayer and put the mix in there.  Pump ups are so convenient because it is easier than the trigger sprayer.  You almost can't overdo the NEEM - it is literally so safe an ingredient that you can bathe in it with no ill effect.  It does cover insects, mites, and fungus, so it should be a great all purpose method that you can use.  Hope this information helps.  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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