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Plant Diseases/A sick plant(?) and a book about plant pathology


Ms. Johnston,

Please suggest a book about plant pathology because I want to try to learn how to diagnose diseases my carnivorous plants may catch.  In college, I took biology, microbiology, paleontology, geology, and marine biology but not botany.  So if I'll need to take any other courses to understand the the book, what ones are they?

Do you know of any illness that would leave grayish spots on an S. purpurea venosa pitcher?  The spots look the way they did when I got the plant, and they're  not spreading to other pitchers.

Thank you for your help.


Dear Bill, You might not think it, but your question may be the hardest one I've ever had.  The reason is that I've been diagnosing plant diseases for about thirty years or more and I've never really thought about how I go about it.  I have worked in many plant industries, and I've had excellent teachers, plus for some reason I just seem to remember anything I learn about plants.  Remembering where I put my car keys, on the other hand, is much harder.  My advice about a plant pathology book so you can diagnose carnivorous plant diseases really involves you buying three types of books.  The first would be a general plant disease book that covers many types of diseases in many types of plants.  There is one by American Horticultural Society on "Pests and Diseases" that would be good, although any comprehensive guide with pictures would work.  Books with good pictures is crucial to identifying pests and diseases because there are many problems that sound similar but appear differently.  The next book I would suggest would be something that works similar to a flow chart and it's called "What's Wrong With My Plant and How do I Fix It?" by Deardorff.  I was impressed with this book as the first section deals with flow charts organized by where the problem occurs (leaves, fruit, roots) and how to break it down to the right pest or diseases and the second part gives organic solutions to the problems.  Lastly, I would recommend getting one or more books on carnivorous plants, as these books will generally have a section with problems and how to troubleshoot them.  Be careful though, plant books can become addicting.  And of course, if you wanted to take botany, you might enjoy that as well, although it wouldn't necessarily help you with the plant disease aspect.  As for the grays spots on the pitcher plant, it actually could have been caused by the soil being fertilized (which you should never do with a pitcher plant, as they gain nutrients from the insects they digest), and this sometimes causes some minor spotting on the pitcher.  It could also have been an old injury that has merely left a gray or sunken area.  They sometimes show up when the individual pitcher is aging and before it dies and new pitchers come along.  I would not worry if the other pitchers aren't affected.  At any rate, good luck, and thanks for such a challenging question.  If I can answer any other questions, let me know.  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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