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Plant Diseases/Expert Profile

John Cawly

On Vacation
returns 12/31/2017

I can help with identification and possible treatment of plant diseases that affect houseplants and horticultural species, to include both biological (fungal, bacterial, viral, parasitic etc.) and environmental/cultural (watering, potting media, etc.) aspects.

Experience in the area

Practical experience with a wide variety of houseplants and greenhouse plants, including cacti, euphorbia, african violets, amaryllus, and many others.


American Phytopathology Society
American Society of Plant Biologists
American Society for Virology


Molecular Plant Microbe Interactions
Proceedings of the National Academy of Science (in print)
Rhodora -- Journal of the New England Botanical Society
Allelopathy Journal


BS, Southern Illinois University - Biological Sciences
MS, Southern Illinois University -- Biological Sciences - Genetic Engineering Specialization
PhD, University of Missouri Columbia -- Plant Microbiology and Pathology
(Viral Diseases specialization/Biotechnology Emphasis)

Average Ratings

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    K = Knowledgeability    C = Clarity of Response    P = Politeness
luca01/09/15101010Thank you a lot, you've been very .....
Armaz02/10/12101010How wonderful that people like John Crawly .....
Jim01/11/12101010Thank you for the prompt response. I .....
green01/03/11101010I could have been more clear, but .....

Recent Answers from John Cawly

2015-03-17 Savannah holly:

Hi Jeff,    By my observations in the photo, it appears that you have some gall formation.  These are usually the result of fungal infestations or, in some species, bacterial infections (e.g._Agrobacterium

2015-02-15 White stuff on leaves:

These look like mealybugs or possibly juvenile scale insects.  Scale insects are problems for most citrus plants.  (I have the same thing in my greenhouse.)  Whether mealybugs or scale insects, the treatment

2015-01-14 trumpet flowers:

Hi Peggy,    Sorry for not answering you sooner, I have been out of town.    It is not unusual for plants to drop leaves when brought into the very dry environment of a home.  With the very low light conditions

2015-01-05 nicotine solution uptake by plants roots?:

Hi Luca,    I am not a biochemist as such, but I will give you what I know.    I am afraid that nicotine will not be taken into the plant easily via the root systems.  The uptake of water and other nutrients

2012-02-27 DISEASE ON BASIL:

Sorry for the delay in answering.      Your photograph shows leaf spots which are characteristic of three fungal diseases (caused by _Cercospora_ spp., _Alternaria_ spp._, and _Colletotrichum_ spp.) that


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