Ask a Question forum→Calathea Maui Queen

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Name: John Osborne
West Sussex, United Kingdom (Zone 9a)
osbornespain
May 3, 2020 9:40 AM CST
I have had this plant for about 3 months. It is(was?) doing very well in a shaded, humidified, temp controlled conservatory. I re potted it shortly after buying it, and it is growing strongly from the bottom . . loads of new leaves pushing up...but... the older original leaves on the end of their long stalks have lost their shine and have a powdery appearance. I can feel the "dust" under the affected leaves . . but I cannot see evidence of red spider mite which (I think) I am familiar with. Powdery mildew springs to mind but I'm not sure about that either. I have treated with the appropriate fungal spray, and I have also used neem oil with soap (not at the same time!)
Questions are should I cut off the "infected" leaves? Can the leaves be saved?
I wonder if the light in the conservatory was too bright - there is no direct sunlight but it can be very bright. I also wonder if it is mould of some type. I keep the humidity at about 70% but maybe I have been over misting as well!! I do have several fans in the conservatory so air is circulating well enough I think.
I attach a photo of one of the infected leaves..
Thumb of 2020-05-03/osbornespain/1490df

Name: Sally
central Maryland
Seriously addicted to kettle chips.
Charter ATP Member Houseplants Keeper of Poultry Vegetable Grower Region: Maryland Composter
Native Plants and Wildflowers Organic Gardener Region: United States of America Cat Lover Birds Butterflies
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sallyg
May 3, 2020 9:49 AM CST
seems like mites attack the young soft new leaves first.. Shrug!
i'm pretty OK today, how are you? ;^)
Name: Will Creed
NYC
Prof. plant consultant & educator
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WillC
May 3, 2020 9:51 AM CST
The mottled appearance of the affected leaf and the "dust" under the leaves are clear indications of spider mites. Each tiny "dust" particle is a mite.

Treat the mites by mixing a solution of water and a squirt of liquid dish soap. Then, spray ALL leaf and stem surfaces until they are dripping wet. It is a very messy task, but unless you get complete coverage and make direct contact even with the ones you cannot see, the survivors will reproduce and the infestation will return.

Be sure to check all of your conservatory plants very carefully for spider mites. Crossing Fingers!


Will Creed
Horticultural Help, NYC
www.HorticulturalHelp.com
Contact me directly at [email protected]
I now have a book available on indoor plant care

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