Ask a Question forum: White spots on Delphinium leaves

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Name: Sharon
Canada (Zone 2b)
Candsgee
Jun 21, 2017 3:59 PM CST
I don't know what this is or why it's occurring. Each year it happens and the plant actually flowers and then gets all grayish and withers. I would like to help it before it gets to the withering stage. Do you think Sevin will work? I don't see any pests on the leaves or underside either.
Thumb of 2017-06-21/Candsgee/1bb1de


Thumb of 2017-06-21/Candsgee/75b7de



Now it's 3 weeks later and it's beginning to bloom but is turning grayish again. No bugs still I have noticed but the whe plant seems to be covered with white blotches on the leaves.


Thumb of 2017-07-07/Candsgee/bef661
Thumb of 2017-07-07/Candsgee/240ac9

[Last edited by Candsgee - Jul 6, 2017 7:08 PM (+)]
Give a thumbs up | Quote | Post #1481092 (1)
Name: Sharon
Canada (Zone 2b)
Candsgee
Jul 6, 2017 7:10 PM CST
Candsgee said:I don't know what this is or why it's occurring. Each year it happens and the plant actually flowers and then gets all grayish and withers. I would like to help it before it gets to the withering stage. Do you think Sevin will work? I don't see any pests on the leaves or underside either.
Thumb of 2017-06-21/Candsgee/1bb1de


Thumb of 2017-06-21/Candsgee/75b7de



Now it's 3 weeks later and it's beginning to bloom but is turning grayish again. No bugs still I have noticed but the whe plant seems to be covered with white blotches on the leaves.


Thumb of 2017-07-07/Candsgee/bef661
Thumb of 2017-07-07/Candsgee/240ac9




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Tisha
Jul 7, 2017 11:16 AM CST
Till someone else becomes available ..........
Do you have low humidity? If you do I would consider spidermites and powdery mildew.
Why is the plant`s support (the string/wire) so constrictive? plts need air circulation. Would you consider loosening it a little?
Simple on a Schedule
Name: Sharon
Canada (Zone 2b)
Candsgee
Jul 7, 2017 11:34 AM CST
The support is very loose. It's just the weight of the plant resting on it. It isn't tied around it just lifting. So open all around.

As well we are quite humid for our liking but definitely not dry or low humidity I wouldn't think. We also have had rain quite a bit lately but that is normal here.

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Tisha
Jul 7, 2017 12:15 PM CST
Thumbs up as to the support system.
Did you look for spidermites?
Simple on a Schedule
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
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sooby
Jul 7, 2017 1:07 PM CST
It looks like it could be the start of powdery mildew. Compare with the pics at the top of this link:

https://www.extension.umn.edu/...

Name: Sharon
Canada (Zone 2b)
Candsgee
Jul 7, 2017 1:24 PM CST
Powdery mildew? So what should help that? Spidermites, that's what I thought before as well but I didn't see any unless really really small
Name: Sharon
Canada (Zone 2b)
Candsgee
Jul 7, 2017 1:32 PM CST
I found info on Green cure for powdery mildew but we live in Canada. Appears only in usa. Sent email to company asking where in Canada.
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
Image
sooby
Jul 7, 2017 1:38 PM CST
Green cure is potassium bicarbonate. You can use baking soda (sodium bicarbonate). You can get that at the supermarket.

Edited to add if you click on "more information on powdery mildew" on the link I gave above you'll find some suggestions for managing it.
[Last edited by sooby - Jul 7, 2017 1:42 PM (+)]
Give a thumbs up | Quote | Post #1495580 (9)

Bookworm The WITWIT Badge Moon Gardener Million Pollinator Garden Challenge Native Plants and Wildflowers Roses
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Tisha
Jul 7, 2017 2:20 PM CST
Yes, they are really small and I think they like the p.m.
@sooby- spidermites also?
Simple on a Schedule
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
Image
sooby
Jul 7, 2017 2:30 PM CST
I don't see any evidence of spider mites in the pictures but it should be possible to see them underneath the leaves, especially with a magnifying lens, if they're there.

BTW although a readly available option, baking soda is not particularly effective used alone for powdery mildew, quoting from a Dr. Linda Chalker-Scott article:

"Other treatments have been more successful in powdery mildew control, including horticultural oils, potassium bicarbonate, potassium phosphate, sulfur, milk, and even water sprays. Probably the most field success has been found in combining SBC (sodium bicarbonate - baking soda) with horticultural oils, including mineral and vegetable oils (see the Fall 2008 MasterGardener magazine). Some mixtures are so effective that they’ve been successful even on serious powdery mildew epidemics."

Full article here:
https://puyallup.wsu.edu/wp-co...

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