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Old May 10, 2018   #16
bower
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Well I did a hunt through my files as well as google and couldn't find that reference to spore timing, which I read maybe 3 years ago or 4 when we had a humid summer and the mildew turned up in greenhouse. At the time they were talking about two different species of mildew on tomato, and now they are talking about three.

There's quite a bit out there if you google "diurnal cycle mildew" or something of the kind, but involving the mildews on all kinds of plants - however there is cross infectivity to tomato from eg onion mildews and others. Weeds (vetch, clover, forgetmenot here) are often hosts. One of the key IPM strategies for greenhouse is also to remove weeds that host the mildew from the area, where they can blow into the greenhouse.

Anyway I may have got it wrong about spores being released at dusk. From what I'm reading now, it looks like the "conidia" (infective particles equivalent to spores) are germinating and developing during the night.

There's a general ref to mildew cycles in
https://www.annualreviews.org/doi/fu....081407.104740
The Powdery Mildews: A Review of the World's Most Familiar (Yet Poorly Known) Plant Pathogens Glawe,2008
"Conidial production and release frequently follows a diurnal pattern, with most spores becoming airborne in the period extending from mid-morning to early afternoon.."

Here's another study, looking at relative humidity, light levels and temperature. This one reports germination occuring in darkness - spore release conversely is prompted by daylight and by rapidly changing temp/light/humidity conditions at the leaf surface as happens on a sunny day.
https://apsjournals.apsnet.org/doi/p...HYTO-98-3-0270

Another study trapping spores in the wild: in dry weather, Erysiphe (one of the mildews), Alternaria, smuts and rusts were most abundant afternoon
Phytophthora infestans max concentration before noon
https://www.sciencedirect.com/scienc...07153653800343

I guess the take home message about the diurnal cycle is that they do land, germinate and produce a new batch of infective particles within the 24 hours. So the worst thing you can do is wait a day.

Some other treatments:
https://www.tandfonline.com/doi/abs/...nalCode=tcjp20
fermented milk byproduct + surfactant
citrus oil + borax
potassium bicarbonate

Some genetic resistance identified here:
http://ipm.uconn.edu/documents/raw2/...ato.php?aid=39
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Old May 10, 2018   #17
Dutch
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Wow Bower,
Absolutely fantastic research, analysis, and write up!!!
Thank you, thank you, thank you!!!
I have one final word of caution on treating diseases and Marsha has often stated it in reference to using copper based products; use it at no more than half strength. This is especially true when using bicarbonate based products on very young plants where I have seen growing tip damage happen even at half strength.
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Last edited by Dutch; May 10, 2018 at 02:11 PM. Reason: Grammar
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Old May 11, 2018   #18
oakley
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Yes, thank you for the research.

This is from 2001, and the advice I followed in the past.
https://attra.ncat.org/attra-pub/viewhtml.php?id=126

I usually drench my summer squash starting mid July and every two weeks. Cucumbers
sometimes get PM so they get a bath as well. Nothing else seems to suffer so this is new.
Like mentioned, last year I did not have much issues with PowderyMildew.
(I was pro-active using just baking soda)

I found my potassium bicarbonate in the barn. Never opened last year. From Amazon.
And the carrier soap/oil I use...
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Old May 11, 2018   #19
oakley
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I've been up in the mountains off-grid a few days. Back last night before sunset so
I sprayed one leaf around 6pm. This morning 12 hours later...(pic)

I used 1/4 tsp SB, and 1/2 tsp carrier oil. Hot water to dissolve, then topped with cold
after 20 min and a few shakes. 1 pint total water.

*I have been removing infected leaves especially those treated earlier with
peroxide/vinegar that died anyway within hours. (just the treated leaf died)
I'm prepared to sacrifice a plant or two by treating the entire plants.

So far this treatment has not caused leaf death.
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Old May 11, 2018   #20
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Soap ingredients. Nice thing about it is the lack of any bubbling during
shaking...very oily and disperses in water easily. Just a test. We shall see how
well this goes.
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Old May 11, 2018   #21
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That looks like lovely stuff, Oakley. And the plants look well pleased!!
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Old May 11, 2018   #22
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Oakley, thank you for starting thread and sharing your experience with this infection. I had a bad infection of powdery mildew run through my greenhouse. I do not know which of the three strains of powdery mildew caused the outbreak, but two tomato varieties were relatively unaffected by it. They were Champion II, a hybrid and Tasmanian Chocolate, an open pollinated variety, from the Cross Hemisphere Dwarf Project.
I am looking forward to learning more from your experiences in dealing with this tomato disease. Thanks again for sharing your methods and observations.
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Last edited by Dutch; May 11, 2018 at 11:47 AM.
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Old May 11, 2018   #23
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Going back through pictures, and why having a cell phone is so valuable being always with
me, I can look back and review...first signs of this were April 19th. (first pics posted above.)

So far no other seedlings, potted up plants in 4inch pots, are showing signs. Just rugosa leaves
from a few dwarfs and the early started micros....fine until April 19th. Now in one gallon grow
bags outside. Everything is outside except micro greens under lights.
All plants are very healthy so I maybe nipping this at first sign is pro-active.
I went ahead and did a spot-hit on the 1/2 dozen other leaves since they seem to be
healthy after spraying.
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Old May 11, 2018   #24
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Yes, Oakley that link is really helpful too. This disease is really devastating. It only affects us here when the weather is hot and humid - usually not for long. But a couple of weeks is enough to defoliate the plants that are in the line of fire - breeze from greenhouse windows. I have since done a lot of work on the area near the greenhouse, made new beds for garlic etc. Weeded right out, and that has reduced the incidence since then. But I didn't know about the potassium bicarbonate or anything else that could be used to protect the plants.
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Old May 12, 2018   #25
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"It only affects us here when the weather is hot and humid -"

What day and year was that?

So we had light rain all night. Damp and intermittent rain all day. I went ahead and hit two plant full
soak. Found one spot on a 4inch pot, potato leaf plant. Soaked the leaf. Rain has stopped and plants
are dry-ish. No signs today. No leaf death on soaked plants. (most are under the eaves hardening
off).

So far so good. If I see a return I may up the potassium Bicarbonate amount in the mix....
baby steps.
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Old May 22, 2018   #26
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Just a quick up-date.

We have had so much wet damp rainy weather.
Last Spring we went from heat on to AC overnight. A few late frosts.
This Spring it has been very wet but comfortable. 65-70, a few 75-80 days.
No late frosts. May have a stellar fruit tree year. No frost in 10 day forecast.

Still finding mold spots. About 10 spots on various leaves, usually rugosa.
No plants are suffering from various applications.
Too hard to tell if this is going to be a big long term issue or not.

I've added a cannabis growers method using peroxide/h2O and wiping spots with a
cotton ball. Easy to mix just a small amount. Still giving a light spray of the soap mix on
larger plants.

Just might have to start a weekly/bi-weekly spray schedule like some do that I've never needed.
The copper, permethrin, SB or some similar rotation.

At this point I'm just keeping one step ahead by inspection.
So far everything looks pretty healthy.
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