Powdery Mildew - Large scale Greenhouse

[redlaser]

G `day DF

I was just looking at this study from Holland .
As far as I know they know their shit when it comes to Green Houses .
But even they are learning on the job .

Ventilation has hardly any effect on spreading mildew spores in rose



The perfect rose is not a perfect rose, as long as powdery mildew stays on its head. Researcher Kirsten Leiss has been trying to get a grip on the fungus since March last year and has already been able to draw several sensational conclusions. With a resilient plant, much profit could be achieved, is the expectation.

Every week on the same day and at the same time, Kirsten Leiss and her researchers from Wageningen University & Research walk through the rose greenhouse to scoop powdery mildew. On one side is the now five-year-old Red Naomi breed. On the other hand, the variety Avalanche, which was only planted last spring. The researchers are looking for powdery mildew and if so, where it occurs in the greenhouse and how heavy the infestation is.For this they have developed a score, with which they have been mapping the entire greenhouse every week since March last year.

No spreading through ventilation
"It is interesting to see what has come out of this," says Leiss, WUR researcher at the business unit Greenhouse Horticulture in Bleiswijk. "Firstly, we see the worst damage on the middle paths. Secondly, young shoots suffer much less from the fungus than the older leaves and thirdly, there is much less mildew infection in the young Avalanche plant than in the older Red Naomi. It is noticeable that the mildew fireplaces remain in the same places during the time.They do not move. This means that ventilation has hardly any effect on the spread of mildew spores, a rather surprising conclusion. "

That she does not find any fireplaces at the young plants Avalanche is also surprising, she says. "I doubt that this is the breed. I hear from many growers that this variety is sensitive to this fungus. I think that it is the age of the crop. This effect can also be seen in the less sensitive young shoots of the Red Naomi compared to older leaf material. It is plausible to think that this has something to do with different leaf structures and components, "Leiss assumes.

Scouting versus climate sensors
The researcher was asked at the beginning of last year to do research on powdery mildew in roses. Colleagues were working on the project 'The perfect rose, the next level', commissioned by Kas as Energy Source and with energy saving as the starting point. How can 25% energy be saved in rose cultivation? By using LED lighting and OPAC heat exchangers, they were able to make progress in energy saving, but the researchers ran into another problem: the entire greenhouse was full of mildew. Spraying with fungicides took place every five days. "They asked me if I could do something about that fungus", says Leiss. "I have started mapping out the current situation in order to get targeted measures from here."

The data from the scouting is related to the data from climatic sensors, which measure the humidity and the temperature. These sensors measure within the crop at three heights: the leaves, the shoots and the buds. There appeared to be no differences in temperature and humidity between sites with and without mildew.

Fungicides do not kill traces
The life cycle of powdery mildew consists of a powdery layer, mycelium, visible on the leaves and traces that you can not see with the eye. In the literature she found that the fungal spores germinate at a humidity of 90% and at a temperature between 20 and 25 ° C, at night. The mycelium, on the other hand, benefits from an air humidity of 60 to 70% humidity and a temperature between 20 and 25 ° C, the situation during the day.

"Because the fungus often returns after spraying, my hypothesis is that fungicides cause the mycelium to die off, but that the spores remain and thus ensure that the fungus returns. This seems to be a problem especially for a crop like rose that stays in the greenhouse for several years. "

Fungicides only kill mycelium
To test their position, the researchers developed a test in which they collect mildew spores and identify and quantify them by molecular determinations. Mildew is a fungus that only grows on living plants and not on artificial media. That is why the researchers hung air samplers between the plants, which suck in air, so that the fungal spores fall on a filter.Through polymerase chain reaction - this is a way to multiply one or more parts from very small amounts of DNA until there is enough of it to analyze it - they could identify the traces and see if there were many or few of them. "We saw that there were many more traces in the leaves package than in the shoots. There was also much more in Red Naomi than in Avalanche. "

Then they took air samples before and after the spraying and it appeared that the sprays had no effect on the amount of spores. "This result therefore answers my hypothesis," says the researcher. "Fungicides only have a hold on the mycelium."

Reduce number of tracks
The logical next question was: What to do? "We have to reduce the number of tracks," says Leiss. "Cutting out the mildew's heads will significantly reduce the number of spores."

In addition, she has three methods in mind to kill traces in a sustainable way. The first is the use of UV-C. This has a disinfecting effect, but requires discipline from the grower, because this has to be done every day. In addition, the researcher wants to test plasma water and thirdly, she wants to start with the greenhouse temperature.

"In the literature, I found that if the greenhouse temperature is more than 30ºC for 1 to 2 hours per day, the number of spores dies significantly. The mildew scouting showed that after the very hot days of last summer with cabinet temperatures of more than 30 ° C, the mildew infestation decreased considerably. But in the context of energy saving and production; which grower wants this now? "

Yet the growers, with whom she regularly consults, thought along with her. They proposed that the temperature rise to 70 to 80 º C for a few seconds per day as a test by driving along the plants with a radiator and seeing what happens next. "So now we're going to try it out in a test setup."

Resilience
But because it involves substantial numbers of spores (up to more than 10,000 per mildew), you do not just manage to reduce spores. "Surviving traces must be able to germinate as little as possible", says Leiss.

She also wants to look more closely at the crop itself. "Nature already shows us a lot. For example, young, less susceptible rose petals look very different from older rose leaves. So the plant already shows us what we can do something with. I would also like to review the leaf morphology to investigate why less spores germinate here. Perhaps with this knowledge we can make plants less susceptible to mildew. "

She has already made a PPP application to compare secondary plant content substances and to relate them to mildew resistance. Meanwhile, she continues scouting. Every week on the same day and the same time. "The results so far are very interesting and will certainly remain so. At one point there will be a tipping point in Avalanche, where a fire will suddenly arise.That is very exciting for us as researchers. "

Resume
Kirsten Leiss, researcher in Bleiswijk, is researching mildew in rose and has already made a number of interesting discoveries. For example, fungicides only kill the mycelium and not the mildew spores. In addition, older leaf material appears to be more susceptible than young shoots. She thinks that a lot of profit can be gained if the plant itself can be made more resilient.

Text: Marjolein van Woerkom.
Picture: Studio GJ Vlekke.

It would be interesting to know what fungicides were used, and specifically if paraffin or other horticultural oils were assessed.

Horticultural oil was one of the most effective treatments at a company I worked at spraying trees and shrubs in landscapes. No resistant build up, no re entry issues, acted as an antisporulant.

Saying ventilation has no impact on the spread of spores is an overreaching conclusion in my opinion. Even the author admits to being knowledgeable enough to know that high humidity/fog/rain/dew needs to be coupled with ideal temps for a few days for an outbreak to occur.

It would seem obvious that the mildew fireplaces are in optimal situations, not surprisingly next to pathways where humans and splashed water frequent.

In the article they speak of having multiple temp and humidity sensors, and from them determined that information could not predict mildew outbreaks, or explain them anyway.

There are already powdery mildew index models available showing otherwise, UCDavis has one I’ve listed in the past for grapes, easily googled. Mrs. Leiss alludes to having done this research by stating known optimal temps and humidity for outbreaks.

This article seems about twenty years old or older, based on the conclusions and observations like pm favoring older leaves versus younger ones as well, for what that is worth

 

[Elmer Bud]

It would be interesting to know what fungicides were used, and specifically if paraffin or other horticultural oils were assessed.

Horticultural oil was one of the most effective treatments at a company I worked at spraying trees and shrubs in landscapes. No resistant build up, no re entry issues, acted as an antisporulant.

Saying ventilation has no impact on the spread of spores is an overreaching conclusion in my opinion. Even the author admits to being knowledgeable enough to know that high humidity/fog/rain/dew needs to be coupled with ideal temps for a few days for an outbreak to occur.

It would seem obvious that the mildew fireplaces are in optimal situations, not surprisingly next to pathways where humans and splashed water frequent.

In the article they speak of having multiple temp and humidity sensors, and from them determined that information could not predict mildew outbreaks, or explain them anyway.

There are already powdery mildew index models available showing otherwise, UCDavis has one I’ve listed in the past for grapes, easily googled. Mrs. Leiss alludes to having done this research by stating known optimal temps and humidity for outbreaks.

This article seems about twenty years old or older, based on the conclusions and observations like pm favoring older leaves versus younger ones as well, for what that is worth

G `day RL

Grapes are out in the elements .
The paper I posted was in green houses ...

Thanks for sharin

EB .

 

[redlaser]

G `day RL

Grapes are out in the elements .
The paper I posted was in green houses ...

Thanks for sharin

EB .

How’s it going Elmer,

The powdery mildew index I referenced is based on temperature and humidity levels, and hours attained of each, scored for consecutive days.

If you don’t consider that relevant I’d be interested in hearing why.

Unless you are assuming different pm’s with different life cyclles?

Mrs.Leiss refers to the hours needed at certain temps and humidity
for consecutive days for outbreaks, same basic outline of the model I reference to.

Pm model is the same indoor or out, control theoretically could be better indoors, or much worse

 

[THC123]

Control the humidity in the greenhouse.

Use a cleanlight uvc system to treat plants curatively and preventatively.

ANd you can also disinfect the air using a uvc light in the air intake and a few more to keep killing the spores.

This method is labor intensive, especially with the cleanlights uvc system. But it leaves no residue, work perfectly and you can use it up to harvest and even during harvest just before hang drying.

Go the the cleanlights website and check crop enhancement for the cleanlights system and air cleaning for the system that kills the spores in the air.

I mean killing PM with light, it doesnt get any safer than this, I havent sprayed fungicides for years in my greenhouse and I get PM every year and I always manage to manage it or remove it completely with these lights!! Forget about spraying, use light!

 

[Elmer Bud]

How’s it going Elmer,

The powdery mildew index I referenced is based on temperature and humidity levels, and hours attained of each, scored for consecutive days.

If you don’t consider that relevant I’d be interested in hearing why.

Unless you are assuming different pm’s with different life cyclles?

Mrs.Leiss refers to the hours needed at certain temps and humidity
for consecutive days for outbreaks, same basic outline of the model I reference to.

Pm model is the same indoor or out, control theoretically could be better indoors, or much worse

G `day RL

I don`t consider it irrelevant .
The temps and humidity are relevant .

The ventilation factor was what I was emphasizing .

The article I posted is from this year .

Thanks for sharin

EB .

 

[redlaser]

Ventilation has hardly any effect on spreading mildew spores in rose

[l
No spreading through ventilation
"It is interesting to see what has come out of this," says Leiss, WUR researcher at the business unit Greenhouse Horticulture in Bleiswijk. "Firstly, we see the worst damage on the middle paths. Secondly, young shoots suffer much less from the fungus than the older leaves and thirdly, there is much less mildew infection in the young Avalanche plant than in the older Red Naomi. It is noticeable that the mildew fireplaces remain in the same places during the time.They do not move. This means that ventilation has hardly any effect on the spread of mildew spores, a rather surprising conclusion. "


The life cycle of powdery mildew consists of a powdery layer, mycelium, visible on the leaves and traces that you can not see with the eye. In the literature she found that the fungal spores germinate at a humidity of 90% and at a temperature between 20 and 25 ° C, at night. The mycelium, on the other hand, benefits from an air humidity of 60 to 70% humidity and a temperature between 20 and 25 ° C, the situation during the day.

It’s an interesting article, I have tried locating it because I’m interested in the fungicides used and any more available info, Mrs Leiss has several other articles that were easier to find.

I’m probably beating a dead horse on this by now, but it’s the first paragraph above that seems overreaching as a conclusion.

Why do established fireplaces of mildew mean it doesn’t migrate throughout the greenhouse, and conditions aren’t right in other places for an outbreak yet?

The second paragraph demonstrates an understanding of conditions needing to be met for that to occur. Either the light bulb hadn’t gone off yet or for Mrs. Leiss, or I am missing something in the translation of her work.

 

[Mountain Kine]

Again -

Look up Peroxyacetic Acid.

You can wave bye to PM.

 

[kalopatchkid]

Again -

Look up Peroxyacetic Acid.

You can wave bye to PM.

Will PAA oxidize trichomes like H202?

 

[Mountain Kine]

Will PAA oxidize trichomes like H202?

Not in my experience, but your experience may vary.

I use PAA in my wet wall tanks and have no algae or scale buildup on my evaporative cooler pads.

Same situation in irrigation lines etc.

I have a 15% concentration PAA preparation that I get from AACC.

Be very careful handling over 2% concentrations.

Correct PPE is required for use!! I have the chemical burns to prove it!

 

[gladysvjubb]

you are going to have to spray. https://search.aol.com/aol/video;_y...+trust+powdery+mildew+killer&v_t=wscreen50-bb

 

[Biologist]

Will PAA oxidize trichomes like H202?

Do you have any references I can read more about hydrogen peroxide affecting trichomes? I'm not seeing a lot when I try to google it.

 

[THC123]

LOl I really can't believe you people are still talking about praying chemicals on plants to combat PM, it is like going back to the stone age

 

[xxPeacePipexx]

LOl I really can't believe you people are still talking about praying chemicals on plants to combat PM, it is like going back to the stone age

We do live in the modern "Stoned Age" after all is said and done!

 

[gladysvjubb]

I do not know how much this is: https://search.aol.com/aol/video;_y...=1332d0fe843fd11b7f50f486de02fe22&action=view

 

[St. Phatty]

Can't help but wonder if this is slightly similar to a problem with condensing humidity in some Air Force electronics.

Is it possible that you could reduce the "habitat" for the PM by keeping temperatures higher ?

When does PM multiply ?

Only had bad PM once in about 20 years. Don't remember what I did - except a whole bunch of cleaning.

 

[Mountain Kine]

Can't help but wonder if this is slightly similar to a problem with condensing humidity in some Air Force electronics.

Is it possible that you could reduce the "habitat" for the PM by keeping temperatures higher ?

When does PM multiply ?

Only had bad PM once in about 20 years. Don't remember what I did - except a whole bunch of cleaning.

You MUST control the wet bulb point in a greenhouse or you'll never be able to chase down the humidity

 

[gladysvjubb]

Here you go, labeled for cannabis. From $15.99. https://www.growerstrust.com/products/powdery-mildew-killer

 

[THC123]

Or if you do not want to spray poison on your plants (many are systemic) use fucking light from cleanlightsystems

 

[Mountain Kine]

Or if you do not want to spray poison on your plants (many are systemic) use fucking light --> https://www.cleanlightdirect.com/en/cleanlight-home-garden.html It works 100%

PAA is organic and works on a large scale

 

[Biologist]

Or if you do not want to spray poison on your plants (many are systemic) use fucking light

Can you imagine painting this uv light over every plant in a greenhouse?