Powdery Mildew -prevention-treatment

Anyone with solid info on the subject feel free to drop it here ill be adding to it as i find more goodies, im gonna crusade against this shit in hopes i can help maybe 1 person not have to trash their buds.
Part 1

How to Beat Powdery Mildew
BY URBAN GARDEN MAGAZINE ⋅ AUGUST 6, 2009 ⋅

If there’s one grower’s gripe we hear lots about at Urban Garden HQ it’s Powdery Mildew. So we asked our heavyweight in the pest control department, Zorro Torro, to lend some expert advice on what this nasty stuff is, what damage it causes your plants, and, most importantly, how to beat the crap out of it!
You’ll know powdery mildew has paid your plants a visit when it looks lot like confectioners’ sugar has been sprinkled on the plant leaves. At first it may be hard to spot as it might appear on just a small portion of the leaf appearing as an irregular circle. But it quickly spreads and soon appears on the surrounding vegetation. Soon the entire leaf is covered and at the same time colonies develop on the surrounding vegetation and in other areas of the garden.
So how does it all start? Well, the plant becomes infected when an airborne spore, or conidia, lands on a leaf and germinates. It soon grows a guide tube that attaches tightly to the leaf. Then it pierces the plant cell wall and membrane and inserts a hollow tube that sucks up plant nutrients, weakening the leaf and slowing growth. Within a week the fungus produces tiny mushroom stalks that release millions of spores, ready to infect more leaf surfaces. The fungus also produces a secondary spore, which over-winters outdoors and may also hide in a greenhouse or indoor garden even after the crop has been harvested.
Powdery mildew is most likely to attack the young leaves, up to two or three weeks old.
A dozen or so different fungus fall under the heading of Powdery Mildew, but two different fungus species are the most likely culprits. L. taurica, tends to attack warmer gardens. It prefers a temperature of about 77 °F (25 °C). S. macularisprefers a cooler temperature; however, the more virulent stain found in indoor gardens today has adapted to tolerate more heat. Both strains thrive in moderate humidity and are not injured by water. Their conidia can live in water for short periods and are mobile in it. However, strong water sprays do destroy some conidia.
CULTURAL CONTROL
Heat

Powdery mildew is sensitive to heat. Neither species will grow at 90 °F (32 °C). and will quickly perish when above 100 ° F (38 °C).
To get a complete kill maintain the temperature for an hour. This may not be a feasible option in most indoor gardens for several reasons. The first is that it may be difficult to heat the space to such a high temperature. The second is that even a single peak of 100 ° F (38 °C) affects the growth of plants. Vegetative plants with flowers or fruits in mid stage growth (weeks 3-7) may stretch a little from the experience. The heat treatment has relatively little effect on first and second week flowers or flowers nearing maturity.
You can minimize heat’s impact on plants in several ways. Heat the garden at the end of the day, as the lights are turned off. Since the plants are not photosynthesizing, they have lower water needs.
If the plants are being grown hydroponically, lower the temperature of the water to 60 degrees. Keeping the roots cool will help the upper plant parts beat the heat. It’s not difficult to do this, even if you don’t have a water chiller. Just add ice to the reservoir or flow through system. Roots of plants growing in soil can also be cooled using thermal ice packs at the base of the stem.
The heat treatment should kill off most of the fungus and its spores. The chances are there will still be some fungal re-growth. These can be eliminated using spot treatments.
Pruning
If one particular plant seems to be infected with a few tiny white spots on a few of its leaves, get a bag large enough to drop the leaves into and then cut them off into the bag. Remove the bag from the room. This prevents spores, the white powder on top of the leaves, from becoming airborne while being removed. Remember to wash your hands and clean the scissors or knife with soap and water, hydrogen peroxide, alcohol or bleach. Spray the plant with one of the sprays listed below after pruning to prevent re-infection and encourage healing.
If, you notice a re-infection a few days later, there is a good chance that this plant is very susceptible to powdery mildew and presents a good location for the infection to start and spread from. The plant should be removed immediately by placing a bag over it and removing it from the space. Then the space should be sprayed with one of the sprays listed below.
ORGANIC and IPM CONTROL
Here are some sprays that you can use to control the powdery mildew in your crop. All of these are safe to use for herb or for edible crops. Sprays are washed away by water, including rain.
Cinnamon Oil and Tea
Cinnamon is an effective destroyer of powdery mildew, with an effectiveness rate of 50-70%. It won’t kill it completely but it will keep it in check somewhat. It also potentiates other suppressive sprays so it is good to use in combination. To make your own, boil water, turn off the heat and add one ounce of ground cinnamon to one and a half pints water. Let the tea cool to room temperature. Add half a pint of 100 proof grain alcohol or rubbing alcohol and let sit. Strain the cinnamon. The spray is ready to use. A faster method is to add 2 teaspoons cinnamon oil to one pint of water and a dash of castile soap. Other herbs are also fungicidal. Clove, rosemary, and wintergreen oils are used in some botanical fungicides. The solution should consist of no more than 2% oil.
Garlic
Garlic is antifungal and anti-bacterial and has several pathways for destroying fungi including its high sulfur content. It can also be added to other anti-fungal sprays. Several garlic sprays are available commercially.
A homemade formula: Soak three ounces of crushed garlic in one ounce of neem or sesame oil and 100 proof or higher drinking alcohol or 70% or higher rubbing alcohol for a day or two. Strain. Then soak the garlic in a cup of water for a day. Strain. Mix the oil/alcohol, soaked water and 1 tablespoon liquid castile soap in a gallon container. Then fill with water and shake. The formula is ready to use.
A simpler brew consists of a teaspoon of garlic oil in a pint of water. To keep the oil and water mixed add a 1/8teaspoon of soap. Use garlic as a vaccination. Spray on new growth before there is a sign of infection.
Garlic is a general purpose insecticide as well as fungicide, so it should be used with caution on outdoor plants. It kills beneficial insects as well as plant pests.
Hydrogen Peroxide
Hydrogen peroxide (hp) is a contact fungicide that leaves no residue. It is an oxidized product of water and has an extra oxygen atom that is slightly negatively charged. When it comes in contact with the fungi the oxygen atoms attach to molecules on the cell walls, oxidizing or “burning” them.
Household hp sold in drug stores has a concentration of 3%. Garden shops sell 10% hp. Zerotol® contains 27% hydrogen peroxide and an unstated amount of peroxyacetic acid. Together they have a more potent chemistry than hp, with an activity of about 40% hp. It is considered hazardous because it can cause skin burn similar to that caused by concentrated acids.
To treat plants with drug store grade 3% hp use 4 1/2 tablespoons and fill to make a pint of solution, or a quart of hp to 3 quarts of water. With horticultural grade 10% hp use about 4 teaspoons per pint, 5 ounces per gallon. With Zerotol® use about 1 teaspoon per pint, 2 1/2 tablespoons per gallon.



Gweedo

How to Beat Powdery Mildew
BY URBAN GARDEN MAGAZINE ⋅ AUGUST 6, 2009

Part 2

Limonene

Limonene is refined from the oil of citrus rinds. It has a pleasant citrus odor and is the active ingredient in many of the new cleaning products. It also has fungicidal qualities. I’ve used pure diluted limonene and it controlled powdery mildew, but did not eradicate it. Perhaps a higher concentration would have been more successful. Start using 0.5-1% limonene in water 1/2-1 teaspoon per pint.
Milk
Milk kills powdery mildew so well that both home and commercial rose growers all over the world have adopted it for their fungicidal sprays. Use one part milk to nine parts water. I’ve only used 1% milk, but other recipes call for either whole or skim milk and use up to 1 part in 5 milk. Some recipes add garlic or cinnamon to the mix. When using more than 30% milk, a benign mold is reported to grow on top of the leaves. Use a milk spray at the first sign of infection then protect the new growth weekly.
Messenger®
Messenger’s active ingredient is a naturally occurring protein called harpin that stimulates the plant’s own natural defense system. It has been proven to promote more vigorous hardier plants that are more resistant to disease and have increased yields. It is used to prevent infection and decrease its virulence
Neem Oil
Neem oil is pressed from the seed of the neem tree (Azadirachta indica), native to Southeast Asia, but now cultivated worldwide. Neem oil has low mammalian toxicity. It degrades rapidly once it is applied so it is safe for the environment including non-target species and beneficial insects.
Neem oil protects plants with its fungicidal properties: it disrupts the organism’s metabolism on contact, forms a barrier between the plant and the invading fungus, and it inhibits spore germination. It has translinear action, that is, it is absorbed by the leaf and moves around using the leaf’s circulatory system – it can also be used as a systemic. When it is applied to the irrigation water it is absorbed by the roots and delivered throughout the plant. Adding a 0.5% solution, about 1 teaspoon per quart, to the irrigation water will protect the plant from infection.
Neem oil is best used before the plant or the garden exhibits a major infection. By using it before powdery mildew appears, it prevents the spores from germinating. It should not be used on buds or flowers.
Oil Spray
Growers have used different oil sprays to prevent and cure fungal infections. Until recently most horticultural oil sprays were made from petroleum distillates. However, most organic growers have switched to using botanical oils. Aside from the safety factor botanicals such as cottonseed, jojoba, neem and sesame oils have fungicidal properties. They can be used in combination with other spray ingredients listed here. The oils are mixed at about 1-2% concentrations. A 1% solution is about a teaspoon per pint or 3 tablespoons per gallon. Add castile soap to help the ingredients mix. Oil sprays should only be used on the leaves, not the buds or flowers. Use weekly on new growth.
pH Up
pH-Up is a generic term for alkaline pH adjustors, used to increase water pH in indoor gardens. They come as either a powder or liquid. Its active ingredient is usually lye (KOH) or potash (K2CO3).
Fungi require an acidic environment to grow and die in alkaline environments. Changing the leaf surface environment from acidic to alkaline clears up the infection. An alkaline solution with a pH of 8 will make the environment inhospitable for the fungus and will stop its growth. This is one of the simplest means of controlling the fungus. It can be used on critically infected plants.
Potassium/Sodium Bicarbonate
Potassium bicarbonate (KHCO3) and Sodium bicarbonate (NaHCO3) are wettable powders that change the pH of the leaf surface toward alkaline. Another reaction takes place; the fungus cell wall actually bursts in the presence of bicarbonate. Potassium is one of the macro-nutrients used by plants and therefore is preferred over sodium, as sodium can build up in the soil. Sodium bicarbonate can be found in your kitchen (baking soda), so some prefer it for ease of obtaining. Both are more effective when used with an oil and spreader such as castile soap. They can be used to cure bad infections and prevents new ones.
Use one teaspoon of bicarbonate powder, a teaspoon of oil and a few drops of castile soap in a pint of water, or 3 tablespoons each potassium bicarbonate and oil and a half teaspoon soap in a gallon of water. Spray on new growth.
Serenade® and Sonata®
Serenade® and Sonata® are composed of different bacteria. They use different pathways to stop mycellial growth. They are considered totally safe to humans and animals since the bacteria attack only fungi. Watch out if you are a mushroom, otherwise you are safe. The two bacteria work well together.
They are easy to use, quite safe and effective.
Sulfur
Sulfur has been used to control powdery mildew for centuries. Sulfur sprays can be used indoors but they are not popular because of residue that remains on the plant. In greenhouses gardeners use sulfur vaporizers that heat elemental sulfur to the point of vaporization. The sulfur condenses on all surfaces including the leaves. A fine deposit of very low pH sulfur granules covers the leaf surfaces. The low pH environment inhibits fungal growth. The heaters use a 60 watt light bulb to heat sulfur which is held in a container above the light. The bulb supplies enough heat to evaporate the sulfur, but not enough for it to ignite. The problem with vaporizers is that they also leave a fine sulfur film on the leaves and flowers.
Active mildew: 7 to 8 hours per night 1 to 2 times a week.
Preventative maintenance: 4 to 5 hours once a week
Vinegar
Apple cider vinegar is toxic to powdery mildew because of its high acidity (low pH). Use it at the rate of 1 tablespoon per quart of water several times a week . Some gardeners recommend alternating using vinegar with potassium bicarbonate and milk.
PREVENTION
· Isolate all new plants in a separate area where they can’t infect other plants.
· Filter incoming air to prevent spores from entering the room in the airstream.
· Install a germicidal UVC light, like the ones used in food handling areas. The light is fatal to all airborne organisms passing through the appliance. This will kill powdery mildew spores that are airborne.
· Spray the leaves with neem oil weekly. Neem oil presents both a physical barrier and a chemical deterrent.
· Cinnamon oil and cinnamon tea can also be sprayed as a powdery mildew preventative. If you are using cinnamon oil use 1 part oil to 200 parts water. (1 teaspoon oil in a liter of water.)
 
Some more good info
Another suggestion from a fellow member @SCJedi

Foliar spray formula and directions


This is what I do but keep in mind that this has a lot of oil and that trichs are also mostly oil. It can be really detrimental to your plant to spray late, or at all.

When using the Essential Oils for the first time, use it at a dose of maybe 2mL per Gallon. If you up to 10mL the first time, the plants, which are not used to the oils, may get burned. Start low and work your way up.

IPM 1-1: Foliar Spray

Container #1
2 cups of Warm Water
1.5 tsp Potassium Silicate (emulsifier)
1 tsp Aloe Vera Extract 200x

Container #2
1 tbs Mixed Essential Oils (ex. Cinnamon, Clove, Rosemary, Thyme)
1.5 tsp Neem Oil
1.5 tsp Karanja Oil

Container #3
1 Gallon of Warm Water (minus the 2 cups from Container #1)


Directions:
Mix Container #2 into Container #1
Stir, stir, stir
Pour into Container #3
Stir, Shake, Stir
Put into a sprayer and use immediately


Use up to 10 ml of mixed essential oils (usually 3 or 4 kinds):
Lavender
Cinnamon
Clove
Thyme
Rosemary (Melts mite eggs)
Citronella
Spearmint
Peppermint
Eucalyptus

Edit to note that I also add a little bit of Bronners as a surfactant.


UVC
Heres a piece on uvc as a control

Uvc is a light spectrum... Not a toxin. It is not toxic to plants.

However, it destroys and mutates DNA on long term exposures.

Germicidal uvc bulbs for horticulture are nothing new, infact cleanlight.nl make a hobby uvc light for use on fungus etc on house plants, weed.

This is not a gimmick, it works. Has been used in the commercial industry for years.

Floweryfields of Austria use uvc in their daily plant maintanace.

But do not ever get your skin exposed to uvc or your retinas / eyes. Small exposure will cause serious sun burn type effects and long term exposures will almost certainly be a trigger for certain cancers.



UVB has no effect on pathogens. You will not get uvc from a mhal bulb of any kind.

Powdery mildew requires around 1800 u watts of uvc to kill the spore. On an 11 watt uvc bulb that means a quick once over with the lamp will kill all spores the light falls on.

Good daily short term use not only kills spores but actually helps the plant to develop thicker leaves.

.........


Ultraviolt light (UV) occurs from the sun. The wavelength of UV is outside of our visible range. The lowest wavelength colour we can see is violet, hence the name for light with a wavelength lower than this is ultraviolet.

UV ranges from 100 nanometres to 400nm. UV is further divided into UV-A, UV-B and UV-C.
UV-C: ranges from 100nm – 280nm (germicidal)
UV-B: ranges from 280nm- 315nm (sunburn)
UV-A: ranges from 315nm – 400nm (blacklight)

We here are interested in the UV-C rays, also known as „short wave ultraviolet radiation“. UV-C`s germicidal properties have been known since the 1930s. They are used in labratories in order to destroy bacteria, mould and viruses. UV-C rays are able to penetrate the outer membrane of microbes and stop them from reproducing. The specific wavelength of 253,7 nm is known to break the DNA of pathogens.

In May 2007, two Dutch inventors, Arne Aiking and Frank Verheijen were granted an International Patent on a method of treating live plants and mushrooms against pathogens with UV-C light. In the past UV-C had only been used to sterilise things like air and water. The difference with proposing to use UV-C to fight pathogens on living plants is that you shouldn`t use any more than is necessary, otherwise there is a risk to health of the plant.

Mr. Aiking and Verheijens invention is a mobile UV-C lamp that travels up and down in commercial greenhouses. The light intensity of a UV-C germicidal light bulb is usually expressed in a term called „microwatts per square centimetre“. Mr. Aiking and Verheijen suggest a range between 2,500 and 150,000 mircrowatts of UV-C energy over a given 24 hour period.

E.g. A 100 Watt UV-C lamp will output approximately 14,000 microwatts of energy over a square centimetre, in one second, from a distance of two centimetres away. If we leave it there for one minute we have to multiply that figure by 60. (840,000 microwatts). Look at the following chart:
1cm 21,000 µW/cm2 UV output
2cm 14,000 µW/cm²
3cm 10,000 µW/cm²
4cm 8,000 µW/cm²
5cm 6,700 µW/cm²

100cm 360 µW/cm²

This shows that a second`s exposure at 1cm distance is roughly equivalent to a full minute`s exposure 1 meter away (360 x 60 = 21. 600µW/cm²).

We use the UV-C light to fight against powdery mildew in our plantation. Tests have shown that powdery mildew is killed when given a dose of 1720 µW of UV-C per square cm. For exemple if I took a 100 Watt UV-C lamp and positioned it two centimetres away from the mildew, I would need to switch on the UV-C lamp for just 1/10 of a second to kill it.

Spider mites could possibly also be effectively treated with UV-C but with amounts that are hundreds of times more compared to something like powdery mildew. We therefore use it only against powdery mildew.

The safest way to use UV-C on plants appears to be regular, smaller doses rather than a single, lager hit. We therefore use the UV-C light every day for a short time. The pathogen must be hit directly with the UV-C rays in order to be affected. If it is protected by a leaf, the UV-C will not be effective, because UV-C will not penetrate through leaves.

WARNINGS:
UV-C light has an intense burning effect on human skin and can quickly damage your eyes.
Protect your eyes with special eyeglasses
Don`t expose your skin to UV-C rays
The wrong amount of UV-C will damage your plant
 

SCJedi

In Bloom
While plants love the KSil/Aloe combo I really only use it if the plant is struggling or visible damage to the leaves would be the result.

I now primarily use 1oz Neem/Karanja mixed 50/50 + 1 oz Isopropyl Alcohol + 1 Tablespoon Salsuds + 0-10 drops of essential oil (optional, but typically rosemary or peppermint)
 

jaguarlax

Tactical Gardener
Staff member
Moderator
Anyone with solid info on the subject feel free to drop it here ill be adding to it as i find more goodies, im gonna crusade against this shit in hopes i can help maybe 1 person not have to trash their buds.
Part 1

How to Beat Powdery Mildew
BY URBAN GARDEN MAGAZINE ⋅ AUGUST 6, 2009 ⋅

If there’s one grower’s gripe we hear lots about at Urban Garden HQ it’s Powdery Mildew. So we asked our heavyweight in the pest control department, Zorro Torro, to lend some expert advice on what this nasty stuff is, what damage it causes your plants, and, most importantly, how to beat the crap out of it!
You’ll know powdery mildew has paid your plants a visit when it looks lot like confectioners’ sugar has been sprinkled on the plant leaves. At first it may be hard to spot as it might appear on just a small portion of the leaf appearing as an irregular circle. But it quickly spreads and soon appears on the surrounding vegetation. Soon the entire leaf is covered and at the same time colonies develop on the surrounding vegetation and in other areas of the garden.
So how does it all start? Well, the plant becomes infected when an airborne spore, or conidia, lands on a leaf and germinates. It soon grows a guide tube that attaches tightly to the leaf. Then it pierces the plant cell wall and membrane and inserts a hollow tube that sucks up plant nutrients, weakening the leaf and slowing growth. Within a week the fungus produces tiny mushroom stalks that release millions of spores, ready to infect more leaf surfaces. The fungus also produces a secondary spore, which over-winters outdoors and may also hide in a greenhouse or indoor garden even after the crop has been harvested.
Powdery mildew is most likely to attack the young leaves, up to two or three weeks old.
A dozen or so different fungus fall under the heading of Powdery Mildew, but two different fungus species are the most likely culprits. L. taurica, tends to attack warmer gardens. It prefers a temperature of about 77 °F (25 °C). S. macularisprefers a cooler temperature; however, the more virulent stain found in indoor gardens today has adapted to tolerate more heat. Both strains thrive in moderate humidity and are not injured by water. Their conidia can live in water for short periods and are mobile in it. However, strong water sprays do destroy some conidia.
CULTURAL CONTROL
Heat

Powdery mildew is sensitive to heat. Neither species will grow at 90 °F (32 °C). and will quickly perish when above 100 ° F (38 °C).
To get a complete kill maintain the temperature for an hour. This may not be a feasible option in most indoor gardens for several reasons. The first is that it may be difficult to heat the space to such a high temperature. The second is that even a single peak of 100 ° F (38 °C) affects the growth of plants. Vegetative plants with flowers or fruits in mid stage growth (weeks 3-7) may stretch a little from the experience. The heat treatment has relatively little effect on first and second week flowers or flowers nearing maturity.
You can minimize heat’s impact on plants in several ways. Heat the garden at the end of the day, as the lights are turned off. Since the plants are not photosynthesizing, they have lower water needs.
If the plants are being grown hydroponically, lower the temperature of the water to 60 degrees. Keeping the roots cool will help the upper plant parts beat the heat. It’s not difficult to do this, even if you don’t have a water chiller. Just add ice to the reservoir or flow through system. Roots of plants growing in soil can also be cooled using thermal ice packs at the base of the stem.
The heat treatment should kill off most of the fungus and its spores. The chances are there will still be some fungal re-growth. These can be eliminated using spot treatments.
Pruning
If one particular plant seems to be infected with a few tiny white spots on a few of its leaves, get a bag large enough to drop the leaves into and then cut them off into the bag. Remove the bag from the room. This prevents spores, the white powder on top of the leaves, from becoming airborne while being removed. Remember to wash your hands and clean the scissors or knife with soap and water, hydrogen peroxide, alcohol or bleach. Spray the plant with one of the sprays listed below after pruning to prevent re-infection and encourage healing.
If, you notice a re-infection a few days later, there is a good chance that this plant is very susceptible to powdery mildew and presents a good location for the infection to start and spread from. The plant should be removed immediately by placing a bag over it and removing it from the space. Then the space should be sprayed with one of the sprays listed below.
ORGANIC and IPM CONTROL
Here are some sprays that you can use to control the powdery mildew in your crop. All of these are safe to use for herb or for edible crops. Sprays are washed away by water, including rain.
Cinnamon Oil and Tea
Cinnamon is an effective destroyer of powdery mildew, with an effectiveness rate of 50-70%. It won’t kill it completely but it will keep it in check somewhat. It also potentiates other suppressive sprays so it is good to use in combination. To make your own, boil water, turn off the heat and add one ounce of ground cinnamon to one and a half pints water. Let the tea cool to room temperature. Add half a pint of 100 proof grain alcohol or rubbing alcohol and let sit. Strain the cinnamon. The spray is ready to use. A faster method is to add 2 teaspoons cinnamon oil to one pint of water and a dash of castile soap. Other herbs are also fungicidal. Clove, rosemary, and wintergreen oils are used in some botanical fungicides. The solution should consist of no more than 2% oil.
Garlic
Garlic is antifungal and anti-bacterial and has several pathways for destroying fungi including its high sulfur content. It can also be added to other anti-fungal sprays. Several garlic sprays are available commercially.
A homemade formula: Soak three ounces of crushed garlic in one ounce of neem or sesame oil and 100 proof or higher drinking alcohol or 70% or higher rubbing alcohol for a day or two. Strain. Then soak the garlic in a cup of water for a day. Strain. Mix the oil/alcohol, soaked water and 1 tablespoon liquid castile soap in a gallon container. Then fill with water and shake. The formula is ready to use.
A simpler brew consists of a teaspoon of garlic oil in a pint of water. To keep the oil and water mixed add a 1/8teaspoon of soap. Use garlic as a vaccination. Spray on new growth before there is a sign of infection.
Garlic is a general purpose insecticide as well as fungicide, so it should be used with caution on outdoor plants. It kills beneficial insects as well as plant pests.
Hydrogen Peroxide
Hydrogen peroxide (hp) is a contact fungicide that leaves no residue. It is an oxidized product of water and has an extra oxygen atom that is slightly negatively charged. When it comes in contact with the fungi the oxygen atoms attach to molecules on the cell walls, oxidizing or “burning” them.
Household hp sold in drug stores has a concentration of 3%. Garden shops sell 10% hp. Zerotol® contains 27% hydrogen peroxide and an unstated amount of peroxyacetic acid. Together they have a more potent chemistry than hp, with an activity of about 40% hp. It is considered hazardous because it can cause skin burn similar to that caused by concentrated acids.
To treat plants with drug store grade 3% hp use 4 1/2 tablespoons and fill to make a pint of solution, or a quart of hp to 3 quarts of water. With horticultural grade 10% hp use about 4 teaspoons per pint, 5 ounces per gallon. With Zerotol® use about 1 teaspoon per pint, 2 1/2 tablespoons per gallon.



Gweedo

How to Beat Powdery Mildew
BY URBAN GARDEN MAGAZINE ⋅ AUGUST 6, 2009

Part 2

Limonene

Limonene is refined from the oil of citrus rinds. It has a pleasant citrus odor and is the active ingredient in many of the new cleaning products. It also has fungicidal qualities. I’ve used pure diluted limonene and it controlled powdery mildew, but did not eradicate it. Perhaps a higher concentration would have been more successful. Start using 0.5-1% limonene in water 1/2-1 teaspoon per pint.
Milk
Milk kills powdery mildew so well that both home and commercial rose growers all over the world have adopted it for their fungicidal sprays. Use one part milk to nine parts water. I’ve only used 1% milk, but other recipes call for either whole or skim milk and use up to 1 part in 5 milk. Some recipes add garlic or cinnamon to the mix. When using more than 30% milk, a benign mold is reported to grow on top of the leaves. Use a milk spray at the first sign of infection then protect the new growth weekly.
Messenger®
Messenger’s active ingredient is a naturally occurring protein called harpin that stimulates the plant’s own natural defense system. It has been proven to promote more vigorous hardier plants that are more resistant to disease and have increased yields. It is used to prevent infection and decrease its virulence
Neem Oil
Neem oil is pressed from the seed of the neem tree (Azadirachta indica), native to Southeast Asia, but now cultivated worldwide. Neem oil has low mammalian toxicity. It degrades rapidly once it is applied so it is safe for the environment including non-target species and beneficial insects.
Neem oil protects plants with its fungicidal properties: it disrupts the organism’s metabolism on contact, forms a barrier between the plant and the invading fungus, and it inhibits spore germination. It has translinear action, that is, it is absorbed by the leaf and moves around using the leaf’s circulatory system – it can also be used as a systemic. When it is applied to the irrigation water it is absorbed by the roots and delivered throughout the plant. Adding a 0.5% solution, about 1 teaspoon per quart, to the irrigation water will protect the plant from infection.
Neem oil is best used before the plant or the garden exhibits a major infection. By using it before powdery mildew appears, it prevents the spores from germinating. It should not be used on buds or flowers.
Oil Spray
Growers have used different oil sprays to prevent and cure fungal infections. Until recently most horticultural oil sprays were made from petroleum distillates. However, most organic growers have switched to using botanical oils. Aside from the safety factor botanicals such as cottonseed, jojoba, neem and sesame oils have fungicidal properties. They can be used in combination with other spray ingredients listed here. The oils are mixed at about 1-2% concentrations. A 1% solution is about a teaspoon per pint or 3 tablespoons per gallon. Add castile soap to help the ingredients mix. Oil sprays should only be used on the leaves, not the buds or flowers. Use weekly on new growth.
pH Up
pH-Up is a generic term for alkaline pH adjustors, used to increase water pH in indoor gardens. They come as either a powder or liquid. Its active ingredient is usually lye (KOH) or potash (K2CO3).
Fungi require an acidic environment to grow and die in alkaline environments. Changing the leaf surface environment from acidic to alkaline clears up the infection. An alkaline solution with a pH of 8 will make the environment inhospitable for the fungus and will stop its growth. This is one of the simplest means of controlling the fungus. It can be used on critically infected plants.
Potassium/Sodium Bicarbonate
Potassium bicarbonate (KHCO3) and Sodium bicarbonate (NaHCO3) are wettable powders that change the pH of the leaf surface toward alkaline. Another reaction takes place; the fungus cell wall actually bursts in the presence of bicarbonate. Potassium is one of the macro-nutrients used by plants and therefore is preferred over sodium, as sodium can build up in the soil. Sodium bicarbonate can be found in your kitchen (baking soda), so some prefer it for ease of obtaining. Both are more effective when used with an oil and spreader such as castile soap. They can be used to cure bad infections and prevents new ones.
Use one teaspoon of bicarbonate powder, a teaspoon of oil and a few drops of castile soap in a pint of water, or 3 tablespoons each potassium bicarbonate and oil and a half teaspoon soap in a gallon of water. Spray on new growth.
Serenade® and Sonata®
Serenade® and Sonata® are composed of different bacteria. They use different pathways to stop mycellial growth. They are considered totally safe to humans and animals since the bacteria attack only fungi. Watch out if you are a mushroom, otherwise you are safe. The two bacteria work well together.
They are easy to use, quite safe and effective.
Sulfur
Sulfur has been used to control powdery mildew for centuries. Sulfur sprays can be used indoors but they are not popular because of residue that remains on the plant. In greenhouses gardeners use sulfur vaporizers that heat elemental sulfur to the point of vaporization. The sulfur condenses on all surfaces including the leaves. A fine deposit of very low pH sulfur granules covers the leaf surfaces. The low pH environment inhibits fungal growth. The heaters use a 60 watt light bulb to heat sulfur which is held in a container above the light. The bulb supplies enough heat to evaporate the sulfur, but not enough for it to ignite. The problem with vaporizers is that they also leave a fine sulfur film on the leaves and flowers.
Active mildew: 7 to 8 hours per night 1 to 2 times a week.
Preventative maintenance: 4 to 5 hours once a week
Vinegar
Apple cider vinegar is toxic to powdery mildew because of its high acidity (low pH). Use it at the rate of 1 tablespoon per quart of water several times a week . Some gardeners recommend alternating using vinegar with potassium bicarbonate and milk.
PREVENTION
· Isolate all new plants in a separate area where they can’t infect other plants.
· Filter incoming air to prevent spores from entering the room in the airstream.
· Install a germicidal UVC light, like the ones used in food handling areas. The light is fatal to all airborne organisms passing through the appliance. This will kill powdery mildew spores that are airborne.
· Spray the leaves with neem oil weekly. Neem oil presents both a physical barrier and a chemical deterrent.
· Cinnamon oil and cinnamon tea can also be sprayed as a powdery mildew preventative. If you are using cinnamon oil use 1 part oil to 200 parts water. (1 teaspoon oil in a liter of water.)

Great thread idea @Gweedo's Growroom... You have great timing, seems we have a bit PM rearing its head across the forum... I posted this a while back, but I figured I would add to the conversation with this article...

 
Great info and thanks for sharing! I just noticed pm last night and started a thread without knowing this one was here. Had I seen this prior, I probably would have given the milk mixture a try. I have the Green Cure mixed and ready to spray in the morning. Very interested to see if I can save my plant. With all the great help and knowledge here, it sounds promising!
 
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