Powdery mildew is a fungal disease that results in a powdery gray or white coating on the leaves and stems of infected plants. It starts out as a few spores on the leaves, and quickly spreads, eventually yellowing the leaves and causing premature leaf drop.
Damage to Plants:
Besides being unattractive, powdery mildew results in leaf yellowing and droppage, stunted plant growth, distortion of buds, blooms, and fruit, and eventual overall weakening of the plant.
Disease Life Cycle:
Spores overwinter on diseased plant parts, and begin asexual production of new spores once the weather warms. New spores are carried on the wind to other parts of the plant, or to other nearby plants. Spores never stop producing more spores, so if infected leaves are not destroyed, the problem will only get worse.
Treatment and Prevention:
Powdery mildew thrives in temperatures between 60 and 80 degrees. Dry, shady conditions are ideal, as are areas with poor air circulation. Planting disease resistant cultivars and making sure you allow for good air flow are two ways to guard against powdery mildew. Inspect plants regularly during warm, dry conditions, and remove any leaves that show signs of infection. Destroy (do not compost!) infected plant parts. A spray made with baking soda, if applied weekly at the first signs of infection, can protect plants against further damage. Plants that are badly infected should be ripped out and destroyed to prevent the disease from spreading further.
A commercially available organic option is Neem oil, which both treats existing powdery mildew and protects the plant against further infection.
Interestingly enough, the most effective measure in preventing and treating powdery mildew is to spray the foliage of your plants daily with plain water from the hose. Powdery mildew hates water! The only caveat with this method is to be sure you do it early in the day so that the foliage completely dries before cooler evening temperatures arrive, otherwise you may invite other fungal diseases, such as black spot, into your garden.
Controlling and Preventing Powdery Mildew on Plants
Powdery mildew is one of the most common and easily recognized plant diseases. Almost no type of plant is immune, however some are more susceptible than others. Lilacs, crab apples, phlox, monarda, roses, grapes, squash and cucumbers are all likely targets for powdery mildew.
Recognizing Powdery Mildew
As the name implies, powdery mildew looks like powdery splotches of white or gray, on the leaves and stems of plants. There are actually several types of powdery mildew fungi, but they all look basically the same. You may not notice a problem until the top surfaces of the leaves turn powdery, but powdery mildew can also affect the lower leaf surface, stems, flowers, buds and even the fruit.Although powdery mildew is unattractive, it is rarely fatal. However it does stress the plant and severe or repetitive infections will weaken the plant. If enough of the leaf surface becomes covered with powdery mildew, photosynthesis is impaired. Infected leaves often fall prematurely. This can be a particular problem on edible crops, since insufficient photosynthesis can diminish the flavor of the fruit or vegetable. If buds become infected, they may not open and mature at all.
Powdery mildew fungi are host specific, meaning the different powdery mildew fungi infect different plants. The powdery mildew on your lilacs will not spread to your grapes or your roses. However all powdery mildews favor the same conditions.
What Causes Powdery Mildew?
Powdery mildew fungi seem to be everywhere. They overwinter in plant debris begin producing spores in the spring. These spores are carried to your plants by wind, insects and splashing water. Conditions that encourage the growth and spread of powdery mildew include:
Dampness or high humidity (Not common during rainy seasons or in extreme heat)
Crowded plantings
Poor air circulation
Controlling Powdery Mildew
Choose healthy plants and keep they growing healthy
Try and find a powdery mildew resistant cultivar, if your area is susceptible
Don’t plant non-resistant varieties in the shade
Once Your Plants are Infected:
Remove and destroy all infected plant parts
Improve air circulation by thinning and pruning
Don’t fertilized until the problem is corrected. Powdery mildew favors young, succulent growth
Don’t water plants from above
Apply a fungicide: There are many fungicides available. Check the label to be sure they are safe and effective on the type of plant that is infected. Look for ingredients such as: potassium bicarbonate, neem oil, sulfur or copper. There is also an organic fungicide by the name of No Powdery Mildew™ which is a dual action foliar treatment. Made from natural plant oils and extracts No Powdery Mildew™has a dual lysis action that attacks mildew spores on contact while penetrating your plants cell walls giving them added strength and vigor. There are also chemical fungicides, such as triforine, that can be used on ornamental plants.
Most fungicides will need repeat applications every 7 – 14 days, for continuous protection. Always follow the label instructions for both application and waiting period before harvest
Powdery mildew is a fungal disease that appears as a dusty gray or white coating on plants. Vegetables such as cucumber, pumpkins, squash and melons; houseplants such as African violet and begonia; and outdoor plants such as phlox, lilac and rose are all susceptible to powdery mildew. Not only is the disease unattractive, but it can distort and stunt a plant’s leaves, buds, tips and fruit. If enough leaves or tissue are affected, the plant may die.
How Powdery Mildew Forms
Wind carries powdery mildew spores. The disease can appear at any time, but it’s more likely to grow rapidly in shady areas, if there is slow or nonexistent air circulation or when the humidity is high. Powdery mildew can reproduce both sexually and asexually.
Prevention
If you’re planting a susceptible specimen, choose an area with as much sun as the plant can handle. Don’t crowd the plant; make sure there is enough room for air to circulate. Use a slow-release fertilizer; avoid liquid fertilizers that may splash spores back onto the leaves. Water the plants at the root level, not from above. Plant varieties resistant to powdery mildew.
Treatments
There are major advancements in natural plant oil extract technologies. There is one that has shown tremendously great results., its called No Powdery Mildew™. No Powdery Mildew™ goes to work immediately and on contact with a dual lysis action that attacks powdery mildew spores on contact, while penetrating your plants cell walls giving them added strength and vigor. No Powdery Mildew™ can be used from germination to day of harvest. It can be sprayed under any lights as often as you like. There is no harmful aroma’ or aftertaste to your valuable fruits and vegetables because the natural plant oils inNo Powdery Mildew™ leave a fresh, clean aroma that is safe for humans and pets.
Powdery mildew is a common problem in areas that have high humidity. It can affect almost any type of plant, appearing on leaves, flowers, fruits and vegetables. A white or gray powder coats the surface of the plant. If left untreated, it can turn more severe, causing leaves to turn yellow or brown. Many people look to a homemade cure for powdery mildew before turning to fungacides. However, finding a powdery mildew homemade preventer is preferable.
Prevention of powdery mildew
The best way to take care of powdery mildew is by prevention. Be sure to start with healthy plants. One powdery mildew homemade preventer is to simply prune back any dead plant material during the normal pruning time. Do not plant things too close together, to allow ample air circulation around the plants. It is important to not plant in damp shady areas, as that is a prime location for powdery mildew. Another powdery mildew homemade preventer is to avoid using the sprinklers in the evening, so the water doesn’t stand on the leaves too long. The water itself doesn’t cause more mildew, but it allows it to be transported to the other leaves on the plant easier.
Organic removal of powdery mildew
But, when prevention fails, it is a good idea to try organic removal of powdery mildew first. If you have a case of powdery mildew, be sure not to compost the infected plant parts. There are a few options to try when trying a homemade cure for powdery mildew.
One powdery mildew organic remedy is to use dilute solutions of hydrogen peroxide. Spray it on the plants thoroughly about once a week. Organic removal of powdery mildew is always preferable to using harsh chemicals on your plants.
There are even some plants, such as the lilac, that can have the powdery mildew on it and it doesn’t hurt the plant that much. So using a homemade cure for powdery mildew on the hardier plants isn’t necessary.
Another thing to remember is that if one type of plant gets it, that particular strain of powdery mildew won’t transfer to the other types of plants. For example, it won’t go from the roses to the lilacs, just to the other roses.
The best powdery mildew homemade preventer is maintain the proper moisture level, without raising the humidity around the plants too high. This, along with careful annual pruning will go a long way toward keeping your plants healthy and beautiful.
A fungus which appears as a dry powdery bloom on the upper sides of leaves, usually in hot dry conditions. Ornamental Malus and fruiting apple trees are most susceptible to the above species. Other species of powdery mildew effect roses, peas, gooseberries, vines, strawberries, turnips, cucumbers and cereals. Ornamental plants like Chrysanthemums, Michaelmas dasies and Phlox are susceptible.
It survives the winter as mycelia in the buds, affected buds and smaller twigs have a silvery appearance. At bud break in the spring the mycelium emerges and grows on the surface of the young leaves (primary mildew) producing asexual spores which are carried in the air, landing on other leaves and developing into secondary mildew. This growth withdraws moisture and nutrients causing premature leaf drop and if young fruit are affected they develop a rough skin – russeting. Sexual spores may be produced in the autumn, but are not important for over-wintering on apple trees as it survives in the buds. The species which infect herbaceous perennial or annual plants spend the winter as sexual spores, ready to attack the new growth.
The white mycelium of Powdery Mildew on the leaf of a rose.
Cultural control in apples is by winter pruning to remove infected buds and open up the tree for good air flow. Other hygeine considerations are important with strawberries and vegetables, ie. removing leaf debris which could overwinter the spores, and good separation of plants. During dry weather keep plants well watered especially roses growing near walls and containerised fruit trees.
Powdery mildew is a common disease on many types of plants. In fact, it is one of the oldest plant diseases on record – Theophrastis wrote of powdery mildew on roses in 300 B.C. Although different species of fungi cause the disease on different plants (Erysiphe infects vegetable crops and flowers; Podosphaera species infects apples and stone fruits; Sphaerotheca species infects berries, roses, some vegetable crops, and stone fruits; and Uncinula necator infects grapes), the infections are all characterized by a powdery white to gray fungal growth on leaves, stems and heads.Contary to popular belief, powdery mildew generally does not require free water to establish and grow. Infection can actually occur on dry leaves. Warm temperatures and shady conditions encourage the fungus to grow and spread. However, the spores and mycelium are sensitive to extreme heat and direct sunlight.
Symptoms
Powdery mildew usually shows up on leaf and stem surfaces and does not directly affect most vegetable fruits. However, it can affect the flavor of melons and squash and reduce their yield. Woody species such as grapes, fruit trees, roses, crape myrtle, and sycamore are more seriously affected; new growth is often distorted. The young fruit of apples and grapes can also develop rough skin due to powdery mildew.
Life Cycle
All species of powdery mildew fungi require living plant tissue to grow. On perennials, they survive on buds and stem tissue. Certain weeds will also act as hosts through the winter. The optimum temperature for infection is between 68 to 77 degrees F and relative humidity between 40 to 100% is sufficient for the spores to germinate. Low, diffuse light also seems to favor powdery mildew development.
The mildew can spread rapidly since the disease cycle can be completed in as little as 72 hours. However, it commonly takes 7-10 days from the time of infection to the development of symptoms and secondary spore production.
Management
In most cases, good cultural practices will adequately control powdery mildew:
Select powdery mildew resistant varieties. This is particularly true of roses. For lawns, shade tolerant grasses such as creeping red fescue can be planted.
Plant in full sunlight in a well-drained area.
Do not crowd plants. Air flow and ventilation will discourage mildew growth.
Powdery mildew thrives where high rates of nitrogen have been used. High nitrogen promotes tender leaf formation, causing dense stands that are more susceptible to infections. Adequately fertilize but avoid stimulating succulent growth. Organic fertilizers or slow-release formulations of lawn fertilizers are good choices.
Prune infected plants to get rid of infected parts and increase airflow. If the infestations are severe, remove and destroy the plants that are infected.
Disinfect your pruning tool in a bleach solution of one part household bleach to four parts water after each cut.
Watering plants in the morning gives the plants the rest of the day to dry off, discouraging establishment of diseases, including powdery mildew.
Organic Sprays
Sulfur is highly effective against powdery mildew if used in a protectant program with a minimum of 7 to 14 days between applications. Garlic naturally contains high levels of sulfur and a few cloves crushed in water can be used to make a homemade spray. Apply a sulfur-based fungicide at first evidence of mildew and repeat applications as necessary. Proper timing of fungicide applications is critical to successful control so make sure to begin at the first sign of the disease.
However, sulfur can be damaging to some squash and melon varieties. Another option is to spray once a week with a solution of baking soda. Baking soda increases the surface pH of the leaf making it unsuitable for the growth of powdery mildew spores. Be sure to spray the undersides of leaves as well as the upper surfaces when using any of these sprays.
Here’s a recipe to make your own spray:
1 teaspoon baking soda
1 quart water
A few drops of liquid soap
Before treating your plants, test the spray on a few leaves to make sure they are not too sensitive.
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Powdery mildew is a common disease on many types of 
