How to get rid of gray mold on roses quickly and effectively

Gray mold is a fungal disease caused by a pathogen of the genus Botrytis cinerea. The infection is unique in that it only attacks weakened, mechanically damaged areas of rose bushes.

A few words about gray mold

It may seem like gray mold appears out of nowhere, like a bolt from the blue. In fact, the fungus is always present near flowering shrubs, reaching them through grass and crop debris. The pathogen also accumulates on the soil surface as sclerotia or mycelium. As soon as favorable conditions arise, it immediately activates, consuming the plants one by one.

The parasitic pathogen first attacks the upper parts of plants, gradually moving downward. The fungus spreads to flowers via wind, precipitation, insects, and birds. Flowers begin to rot when humidity is high and the weather is cool. Gray mold develops especially quickly during heavy morning dews, temperature fluctuations, fog, and excessive overwatering. Even in winter, roses can be affected by this disease: under cover, ventilation is often poor, and during a thaw, condensation forms inside, the temperature rises, and the environment becomes excessively humid—perfect conditions for the fungus to thrive. Fluffy, light-gray mycelium immediately begins to grow on various parts of the rose bushes. If the infection has begun to spread, the plant will not survive until spring—the disease will infect the entire bush, right down to the root collar.

Causes of the disease

There can be many reasons for the pathogen's activation, most of which are related to poor agricultural practices. Naturally, climate conditions also play a role—the fungus attacks plants en masse during cool, humid summers.

Infection occurs when:

• Air humidity is high (over 70%), and the average daily temperature is between 20 and 23 degrees Celsius. This climate is the ideal habitat for a rapidly reproducing fungal colony;

• Roses are planted too densely. If the bushes are too close together (the leaves of adjacent plants touch), they are poorly ventilated, causing air and moisture to stagnate. Condensation accumulates in the thicket, which favors fungus;
• The soil lacks nutrients. Due to a deficiency of the chemical elements necessary for healthy plant development, roses' immunity weakens. Plants are unable to fight off pathogens;
• The plants are damaged. Poor pruning leaves open wounds on the cuts, allowing not only infections but also various pests to enter the plant.

Symptoms

Excessive moisture causes damage to the tips of rose stems and leaves, buds, and flower stalks. These are the areas where mold first develops. Slightly sunken dark spots appear on the leaf margins and quickly grow, spreading across the entire leaf blade. The same phenomenon is observed on young stems and inflorescences. The affected areas become covered with a "hairy" light-colored coating—fungal sporulation. Then, after drying out, black, rounded bodies—sclerotia—begin to form on the moldy areas. The affected stems and leaves dry out and crumble.

Once the plant's most vulnerable organs are attacked, previously healthy areas begin to suffer as well. Flower buds die before they even open. The mycelium completely envelops them, mummifying them. If flowers that have already opened are affected by the rot, numerous small whitish spots can be seen on the petals, which darken over time, forming the mycelium. The flower quickly becomes completely covered in an unsightly coating, while the leaves turn yellow, shrivel, and rot.

How to cure the disease

If the infection is detected early, there's a good chance the roses will be saved from complete destruction. It's important to prune out all damaged areas and remove them, as well as create a dry, warm climate for the plants. To achieve this, watering should be completely suspended for a while, and the soil should be loosened to improve aeration.

Biological treatments are a good aid in the fight against gray mold. They pose no danger to plants or humans, yet offer relatively effective protection against pathogens. They are primarily used as a preventative measure and in the early stages of the disease.

Frequently used tools:

1. Fitosporin is a systemic fungicide. Its active ingredient is beneficial bacteria that penetrate the plant, inhibiting pathogenic fungi. Roses are treated with 1.5 grams of the product. Treatment is carried out every two weeks.
2. FitoDoctor, which contains Bacillus subtilis, is destructive to many types of fungi. This product is used primarily as a preventative measure. For treating roses, a typical dose is 20 grams per 10 liters of water.
3. Trichophyte is a concentrate containing a mixture of Trichoderma fungi. It is similar to the medications Trichodermin and Fitosporin. For garden crops, 200 grams of the preparation is diluted in a bucket of water. Treatment is repeated 2-3 times, every 10 days.
4. Fundazol—the main active ingredient, benomyl—prevents fungal growth. It's highly effective at the first signs of disease—it can completely cure a plant in just a few applications. To spray flowering shrubs, mix 1 gram of powder with a small amount of water, then dilute the concentrate with another liter of water. Repeat the procedure 3-4 times until the shrub is completely cured.
5. Planriz is a biological product based on soil bacteria. Pseudomonas fluorescens, the product's main ingredient, inhibits the growth of pathogenic microorganisms that cause numerous diseases. Roses are treated with a 0.5% solution every 12-14 days during the growing season.
6. Mikosan's active ingredient is an extract from the polypore fungus. By penetrating the plant's soft tissues, beneficial microorganisms activate the growth of enzymes that destroy pathogens. For garden flowers, prepare a solution of 100 milliliters of the treatment solution and 3-4 liters of water.

Spraying with these preparations can be carried out repeatedly, at intervals of 7-9 days until the white coating that has appeared completely disappears.

Chemical treatments are only used when biological treatments fail. Most often, gardeners use:

1. Teldor is a broad-spectrum product. To treat flower beds, prepare a solution of 8 grams of Teldor and 10 liters of water. Spray three times per season, at intervals of 1.5 to 2 weeks.
2. Switch is a two-component product (37% cyprodinil and 25% fludioxonil) that inhibits fungal mycelium. A solution is prepared from 2 grams of the product and 10 liters of water. Two treatments are recommended per season.
3. Hom – copper oxychloride – affects the microorganism, disrupting its vital functions and neutralizing it. Dissolve 30 grams of crystalline powder in a bucket of water. Spray before and after flowering.
4. Horus is a modern pesticide designed to combat fungal diseases. The substance cyprodinil inhibits the biosynthesis of the pathogen, disrupting its life cycle. To treat one hundred square meters of plantings, prepare a solution of 3 grams of fungicide and 10 liters of water. This product can be combined with other chemicals.
5. Kurzat is a highly effective contact fungicide. It has a rapid and long-lasting effect. Depending on the severity of the disease, a solution requires 30 to 60 grams of powder, which should be diluted with 10 liters of water. Roses can be treated up to four times per summer.

Additionally, medicinal solutions can be applied to the soil beneath the bushes before covering them for the winter, and again in the spring after they are uncovered. Simultaneously with applying fungicides to the plants, the bushes should be treated with the silicon-containing preparation "Siliplant" (for routine treatment, 50 milliliters of the preparation per 1,000 liters of water is required. To protect plants from fungi and pests, the concentration can be increased to 300 milliliters per 1,000 liters).

If the fungal disease is caused by phosphorus, potassium, or boron deficiency, the bushes are treated with complex fertilizers. First, the diseased areas are cut off, and the remaining shoots and buds are sprayed with one of these universal fertilizers:

• Agricola Aqua – for flowering plants, prepare a solution of 5 milliliters per 2 liters of water. Roses are treated once every 14 days;
• microvit standard T - affected rose bushes are sprayed at intervals of 12-14 days with a working solution of 1 milliliter of fertilizer mixed with 10 liters of water;
• Fertika Kristalon Flower – spray with a broad-spectrum solution every 7 days. To prepare a beneficial solution, dilute 10 grams of the product in a bucket of water.

At the same time, organic and mineral fertilizers are added to the soil. Both general-purpose and specialized fertilizers, such as "Omu for Roses," can be used.

Of the traditional remedies, Bordeaux mixture is still popular – a 1% solution is used to spray heavily affected bushes once every two weeks.

To prevent fungal infections on roses, gardeners recommend using an ash-water solution (300 grams of ash per 10 liters of water).

A whey solution (1 liter of whey per 10 liters of water) works well for protecting rose bushes. After spraying, a film forms that prevents fungus from penetrating the plant.

Preventive measures

Unfortunately, it's impossible to completely eliminate the fungus, but it's possible to create conditions that will inhibit its growth. Prevention is essential throughout the year.

In the spring, as soon as the snow melts, it is necessary to clear the rose garden of plant debris and old leaves, since they are often the carriers of all kinds of infections.

Before the plants enter the growing season, they should undergo sanitary pruning, removing all damaged areas. The cuts should be sealed with garden pitch or crushed charcoal.

To prevent the disease, plants should be treated with copper sulfate or Bordeaux mixture. The first treatment should be in mid-April. Subsequent treatments can be repeated in late May and mid-July.

Over the winter, most of the nutrients are washed out of the soil, so the first feeding should be done in early spring with a complex mineral fertilizer. Ammonium phosphate (AMP) and azophoska (NPP) are suitable for this purpose. As for organic matter, rotted manure is used. A useful fertilizer is prepared as follows: 10 kilograms of manure are poured into water and left to steep for 10 days. The resulting solution is then applied to the areas under the bushes. It's a good idea to "cover" the roses with humus before wintering.

In the fall, the soil in the flowerbed must be thoroughly cleared of plant debris, the soil must be loosened, and phosphorus-potassium fertilizers must be added to help the roses survive the winter better.

Basics for normal functioning of roses:

1. Roses often get sick due to unfavorable neighbors. Grapes, strawberries, pumpkins, and fruit and berry bushes are known to suffer from the same diseases as roses. To prevent roses from becoming infected with fungi, they are planted away from such crops.
2. Rot occurs in dense plantings. Therefore, avoid planting bushes too close together. The optimal distance is 50-60 centimeters.
3. Late evening watering can trigger mold on roses. The foliage doesn't have time to dry, which activates the pathogen, and causes rotting. Therefore, it's best to water early in the morning or after lunch. Apply water at the roots, avoiding the green parts of the plant. Avoid allowing moisture to accumulate at the base of the bush.
4. To maintain the immunity of roses, they need to be regularly treated with traditional remedies that are harmless to humans but lethal to fungi: a soap-soda solution, potassium permanganate, garlic infusion, and liquid manure.
5. It's important to remember that any plant will only grow healthy and strong in nutritious soil, so it's important to apply fertilizers wisely, depending on the needs of the flowers at each stage of the growing season. For example, roses require nitrogen in the spring, potassium in the summer, and phosphorus in the fall.
6. Winter shelter should be warm but still allow fresh air to pass through. Only with good ventilation will roses survive the temperature fluctuations of winter and spring.

Pro Tips:

• Feed your roses with long-lasting fertilizers. Firstly, they save money, time, and effort. Secondly, these fertilizers contain the optimal amount of nutrients that will evenly distribute them to the soil and plants. This will prevent roses from starving or overdosing.
• Roses grow healthy and strong in light, well-aerated soil with a slightly alkaline reaction. Therefore, it's best to dig over the soil in the rose garden every spring, loosening it with compost, straw, or peat.
• Mulching with nutshells, pine needles, and tree bark will help prevent diseases from penetrating the soil. However, the soil must be completely weed-free;
• If buds have appeared on the bushes, but the weather is not favorable, then it would be more rational to thin out the flower stalks, freeing up the plant’s energy to maintain viability in unfavorable conditions;
• If roses are affected by rot, it's likely that all neighboring plants have also become infected. Therefore, the pathogen must be eradicated from the entire garden at once, treating all crops.
• You can’t plant roses next to strawberries, since it is the strawberries that the gray mold “chooses” for its meal and only then moves on to neighboring plantings;
• If it rains for several days, a tent stretched over the roses will help reduce humidity. Alternatively, you can cover the bushes with a plastic bag until the weather clears.

Fungus-resistant varieties

Thanks to the efforts of breeders, many rose varieties have emerged that are resistant to fungal infections. These are often hybrids of different species.

Best varieties:

• hybrid tea - Eliza, Happy Day, Gand Amor;
• floribunda - Fortuna, Cherry Gold, Black Forest;
• scrubs – Postillion, Hercules;
• climbing – New Down, Jasmine, Golden Gate;
• ground cover and miniature roses – Larisa, Topolina, Veg Der Shine.

Conclusion

Gray mold is an insidious infection that can spread rapidly throughout a rose garden. If left untreated, the disease will consume all flowering shrubs within 7-10 days. The pathogen's development can only be prevented through systematic agricultural practices, which will prevent not only the rot but also other dangerous diseases and pests.