Powdery mildew is an incredibly common problem for roses, but it attacks a variety of plants and spreads quickly. It can grow on their foliage, stems, and flowers, requiring treatment and prevention techniques as soon as possible.
If you spot any white flour-like fungal growths this season, these tips may save your shrubs as well as other plants around your garden.
Remove Affected Areas
It will stop the issue from spreading from that point, making the disease much easier to manage.
If only a small section of your rose has powdery mildew, the first line of defense is to simply remove the affected growth. This may not remove the problem completely, as it takes a couple of days for spores to develop visible symptoms. But it will stop the issue from spreading from that point, making the disease easier to manage.
Don’t remove too much of the plant at one time. If more than one-third of the rose is affected, it’s best not to chop it completely, as this can lead to stress and slower recovery. Unless it’s the right time of year to cut back significantly, rather remove only the most affected growth and apply other treatments to the rest of the plant.
Natural Solutions
Avoid spraying on sunny days, as the mixture can burn the leaves.
For larger issues, natural treatments can manage the spread and lessen the intensity of the problem. While they won’t cure fungal diseases completely, they will reduce the severity and give heavily diseased shrubs a fighting chance. Plus, many natural solutions are commonly found around our homes.
Baking soda is often recommended to treat and prevent powdery mildew on roses, although evidence suggests it’s much better for prevention than treatment. Dilute one tablespoon into a gallon of water, with a few drops of castille soap, and spray it on the leaves. Avoid spraying on sunny days, as the mixture can burn the leaves.
An even more effective method you may not have considered is milk. Milk has been studied as a treatment for fungal pathogens and a preventative spray, with some researchers finding better results using milk than conventional fungicides. High concentrations work best, so use a mixture of equal parts milk and water once per week until the mildew subsides. Note there will be a smell that accompanies this treatment, especially in warm climates.
Plant in Full Sun
Higher sunlight is generally better for strong growth and flowering
It’s far easier to prevent powdery mildew on rose bushes than to treat it once it becomes a problem. Prevention starts with creating the right environment to keep plants healthy and deter fungal pathogens from settling in. One important environmental condition to consider, not just for mildew but for healthy roses overall, is sunlight.
Most roses prefer at least six hours of direct sunlight to thrive. Some can tolerate less sun, but higher sunlight is generally better for strong growth and flowering. Full sunlight also makes e pathogen less severe, as it spreads better in shady areas.
That doesn’t mean a rose in full sun can’t be affected by powdery mildew. But it does reduce your chances of it becoming a serious problem. Plus, it’s just better for your shrubs overall. If you do have to plant in a shadier area, keep a closer eye for signs of disease.
Don’t Overcrowd
At planting time, always take note of the spacing requirements of your chosen variety.
Fungal spores don’t mind traveling a fair distance before settling in. However, having easily accessible leaves and flowers close by does make spreading a lot simpler. Planting too close together or leaving dense growth that limits airflow can almost guarantee that a small problem becomes a big one.
At planting time, always take note of the spacing requirements of your chosen variety. Consider the size of the mature plant and provide enough room for it to grow without limiting airflow. They may look sparse at first, but growth will fill in over time.
Pruning is also essential to improve airflow, particularly for climbing varieties. Keep the center clear by removing any canes growing towards the middle of the plant. Also, trim dense areas of leafy growth, especially if your climbing roses are planted against a wall. This is a prime spot for fungal problems, so monitor airflow closely in these areas.
Water Consistently
Avoid this issue by watering consistently to keep your roses healthy and strong.
A stressed rose is far more susceptible to problems with pests and diseases, including powdery mildew. This disease often attacks when the soil is left to dry out for long periods. Avoid this issue by watering consistently to keep your roses healthy and strong.
This doesn’t mean overdoing it or watering as soon as the top soil layer appears dry. Rather, only water just as the soil dries out by keeping an eye on soil moisture and environmental conditions. Watering every few days one week and then forgetting to water the next can lead to the same stress as not watering enough overall.
Don’t wait for your shrubs to wilt before watering them. If the leaves are drooping, you’re likely already too late. Instead, monitor the soil daily to irrigate at just the right time.
Water Overhead
When it comes to pathogens, overhead watering can actually be an effective defense strategy.
One piece of advice you’ll often see to prevent disease on roses is never water overhead. This is generally good advice, as water sitting on the foliage or splashing onto leaves from soil, particularly in the evenings, can cause a long list of problems. However, when it comes to this disease, overhead watering can be an effective defense strategy.
Unlike many other fungal diseases, powdery mildew does not like water. It settles in when foliage is dry. That’s why research shows that overhead watering can actually prevent spore germination in certain species. This should be done in the middle of the day when conditions are dry to ensure there are no water droplets on the leaves by the evening.
Unfortunately, overhead watering can still encourage other fungal diseases, particularly if done too late in the day. Consider the risks before you try this prevention tactic.
Always clean and disinfect your gardening tools before you use them on any plants, including roses.
You don’t want to go to the trouble of treating and preventing powdery mildew on your rose bushes only to find you’re the one spreading it in the first place. These spores can spread easily through garden tools like pruning shears, turning a small problem into a large one.
Always clean and disinfect your gardening tools before you use them on any plants, including roses. If you’re pruning to prevent spread, disinfect your pruning shears as you go to avoid transferring the issue to healthy parts of the plant.
Tidy Garden Debris
Discard any affected foliage to prevent spores from spreading.
Powdery mildew can survive on rose prunings and other garden debris throughout winter, ready to attack again when spring and summer arrive. Garden debris provides a perfect home for these spores. Keeping the area around the base of your roses clear, especially toward the end of the season, can remove this home and keep your roses safe next spring.
Clean any fallen leaves or trimmed canes from around the base of the plant. If they already show signs of disease, don’t compost them. Discard any affected foliage to avoid spreading spores around your garden.
Don’t Overfertilize
Unfortunately, fertilizing incorrectly can increase susceptibility.
Fertilizing is an important part of rose care. Unfortunately, incorrect fertilizing can lead to several problems, including increased susceptibility to pathogens.
Overfertilizing stresses roses, much like incorrect watering. It leads to the growth of new leaves and stems that may not develop properly. Excess fertilizer also causes nutrient imbalances in the soil. These issues create the ideal opportunity for infection.
Only fertilize your roses when they need it based on growth rate, soil conditions, and seasonality. If you notice issues with growth, don’t look to fertilizer to resolve your problems. Always follow the instructions on the packaging.
Choose Less Susceptible Varieties
Many rose varieties are labeled powdery mildew resistant, a great choice if you have continuous issues.
The final preventative measure is to start with roses that are less susceptible to powdery mildew in the first place. Many rose varieties are labeled powdery mildew resistant, a great choice if you have continuous mildew issues in your garden. It doesn’t mean it’s impossible for these roses to get powdery mildew, but it will be far less likely compared to other varieties. There are a few disease-resistant roses with beautiful blooms to choose from. Varieties like ‘White Drift’ or ‘Knock Out’ are great choices to keep your rose garden powdery mildew free.
