Mildew is the bane of all dedicated Rosarians. The most common type of mildew is powdery mildew, which is caused by the sphaerotheca pannosa var. rosae fungus. Powdery mildew is characterized by white or grayish powdery growth on the leaves, shoots, buds, and sometimes even appears on the petals of rose bushes.
These small patches of mildew spread in white strands across the plant’s foliage. As the fungus draws moisture and nutrients from the leaves, the leaves will begin to crinkle and fall.
Powdery mildew is not directly caused by the presence of free water on surfaces of the plant, but instead seems to thrive on hot, dry weather. Direct overhead watering during the midday may actually help the plant by breaking up spores that are released during the day. Fungicides may also be effective, although their application must be well timed in order to be effective.
The other most common type of mildew is downy mildew. Downy mildew is caused by the Peronospora sparsa fungus. Unlike powdery mildew, downy mildew thrives on moist and humid conditions. Downy mildew is most commonly observed under the leaves of the plant.
Other characteristics include purple, red, or brown spots on leaves, usually followed by yellowing of the leaves, then loss of leaves. Downy mildew is hard to control. Fungicides are not very effective, although regular pruning for increased air circulation and reduction of humidity can be helpful.
If you prefer to garden without the use of harsh fungicides, here are three easy ways to rid your prized roses of these common types of mildew.
Prune, prune, prune! Pruning is one of the easiest ways to keep your plants healthy and vigorous, and to prevent the formation of mildew on your prized roses. Practicing good pruning techniques allows your rose plants to receive good air circulation and even sun light distribution, which is crucial for preventing mildew. During the pruning season, when the plants are dormant, prune each plant, cutting above new buds so that growth is directed outward.
You should inspect your roses carefully on a regular basis throughout the growing season. Remove any dead or diseased shoots or stems. Carefully dispose of the rose debris by either burning it, or sealing it in a bag so it cannot spread disease.
Also, when you are determining plant placement, make sure your rose bushes are spaced appropriately. It is recommended that you space hybrid teas at 3 ft distances, and larger rose bushes at 4 ft. This allows your rose plants to dry out faster between watering, thus preventing conditions that may make them more susceptible to mildew.
Make sure your plant will receive enough sunlight. Rose plants that receive little light will produce thin leaves, be much more susceptible to nutrient deficiency, and will become ideal candidates for developing mildew.
Water roses carefully. Your watering practices are crucial in preventing the growth and spread of mildew. To prevent mildew, water your roses well at the root level, especially during hot weather. Try to keep water from getting and settling onto leaves, particularly before night falls. Most importantly, make sure you water regularly. Rose plants that receive insufficient water at the root level will become dehydrated. Dehydration is one of the most common triggers of mildew fungi.
Try concocting this easy home remedy for your roses. Some gardeners swear by the power of stinging nettle. Make a stinging nettle spray by gathering stinging nettle, placing them in a sack or old pillowcase, and crushing the leaves. Place the bag in a bucket of water and let sit in a warm location for roughly a week. When i’s time, strain the stinging nettle concentrate, and dilute it with five parts water. Pour this solution into a spray bottle and use it on your rose plants once every two weeks.
If you don’t have access to stinging nettles, try this easy to make baking soda-Based solution for fighting off mildew. You will need the following ingredients:
– 1 tbsp vegetable oil
– 1 gallon of water
– 1 tsp regular-flavored Listerine
– 1 tbsp liquid soap
– 1 ½ tbsp baking soda
– 1 tbsp vinegar
Mix one cup of water with baking soda, soap, Listerine, and vinegar. Add these ingredients into one gallon of water, and pour the solution into a plant sprayer. Make sure to shake well so the ingredients combine. Spray your rose bushes, saturating them thoroughly.