Bulbs
Flower Basics
Flower Beds & Specialty Gardens
Flower Garden
Garden Furniture
Garden Gnomes
Garden Seeds
Garden Sheds
Garden Statues
Garden Tools & Supplies
Gardening Basics
Green & Organic
Groundcovers & Vines
Growing Annuals
Growing Basil
Growing Beans
Growing Berries
Growing Blueberries
Growing Cactus
Growing Corn
Growing Cotton
Growing Edibles
Growing Flowers
Growing Garlic
Growing Grapes
Growing Grass
Growing Herbs
Growing Jasmine
Growing Mint
Growing Mushrooms
Orchids
Growing Peanuts
Growing Perennials
Growing Plants
Growing Rosemary
Growing Roses
Growing Strawberries
Growing Sunflowers
Growing Thyme
Growing Tomatoes
Growing Tulips
Growing Vegetables
Herb Basics
Herb Garden
Indoor Growing
Landscaping Basics
Landscaping Patios
Landscaping Plants
Landscaping Shrubs
Landscaping Trees
Landscaping Walks & Pathways
Lawn Basics
Lawn Maintenance
Lawn Mowers
Lawn Ornaments
Lawn Planting
Lawn Tools
Outdoor Growing
Overall Landscape Planning
Pests, Weeds & Problems
Plant Basics
Rock Garden
Rose Garden
Shrubs
Soil
Specialty Gardens
Trees
Vegetable Garden
Yard Maintenance
Powdery Mildew on Maple Trees
Powdery Mildew on Maple Trees. Powdery mildew is a common problem of maple trees, and trees in general, and is caused by a range of different fungi. The underlying fungus is different for different species, but all these fungi cause the growth of a white mold on the tree’s leaves and stems. Though this mildew can be unsightly, the damage it...
Powdery mildew is a common problem of maple trees, and trees in general, and is caused by a range of different fungi. The underlying fungus is different for different species, but all these fungi cause the growth of a white mold on the tree’s leaves and stems. Though this mildew can be unsightly, the damage it causes a maple tree is minimal. The mold looks like a dusting of fine, white powder, hence its name.
Life Cycle
The white patches visible on maple tree leaves are the means by which the fungus produces its spores. The spores are then spread to other parts of the maple, or to other plants, by the wind. The spores are highly specific, so the fungus that causes powdery mildew on a maple is only able to colonize other maples or similar plant species. The fungus overwinters on infected leaves or fallen leaves, and releases its spores in the spring.
Symptoms and Damage
The white mold patches caused by powdery mildew fungi are the most obvious sign of this fungal infection. These patches can grow to cover entire leaves or patches of leaves. The leaves may then turn yellow, drop early, or become twisted. The white patches may develop black spots as the fungus prepares to survive the winter.
Environment
Powdery mildews don’t require the same wet conditions that many fungi do. While high relative humidity promotes the fungus’ spore germination, the fungus does not need wet leaves to infect a maple. Air circulation through a maple’s branches can keep the environment from becoming damp enough for the fungus to germinate its spores. Pruning branches to increase air flow is a good idea, but improper pruning can harm the health of the tree, and stressed, unhealthy maples are more susceptible to fungi and other problems.
Management
Because the fungus causing powdery mildew overwinters in leaf debris, one way to manage it is to gather up and destroy all fallen leaves in the autumn. Fungicides can be applied during the growing season as soon as you notice white patches on your maple. You should also avoid applying nitrogen fertilizers after you’ve spotted the fungi. Nitrogen increases the production of foliage and provides more material for the powdery mildew to inhabit. Avoid overhead watering to help reduce dampness and humidity.
