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  • Roses
    • Types of Roses
    • Easy Roses
    • Climbing Roses
    • Portland's Rose Test Garden
    • Rose Insects & Diseases
    • Pruning Roses
    • Rose Sawfly
    • Rose Bloom Balling
  • Pruning Basics 101
    • Pruning Tools
    • Winter Pruning
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    • Pruning Clematis
    • Prune Your Own Garden Registration
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    • Sheet Mulching, Lasagna Gardening
    • Cover Crops
    • Composting
    • Compost Tea
    • Houseplant Winter Care
    • Hummingbirds in Winter
    • Winterize Your Garden
    • Ponds in Winter
  • Growing Food
    • Spring Veggie Gardening
    • Crop Rotation, Succession & Companion Planting
    • Harvesting
    • Growing Potatoes
    • Winter Veggie Gardening
    • Taming Tomatoes
    • Speeding up Tomato Harvest
    • Tomato Tips
    • Saving Tomato Seeds
    • Tomato Troubles
  • Plant Pests 1
    • Plant Pests Part 2 - Controlling Insects
    • Garden Inspections
    • Helping Pollinators
    • Dogwood Anthracnose
    • Viburnum Leaf Beetle
    • Dormant Oil/Lime Sulfur
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Plant Rusts

Amanda's Garden Consulting

Plant Rusts 

plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
It's difficult to grow hollyhocks without them suffering a bit of rust.
​Rust (Phragmidium spp.) is a common disease found on roses, beans, tomatoes, snapdragons, hollyhocks, fruit trees and many other plants. I admit it’s difficult to grow susceptible plants, such as hollyhocks, without them getting rust. Since they are not perennials, most people don’t bother with treating them with fungicides, as they often soldier on despite the infection. 
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
Whitish pustules develop on the leaf undersides.
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
The yellow patches on these foxglove leaves show symptoms of rust.
Symptoms: Lower leaves show the first symptoms with yellow spots on topside with whitish pustules on the undersides. The pustules mature to a reddish brown then become black and penetrate through to the topside of the foliage. As the infection progresses, the pustules drop off leaving small holes. Leaves yellow, becomes distorted and eventually fall from the plant. 
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
Pustules on the undersides of the foliage appear as yellow spots on the upper leaf surfaces.
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
The pustules mature to reddish brown then turn black.
Conditions: Rust is a common summer disease as it prefers warm temperatures, long days, high humidity and/or precipitation. The fungus is more prevalent when leaf surfaces don’t dry off quickly when it’s foggy, rainy and muggy. 
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
Rust on a hollyhock stem.
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
This infected red-twig dogwood stem must be removed and the pruners disinfected.
Disease Control: Remove all infected parts from the plant when they first show symptoms. Pick up any that have fallen on the ground. Discard diseased parts, don’t compost. Avoid touching infecting plants when they are wet to prevent spreading the disease. Disinfect pruning tools after each cut. 
Picture
An infected hollyhock leaf.
Picture
Leaves develop holes where the pustules form.
Prevention: Fall cleanup is essential as their spores overwinter, ready to re-infect in spring. Select rust resistant varieties where available. Don’t plant susceptible plants where rusty plants were previously located. Water in the morning as plants shouldn’t be wet at nightfall. Avoid placing susceptible plants where they will by dripped on by overhead tree limbs and drippy eaves.  Use soaker hoses and drip irrigation where practical. Too much nitrogen makes plants more susceptible, especially new growth. Improve air circulation by trimming neighbouring plants, and thin overcrowded areas. Treat susceptible trees and shrubs with dormant oil and lime sulfur in late winter just before bud break in spring. This combo organic spray kills overwintering insects as well as diseases.
 
Rake soil of infected debris then apply a 3 inch layer of organic mulch on top of the soil and around the plants. If mulch exists, top it up to 3 inches, where needed. Use broad spectrum organic fungicides: sulfur, copper or the bio-fungicides Bacillus subtilis. Follow the manufacturer’s full instructions and precautions. Reapply as instructed and cover the entire plant and surrounding soil to kill lingering spores. 
plant rusts,Phragmidium,plant rust symptoms,controlling plant rusts,plant diseases,plant fungus,hollyhock rust,the garden website.com,Amanda’s Garden Consulting,Amanda Jarrett
Despite being infected with rust, these hollyhocks still look pretty good.

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Copyright © 2017
  • Home
  • About, Services, Contact
  • Ask Amanda
  • Roses
    • Types of Roses
    • Easy Roses
    • Climbing Roses
    • Portland's Rose Test Garden
    • Rose Insects & Diseases
    • Pruning Roses
    • Rose Sawfly
    • Rose Bloom Balling
  • Pruning Basics 101
    • Pruning Tools
    • Winter Pruning
    • Pruning Grapes
    • Pruning Clematis
    • Prune Your Own Garden Registration
  • Lawn Basics
    • Lawn Reno, Seed & Sod
    • Lawn Maintenance Schedule
    • Spring Lawn Care
    • Moss in Lawns
    • Lawn Alternatives
    • Lawn Grub Control
  • Mulch & Mulching
    • Living Mulches - Groundcovers
  • Propagation
    • Growing Seeds Outdoors
    • Growing Seeds Indoors
    • Taking Cuttings
    • Seed & Plant Catalogues
  • How to Garden Topics
    • Fall Garden Chores
    • Planting Know-How
    • Soil Building
    • Watering Tips & Techniques
    • Drought Gardening
    • Sheet Mulching, Lasagna Gardening
    • Cover Crops
    • Composting
    • Compost Tea
    • Houseplant Winter Care
    • Hummingbirds in Winter
    • Winterize Your Garden
    • Ponds in Winter
  • Growing Food
    • Spring Veggie Gardening
    • Crop Rotation, Succession & Companion Planting
    • Harvesting
    • Growing Potatoes
    • Winter Veggie Gardening
    • Taming Tomatoes
    • Speeding up Tomato Harvest
    • Tomato Tips
    • Saving Tomato Seeds
    • Tomato Troubles
  • Plant Pests 1
    • Plant Pests Part 2 - Controlling Insects
    • Garden Inspections
    • Helping Pollinators
    • Dogwood Anthracnose
    • Viburnum Leaf Beetle
    • Dormant Oil/Lime Sulfur
    • Japanese Beetles
    • Peony Blotch/Measles
    • Slugs & Snails
    • Horsetail, the Weed
    • June Beetle
    • Powdery Mildew
    • Soil Solarization
    • Rhododendron Leaf Spot
    • Plant Rusts
    • Black Knot
  • Container Growing
    • Choosing a Container
  • Feeding Plants 101
    • Fertilizers & Ratios
    • Nutritional Deficiencies & Toxicities
    • Organic Plant Food
  • Plant of the Month
    • Spring Flowering Bulbs
    • Colourful Fall Plants
    • Abelia
    • American Sweetgum
    • Ash (Fraxinus) Trees
    • Astilbes
    • Aubretia, Rock Cress
    • Aucuba, Japanese Spotted Laurel
    • Autumn Crocus
    • Bear's Breeches
    • Beautyberry, Callicarpa
    • Black-eyed Susans
    • Bleeding Heart, Lamprocapnos spectabilis
    • Calla Lilies
    • Dahlias
    • Daylily
    • Delphiniums
    • Devil's Walking Stick, Aralia spinosa
    • Dwarf Alberta Spruce
    • Dwarf Burning Bush
    • Fall Asters
    • Flowering Currants
    • Flowering Quince
    • Fritillaria
    • Garden Peonies
    • Garden Phlox
    • Ginkgo biloba
    • Grape-hyacinths
    • Handkerchief or Dove Tree
    • Harry Lauder's Walking Stick
    • Heathers
    • Hellebores, Lenten roses
    • Himalayan Sweet Box
    • Jack-in-the-pulpit, Cobra Lily
    • Japanese Anemones
    • Japanese Forest Grass
    • Japanese Maples
    • Japanese Skimmia
    • Japanese Spurge
    • Laurustinus viburnum
    • Lavenders
    • Lily-of-the-Valley Shrub, Pieris japonica
    • Mediterranean Spurge
    • Mexican Mock Orange
    • Montana Clematis
    • Mountain Ash
    • Oriental Poppies
    • Oriental Lilies
    • Paperbark Maple
    • Pink Dawn Bodnant Viburnum
    • Poinsettias
    • Oregon Grape Holly
    • Ornamental Kale
    • Peruvian Lily, Alstroemeria
    • Phalaenopsis, Moth Orchids
    • Persian Silk Tree
    • Portuguese Laurel
    • Rose of Sharon
    • Sneezeweed, Helenium
    • Snowberry
    • Snowdrops
    • Star Magnolia
    • Strawberry Tree, Pacific Madrone
    • Stewartia
    • Torch Lily, Kniphofia uvaria
    • Tree Peonies
    • Tuberous Begonias
    • Virginia Creeper
    • Weigela
    • Winterhazel, Corylopsis
    • Winter Camellia, C. sasanqua
    • Wintergreen, Gaultheria procumbens
    • Witch Hazel
    • Wood Anemones
    • Yews
  • Garden Tour Blogs
  • Monthly Flower Arrangements
  • Website Index
  • Subscribe
  • Need Help?