Sacramento Digs Gardening Article
Your resource for Sacramento-area gardening news, tips and events

Articles Recipe Index Keyword Index Calendar Twitter Facebook Instagram About Us Contact Us

No sugar-coating powdery mildew

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED MAY 18, 2020

Powdery mildew overwhelms the buds and new leaves on

this Dorothy Perkins rose. (Photos: Debbie Arrington)

This fungal disease loves mild spring weather, hates water

Does it look like someone dumped powdered sugar all over your roses and other plants? That’s an outbreak of powdery mildew, a very common condition this spring.

This fungal disease thrives in mild spring weather with afternoon temperatures in the 70s. It particularly likes roses but also can infect crape myrtle and sycamore trees plus azaleas, rhododendrons, begonias, mums, dahlias, sunflowers, coral bells, calendulas and zinnias as well as many other ornamentals. It can be problematic on apple and peach trees as well as raspberry vines. In the vegetable garden, it attacks the foliage on melons, pumpkins, squash, cucumbers, beans and peas.

Powdery mildew particularly likes plants growing in partial shade or next to a wall or fence. Those factors keep air temperature cool and just the way this fungus likes it. Walls and fences also cut down on air circulation, allowing powdery mildew to thrive undisturbed.

Once you see the telltale white fungus, it’s too late; the spores have already launched their attack. But you can minimize their spread. Clip off infected plant material, bag it up and dispose of it in the trash.

Sulfur sprays or powders are effective only before the disease appears. Neem oil may help contain an outbreak, but only if applied in the very early stages (and coverage must be thorough).

Two other tricks are more effective, easier and cheaper:

* Plain water works wonders against powdery mildew. Although it’s a fungus, it hates wet conditions. Keep the plant (and the soil beneath it) well watered. Water on plants inhibits the fungi’s germination and kills spores.

To knock off spores before they “sugar coat” your roses, give your plants a shower. Sprinkle water on the foliage from above, preferably in the morning. That gives the plant plenty of time to dry so the leaves don’t stay wet (and cause other fungal problems).

Before the white powder shows up, infected leaves will pucker

and become deformed.

* Inspect your susceptible plants regularly (daily if possible) and be on the look out for puckered or deformed leaves. Before releasing its white powdery spores, this fungus creates a spore-generating fruiting body, usually on the underside of a leaf. As it sucks energy from the leaf, the spore factory deforms its host. When it’s ready, it explodes with white spores all over that leaf and neighboring foliage.

Don’t wait; clip that puckered leaf off the plant and dispose of it before it can spread spores everywhere.

The good news: Powdery mildew will all be gone soon. It can’t stand temperatures above 90 degrees; 95 degrees pretty much wipes it out. Damaged foliage will fall off to be replaced by healthy leaves.

For more tips, check out the UC Integrated Pest Management pest notes on powdery mildew: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7493.html

Comments

0 comments have been posted.

GENERAL GARDENING

An article about gardening.

Keywords:

neem oil gardening powdery mildew Sacramento spring weather vegetables fungus pests roses UC IPM flowers

Newsletter Subscription

Sacramento Digs Gardening to your inbox.

Taste Fall! E-cookbook

Find our fall recipes here!

Thanks to Our Sponsor!

Local News

Sites We Like

Garden Checklist for week of Nov. 3

November still offers good weather for fall planting:

* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.

* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.

* Set out cool-weather annuals such as pansies and snapdragons.

* Lettuce, cabbage and broccoli also can be planted now.

* Plant garlic and onions.

* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.

* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.

* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.

* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.

* Give your azaleas, gardenias and camellias a boost with chelated iron.

* For larger blooms, pinch off some camellia buds.

* Prune non-flowering trees and shrubs while dormant.

* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.

Taste Spring! E-cookbook

Find our spring recipes here!

Taste Summer! E-cookbook

Find our summer recipes here!

Taste Winter! E-cookbook

Find our winter recipes here!