Our moist climate is ideal for fungus diseases on trees and other landscape plants. Cherry, Dogwood, Rose, and Photinia are particularly susceptible to leaf diseases such as anthracnose, mildew, black spot, or shot hole, during the spring and early summer. If you have plants which have been severely infected by one of these diseases in previous years, you may want to consider preventative measures.

Most of these diseases infect new leaves by producing spores from old infected leaves. This includes old, dead leaves which have fallen onto the ground. Raking up and disposing of these old leaves is the most important preventative measure you can take. I also usually remove black spot infected leaves on rose plants.

Several different pesticides (including natural ones) are available for preventing infection of new leaves. Three systemic chemicals are available which will actually stop the fungus from spreading in already infected leaves.

The three systemic fungicides are Propiconazole, Myclobutanil, and Tebuconazole. Propiconazole is available in Ferti-lome Systemic Fungicide. Myclobutanil is in Spectracide Immunex Fungicide. Tebuconazole is in Bayer All-in-One Rose and Flower Care.

Daconil and Chlorothalonil are also widely available and effective, but are not systemic and therefore protect only new uninfected leaves. In most cases you will have to look at the list of ingredients to find the technical, chemical names.

The three organic or natural fungicides are Messenger, Neem Oil, and Calcium Polysulfide. None of these are systemic and only protect uninfected leaves.

Spraying should begin as new leaves are emerging and continue every 2 to 3 weeks until weather becomes dryer in May.

March 6, 2015

Leaf Diseases on Flowering Trees and Shrubs

Our moist climate is ideal for fungus diseases on trees and other landscape plants. Cherry, Dogwood, Rose, and Photinia are particularly susceptible to leaf diseases such […]
March 6, 2015

Summer Insects

Insects multiply much faster in warm weather. Aphids and mites are two pests to watch for. Aphids (often called plant lice) are small soft bodied sucking […]
March 6, 2015

Insect Control

The best way to keep ahead of pests is to inspect the garden frequently and regularly. That way pests can be observed and controlled before much […]
March 6, 2015

Organic Insecticides

Many gardeners like to control insects organically or naturally as much as possible to avoid dangers in handling pesticides and residues on plants. An increasing number […]
March 6, 2015

Moss Control

Moss loves shade and wet areas. Moss is easily controlled. Moss Control products for plants contain a natural iron compound which not only kills moss but […]
March 6, 2015

Leaf Diseases on Flowering Cherry, Dogwood, Photinia and Peaches

Leaves of these trees and shrubs should be protected with a fungicide application as they begin to grow in late March and April. Most effective are […]
March 6, 2015

Rose Disease and Insect Control

Roses need repeated applications of fungicides and insecticides to protect them from diseases and insects through the growing season. The three main rose diseases prevelant in […]
March 6, 2015

Controlling Blackberries

The wild Himalayan blackberry is one of the most difficult weedy plants to control in the Pacific Northwest. Blackberry vines are so difficult to control because […]
March 6, 2015

Weed in Bites

I like to weed early in the morning. It is cool, and I can listen to the birds singing their morning songs. By weeding 10 to […]