garden diseases

Powdery Mildew

Powdery Mildew is caused by several different fungi. The white, sometimes cottony growth attacks most any part of a plant under both humid and dry conditions. It can cause disfiguring to the leaves and flowers, defoliation, and in uncontrolled situations, prolonged infection can cause death in some plants. Spores are carried into the garden by wind and can grow on most any plant they land on. Good garden hygiene and proper plant culture can reduce the chances of infection in your garden.

Management

Remove all infected material from the garden. Do not put clippings in the compost. You can control powdery mildew with a variety of materials. Sulphur and copper are two common controls that have very little impact on the environment. They control the spread of the mycelium of the fungi by affecting the pH of the leaf surface. Sprays that directly control the fungi are available. We have found controlling powdery mildew is easier to achieve by varying the products used with each application.

Rust

Rust looks just as it sounds, orange to yellow orange fungal growth typically on the leaves and stems of many plants. When mature, orange, dust like spores are produced. These spores spread through the garden by wind, are carried by insects, or fall on other plants where growth can then begin again. Other signs of infection can include irregular patches of yellowing tissue with either orange or brown centres or mottling of the leaf. Favourable conditions for most rusts are; high humidity and temperatures between 55-75 degrees.

Management

Control with applications of copper or sulphur containing fungicides through the period when the conditions are favourable for fungal growth. Remove any infected part of the plant and discard all clippings and debris collected from around the plant. Sulphur and copper are two common controls that have very little impact on the environment. They control the spread of the mycelium of the fungi by affecting the pH of the leaf surface. Sprays that directly control the fungi are available. We have found controlling rust is easier to achieve by varying the products used with each application.

Sooty Mould

This is one of several types of fungi that grow and feed on the sugary excretions left on the surfaces of plants by several types of sucking insects, such as, Aphids, Mealy Bugs, Scale, Thrips, and Whiteflies. This mould does not attack the plant directly but can threaten the health of the plant by inhibiting light from reaching the leaf surface, which, in turn, stops photosynthesis. Without being able to photosynthesis the plant will die.

Management

Control with applications of copper or sulphur containing fungicides through the period when the conditions are favourable for fungal growth. Remove any infected part of the plant and discard all clippings and debris collected from around the plant. Sulphur and copper are two common controls that have very little impact on the environment. They control the spread of the mycelium of the fungi by affecting the pH of the leaf surface. Sprays that directly control the fungi are available. We have found controlling rust is easier to achieve by varying the products used with each application.

Gummosis or Bacterial Canker

This bacteria attacks trees that produce stone fruit, such as, cherries, apricot, plums, peaches, and nectarines. Sunken areas of soft tissue form along branches and on the trunk. These areas ooze thick, amber coloured, sour smelling gum in fall, winter, and spring. Some of these trees will naturally ooze this same gum from cracks in the bark which occur during years with severe weather; this is a natural thing for the plant and treatment is not necessary. The difference between natural gum and bacterial gum is the smell. The bacterial gum will have a distinct sour smell where the natural gum will not have a fragrance or be slightly sweet smelling.

Management

Bacterial canker is difficult to control. Clean out infected lesions along the trunk and main branches. Be sure to remove all infected material from the site. Prune out the smaller branches, sterilizing your cutting tools after every cut. It is best to prevent infection by keeping your plant healthy.

Verticillium

This bacterium attacks many trees and shrubs. It resides in the soil and enters the plant through the roots. The disease travels up the plant through the water conducting pathways. As it becomes established in these pathways, water can no longer pass through and the reliant parts of the plant die. Dark brown or purple streaking along the branches will confirm infection. The leaves along the infected branches may become yellow and drop, wilt unexpectedly, or not emerge in spring. Remove all dead wood. If leaves wilt and drop in mid summer, do not remove the suspect branch until the following spring to ensure the branch is dead. Many times a branch will re-leaf and resume healthy growth.

Management

There is no chemical control. To avoid infection keep your plants healthy, avoid over watering any plant. If you have lost a plant to verticillium, plant a verticillium resistant plant back in the same area.