Gardening Tips: Keep an eye out for disease

May diseases that affect plants are spread by water droplets the hitting leaves. This may be caused by rain or even your watering habits. If you water gardens with sprinklers or stand with a hose and spray the foliage, there is more chance for diseases to spread.

You can't control the rain, but you can deliver water to the roots of plants rather than soaking the leaves. Also, water in early morning so foliage has a chance to dry before strong sun hits it or early evening, so that foliage doesn't stay wet overnight.

It is much easier to prevent disease than cure it, so keep an eye out for the start of problems and catch then quickly. You can also take note of plants you have that regularly have the same problem.

Use the correct fungicide early to prevent the disease from taking hold. You can even use lime sulphur as a dormant spray in early April before leaves emerge. This treatment will kill some of the over-wintering disease spores that are on the plant.

There are three main fungicides available in Ontario: copper sulphate and sulphur are powders that when mixed with water are sprayed on leaves and stems; Natria is a liquid, broad spectrum fungicide that protects plants from many common fungal and bacterial diseases.

It is made from a unique strain of Bacillus subtillis, a naturally occurring bacteria found in soil. It prevents and destroys disease but is not harmful to beneficial insects, pets or wildlife.

Natria can prevents powdery mildew, downy mildew, leaf spots, botrytis blights, grey mold and anthracnose and can be used on a wide range of plants. This is the product to use on roses, garden phlox, bee balm, geraniums, petunias and more. 

It is also safe for edible crops, such as cucumber and zucchini, right up to the day of harvest. This is the fungicide that thousands of farmers use to grow disease-free fruits, vegetables and flowers.

Right now, examine trees in the plum family for the disease black knot. It is very evident on branches as a swollen, black mass of tissue. Prune out as soon as you notice by cutting eight inches below affected areas.

Dip pruning tools in rubbing alcohol between cuts to help prevent the spread of disease. Bag and discard diseased branches or burn them. Spray the remaining plant with copper sulphate to help control this problem. Next spring, use lime sulphur as a dormant spray.

Also keep an eye out for the destructive disease Fire Blight. It can hit many in the fruit family, including Mountain Ash. In the early stages of infection, blossoms appear water soaked and gray-green but quickly turn brown or black. Generally, the entire flower cluster becomes blighted and killed.

The most obvious symptom of the disease is called the shoot blight phase, which first appears after petal fall. The leaves and stem on young, succulent shoot tips turn brown or black and bend over into a characteristic shape similar to the top of a shepherd's crook.

Small droplets of sticky bacterial ooze often can be seen on the surface of these blighted shoots when the weather is warm and humid.

Under favourable conditions, shoot blight infections will multiply and continue to expand down the stems, causing the tree to appear scorched by fire. Shoot blight infections can expand beyond the current season's growth into the older supporting wood, causing dark sunken cankers to form.

There is no cure for fire blight and the best way to deal with the infection is to remove infected stems and branches. Use the same pruning and discard method as outlined above with Black Knot.

Unfortunately, if Black Knot or Fire Blight gets in the main trunk of a tree, the entire tree will have to be removed. Early detecting and control is important.