Common Plant Diseases—And How to Tackle Them (2)

Clearing Out Old Material from the Garden and Keeping Plants Well Spaced
Avoid overcrowding so that air can circulate between plants, discouraging certain problems that thrive in damp places; keeping the plants further apart also means that disease is less likely to be spread directly from one plant to another. Basic maintenance, including mulching and clearing out old material (dead leaves or last season’s plant stalks, for example) will also help to prevent problems from developing. Many diseases are soil borne—so, keeping leaves from trailing in the soil will also be helpful. Use stakes and wire cages for plants like tomatoes.



Mulch
Using a mulch cuts down on weeds that may help spread disease or harbour insects that can both cause damage and help to spread disease from plant to plant. Mulching also creates a barrier between the soil and the plants in the garden. The less contact there is between the soil and the surface of the plants (including stem, leaves, and fruit), the less chance there is for soil-borne disease to be spread.

Powdery Mildew
Powdery mildew can be identified by the white or gray powder that coats flower buds, leaves and stems. Flowers become discoloured and distorted; white or gray patches can spread over the entire surface of the plant, including the flowers and the fruit. Keeping plants well spaced and encouraging air circulation is key; remove infected areas, wash, or spray infected plants and keep a close eye on affected plants to prevent the spread of the disease. Don’t assume that the disease will only take over when conditions are damp; spores can spread in dry conditions as well—so keep an eye on plants such as cucumber, rose, and zinnia in all weather conditions.

Wilt
Beginning at ground level, vegetables and some annuals will simply wilt and become discoloured. The disease may affect certain parts of a plant, or else the entire plant—in which case the plant should be removed and destroyed, ideally bagged first and disposed of away from other areas that could be contaminated. Fusarium and verticillium wilt are soil borne diseases. The disease works its way up from the roots through the water vessels, eventually cutting off the water supply to the leaves of the affected plant. If the problem persists or is particularly prevalent, you may need to completely change over the soil. Simply rotating crops from year to year will help prevent wilt, and in many cases it can clear up on its own with little fuss.