What is wrong with my canola?

Do the leaves have yellow-brown, concentrically ringed spots?

Are the plants rapidly wilting and dying, often without turning yellow, small black fungal bodies may be present on the surface of the root just below the soil line?

Are the seedlings dying and the stems are girdled or rotted at the soil line?

Are the roots enlarged and clublike, plants are stunted with yellowish leaves that wilt during the day?

Do the leaves have pale areas on upper surfaces and "downy" patches underneath?

Are there any white blisters on the undersides of the leaves?

Are there any round or irregularly shaped gray necrotic lesions on leaves with dark margins?

Yellow-brown and concentrically ringed spots are caused by fungal disease - Alternaria blight. This disease attacks lower leaves first. As the disease progresses leaves and eventually the whole plant will die. Spray plants with copper at the first signs of disease.

Sclerotinia stem rot (white mold) is a fungal disease that causes these symptoms. Wet weather conditions favor this disease. The disease is usually introduced to non-infected areas by infected seeds. Plant only certified seed. If the disease is known to present rotate crops with non-hosts such as cereals.

If your seedlings are falling over and the stems are girdled or rotted at the soil line, the most likely cause is a damping-off disease. Remove and destroy all infected plants. To prevent damping-off let the soil surface dry between waterings, thin seedlings to avoid overcrowding, and do not add nitrogen fertilizers until plants have developed leaves.

Enlarged and clublike roots are most likely caused by fungal disease - Clubroot. Remove and destroy any infected plants. Applying lime to the soil can reduce fungus sporulation.

Pale areas on upper surfaces of the leaves and "downy" patches underneath are caused by Downy mildew. This fungus spreads quickly during cool, wet nights and warm, humid days. Leaves will wilt and die. Remove and destroy all affected plant parts and encourage good air circulation around plants by thining them. Water plants early in the morning to make sure they dry before nightfall.

If there are white blisters on the undersides of the leaves the culprit is a fungal disease White rust. Destroy infected leaves or plants. Prevent problems by thinning plants to increase air circulation and by planting tolerant cultivars.

Round or irregularly shaped gray necrotic lesions on leaves with dark margins indicate a fungal disease - Blackleg. Other symptoms include stem with sunken areas that enlarge over time. Dead leaves will stay attached to the plant. Spray plants, especially the stems, with copper at the first sign of disease.

Three viruses infect canola, Turnip yellows virus (TuYV), Cauliflower mosaic virus (CaMV), and Turnip mosaic virus (TuMV). Symptoms are very variable, from no visual indication to stunted red plants and stiffening of leaves for TuYV, chlorotic ring spots and mottling for CaMV, and yellow mosaic patterning and tip necrosis for TuMV. Control broadleaf weeds as they can act as reservoirs for the viruses. Control aphids. Destroy infected plants.