Bacterial, viral and aster yellows-type diseases are usually of little or no consequence in canola and are not affected by tillage. Disease Control in Traditional Cultivation Traditionally, deep cultivation or plowing under of canola residue was used to bury fungal structures that carry over disease from one season to the next, or next several seasons. In moist soils, burial also greatly hastens crop residue decay. The amount of disease control is usually proportional to the effectiveness of residue burial. Disease Control in Direct Seeding Systems Crop rotation Crop rotation is essential to control canola diseases under direct seeding.
Rotation also allows better control of weeds, volunteer canola and insect pests.
If sclerotinia is a persistent problem, switch to Polish varieties which have lighter canopies and generally much lower infection levels, or use a recommended fungicide. If alternaria black spot is a persistent problem, use an Argentine variety if one is available for your area. Generally only Polish varieties suffer significant yield and quality losses from this disease. The waxier leaves of the Argentine types are much more resistant, but in wet weather there can be significant losses. Establishing healthy canola stands In direct seeding systems, as in any crop management system, growers must strive to establish a healthy, vigorous crop that is better able to withstand disease.