If rust pustules are visible on the corn leaves prior to tassel emergence, then fungicide applications may be justified. Black rot and Alternaria spot has been found in several areas of Ontario. Bacterial spot of cauliflower has also appeared and should be monitored carefully as wet weather continues. Clubroot disease is also present in areas of fields with high clubroot levels. Rhizoctonia wirestem and head rot are also common in many fields.
Diseases continue to increase quickly in Asian crucifer greens also.
In Nappa cabbage bacterial soft rot, Alternaria, black rot and downy mildew are common. Numbers of diamondback moth larvae and imported cabbageworm have not increased this past week in southern Ontario. Careful monitoring, use of thresholds and rotation of pest management methods will help to reduce damage. Do not use the same material twice in a row for diamondback moth control. Formulations of Bacillus thuringiensis, Dipel or Thuricide are recommended whenever possible.