A number of diseases have appeared in lettuce fields. Botrytis gray mold, Sclerotinia drop and Rhizoctonia bottom rot have been observed at moderate levels in many areas. Also monitor carefully for downy mildew and bacterial soft rots. Celery has also developed several common diseases during this wet period. Septoria late blight, Cercospora early blight and bacterial blight have increased quickly in many areas including Ontario and Michigan.
Bacterial blight appears to be the most prevalent currently.
Carrots have also developed a number of major foliar and root diseases in the past few weeks especially in areas where heavy rains have been received. Cercospora and Alternaria leaf blights and bacterial leaf blight are increasing quickly especially on susceptible cultivars. In addition, high levels of Pythium root dieback have been seen in some areas. Early symptoms of violet root rot and crown rot have also appeared in some areas of SW Ontario. Aster leafhopper numbers are moderate in most areas of southern Ontario on celery, carrots and lettuce.