The disease has also been found in Ohio and has been spreading throughout the southern United States. With the unsettled weather conditions in Ontario over the last week, which was favourable for infection and disease development, more cases of downy mildew will most likely be reported in Ontario over the next week. However, with the return to warmer dryer conditions forecasted for many parts of Ontario over the next few days, disease spread and infections should slow down a bit.

Since downy mildew is spreading around the province, growers should keep up to date on the progress of this disease. Successful management of this disease is accomplished when fungicides are applied prior to the disease infecting the crop so it is imperative that growers apply a fungicide to prevent the establishment of downy mildew in their crops on a five to seven day schedule. If possible, apply a fungicide before a rainfall event, dew or prior to overhead irrigation.

There have been several reports that Bravo tank mixed with mancozeb has done a very good job of keeping downy mildew at bay this year. In my experience, Bravo tank mixed with mancozeb for many diseases in other crops works very well when applied early and on continual program. Although there is a low risk of resistance developing to Bravo or mancozeb, it is important to avoid the potential of resistance developing to any fungicides by rotating between fungicides from different chemical families. Never apply the same fungicide from the same family back to back in the field.

There have been a few fields with some plants showing symptoms of angular leaf spot, gummy stem blight and Fusarium wilt. There have also been a few fields with cucumber beetle damage. Cucumber beetles can transmit the bacteria pathogen that causes bacterial wilt, so growers should keep an eye out for symptoms of this disease over the next couple of week particularly in fields that have cucumber beetle damage.