The downy mildew scouting program is sponsored by the Ontario Cucumber Research Committee. Field scouting in Norfolk County is managed by Tania Keirsebilck-Martin at the Norfolk Fruit Growers’ Association. Field scouting in Kent County is managed by Cheryl Trueman at the Ridgetown Campus, University of Guelph. We thank Elaine Roddy, OMAFRA vegetable specialist, for her guidance with implementing this program.
In 2016, Cheryl Trueman compared several different cucumber downy mildew control programs in plots at the University of Guelph Ridgetown Campus. These studies indicated that the highest level of control was achieved using a three product rotation of Orondis Ultra A+B, Torrent and Zampro.
Several different product rotations were compared including:
Bravo-only applied 6 times.
a high input strategy that focused on optimal control and resistance management: Orondis Ultra A+B; Torrent; Zampro; Orondis Ultra A+B; Torrent; Zampro.
a low-input strategy that focused on early control and resistance management, switching to lower-cost fungicides in the final weeks of harvest: Orondis Ultra A + B (plus Bravo); Torrent; Zampro; Bravo; Bravo; Bravo.
a single application of Orondis Ultra, applied early followed by the other targeted downy mildew fungicides (Orondis Ultra A + B; Torrent ; Zampro; Torrent; Zampro; Torrent).
Control – no fungicides applied
Leaf Area Infected
Single Orondis Ultra in rotation
Final yields for both the high input and single Orondis Ultra (in rotation) were both significantly higher than the Bravo only programs. The yields for the high input program, were significantly higher than all other treatments.
Trace amounts of downy mildew were found in a Kent County cucumber field today by the University of Guelph, Ridgetown Campus, scout.
All cucumber growers in Ontario are advised to begin a preventative downy mildew spray program using targeted downy mildew fungicides. For more information fungicide selection, see the Ontario 2015 Downy Mildew Control Strategy for Cucumbers. Growers are also encouraged to monitor their own fields for early signs of infection (see figure 1, below).
Current weather conditions are very suitable for the spread of this very aggressive disease. Under these conditions, with downy mildew in the area, a 7-day spray schedule is warranted.
Cucurbit Downy Mildew has been identified in a cucumber field in Chatham-Kent, Ontario. Levels were very low (< 1% of the field). The infection likely occurred within the past few days. However, this does indicate that all area cucumber and melon fields are at a high risk of developing downy mildew at this time.
Continue to use a preventative fungicide program, rotating between the targeted downy mildew fungicides. For more information on fungicide selection, see the Downy Mildew Report – July 11, 2014.
Cucumber beetles are the primary vector of bacterial wilt. Even a fairly low population of beetles can spread this disease across the field. Once infected, there is no cure for this disease. Plants will rapidly wilt and die, effectively reducing the plant stand and the yield potential. Cucumbers are the most susceptible to bacterial wilt followed by melons, pumpkins and zucchini.