Vegetable Crop Update - Vine Crop Edition

by Elaine Roddy, Vegetable Crop Specialist, OMAFRA, Ridgetown

Over the past 3 years downy mildew has shown up first in early-planted cucumbers grown under row covers.  Cucumbers grown in small hoop houses also appear to be particularly susceptible to early-season downy mildew infections.

While many of these crops are just getting established in the field, there are some key steps that growers can take to ensure the health and productivity of this crop.

1. Ensure all transplants are free from disease.  Plant only vigorous plants, the health of the plant will not improve in the field.

2. Produce vegetable transplants in greenhouses used solely for transplant production.

3. Where row covers are used; apply either Ranman 400SC immediately after field-setting, just prior to covering plants with row covers or tunnels.

4. Immediately after the row covers or tunnels are removed, apply Tattoo C.¹

5. Follow a 7-day preventative fungicide program using Ranman 400SC and Tattoo C.¹

6. Always rotate between chemical families.

Very low levels of downy mildew have recently been reported in greenhouses in Southwestern Ontario.  While this information is anecdotal, this is the first report of this disease in Ontario for the 2009 season.  Disease levels have been effectively controlled through preventative fungicides and environmental management practices. There have been no indications of further spread in the commercial greenhouse industry.  

While this may seem an early development of disease in Ontario, it is actually consistent with reports made in previous years.  Given recent wet, cool weather conditions, cucumbers grown in small-scale hoop houses, high tunnels and under row covers should be intensively scouted for signs of downy mildew.

All growers of direct-seeded cucumbers should maintain a strong preventative fungicide program, starting no later than vine development.  If weather conditions during the seedling stage are cool and wet; sprays should be initiated earlier.  Banded applications during the seedling stage will allow growers to drastically reduce the cost of spraying.

¹Tattoo C is pending final approval from the PMRA.  Before you spray, contact the OMAFRA Vegetable Crop Specialist (519-674-1616 or elaine.roddy@ontario.ca) or the Ontario Processing Vegetable Growers  (519-681-1875) to confirm its registration status.