There has been a new development in the late blight situation this week. Recently late blight symptoms were observed on tomato plants in Ottawa County in Eastern Ontario. Industry specialists that were able to see extensive photos of the infected plants are confident that the symptoms are late blight and samples were collected for laboratory testing.
Usually, late blight spores are blown in on strong winds from the south. However, given that there have been no recent reports in U.S. border States or other parts of Ontario, it is unlikely that infections will appear in other growing regions.
Tomato and potato growers in Ottawa County should scout for late blight symptoms in their fields and maintain a fungicide spray program that includes broad spectrum fungicides with activity against Phytophthora infestans. Consider the application of a late blight specific fungicide if risk is very high, such as when symptoms are observed in the field or nearby fields.
Growers in other tomato and potato growing areas should continue to monitor the situation in Eastern Ontario and the bordering U.S. states and judge their risk accordingly.
A summary of fungicides for late blight management in tomato is available here.
If you suspect late blight in your crop, please reach out to the appropriate OMAFRA specialist to confirm the diagnosis.
Tomato – Amanda Tracey (firstname.lastname@example.org, 519-350-7134)
Potato – Dennis Van Dyk (email@example.com, 519-766-5337)