Category Archives: late blight

Disease, Fungicides, late blight, Pest Management, Tomatoes

Late blight alert – July 27th, 2017

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This information is updated from an earlier article by Janice LeBoeuf.

We have had multiple reports of late blight in conventionally managed tomato fields this week.  Typically, this disease is well managed in tomatoes with a broadspectrum fungicide program including chlorothalonil.  However, high disease pressure due to environmental conditions, combined with a dense leaf canopy and rapid growth may have resulted in poor spray coverage and reduced efficacy.

Commercial growers should scout often and ensure they are using fungicides with good late blight activity in their fungicide program.  When late blight is in the area, spray intervals should be shortened.

Under continued high disease pressure, growers should consider adding a targeted late blight fungicide to the spray program.  If late blight has been identified in a field, use a fungicide with curative and antisporulent activity, see the table below for late blight fungicides and their properties. Continue reading Late blight alert – July 27th, 2017 →

Disease, Fungicides, late blight, Pest Management, Tomatoes

Late blight alert – June 28

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Late blight foliar lesionLate blight has been confirmed on tomatoes in Chatham-Kent.

Recent weather has been conducive to the development and spread of late blight.  Commercial growers should scout often and ensure they are using fungicides with good late blight activity in their fungicide program.  When late blight is in the area, spray intervals should be shortened. Continue reading Late blight alert – June 28 →

Disease, late blight, Pest Management, Tomatoes

Late blight spores detected in Dufferin and Simcoe counties – 2

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Advanced late blight symptoms

The Ontario Potato Board reports that for the second time this season, late blight spores have been detected in their spore traps in the Shelburne and Alliston areas. Late blight symptoms have not been detected, but it means that spores were present in the area. Continue reading Late blight spores detected in Dufferin and Simcoe counties – 2 →

Disease, late blight, Pest Management, Tomatoes

Late blight update – July 28

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Early foliar symptoms of late blightTo date, I know of no confirmed cases of late blight in Ontario, but there have been a couple of reports out of Michigan (on potatoes). Nevertheless, our experience of recent years would indicate we are likely to see it in Ontario tomatoes at some point in the season.

Remember that conventional tomato growers using a recommended fungicide program for early blight, septoria leaf spot, and anthracnose, are also protecting the crop from late blight infection. Cloudy and high humidity or wet conditions are favourable for late blight.  The pathogen prefers cool temperatures.  The disease is suppressed by hot, dry weather, but it can continue developing and spreading when suitable conditions return.

If late blight is found in the area, tomato growers should: Continue reading Late blight update – July 28 →

Disease, late blight, Pest Management, Tomatoes

Late blight spores detected in Dufferin and Simcoe counties

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Advanced late blight symptoms

The Ontario Potato Board reports that late blight spores were detected in their two spore traps in the Shelburne and Alliston areas on July 7. Late blight symptoms have not been detected, but it means that spores were present in the area. Continue reading Late blight spores detected in Dufferin and Simcoe counties →

Disease, late blight, Pest Management, Tomatoes

Late blight update – July 10

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Early foliar symptoms of late blightTo date, I know of no confirmed cases of late blight in Ontario, but it has been found on potato in Branch County, Michigan (south of Battle Creek). Nevertheless, our experience of recent years would indicate we are likely to see it in Ontario tomatoes at some point in the season.

Remember that conventional tomato growers using a recommended fungicide program for early blight, septoria leaf spot, and anthracnose, are also protecting the crop from late blight infection. Cloudy and high humidity or wet conditions are favourable for late blight.  The pathogen prefers cool temperatures.  The disease is suppressed by hot, dry weather, but it can continue developing and spreading when suitable conditions return.

If late blight is found in the area, tomato growers should: Continue reading Late blight update – July 10 →