Category Archives: late blight

Late blight alert – July 27th, 2017

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

Late blight alert – June 28

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

Late blight spores detected in Dufferin and Simcoe counties – 2

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

Late blight update – July 28

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

Late blight spores detected in Dufferin and Simcoe counties

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

Late blight update – July 10

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

Fungicide efficacy summary tables for management of diseases in field tomatoes

By Cheryl Trueman, Ridgetown Campus – University of Guelph

About these tables:

  • Efficacy Table - AnthracnoseThese tables were created using results from replicated processing tomato field trials at the Ridgetown Campus, University of Guelph. Please contact the author for more information on research methods and copies of full reports. The tables are for information only and do not guarantee successful results with the use of any product.
  • Always check the most recent version of the product label before applying any product.
  • Only products labelled for ‘control’ of the specific disease are included in each table except where noted.
  • Click on each table to see larger versions.

Continue reading Fungicide efficacy summary tables for management of diseases in field tomatoes

New pesticide registrations or label expansions for tomato, pepper, eggplant

There’s quite a bit new in field tomato, pepper, and eggplant crop protection in the last year or so. Here’s a quick reference for Ontario growers (this is probably not even a complete list). Unless otherwise noted, products are registered for control1 of the listed pests.

Fungicides, Bactericides

Aprovia (benzovindiflupyr)

  • Crops: Fruiting vegetables
    • Early blight, anthracnose, powdery mildew, septoria leaf spot
  • Notes: Group 7 fungicide.

Bravo ZN (chlorothalonil)

  • Crops: Tomato
    • Early blight, late blight, septoria leaf spot, anthracnose, botrytis gray mold
  • Notes: Group M fungicide.

Continue reading New pesticide registrations or label expansions for tomato, pepper, eggplant

Top posts of 2015

Did you have a favourite ONvegetables.com post in 2015? Is there one you keep referring back to — or sharing with others?  Here’s a list of the ten or so of the most popular articles of 2015.

Fusarium#1 Fusarium basal plate rot of onion and garlic

This is actually a 2012 post, but with a catchy title like that, no wonder it’s still popular!

Weed growth at 300 CHU or 450 GDD after clean weeding#2 How fast do weeds grow?

That’s the question on everyone’s mind, isn’t it? This 2011 post is still getting a lot of views.

Late blight fruit symptoms#3 Tomato late blight photo gallery

A picture is worth 1000 words, they say. This post has 23 pictures, so it’s worth 23,000 words. Aren’t you glad you didn’t have to read that many! And I’m even more glad I didn’t have to write them! Continue reading Top posts of 2015