Plants showing late blight symptoms have been found at two sites in Chatham-Kent. These plants had not received any fungicide applications.
Growers should ensure that they have good fungicide coverage on their tomato fields. Standard fungicide programs containing the products listed below should offer good protection against the disease. Scout your fields and please let me know if you find suspicious symptoms. I can come out to confirm and to collect samples for the Agriculture and Agri-Food Canada team who are working to determine the strains occurring in Ontario.
If additional late blight infections are found, notifications will go out. If late blight appears to be spreading through the area, growers might need to consider tightening up their spray intervals.
Refer to the July 19, 2011 article, Tomato late blight management in Ontario, for more information on late blight. You can find links to more information at http://onvegetables.com/2011/07/19/late-blight-previous-posts/.
Fungicide recommendations (updated June 2012):
- chlorothalonil (Bravo, Echo), mancozeb (Manzate, Dithane), metiram (Polyram) – contact fungicides – have been very effective
- Tanos, Revus – translaminar, some “kickback” activity – have some ability to move into the plant – can add to the fungicide program, but rotate chemistries and use in combination with protectants for resistance management
- Acrobat – translaminar – has some ability to move into the plant – must be tank-mixed with another late blight fungicide from a different chemical family – can add to the fungicide program, but rotate chemistries
- Presidio – translaminar, some “kickback” activity – registered (in tank mix with Bravo), but note that after using it, rotation to any crop except brassica (head and stem), bulb vegetables, cucurbit vegetables, fruiting vegetables, leafy vegetables (except brassica), root and tuber vegetables (except carrot and sugar beet) is prohibited