Disease Late Blight Pest Management Tomatoes

Suspected late blight found in tomato in Essex

Previous 2012 late blight updates: May 31June 4July 20July 27,  July 30August 16August 21, August 22.

OMAFRA staff have identified a suspected case of late blight in Essex County in tomato. Symptoms on leaves, stems, and fruit are consistent with late blight and show a positive using an Immunostrip test for Phytophthora. The sample will be submitted to Agriculture and Agri-Food Canada for lab confirmation. Update: 2012 08 30 10:20 am – Agriculture and Agri-Food Canada has confirmed the presence of late blight in the sample.

Numerous new late blight findings have also been reported in the US northeast over the past week.  Rainfall, fog, and cool nights create favourable conditions for the pathogen.  Growers in southwestern Ontario should now shorten fungicide intervals and use only fungicides with good late blight activity.  Under current conditions, a fungicide should be applied every 5 – 7 days to protect against late blight.  Keep in mind that TOMcast does not work for timing late blight fungicide applications.

In other areas of Ontario, farther from confirmed cases, growers should scout their crops often and ensure that they are using good late blight protectants.  See below for recent US reports, some not too far from Ontario.

Fungicide recommendations:

  • 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

Recent US late blight reports:

  • August 28 — Grafton County, NH (tomato)
  • August 27 — Schuylkill County, PA (tomato)
  • August 27 — Northumberland County, PA (tomato)
  • August 27 — Cambria County, PA (tomato)
  • August 25 — Steuben County, NY (tomato)
  • August 23 — Ulster County, NY (tomato)
  • August 23 — Herkimer County, NY (tomato)
  • August 23 — Westmoreland County, PA (tomato)
  • August 23 — Perry County, PA (tomato)
  • August 23 — Wayne County, northern OH (tomato)
  • August 22 — Chenago County, NY (tomato)
  • August 22 — Columbia County, NY (tomato)
  • August 22 — Clinton County, NY (tomato, US-23)
  • August 22 — Geauga County, northern OH (tomato, US-23)

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