Managing Late Blight in 2011 SSPGA/SVGA 2010

2010 Late Blight widespread across N. America Arrives in SK in July Commercial growers (SVGA, SSPGA, SGGA) warned in advance Backyard tomatoes wiped out. Ghse = ?? Potatoes – mixed bag

Why so much Late Blight in 2010?

blight arrives across SK late in the season - causes minor crop loss but did it get into the seed potatoes?

Why so much Late Blight in 2010? ideal weather for development and spread of blight (cool, windy and wet) - very difficult to maintain a decent spray program

So, what about 2011?

So, what about Blight in 2011 ? Pathogen - Late blight overwinters in infected tubers - Disease spreads into next year if.... a) diseased tubers discarded as culls are not disposed of correctly b) diseased tubers used as seed

So, what about Blight in 2011 ? Pathogen Diseased seed - heavily infected tubers... - easy to detect - will likely rot after planting = no spread - may spread spores to otherwise healthy seed at cutting time

So, what about Blight in 2011 ? Pathogen Diseased seed - Lightly infected tubers... - infected late in fall or at cutting time - no visible signs of rot - will likely sprout and develop into diseased plant = starting point of field infection

Al-Mughrabi

So, what about Blight in 2011 ? Managing the Pathogen - Plant certified seed... but Late Blight is not specifically covered in Certification Standards - Ask your supplier about Blight pressure and their blight management program - Grow out test results ? - Check the seed carefully yourself

So, what about Blight in 2011 ? Managing the Pathogen - Blight bioassay - randomly select 50 (100 ?) tubers - cut + hold at 20 o C at high RH for 2 weeks - look for Late Blight sporulation (3 days

So, what about Blight in 2011 ? Managing the Pathogen Standard conditions for curing cut seed = ideal for sporulation of Blight CUT... then PLANT Disinfect cutting, handling equipment regularly Cut “problem” seed lots last

So, what about Blight in 2011 ? Managing the Pathogen - need to stop infected seed from sporulating and infecting adjacent healthy pieces - grade out any diseased pieces - apply seed piece treatments immediately after cutting

Immediate application of seed treatments both stops infection and prevents spore formation

So, what about Blight in 2011 ? Managing the Pathogen Seedpiece treatments Poor – Easout and Maxim Good – Tuberseal, PST, Maxim MZ Evolve = TBZ + MZ + cymoxanil

Seed Piece Treatments Work !!

So, what about Blight in 2011 ? Environment - Avoid high risk fields in low spots - problem access fields - proximity to problems - Pay attention to weather at emergence - What’s going on next door ?

So, what about Blight in 2011 ? Managing the Pathogen Scout field at emergence Start preventative spray program early High risk fields curzate MZ at 80% emergence, then again 2 weeks later

So, what about Blight in 2011 ? Host - Cultivar sensitivity Sensitive – all reds, Shepody Moderate – Norkotah, Burbank, Yukon Gold Tough – Alpine, Classic, Milva, Yukon Gem

Milva Burbank Y. Gold Shepody Research Supported by ADF