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Managing Late Blight in Potatoes and Tomatoes. Gardenscape 2011. Late Blight . Fast moving fungal disease attacks members of the Solanaceae family Sensitivity Tomato + potato > eggplant and pepper Damages leaves + stems = reduced yields Infects tubers and fruit = storage decay.
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Managing Late Blight in Potatoes and Tomatoes Gardenscape 2011
Late Blight • Fast moving fungal disease attacks members of the Solanaceae family • Sensitivity • Tomato + potato > eggplant and pepper • Damages leaves + stems = reduced yields • Infects tubers and fruit = storage decay
Late Blight on the Prairies • Relatively rare problem .. Primarily because “typical” Prairie summer conditions (hot and dry) are not conducive to the development and spread of Late Blight
2010 • Late Blight widespread across N. America • Widespread across SK by July • Hits commercial potato growers as well as backyard gardens • Many backyard gardens wiped out. • Commercial growers – mixed bag … even with advance warning and $$$ spray programs
Why so much Late Blight in 2010? 2009 - blight widespread across eastern N. America - blight blows into SK late in the season - causes minor crop loss due to late arrival - but did it get into the seed potatoes?
Why so much Late Blight in 2010? 2010 - planted seed contaminated with blight ?? + - ideal weather for development and spread of blight (cool, windy and wet)
So, what about Blight in 2011 ? Pathogen - Only way late blight can overwinter in SK is infected potato tubers - Disease carries into next year if .... a) diseased tubers discarded as culls manage to sprout b) diseased tubers used as seed
Managing Blight in Potatoes in 2011 ? Pathogen Diseased seed - heavily infected tubers ... - easy to detect and discard - will likely rot after planting = no spread - may spread spores to otherwise healthy seed at cutting time
Managing Blight in Potatoes 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
Managing Blight in Potatoes in 2011 Managing the Pathogen - Plant certified seed ... but even the commercial seed growers struggled to keep blight under control in their crops in 2010. - Ask your supplier about Blight pressure and their blight management program in 2010 - Check the seed carefully yourself
Managing Blight in Potatoes in 2011 Host - Cultivar sensitivity Sensitive – all reds, Shepody Moderate – Norkotah, Burbank, Yukon Gold Tough – Alpine, Classic, Milva, Yukon Gem
Shepody Y. Gold Milva Burbank Research Supported by ADF
Managing Blight in Potatoes in 2011 Managing the Pathogen Warming seed prior to planting = ideal conditions for spore formation of Blight Hold seed cold until planting Disinfect cutting equipment/surfaces regularly Cut “problem” seed lots last
So, what about Blight in 2011 ? Managing the Pathogen Scout field ... starting at emergence “When in doubt ... Pull it out”
Managing Blight in Potatoes in 2011 Managing the Environment - Avoid high risk fields in 2011 - low spots - spots with poor air movement - proximity to problems ??? - What’s going on next door ?
Managing Blight in Potatoes in 2011 Managing the Potato Crop Wider spacing = more air flow = dry canopy Avoid excess N fertility and water … as bushy plants = wet canopy Water early in the day so canopy dries before nightfall Water hills … not the foliage
Managing Blight in Potatoes in 2011 Managing the Potato Crop Good soil coverage minimizes infection of the tubers - gradually build a deeper than normal hill - re-hill following heavy rain - tubers set high in the hill = high risk
Managing Blight in Potatoes in 2011 Sprays to Manage Late Blight ? Limited options available to gardeners Copper spray (Bordeaux) Need to be applied preventatively = BEFORE the BLIGHT ARRIVES Need complete coverage of foliage Need to cover both leaf surfaces Need to re-apply as crop grows and after every rain/irrigation event
Managing Blight in Potatoes in 2011 Managing the Potato Crop Harvest after vines are dead/dried/removed Grade out suspect tubers going into storage ** If more than 5% of tubers rotten … Forget About Storage Store cool (4-6C) and dry Inspect frequently (visual + sniff test) and re-grade
Managing Blight in Tomatoes in 2011 ** Late Blight cannot be transmitted or carried over on tomato seed ** Late Blight can be introduced on transplants Some cultivars more Blight resistant - Juliet (Ve) and Santa (grape types) - Legend (T+M) (standard type) - Defiant (J) (standard type)
Managing Blight in Tomatoes in 2011 Many of the same management recommendations as for potatoes … Site selection Fertility and water management Row spacing + …. - prune and stake to further improve air flow Protective spraying
Managing Blight in Tomatoes in 2011 Protected cultivation - Late Blight not a problem in greenhouses as do not have continuous wet foliage
Managing Blight in Tomatoes in 2011 At harvest time … - Blight risk increases in fall due to higher RH and cooler temps + big canopy - consider benefit vs cost of harvesting mature green - keep harvested tomatoes separate during ripening + regrade frequently - grow to love green tomato pickles
Future ... 2011 will be a challenging year as ... - commercial seed system is not free of late blight - many backyard potato growers save seed for replanting = 10,000 starting points across SK? - backyard gardeners still unfamiliar with blight and blight management
Future ... If ... - 2011 is hot and dry - we educate ourselves on blight management It is possible that Late Blight may “recede” through 2011 ... and by 2012 or 2013 we will be back to “normal” If not .....
