Thursday, March 25, 2010

Steps to Prevent Late Blight for the 2010 Growing Season

Late blight (Phytophthora infestans) occurs commonly each year in many places around the United States and the world. There are steps that we, as home gardeners, market farmers, and commercial growers alike, can take in order to reduce late blight recurrence this growing season.

  • Pull up and throw away or burn any volunteer potato plants -- these sprout from tubers that may have gone unseen in the soil last fall during clean up and/or in the compost pile.
  • Plant certified disease-free potato seed pieces -- do not use seed pieces saved from last season.
  • Grow or purchase tomato seedlings that are healthy -- do not purchase or plant any seedlings that have disease symptoms.
  • Keep plants healthy and thriving to help them stave off disease pressures.
  • Follow recommended crop spacing and soil fertility, maximize greenhouse and hoop house air circulation, reduce insect pressures.
  • Cull any and all tomato or potato plants if they display late blight symptoms by throwing away or burning plant debris.
  • Treat plants with a preventative copper spray. We recommend item #9778, Champ® WG Copper Fungicide (OG).
  • Treat plants with hydrogen dioxide for prevention and treatment of late blight infections. We recommend item #9719, Oxidate® (OG).


In the Northeast US, only one type of late blight is found, so the measures outlined above will help reduce late blight disease pressure for the current growing season. In some parts of the US and the world, two different types of late blight can be found in the same location thus allowing the pathogen to mate and produce oospores which are capable of surviving temperature extremes. In this case, crop rotation is very important in reducing oospore inoculum on possible plant hosts. Crop rotation is important in all growing areas, no matter the size of your garden/field

For more on preventing late blight from overwintering, please read the Johnny's tech sheet pertaining to that topic.

1 comment:

Kathryn Maleney said...

I keep hearing that I should be sure not to plant this year's tomatoes where I planted them last year. That's fine, but how far from the first spot must they be? Is 25 feet away from last year's tomatoes alright? (I'm not sure I had late blight, but something ended their season early, and since the blight was prevalent in our area, I'm working on the assumption that that was the issue.