Friday, September 18, 2009

Late blight- will it return next year?

Over the Labor Day weekend I had to pull out the 22 tomato plants in my home garden that were infected with late blight. I harvested the green tomatoes, stuffed the plants in large plastic bags and put them out with the trash.

A number of my neighbors and co-workers in Howard Co. had tomato plants that succumbed to this wicked disease. This summer, Home and Garden Information Center staff communicated with dozens of home gardeners across the state who reported late blight symptoms on their tomato plants.

I recently spoke with Karen Rane, Director of the Plant Diagnostic Lab at the U of MD. She said that the fungus-like pathogen that causes late blight- Phytopthora infestans- could only survive the winter on living host tissue. Tomato and potato plants die with the first hard frost, but pieces of un-harvested potato could remain in the soil. It's very important that all tomato and potato plants, especially potato tubers, be removed and discarded.

So will we see a repeat of this problem next year? Very unlikely, because three factors must be present at the same time and place- the host plant (potato or tomato); cool to mild, wet weather; and lots of disease spores. In 2009,large numbers of infected Southern-grown transplants were shipped into MD and other states for sale to home gardeners. Spores were blown around to new host plants and the disease spread from garden to garden.

There is no need to sterilize stakes and cages. It's always a good idea to rotate crops if you have the room in your garden. But it's ok to plant tomatoes in the same spot next year if that's the only good spot you have.

Read this excellent list of FAQs from Meg McGrath, Plant Pathologist at Cornell University.


2 comments:

  1. Useful article, but the McGrath link isn't working...

    ReplyDelete
  2. Thanks for letting us know. Try again, the link should work now.

    ReplyDelete

Comments with links to business websites will not be published.