Photo and text - Missouri Botanical Garden
A strain of the fungus, Phytophthora infestans, causes late blight in tomatoes. As the common name implies, Phytophthora is prevalent on tomato hosts in late summer, after the plants have bloomed. Late blight is more common in north central and northeastern states, but is observed in the Midwest when the humidity is high and temperatures are around 68 degrees F late in the growing season. Watch for the disease when cool, moist nights are followed by warm, humid days.
There are many reports of "late blight" or Phythophora hitting tomato plants in the northeast. Phythophora is a water mold that we occasionally dealt with back in my days in the interior plantscaping business. It was almost always associated with a watering problem, as in too much. If you're in the northeast you know what a wet and cloudy spring we have had. Phythophora is no surprise to me.
I am in Knoxville TN. Although the ground, in which I have planted rooted tomato suckers, had never been planted in before (except grass), I have a major problem with late blight. The parent plants are perfectly healthy and bearing heavy fruit. I have thrown away at least 2 dozen tomatoes, so far. I have read that copper is needed, but your site indicates it's too late for that. I have no intention of throwing everything away. Any suggestions? By the way, this has been a cooler than usual, and wet, summer.
Posted by: Pat Serio | July 30, 2009 at 05:10 PM