Last week I visited 4 community gardens in different areas of Connecticut and found the same results in all of them when it came to tomatoes and squash. Most tomato plants were halfway defoliated by the verticillium and fusarium wilts and in a couple of cases some had contacted late blight.
The majority of squash plants were either decimated by the squash vine borer larvae or invaded by the squash bug, which is almost as detrimental because it makes pot marks on the fruit and renders it unappealing and unpalatable.
To protect my tomato plants from the above afflictions, I use liquid copper or Bordeaux mix exclusively, starting at seedling stage and continuing throughout the growing season. Healthy tomato plants should yield a minimum of 35 lbs. of fruit each, and if yours are not that productive, chances are that you’re neglecting them. In case you’re afraid of copper buildup in your soil, don’t go to the internet for answers, have a soil test instead. A soil test will determine the amount of copper in your soil, and if you’re afraid of drippings, they can always be caught with some type of a mulch or by a couple of layers of black ink newspaper, but remember, copper is a micronutrient and is necessary for plant growth. Having used copper for the past 25 years on my tomatoes and grapes, the level in my soil is at 0.3 ppm, and the range for vegetable gardening is from 0.3 to 8.0 ppm.
For the squash vine borer, tulle and Kaolin clay has worked well by me, and removing the eggs of the squash bug by being vigilant it has also kept them under control.
Nick Mancini, THE ORGANIC ITALIAN