We just discovered this great visual resource from the University of Maryland, their:

Home and Garden Information Center's Landscape Problem Solver Website

The site offers photographic keys to help diagnose and solve plant problems, using Integrated Pest Management principles.

There's a great section on diseases & insects that target vegetables - look for it on the left hand column.

To give you an idea of how their site works we've included their site directions:

  • "From the menu on the left, select a category or type of plant and the part of the plant that is having problems.
  • A new page will be displayed with symptoms and possible causes with photos.
  • Browse the causes for each symptom and click on go to select that cause.
  • From there simply read the information, on the problem and solution, that appears.
  • You can go to another plant part by selecting from the menu at the top of the page."

Try it out!