Greenhouse Tomatoes

What is the fuzzy looking gray colored mold growing on my plants?

This is called gray mold (pathologists are also really good at naming diseases). The disease is also known as Botrytis, which is the causal organism. This fungus can become very serious, especially during a period of cloudy weather. It appears as a fuzzy greenish-gray mold, often growing on dead tissue. The first place to notice it is on dead flower petals, dead areas on leaves (i.e. from spray burn or mechanical damage), etc. In humid conditions, it can spread rapidly, while in dry conditions, it spreads only slowly. Improve ventilation, air movement, and apply fungicides as needed.