Hi! I have a few raised beds and I’m noticing that my pepper, tomato, and squash plants are starting to get yellow and dried out leaves toward the base of the plants over the last couple weeks. There seems to be something like a fungus or mold attacking my squash, but the tomatoes seem to just be in need of something. I only water when the soil dries out more than an couple inches below the surface. All of the plants are starting to bear fruit. All of them are actively blooming. What can I do to help them or reverse the problems? They seem stressed or sick.
Hennepin County Minnesota
You have several things going on. There are many things that cause tomato leaves to yellow, but in this case it looks like a fungal infection since things are dying from the base of the plant. It is a little hard to tell from the picture, but I think it is Septoria leaf spot. Here is reference from the U that will help you diagnose the problem: https://extension.umn.edu/plant-diseases/tomato-leaf-spot-diseases. Please take note of the section on how to avoid tomato diseases. You can remove all the diseased leaves and leaves with spots, it won't hurt the plant. Be sure to water the plants at their base and not on the leaves.
Have you been planting in the same soil in the raised bed for a couple of years.
If so you need to replace the soil or move the tomatoes next year.
As far as the squash goes it is probably a squash borer: https://extension.umn.edu/yard-and-garden-insects/squash-vine-borers.
From the pepper plant stems it looks like the plant has verticillium wilt. Here is a reference from the U on growing peppers: https://extension.umn.edu/vegetables/growing-peppers-home-gardens
As I said above I think you should consider replacing the soil in your raise beds. All of the diseases I have mentioned winter over in the soil. After that you need to plan a crop rotation: https://extension.umn.edu/yard-and-garden-news/rotate-crops-your-small-garden