How do I deal with wilt and powdery mildew?
I grow cucumbers and tomatoes indoors and can not feel if the surface is dry. The digital meter did not give a percentage and websites go from 10 to 80%. The problem is wilt and powdery mildew, both do better at 30-35% with treatments, but plants are slow growing at that level.
Lynne Holland, Community Education Assistant, Androscoggin-Sagadahoc Counties Office
Since you are working with an existing set-up I think it is wise of you to anticipate the same problems this year with powdery mildew and try to get ahead of it.
There are three things a disease needs to become a problem, the disease itself, the host plant, and the environment. Let’s look at all of these, one by one.
The disease is prevalent so there is not much you can do about that. It is always a good idea to do a thorough cleaning of the greenhouse as you change crops. Even though you are working with dirt, cleanliness in the greenhouse can go a long way to preventing disease issues. Here is a bulletin with more information, Cleaning and Disinfecting the Greenhouse.
When you are choosing your plants please consider varieties that are resistant so you can go into the process with at least that in your favor. This list (from Cornell) has some information and varieties noted for their resistance. Most seed catalogs will also not that in their descriptions as well.
Lastly, I suggest you consider putting a barrier between the ground and the bottom leaves of the plant. Leave a wide enough hole in that barrier to allow for watering but have as little dirt as possible near the leaves themselves. This will do two things. The first it will prevent splash up from the soil that may have bacteria or fungus in it. The second thing is that it will moderate the soil temperature and moisture so it is more consistent. There are some great ideas in this bulletin from Utah State, Cucumber in the Garden.