Please help! I moved into a new property last spring and tried tomatoes in the greenhouse (polyhouse) which had previously grown tomatoes very successfully. They succumbed to late blight (in mid-July), as did my potatoes grown outside, but nearby. I would like to try tomatoes again this year in the polyhouse, which is set up with irrigation (soaker hoses) in a different row than last year, but one that probably had tomatoes previously. I am looking for advice on how to avoid the blight. One thought was to plant tomatoes in 5 gallon pots and sink them into the ground so I can still use the soaker hoses but in fresh new soil. Replacing all the soil in the greenhouse is not feasible at this point. Any help is greatly appreciated! Note that I did water primarily with the soaker hoses and was careful when liquid feeding them not to splash. I kept good distance and air circulation but they never seemed like very healthy tomato plants. I planted approximately 7 varieties, all purchased as plants by a very reputable local organic grower. The polyhouse is ventilated with air flowing through all sides in the heat of the summer. I did use twine that was strung from the frame and used for climbing tomatoes previously. It's poly twine, should i bleach it?
Last year I only had a problem with a tomato planted outside of the green house. I had ten or twelve 5-7 gallon pots inside that all did quite well. These pots were not sunk into the soil. For watering I bought a couple of those kits with the small tubed hoses with different sprinkler heads. I also got a pressure valve for the end of the hose. The irrigation can be directed and flow regulated at each emitter. The initial investment will pay off in a couple of years, as my crop loss is minimal. I found that the soaker hoses sprays in too many directions. That could be part of why your crop ended up the way it did.
Late blight is caused by a fungus spreading through spores that will only germinate on wet leaves. If the tomato plants were kept dry, it is more likely that the problem was a virus transmitted through the soil or by insects. I suppose that condensation on the leaves could provide enough moisture for the fungal spores. In that case, increased ventilation during the night might prevent condensation when the temperature drops.
Thank you for your replies! The soaker hoses that are in the greenhouse only drip into the soil, there are no wayward sprays, but the condensation is a point. I keep the sides rolled up day and night through the summer, but there is still condensation, and I did have a lot of pest problems this year. The reason I was going to sink the pots is so that could line them up with the current irrigation system, but maybe I should just put them in there, with a barrier underneath so here is no exposure, even through the holes in the pots, to the soil underneath in case there is blight in that raised bed as well. Now as for my potatoes... I want to plant them far from my tomatoes, but near where I have relocated some of the soil from last year's blighted potatoes (perennial flower bed, no veggies). It will be a few meters away, is that safe? Or should I try potatoes in a container as well? Thank you!
When the weather is bad, fungal spores are everywhere. Changing the location won't make any difference. I've had some success at holding late blight at bay by using fixed copper spray on tomatoes with no other protection. It should work on potatoes as well and is considered acceptable to organic growers.
