I have grown tomatoes all my life and have come to the concussion that blite is in the air and blossoms when the temp and humidity gets right. I live on Coonlake so I have all the seaweed I need for munching, and have plenty of wind for air movement. I have tried fungicides, spayed epsom salt , last year I tried hydrogen peroxide. nothing. but I had put a red plastic cage covers over 2 tomates for early frost protection and left them on. they had no blite, and growing right next to them are blite covered plants.am I on to something?
Anoka County Minnesota
Thanks for the question.
Tomato blight is quite common in Minnesota and may be difficult to completely prevent. You certainly have discovered this. One of the simplest ways to do this is only planting tomatoes that are resistant to blight. You can easily determine this by looking for the designation “EB Resistant” on the labels of the tomatoes you purchase. The fungal spores responsible for this disease are carried by the wind from plant to plant. This is the major reason why you did not see the blight on the tomatoes you had covered. Unfortunately by covering tomatoes you may damage the plant by limiting available light. Also, this covering may decrease the amount of insect and wind pollination that might occur. This would result in reduced tomato production. The fungal spores typically remain in the ground over the winter in the soil and/or tomato plant debris. For 2020 besides using blight resistant tomatoes, I would suggest you plant your tomatoes in a spot as far removed as possible from the planting location you used in 2019.
Here are some publications that will provide you further information on these and other points regarding tomato blight:
Thanks for using this forum. Please contact us again if you have any further questions. Good Luck with your 2020 tomatoes.