We are in the middle of a period of wet weather that is predicted to deliver multiple inches of rain to central Ohio and even more to other soaked parts of our state. Tomatoes are a crop that can suffer several problems related to heavy rainfall that can shorten the harvest period and affect yield. There are a few things that the backyard grower, community gardener and urban farmer can do to keep their tomato plants healthy and productive though heavy rain periods.
Key Garden Tasks to Keep Tomatoes Healthy in Wet Weather
- Mulch – organic or non-organic can both be used. Be careful if your plasticulture is not permeable to air and water, the heavy constant rainfall may saturate the soil and drown the roots if the soil cannot dry out. Mulch also acts as a barrier to keep soil borne fungal spores off lower tomato leaves.
- Fertility – contstant rainfall can leach fertility from soil making it unavailable to the plants. Make sure to monitor plant growth and health carefully to avoid a nutrient deficiency. Foliar feeding can be used when the ground is too saturated to irrigate with water soluble fertilizer.
- Pruning – promote air circulation by pruning lower leaves. Try to minimize lower leaf contact with soil. Use sterilized pruners to remove any diseased leaves and make sure to put diseased leaves in the garbage and not the compost after pruning.
This plant needs mulched around the base to prevent soil borne fungal spore contact with leaves. Pruning of the lower leaves will also promote air circulation to assist in disease prevention.
These discolored leaves suggest fungal disease in this tomato plant. The leaves need pruned with sterilized pruners and then discarded into the garbage and not the compost pile.
This tomato has both organic and plasticulture mulch at the base to keep fungal spores in the soil and off plant leaves. Pruning needs to be done to allow air circulation at the base of the plant.
This tomato plant has had lower leaves removed for air circulation with a combination of compost and plasticulture mulch at the base of the plant.
Monitor tomatoes carefully for signs of blight, remove the diseased leaves promptly with sterilized pruners and dispose of disease materials in the garbage, not the compost pile.
Make sure to address fertility needs as production increases. Heavy rain can leach nutrients into the subsoil where they are unavailable to plants, decreasing yield as the season progresses.
Feel free to email mcdermott.15@osu.edu pictures of tomato problems to assist in diagnosis.
Ohio State University Extension has an excellent fact sheet on Growing Tomatoes in the Home Garden. There is also a plant disease diagnostic laboratory on campus where the grower can send samples if an accurate diagnosis needs confirmed on possible diseased leaves.
The pictures are most helpful, you can actually see what the plant will look like with the conditions described, thanks!
Thanks so much for your timely advice. I also think the pictures speak volumes.
I had tomato leaf wilt after very much rainfall. I cut off all the leaves with the wilt and built trenches around outer edge of each plant. I was told that this would help prevent too much rain/water from reaching the roots of each plant. Plus, I used tomato plant calcium food to each plant.( Let it be known that I only have two tomato plants in my above ground garden this year.! ) Also, removed all lower leaves to help the plants. The photos above are very helpful. Thank you.
So far so good, but we are getting rain for the next 48 hours. Have removed lower shoots from base of plants and mulched with plastic and some with straw. Hoping Saturday can spray copper fungicide on all my plants
does water on tomato leaves help cause fungal growth? sprinkler system also hits tomato leaves, as does rain, although they are watered below plastic mulch. I trimmed off lower and diseased leaves. Should I shield tomato leaves from the occasional grass sprinkler system? Thanks!
The goal would be to keep the leaves as dry as possible, knowing that it is not possible in every case. Try to let the leaves dry out during the day as excess moisture, heat, and humidity will potentially predispose the tomatoes to fungal disease.
ok, so tell us. do we have to spray with copper after rain or just before it rain
You need to follow the label guidance for all pesticide use. We are required to read, understand, and follow the pesticide label according to Federal Law.