How can I salvage my tomato crop?
Question:
I’m wondering if my tomato patch can be saved? I have been vigilant about pruning my plants from the bottom, and trimming what I thought was blight. But whatever this is, it keeps spreading. A few weeks ago it was a small branch or two, now it seems to be spreading by the hour and every plant is affected. I’m afraid to cut off more branches lest I totally denude the plants! The fruit, however, seems to be fine. I did read an extension article about bleaching my pruners (which I started doing today). Next year, I’ll rotate, and not plant so close together, but is there anything I can do now to salvage my crop this year? (And why are my tomatoes taking so long to ripen?)
Answer:
The answer to your question is “it depends” leaning toward “probably!”
So, this looks like septoria leaf spot to me, a common tomato issue and one we see a lot of. It’s a fungal disease that spreads during hot, humid conditions (like we’ve had this summer), particularly where airflow through the infected plants is inhibited by thick leafy growth. The pathogen likes still, warm, moist air in the interior of the tomato and it can spread quickly under those circumstances. The good news is that–depending on the severity of the infection–it can often be mitigated/managed long enough to get a harvest.
(I should note that my diagnosis is based on your photos and visual evaluation isn’t always 100% accurate. If you remain concerned, you could also always submit your photos and/or a physical sample to the UMaine Plant Disease Diagnostic Lab for confirmation. There is a small fee for their service, but they are top notch folks and lab testing is inherently more reliable.)
Here’s what I’d recommend:
1) Prune off all the affected leaves–your concern over denuding the plant entirely is 100% valid, but you’re going to shoot for a running balance for the rest of the season, taking off as much poor foliage as possible, while preserving what you can. Tomato fruits can do pretty well with a sometimes surprisingly low number of leaves, but we don’t want to get crazy. And do clean and sanitize your tools after any infected tissue pruning, as you don’t want to transfer anything to healthy tissue you might prune later.
2. All supplemental irrigation (i.e., anything not rainfall) should be aimed at the soil below the plant–no overhead watering. Septoria loves wet conditions on the leaves, so the drier you can keep the foliage while still keeping the root ball nice and moist, the better. You can’t do anything about the rain, but if you find yourself in the garden after precipitation, it doesn’t hurt anything at all to give the plants a little shake to shed some water. 🙂
3. Scout for and prune out any suckering branches inside the tomato to remove leaf mass and get more air flowing through there. Suckers through the body of the plant aren’t doing anything for you, anyway, except using up plant resources for weak returns. Removing them typically gives you fewer, but higher quality, fruit and in this case it will also help thin things out in the infection zone.
4. Mulch, if you don’t already. Mulching offers multiple benefits, but for this case it will also help prevent infected soil particles from splashing up during rainfall or watering (septoria overwinters in the soil) and adding to the fungal load the plant is under. Leave a little space around the tomato base so there aren’t any stem rotting issues, but a nice thick mulch layer just out past the plant’s drip line will be great.
5. If the above isn’t slowing the spread, or if you really can’t tolerate losing the plants, consider a fungicidal application. If you do wind up using chemical intervention, please read carefully and follow conscientiously all instructions on the label. More is not better.
Your crop rotation plan is great, as is spacing the plants farther apart next year (the importance of that extra airflow is hopefully obvious given my explanation above).
For your second question–why the fruits are slow to ripen–there are a number of reasons this can happen:
* High temperatures
* Insufficient light (tomatoes really want 8 hours a direct sun a day, minimum)
* High nitrogen input (if you are adding supplemental nitrogen, you could scale it back to see if that helps)
* Steady irrigation (consistently moist and well-drained)
* Overabundance of fruits ripening–you could remove any small/misshapen fruits that are visibly lagging to focus plant resources on the best fruits
I would mostly just advise patience for now.
Happy gardening.