Mine have some curling. Is yours mulched heavy?

Hi Mo,

Tomato leaf curl is normally just a tomato plant's reaction to physiological stress and, in the current climate, I'd guess it is likely to be heat stress. Sometimes it is a symptom of herbicide drift exposure. Herbicides can easily drift a mile or so in strong enough concentrations to harm your plants. It also can be an early sympton of some viral diseases.

To distinguish between the three:

PHYSIOLOGICAL: Physiological leaf roll can be associated with various environmental factors that stress the plants, including excess moisture, excess nitrogen or low moisture in combination with high heat. Also, sometimes improper cultural practices like excessive pruning of foliage or improper soil cultivation in the root zone can stress plants and cause physiological leaf roll.

If your plants are showing physiological leaf roll, it first appears as a slight upward cupping of the leaves and can progress to an upward/inward rolling of the leaves. In the most extreme cases where the stress is not alleviated, the leaflets can overhap one another. If the physiological leaf roll persists, the leaves can become abnormally coarse and almost leathery. You'll most often see physiological leaf roll on the taller and more vigorous indeterminate tomato plants, although it does appear (though less often) on determinate varieties.

HERBICIDE INJURY: Sometimes herbicides can drift onto your plants and an early symptom is a form of leaf roll. The herbicide drift can come from 2, 4 D broadleaf weed killers or from glyphosates like Round-Up. This can happen even if the herbicides are sprayed as far as a mile away if the winds are strong enough. When your plants have herbcide damage, the kind of leaf roll you see is mostly a downward curling and it is accompanied by deformed and twisted growth. It often progresses to stem damage in which the stems turn a whitish-tannish color and may begin to split open and break in severe cases. Sometimes tomato plants can recover from herbicide damage and sometimes they cannot.

VIRAL INFECTION: Leaf roll can be an early symptom of some viral diseases. One way you can sometimes distinguish leaf roll caused by a viral infection from physiological leaf roll is that the physiological leaf roll tends to affect most, if not all, your plants because they are growing in similar conditions but viral infections are more of a hit and miss occurrence although the viral infection on a limited number of plants can then be spread by insects or even by you if you touch healthy plants after previously touching sick plants.

Still, as I said in the beginning, I'd bet it is physiological leaf roll caused by last week's heat wave and the excessively high temperatures and heat index numbers in concert with low rainfall.

To help combat physiological leaf roll, try to keep the soil uniformly moist, water with soaker hoses or drip irrigation to keep water off the foliage, be sure the plants have adequate nutrition but not excess nitrogen, and mulch heavily to keep soil cool (unmulched soil can get much hotter than the air temperature) and moist.

During this weekend's more moderate temperatures you might have seen a little relaxing of the leaf curl.

And, if it were an early sign of viral disease, the solution would be to immediately begin a regular spraying program using the fungicide of your choice, whether organic or chemical in nature, in order to save the plants and hopefully prevent the spread of the viral disease. Of course, if you had additional symptoms that confirmed the presence of a viral disease, additional steps would have to be taken to stop the disease from spreading.

Herbicide injury-caused leaf roll is the hardest to deal with. Mostly you just have to wait and see it if progresses or if the plant outgrows it.

Dawn

I've got the physiological leaf roll on all my larger plants (which is only 4), but not the smaller ones (which is 20 or so). They're all mulched pretty thoroughly and I've been keeping them moist, so it must be the heat. They seem okay otherwise, growing, ripening fruit, being green, etc.

Thanks for all your replies. I believe that it is physiological. That is a relief. , sorta; LOL
the weather radio went off all yesterday afternoon teasing with thunderstorms. we got nary a drop. seems like it has been summer forever.
thanks a bunch
jsutsaymo

Hey Mo,

Regarding your statement "seems like it has been summer forever", all I can add is AMEN! Seems like we went from a wet, soggy, cloudy and late spring to instant summer.

I'm ready for fall and it seems so very far away.

Dawn

How do you provide adequate nutrition without excessive nitrogen? I have very sandy soil.