tomato leaf curl

646-976 Use resistant or tolerant cultivars. Use healthy transplants. Protect seedlings with fine meshing (60-mesh or finer) to exclude whiteflies. 70-443 Use insecticides such as Confidor/Admire (imidacloprid) or Asana (esfenvalerate) and rotate insecticides to reduce build-up of insecticide-tolerant whiteflies. Eliminate other virus sources near the susceptible crop. Have a 60-day fallow period between old infected crop and new crop.
1D0-541

There are three different possible reasons for leaf curl on tomatoes: environmental stress, viral infection, and herbicide damage.

Stress:
Too much water or too much fertilizer can stress a tomato plant and cause the leaves to temporariy roll or curl. Extreme heat and drought can do it too, as well as improper pruning or cultivating too deeply and damaging the roots. "Early Girl" and "Big Boy" seem to be more commonly affected than other varieties. Environmental stress leaf roll typically appears first in the lower leaves, though, so that's probably not what's happened to your plants. Leaf curl due to stress is often a temporary thing, and the plants can fully recover.

Viral Disease:
Tomato leaf roll may be associated with viral infection. Tomato yellow leaf curl virus is transmitted by sap-sucking insects and causes leaf roll symptoms in infected tomato plants. Purplish veins on the leaf underside help to distinguish this virus from stress leaf roll or herbicide injury. In addition, new leaves appear chlorotic (pale green) and cupped, and overall plant growth becomes stunted. Early infection often inhibits fruit production. Tomato mosaic virus has also been known to cause leaf roll symptoms. Other symptoms of this virus include mottled leaves and smaller than normal leaflets. Infected fruit appears brown on the inside and blotchy on the outside

Herbicide Damage:
2,4-D is a herbicide commonly used on lawns to control broadleaf weeds such as dandelion and chickweed, and unfortunately it volatilizes into a gas at higher temperatures (like we've had lately) which is spread about by the breeze. Even if you have not been spraying weedkiller in your yard lately, one of your neighbors might have, and the spray drifted onto your plants. (It can drift a long way, so it will probably be impossible to figure out who did it)

Tomato plants that have been exposed to 2,4-D drift exhibit downward curling of the leaves and overall deformed, twisted growth. Leaf veins are light colored and very prominent. The vein pattern may be more parallel in symptomatic leaves. Affected stems turn whitish, thicken and often split. Plant recovery depends on the severity of the exposure.

Here is a link to a K-State publication on herbicide drift damage.

We've been getting a lot of visitors to the extension office bringing in samples of herbicide damaged plants this week.

Meg - Johnson County Extension Master Gardener