Tomato Leaf Curl and Leaf Roll
Why are my tomato leaves curling or rolling up? Tomato Leaf curl or Leaf roll is a physiological disorder (not a disease) that can be caused by different factors. The tendency for leaf roll symptoms is somewhat cultivar dependent. Studies have shown, cultivars selected for high yields tend to be most susceptible to physiological leaf roll. Indeterminate varieties are also more vulnerable than determinate-type tomatoes.
Leaf Curl Causes
- Plant stress - This is the most common and widespread physiological cause.
- Herbicide damage - This is becoming more common and is typically accidental in nature.
- Viral infections - Not very common, but these infections are transmitted either by insects or by garden hand tools. Importantly, choose hybrid varieties that are resistant. TMV, T, or ToMV are all codes commonly used to indicate tomato varieties with resistance.
Leaf Curl Symptoms & Causes
Plant Stress Leaf Curl Symptoms
- Typically affects the older (lower) leaves first, but not always.
- From stress, the leaves curl lengthwise, from the margins inward toward the center vein, commonly, upward cupping leaves.
- Leaves also will develop a leathery thick texture and may become brittle, but leaves will hold their normal green color.
Plant Stress Leaf Curl Causes
- Excess nitrogen
- Phosphate deficiency
- Plants pruned during dry soil conditions.
- In some instances, physiological leaf roll can be caused by excess soil moisture during hot summer growing conditions.
Herbicide Leaf Curling Symptoms
- Herbicide-damaged leaves have a shocking appearance to the gardener.
- Leaves usually maintain normal green color, with a slight silvery look.
- Herbicide exposure makes tomato foliage grow into very distorted and freakishly abnormal, and club-like forms. Especially at the tips and the new growth.
Herbicide Leaf Curling Causes
- Many herbicides like 2,4-D Amine, cause uncontrolled and accelerated cellular growth in plants like this, with the causing chemical being used in over 1,000 different home garden products.
- Damage is usually concentrated at the apical meristem points. Tips, tops, or mostly new growth.
- Some pruning may be done to try and correct afflicted plants along with keeping them as healthy as possible by proper watering, fertilizing, and mulching.
- Avoid accidental exposure to ultra-sensitive garden plants like tomatoes by limiting herbicide use in your garden and surrounding area if possible. Volatile chemical drift can travel up to 1/2 mile.
- Never compost herbicide-sprayed plant materials, or suspected herbicide-damaged debris.
Viral Infection Leaf Curl Symptoms
- Associated with mottled yellow or pale green colorations on the leaf surfaces.
- Tomato yellow leaf curl will typically show cupped and pale green leaves with plants that have overall stunted growth and declining fruit set.
- Some leaves may show yellow margins with pronounced purple veins on the underside.
- Along with the typical viral leaf symptoms, the Tomato mosaic virus will cause internal browning of fruits just under the skin (a.k.a. brown wall).
Viral Infection Causes
- Can be spread by insects such as aphids, thrips, or whiteflies or it is transmitted by hand tools from one infected plant to another.
- Keep garden debris to a minimum and clean meticulously at the end of every season.
- Practice proper variety rotations.
- Use proper, safe, and effective pest control options to limit insect exposures.
- Only purchase seeds from reputable dealers or retail outlets that offer virus-free seeds.
- If viral problems have been a problem in the past, always choose Virus Resistant varieties like 'Mountain Merit' Hybrid, 'Invincible' Hybrid, 'Plum Regal' Hybrid, or 'SunSugar' Hybrid tomato.
- Like with herbicide-damaged plants, never compost suspected virus-infected plants to limit unintentional and accidental spread.
Basic Leaf Curl Management Practices
- Choose determinate tomato varieties with disease resistance.
- Plant tomatoes in well-drained healthy soil with a pH range of 6.0 to 6.5.
- Maintain consistent soil moisture (1 inch of water per week, per plant)
- Apply adequate mulch around the base of each plant.
- Avoid pruning indeterminate types, especially during periods of high temperatures.
- Limit nitrogen fertilizer applications.