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Tomato yellow leaf curl virus ICTV species: Begomovirus coheni · formerly or also: TYLCV
Tomato yellow leaf curl is caused by a virus spread by the whitefly Bemisia tabaci. Infected tomato plants have small, upward-curled, yellow-edged leaves, stop growing and set little or no fruit. Where whiteflies are abundant it can destroy whole crops, and infected plants cannot be cured, so protection relies on resistant varieties and keeping whiteflies off young plants. Several related begomoviruses cause similar leaf curl diseases of tomato, chilli and other crops.
Tomato yellow leaf curl disease is caused by Tomato yellow leaf curl virus, a virus (begomovirus with a single-stranded DNA genome), spread by whiteflies (order Geplafuvirales, family Geminiviridae).
Older or alternative scientific names: TYLCV.
First described in the Middle East in the 1960s, it has spread with the invasive whiteflies MEAM1 and MED to the Mediterranean, Africa, Asia, the Americas and Australia. It is a regulated pest in some regions. Other tomato leaf curl begomoviruses dominate in parts of South Asia and Africa.
| Region | Status |
|---|---|
| Middle East and Mediterranean | Widespread since the 1960s-1990s |
| Sub-Saharan Africa | Widespread alongside related begomoviruses |
| South, Southeast and East Asia | Widespread; related tomato leaf curl viruses also common |
| Americas | Widespread in the Caribbean, Mexico, the southern US and parts of South America |
| Oceania | Present in parts of Australia |
Virus particles are 'twinned' (geminate) icosahedra and are detected by laboratory tests (PCR or serological tests), which are needed to separate it from related begomoviruses. It is transmitted by adult whiteflies in a persistent, circulative manner: after acquisition a whitefly can transmit for most of its life. It is not spread by touch; reports of seed transmission are disputed.
| Crop stage | What you see |
|---|---|
| Seedling and early growth (infected young) | Severe stunting; leaves small, cupped upward and yellow at the margins; plants bushy and upright; almost no fruit. |
| Vegetative to flowering (later infection) | New leaves curl upward and yellow between the veins and at the edges, while older leaves look normal; flowers drop. |
| Fruiting | Fruit set stops after infection; fruit already set may ripen but is small. |
Whiteflies acquire the virus by feeding on infected plants for some minutes to hours; after a latent period of several hours the virus passes through the insect and is transmitted for days to weeks, often for the whitefly's life. Symptoms appear two to three weeks after infection. The virus survives between tomato crops in other hosts, weeds and volunteer plants, and in infected transplants.
| Stage | Duration | Notes |
|---|---|---|
| Acquisition by a whitefly | From about 15-30 minutes of feeding; efficiency rises with time | Adults and nymphs feed on phloem. |
| Latent period in the whitefly | About 8-24 hours | Virus circulates through the insect. |
| Transmission to a healthy plant | From minutes of feeding; whitefly remains infective for long periods | Persistent, circulative. |
| Symptom development | About 2-3 weeks | Plants infected young suffer most. |
Epidemics follow whitefly populations, which peak in hot, dry seasons; high temperatures also shorten symptom development.
Spread continues as long as infective whiteflies and susceptible plants are present.
High whitefly numbers (hot, dry weather), continuous tomato or overlapping plantings, infected transplants, weed reservoirs, and susceptible varieties.
There is no economic threshold for the virus or its vector once the virus is present: a few infective whiteflies on young plants can cause major loss. Management is preventive, from the nursery onward.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Yield losses range up to 100% when plants are infected in the first weeks after transplanting; later infection causes smaller losses. Epidemics have forced tomato production out of open fields into screened houses in parts of the Mediterranean and the Middle East.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
No chemical controls the virus; insecticides are used against the whitefly vector, especially on transplants and young plants, and cannot fully stop transmission. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
| Scheme | Group | Mode of action | Notes |
|---|---|---|---|
| IRAC | 4D | Nicotinic acetylcholine receptor competitive modulators (butenolides), against the vector | Systemic; check local resistance. |
| IRAC | 28 | Ryanodine receptor modulators (diamides, systemic uses), against the vector | Reduces feeding. |
| IRAC | 9B | Chordotonal organ TRPV channel modulators, against the vector | Feeding inhibitor. |
Tomato is the main host and suffers most. Common bean, pepper (often with mild or no symptoms), tobacco, eggplant, lisianthus and weeds such as Datura, Malva and nightshades are also infected and can act as reservoirs.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.