Upward-curling, puckered leaves, bushy, stunted plants, and flowers that drop before they set fruit. That is chilli leaf curl, the most destructive virus disease of chilli in South Asia, and an important one across Southeast Asia, the Middle East and parts of Africa.
In fields infected early, losses of marketable fruit can reach one hundred per cent. Average losses in affected regions of South Asia are often reported at twenty to sixty per cent.
In this video: the cause, the symptoms, how it spreads, the look-alikes, why the nursery decides everything, protecting the field, insecticides against the vector chosen by IRAC group, and safety.
The advice is general and global.
Your local extension service and the product label always come first.
Chilli leaf curl is caused by several begomoviruses,
small viruses with single-stranded DNA, including chilli leaf curl virus.
They are often accompanied by a small DNA satellite that makes the symptoms worse.
Different virus species dominate in different regions.
The virus is spread by the whitefly Bemisia tabaci, in a persistent, circulative way, and by grafting. It does not spread through seed, or by touch.
Chilli and sweet pepper are the main hosts.
The same or related viruses infect tomato, papaya, tobacco, okra and several weeds, which act as reservoirs.
Symptoms appear about two to three weeks after infection,
and young plants suffer most.
On seedlings and young plants, the young leaves curl upward and cup, with thickened veins and puckering.
Infected seedlings stay severely stunted. As the plant grows, the leaves become small, crinkled and leathery, crowded on shortened stems, so the plant looks bushy. Leaf margins may turn pale or yellowish. At flowering, flowers drop, and the few fruit are small and deformed.
Plants infected early bear almost nothing.
Only a laboratory test can confirm the virus, by PCR.
So send samples of suspicious plants where you can.
Whiteflies pick up the virus while feeding on infected chilli, tomato, papaya or weeds.
Feeding for minutes to hours is enough, and the longer they feed, the more efficiently they pick it up. After a latent period of several hours, the whitefly stays infective for days to weeks.
Infection often starts in the nursery.
And the virus survives between seasons in perennial and weed hosts,
and in overlapping crops.
Epidemics follow whitefly numbers, which peak in warm, dry seasons.
High whitefly populations, nurseries raised in the open next to infected fields, continuous chilli and tomato cropping,
weed reservoirs and susceptible varieties all favour the disease.
Two pests cause damage that looks similar, and they often occur together with the virus.
Chilli thrips also cause upward curling, but with silvery or bronze streaks on the underside, and you can find tiny thrips in the growing tips.
Broad mites cause downward curling, with narrow, bronzed leaves and twisted tips. The mites are visible only with a strong lens.
Herbicide drift can also twist and cup leaves. But it appears on many plants at once after a spray,
and does not spread over time.
Knowing the difference matters, because thrips and mites need their own control, and spraying for the wrong cause wastes money.
There is no cure.
No chemical controls the virus, and there is no economic threshold:
a few infective whiteflies in the nursery can lead to heavy losses.
So management is preventive, and it starts in the nursery.
Raise seedlings under fine, insect-proof net. Keep nursery trays raised and away from older chilli, tomato and other nightshade plants. Inspect nursery seedlings and young plants twice a week for upward curling.
And transplant only symptom-free plants.
In the field, remove and destroy infected plants in the first month, and keep the field free of weed hosts. Avoid planting next to older chilli, tomato or papaya fields,
and keep a host-free period where possible.
Barrier crops of maize or sorghum around the field reduce whitefly entry.
Reflective or silver mulches and yellow sticky traps reduce whitefly landing in young crops, and the traps also help you monitor them.
Protect ladybirds, lacewings and parasitic wasps that feed on whiteflies.
They help, but they cannot stop the virus on their own.
Tolerant chilli lines have been identified,
and public breeding programmes are using them. But few commercial varieties are strongly resistant yet,
so combine all these measures.
Insecticides cannot cure an infected plant.
They are used against the whitefly, in the nursery and the early crop, when infection does the most harm.
Laisha names them only by IRAC group.
IRAC group four A, the neonicotinoids, are used in the nursery and early crop, but whitefly resistance to them is widespread.
Group twenty-three, inhibitors of acetyl CoA carboxylase, act against whitefly nymphs and are selective.
Group nine B, the chordotonal organ modulators, stop the whitefly feeding.
Rotate groups, and do not repeat the same group in the nursery and the field.
Use acaricides or thrips control only when mites or thrips are the cause.
And use only products registered for your crop in your country, at the label dose.
Registrations differ and change over time.
Now, safety.
Read the label before you buy, mix or spray.
Wear what the label asks for: chemical-resistant gloves, long sleeves and trousers, boots and eye protection.
Gloves matter most, because most farm poisoning happens through the skin,
and handling the concentrate while mixing is the riskiest step. Mix outdoors, measure carefully, and do not eat, drink or smoke while you work.
Calibrate your sprayer, spray when the wind is light, and leave a buffer zone near water.
Respect the pre-harvest interval before picking.
Store pesticides locked, in their original containers, away from food, feed, children and animals.
Triple-rinse empty containers, puncture them, and never reuse them. If someone is exposed, remove contaminated clothing, wash the skin with plenty of water, and get medical help at once, taking the label with you.
To recap.
Chilli leaf curl is a whitefly-borne virus with no cure.
Learn the signs: upward, cupped, puckered leaves and bushy, stunted plants.
Rule out thrips, broad mites and herbicide drift.
Raise seedlings under insect-proof net and transplant only clean plants.
Rogue early, control weeds, avoid old host crops, and use barrier crops, reflective mulch and yellow traps.
And if you spray against the whitefly, rotate IRAC groups and follow the label.
For every pest and disease, visit laisha.ai. Thank you for watching.
