Tomato yellow leaf curl virus

What you see

New growth becomes small, cupped upward and yellow at the margins. The plant looks stunted and bushy, flowers drop, and fruit set collapses. Older leaves below may look almost normal, which is confusing.

Conditions

Transmitted only by whitefly - the disease follows the insect, so it arrives in hot years and in sheltered, still corners where whitefly build up. Warm autumns in southern Portugal are prime conditions.

Treatment

No cure. Remove the plant, bagged, so the whitefly on it do not simply move next door. Everything else is whitefly control: yellow sticky traps, insecticidal soap on nymphs, and encouraging Encarsia wasps.

Prevention

Grow TY-resistant varieties - they are widely available and they work. Use fine insect mesh over young plants through the whitefly season, and never plant new tomatoes next to an old, infested crop.

Months: June, July, August, September, October

Plants

Tomato, Sweet pepper, Green bean

Remedies

Yellow sticky traps, Insecticidal soap spray, Insect mesh and fleece barrier, Encourage predators

The thing people get wrong

The cupped-up yellow new growth is very often blamed on herbicide drift or overwatering, and the plant gets nursed along for a month while its whitefly keep feeding and carrying the virus to the rest of the row. If you see this pattern, check leaf undersides for whitefly - if they are there, act fast on the whole bed, because the sick plant is now a transmitter.