Verticillium wilt: how to recognise and treat it

Disease

Symptoms

Lower, older leaves yellow first — at the margins and between the main veins — then turn brown and wither; the damage moves up the plant.
Wilting, often on one side of the plant or in scattered parts of it; symptoms often appear in warm weather.
Brown streaks inside the stem — a brown ring when cut across, brown lines when cut lengthways — instead of healthy pale tissue; chrysanthemums and roses usually lack these marks.
On raspberries and blackberries the fruiting canes can turn bluish-black and die as the fruit ripens.
Plants are stunted and may die over several weeks; trees and shrubs show branch dieback.

No treatment cures an infected plant. Remove it with as much of the root as possible and destroy it — do not compost it.
Do not spread soil from around the plant on tools or boots — the fungus lives in the soil.
Woody plants can sometimes recover with heavy watering and a nitrogen feed over the root area — sulphate of ammonia at 25 g per m² once or twice in the growing season, hoed or watered in.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Grow resistant varieties — tomato varieties marked "V" resist the disease.
Buy healthy plants and do not plant susceptible crops where the disease has occurred; the fungus survives in the soil for years.
Clear all crop remains, including roots, after harvest; solarise the soil before planting where the disease is known.
Control weeds — some are hosts without showing symptoms.
Keep plants vigorous with good care; stressed plants show damage sooner.

Figures checked against these sources.