Verticillium wilt

What you see

Wilting in the heat of the day that recovers overnight, then stops recovering. Older leaves yellow in wedge-shaped patches between the veins. Cut a stem and the inner ring is discoloured pale brown, usually higher up the plant than with Fusarium.

Conditions

Cooler soil than Fusarium - it does its damage at 20-25C, so it shows in spring and autumn rather than midsummer. The resting bodies survive in soil for over ten years, which is what makes it so serious.

Treatment

No cure. Remove and bin affected annual plants. On a valuable tree or olive, prune out dead wood in dry weather, keep it well watered and well fed, and give it several years - trees do sometimes wall the infection off and recover.

Prevention

Avoid planting susceptible crops where it is known. Never follow with tomato, aubergine, strawberry or olive. Grow grasses or cereals in that ground for several years - they are non-hosts and reduce the soil load.

Months: April, May, June, September, October

Plants

Tomato, Aubergine, Olive, Strawberry, Rose, Maple, Sweet pepper

Remedies

Seaweed extract, Mulch

The thing people get wrong

The mistake here is replanting the same thing after pulling a dead plant. Verticillium resting structures last a decade in soil - so the ground is a lost cause for that family, not the plant. In olive groves this is now the single most serious disease in Iberia, and it usually arrives on infected nursery stock or in irrigation water from an infected field.