Verticillium wilt
Verticillium dahliae, Verticillium albo-atrum
Role in the garden
A soil fungus that invades the conducting vessels: wilting on one side of the plant, leaves that yellow then dry out while keeping their shape, brown vessels visible when the stem is cut. Its microsclerotia persist for years in the ground.
Activity period
Symptoms from June to September, worsened by heat after a cool spring
How to attract / manage it
Long rotation, resistant varieties and rootstocks, no nightshades before strawberries and stone fruit, solarisation.
Practical guide
Where to find them
Nightshades (tomato, aubergine, potato, pepper), strawberry and raspberry, olive and stone fruit (apricot, peach, cherry, plum, almond), as well as many ornamental trees. The fungus lives in the soil and enters through the roots.
Prevention
Do not plant strawberries, raspberries or stone fruit where nightshades grew in previous years (the inoculum builds up there), a rotation of at least 4 years, resistant varieties and rootstocks (tomatoes bearing the letter V), grafting tomatoes onto a resistant rootstock, drainage and regular watering to limit stress.
Early signs
One-sided wilting by day with recovery at night at first, V-shaped yellowing of the lower tomato leaves, leaves drying while staying attached; when a stem is cut, a ring or brown streaks in the wood.
Action / control
Pull up and dispose of affected plants with their roots (without composting), do not replant a susceptible species in the same spot for several years, solarise the soil in summer under a clear sheet in hot regions. No curative fungicide in the garden.
Sources
- INRAE, Ephytia : Tomate, Verticillium dahliae (verticilliose)
- UC IPM : Verticillium wilt (ipm.ucanr.edu)
- PNW Plant Disease Management Handbook : Verticillium wilt
Favourite plants / resources
Related plant entries
Tomato
Central plant of the tomato guild. The neighbouring basil is reputed to hinder aphids through its volatile compounds.
Potato
A nightshade with traditional planting (April) or grown under mulch (Charles Dowding) requiring zero earthing-up. Demanding in manure, it readily heads the rotation on an enriched bed (GAB/FRAB Bretagne). Not to follow or precede a tomato on the same bed (shared blight, Phytophthora infestans).
Sweet pepper
A fruiting nightshade, hungry for both warmth and fertility: it calls for rich soil and a well-exposed bed among the summer crops. Basil, a classic companion to both tomato and pepper, is reputed to keep certain pests away through its aromatic compounds, while the French marigold, in a dedicated, dense planting, reduces soil nematodes (see its own entry) and draws in beneficial insects. Its flowers are visited by bees and by hoverflies, whose larvae devour aphids. Like any nightshade, it belongs in a rotation that avoids following tomato or potato, so as not to concentrate the family's shared soil diseases (verticillium wilt, for instance). Finally, it is kept away from fennel, reputed to hinder its neighbours.
Aubergine (eggplant)
A tropical nightshade that needs a lot of warmth (>20 °C at night), often grown in a cold greenhouse in northern France. Vibration-pollinated (buzz) by bumblebees, hence the value of attracting them. High demand for water and nutrients. Against Meloidogyne nematodes, the French marigold (Tagetes patula) only works as a dedicated, dense crop over a whole season, not as a mere border (see its fact sheet).