Fusarium wilt

What you see

One side of the plant wilts while the other stays turgid - often a single branch, or leaves on one side of the midrib. Yellowing climbs from the bottom. Slice the stem near the base lengthways and you find a chocolate-brown stain in the wood just under the skin.

Conditions

Warm soil, 25-30C, slightly acid, and a field that has grown the same family too often. It enters through root tips and plugs the water-conducting tissue from inside.

Treatment

There is no cure once a plant is infected - pull it out with its root ball and bin it. Do not add it to the compost heap. Keep the remaining plants unstressed and evenly watered so they finish their crop.

Prevention

Grow resistant varieties - the letter F on a seed packet means exactly this. Rotate on a four-year cycle, raise soil pH slightly toward neutral, and graft onto resistant rootstock if the ground is known to be infected. Solarising the bed under clear plastic through August helps.

Months: June, July, August, September

Plants

Tomato, Basil, Melon, Cucumber, Sweet pepper, Green bean

Remedies

Not recorded — the field is blank rather than guessed.

The thing people get wrong

The one-sided wilt is the diagnosis. Verticillium and drought both wilt the whole plant evenly; Fusarium is famously lopsided because it colonises the vascular strands on one side first. And note there is nothing to spray - anyone selling you a Fusarium cure for open ground is selling you nothing. The real decision is which resistant variety to grow next year.