Q&A: What’s killing my tomatoes?

Wondering what's killing your tomatoes? Find the answer, here.

Reader’s question: My usually prolific tomato plants have been a disaster this year, with all the leaves curling, browning, drooping and dying back. First, the Grosse Lisse, then the Burnley Surecrop and now the Romas have all succumbed. If it is verticillium wilt, how long will it persist in the soil?

Phil Dudman says: Verticillium wilt is a fungal disease that lives in the soil and enters the roots of susceptible tomatoes before spreading throughout their vascular system. Once affected, a plant can’t be saved. If you cut across a stem near the base, you will see a brown ring, which indicates where the fungus has invaded.

Collect any mature fruit that can be ripened off the vine, then pull up the plant and throw it into the general waste bin, being careful not to spread infected soil to other parts of the garden.

This is a seriously damaging disease, which persists in the soil for many years, so it’s advisable to grow other, unrelated crops in the bed for a few seasons before planting tomatoes again. You may also like to consider solarisation, which has proven helpful in controlling verticillium wilt. Cover soil with a clear plastic sheet for 10 weeks. The build-up of heat in the soil is normally enough to kill the fungus.

Another tactic to incorporate is to grow tomato varieties that display good levels of resistance to the disease. Super Beefsteak and Super Marmande are open-pollinated varieties to look out for. You could also try some of the F1 hybrids, such as Ferline and Mighty Red. If you have your heart set on varieties that are susceptible to the disease, you could graft them onto the disease-resistant plants, which is easy to do using a simple splice or cleft graft. Despite some plants showing good resistance to verticillium wilt, they are not necessarily 100 per cent immune, so for best results, use them in combination with the crop rotation and solarisation approaches.

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