Root-knot nematode

What you see

Microscopic. Diagnosed by the roots: rounded knobbly galls swelling along the fine roots - quite different from the beneficial nitrogen nodules on legumes, which rub off easily and are smooth and round.

Damage

Plants stunted, yellowing and wilting in the heat despite plenty of water. Poor yields. Pull one up and the roots are beaded with galls.

Lifecycle on this coast

Several generations a season in warm sandy soil - which describes much of coastal Portugal. Survives in soil and roots for years.

When to act

There is no rescue for an infested plant. Manage the soil, not the plant.

Months: May, June, July, August, September

Plants it bothers

Tomato, Carrot, Lettuce, Cucumber, Melon, Aubergine, Sweet pepper, Potato

Natural enemies

Beneficial soil fungi, Earthworm

Remedies

Mulch, Encourage predators

The thing people get wrong

Do not confuse these with the pea and bean root nodules that fix nitrogen - those are a good sign, sit loosely on the root and rub off between your fingers, while nematode galls are swellings OF the root itself and cannot be removed. If you have them, a season of French marigold or a mustard green-manure crop measurably reduces the population, and grafted or resistant tomato varieties sidestep the problem entirely.