By: Zvi Howard Wener / Chief Agronomist / Zviw@zeraim.co.il

Question: How to treat nematodes when growing field tomatoes in hot climates?

Answer: Root knot nematodes, especially Meloidogyne incognita, can cause great economic loss to tomatoes especially in warm, sandy soils. There is a nematode resistance (Mi) gene, but it tends to be ineffective at soil temperatures of 27°C and higher and it may also not be effective against isolated populations. Besides, there is no resistance to other nematode genera.
The root-knot nematode has a wide range of hosts among cultivated crops and can also survive on many weeds. They can be active throughout the year in warm moist soils that support the growth of host plants and weeds. They can, therefore successfully survive and complete their life cycle because of the availability of plant roots offering shelter and nutrition.
In areas where root-knot nematodes are a problem it is recommended to grow nematode resistance tomato varieties or to use grafted resistant rootstock. Crop rotation with grasses, other monocots and any other crops not affected by nematodes, should be introduced to help reduce the nematode population. Soil fumigants, nematicides and solar sterilization (solarization) can be used to reduce populations and help plants get a better start. These methods are especially important in areas where the soil temperatures during the early part of the crop are 27°C and higher as the resistant gene does not work properly in the heat. The combination of resistance and these other control methods enables a good start for the tomato crop and then as soil temperatures drop, their natural resistance becomes more effective.