Nematocide residues in plants

Abstract

Although one nematocidal chemical was in use before 1900, widespread use of chemicals for the control of plant-parasitic nematodes in soil is a development of the past 16 years. The most popular and useful of these are volatile materials popularly known as “soil fumigants”. These are usually applied by placement 15 or 20 cm. beneath the soil surface in lines about 30 cm. apart. This application method is known as “area treatment”. A popular alternative method is placement of the nematocide beneath the planting rows only, leaving the intervals between rows untreated. This is known as “row treatment”. The fumigants diffuse from the application points through the upper 45 to 60 cm. of the soil. Other soil nematocides are applied in water solution or emulsion or are in granular form to be mixed with the soil. All are more or less toxic to plants and are usually applied to the soil several days or weeks before planting; a few are sufficiently non-toxic to certain kinds of plants so that they can be applied at planting time or even around the roots of growing plants. In any case, there is ample opportunity for crop plants growing in soil treated with nematocides to take up the undecomposed nematocides or the products of their decomposition.