The species of nematodes described above spend most of their life cycle inside plant tissues (endoparasites). Some species, however, feed only from the outside of the root (ectoparasites). The dagger nematodes (e.g. Xiphinema diversicaudatum) and needle nematodes (e.g. Longidorus elongatus), which reach lengths of 0.4 and 1.0 cm respectively, attack the young roots of crops such as rose, raspberry and strawberry, and cause stunted growth. In addition, these species transmit the important viruses, arabis mosaic on strawberry and tomato black ring on ornamental cherries. The nematodes may survive on the roots of a wide variety of weeds.
Control is achieved by professional growers by the injection of a fumigant chemical, e.g. dichloropropene or incorporation of dazomet in fallow soils.
Figure 14.30 Root knot nematode damage on cucumber
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