COVER CROPS in South African Vineyards

CHAPTER 9 PESTS

Counts of root-knot nematodes ( Meloidogyne species) per treatment are shown in Figure 9.8. The numbers declined steadily over the four-year period in the control, possibly as a result of mechanical weed control, as this was not practiced in any of the other treatments. Overall, there were no clear trends in nematode numbers associated with different cover-crop treatments. Although the four-year mean nematode count was highest inWoogenellup clover, the numbers declined every year. In all the annual cover-crop treatments, there were more nematodes in the vine than the work rows, whereas the opposite was true for perennial dwarf fescue. Nematode count per 250 centimetre 3 of soil FIGURE 9 .8. Counts of root-knot nematodes per 250 centimetre 3 of soil in cover-crop treatments and a control in the Lower Orange River region. Adapted from Addison and Fourie (2008). Counts of root-lesion nematodes ( Pratylenchus species) per treatment are shown in Figure 9.9. Counts varied between years and were generally low, with no clear trends being observed. However, more root-lesion nematodes were detected in the vine rows than in the work rows. Counts of ring nematodes ( Mesocriconema xenoplax ) per treatment are shown in Figure 9.10. Numbers were very low in the first year, and increased in most treatments and the control thereafter.There was no clear association between nematode counts and any particular cover crop.As for the other two nematode types, more ring nematodes were detected in the vine row than in the work row. 300 250 Henog rye Overberg oats Saia black oats Dwarf fescue Grazing vetch Pink serradella No cover crop 200 150 100 50 0 1995 1996 1997 1998

Woogenellup clover Paraggio bur medic

174