COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

The changes in nematode populations in the vine rows during winter are shown in Figure 9.5 for selected treatments.Winter is when cover crops and weeds grow, so the data reflect the change in nematode numbers associated with actively growing cover crops and weeds.

400

200

0 Change in nematode count per 250 centimetre 3 of soil FIGURE 9 .5. Change in nematode counts in the vine row during the winter in selected treatments. Chemical: full-surface chemical control at bud-break and dry matter left standing. Mechanical: cover crops and weeds slashed and mechanically incorporated into soil of work row. Adapted from Fourie et al (2016). In general, nematode numbers increased slightly during the first winter, and declined sharply during the second and third winters, with variable results in the final winter. On average, over all four winters, ring nematodes appeared to decrease more in Jade canola and Caliente, regardless of management practice, and in the treatments where Pallinup oats and Nemat were incorporated in the soil, than in any of the treatments without a cover crop. The treatments where nematicides were applied also produced below- average reductions in nematodes during winter over the course of the trial. The changes in nematode populations in the vine rows during the 60 days after bud-break are shown in Figure 9.6 for selected treatments. Chemical and mechanical control were carried out just before bud-break, so changes in nematode populations during this period reflect the impact of these management practices. -200 Pallinup oats Mechanical Jade canola Chemical Jade canola Mechanical Caliente Chemical Caliente Mechanical Nemat Mechanical No cover crop Chemical Nematicide Chemical Average change in nematode count for all treatments -400 -600 -800 -1000 -1200 -1400 -1600 2009/2010 2010/2011 2011/2012 2012/2013 4-year average

171