COVER CROPS in South African Vineyards

CHAPTER 9 PESTS

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0 Change in nematode count per 250 centimetre 3 of soil FIGURE 9 .6. Change in nematode counts in the vine row during the first 60 days after bud-break 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 populations declined during this period, regardless of treatment. On average, declines tended to be greater when cover-crop residues were mechanically incorporated into the soil than when residues remained standing. On the other hand, in treatments where no cover crop was sown, better results were obtained in the treatments with full-surface chemical weed control than in the mechanical-cultivation treatments. When comparing the 4-year average decline in nematode counts, the mechanical incorporation of Jade canola gave similar results to nematicide application.These two treatments were associated with the greatest declines in nematode numbers. The changes in nematode populations in the vine rows during the period from 60 days after bud-break to the following April are shown in Figure 9.7 for selected treatments. These changes indicate the ability of nematode populations to recover during the summer after the application of the different treatments. Nematode numbers increased in all treatments during the summer.When comparing full-surface chemical control to mechanical cultivation, the opposite trend was observed as noted above for the 60 days after bud-break. Pallinup oats Chemical Pallinup oats Mechanical Braco white mustard Mechanical Jade canola Mechanical Nemat Mechanical No cover crop Chemical Nematicide Chemical Average change in nematode count for all treatments -100 -200 -300 -400 -500 -600 2009 2010 2011 2012 2013 4-year average

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