WINETECH Technical Yearbook 2021

included Pinotage and Shiraz, and all three vineyards were irrigated with micro- sprinklers. It should be noted that the 2017/2018 season was characterised by drought conditions, which may well have influenced our results. For example, we sampled Eremnus occatus , which is not commonly found in vineyards, but not E. setulosus or E. cerealis , which were generally regarded as widespread in vineyards. It is not possible to determine the exact reasons for this. Seasonal cycle BFW numbers peaked during December 2017 and were not detected after April 2018. Eremnus occatus and E. setifer numbers peaked one month earlier, followed by the other weevil species, and numbers also decreased after April (figures 2 and 3). Pest status Damage was monitored by checking leaves and berries for feeding injury (figure 4) during middle December 2017 and March 2018 (before harvest). It was found that if BFW was excluded from the analysis, the remaining eight weevils’ effect on fruit damage was significant. The same analysis only for BFW was also significant, but the correlation was stronger. This suggests that BFW is likely responsible for the majority of damage in vineyards, but that the other

FIGURE 2. Seasonal cycle of BFW, as monitored in three vineyards in Stellenbosch and Elgin during the 2017/2018 growing season. Monitoring took place every two weeks using double-sided cardboard bands on 20 evenly space vine plots (all vines between two trellis poles).

FIGURE 3. Seasonal cycle of eight weevil species, as monitored in three vineyards in Stellenbosch and Elgin during the 2017/2018 growing season. Monitoring took place every two weeks using double-sided cardboard bands on 20 evenly space vine plots (all vines between two trellis poles).

nematodes (EPNs) and entomopathogenic fungi (EPF) hold promise to supress BFW populations, and could easily be incorporated into an IPM programme. OUTCOMES Weevil complex Nine different weevil species were found to occur in three vineyards in Stellenbosch and Elgin (figure 1). The cultivars sampled

per year, with a second generation usually only developing in irrigated vineyards. Several other weevil species may be found in vineyards, which may be of economic concern. For example, Sciobius weevil (figure 1) has been shown to damage deciduous fruits, but this weevil, along with some other species, are very sporadic. Not much is known about their seasonal cycle and pest status in vineyards.

Due to the weevils lacking wings, they climb up the vine trunks or trellis poles at night, when they are active, and feed on developing bunches, stems and leaves. For this reason, trunk barriers have been recommended for their control. Full cover applications are registered, but are not always compatible with an integrated pest management (IPM) programme. Initial research found that entomopathogenic

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