Development of integrated snail management systems in vineyards of the Western Cape
Vermeulen, A K
Du Toit, E C
Snails have been a huge problem in many vine growing areas of South Africa, especially in the Vredendal, Swartland, Robertson and Worcester areas. Snails cause feeding damage to vines from early in the spring to mid-summer. From mid-summer onwards snails seek shelter among bunches and leaves.
Many toxic baits, containing carbaryl/metaldehyde, metaldehyde or thiodecarb and copper salt/sodium salt mixture, like Kaput are available, but knowledge of the biology (life history, host preference) of the two dominant snail species (Helix aspersa and Theba pisana) in and around vineyards in different geographical regions and under different cultivation practices is lacking. This results in available control methods not being used effectively. The toxic baits seem to work well against the brown garden snail (Helix aspersa), but not as well against the white dune snail (Theba pisana). Current control methods aim to keep snails out of the vines, but often small snails are already present in the canopy at the start of the season. Snail control does not fail primarily because there are not tools available, but because we lack the knowledge of how to apply them effectively under various conditions.
The ultimate objective of this study will be to develop guidelines/strategies for integrated management of the brown garden snail and the white dune snail in vineyards under different cultivation conditions.
The main objectives of this project are:
1. To do a comprehensive literature study to summarize available information on the prevalence of the two snail species in the different vine growing regions, life cycle and seasonal abundance of snails, and host plant preferences.
2. To do a survey via VinPro consultants to determine which snails are dominant in which region and to identify trial sites.
3. To identify weeds in and around vineyards favoured by the two snail species.
4. To investigate to what extent different cultivated cover crops serve as over wintering hosts and breeding sites for the two snails species.
5. To determine where snails breed under different cultivation practices, i.e. winter cover crops sown or natural winter weed cover.
6. To determine the effect of natural water courses and irrigation canals and the weeds or natural vegetation around them on snail occurrence in adjoining vineyards.
7. To investigate how timing of control in relation to spring weed and cover crop control affects efficacy of snail control.
8. To investigate how aestivation and over wintering of small snails under loose bark on vine trunks and cordons affect efficacy of control measures.
9. To investigate how knowledge gained above can be used to improve snail management e.g. if snails breed in weeds along water courses or canals, can toxic bait and products like Kaput be used to prevent snails from entering vineyards.
10. To evaluate possible new snail control methods for efficacy and their integration into an integrated snail management strategy.
Vermeulen, A K. 2013. Ken en verstaan you viand: Slakke. Winetech VinPro Information Day. 23 May, Klawer, Vredendal en Lutzville, South Africa