Effects of cover crop management on grape pests in a Mediterranean environment

A study was conducted in a vineyard of Southern Sardinia from 2002 to 2004 to determine the effect of soil management on grape pest populations. Observations were carried out in two plots of 0.5 ha each of the white berry cultivar “Malvasia”: one with soil cultivation and weed removal, and the other with natural ground cover since 1995. In that environment, during summer, resident vegetation dries up and does not compete with the grapevine for water and nutrients. The results showed that leafhoppers and thrips populations were not influenced by the ground cover. The attacks of European grapevine moth (Lobesia botrana) were always higher in the tilled plot, which showed a percentage of damaged bunches at harvest of 12%, 42% and 14% in 2002, 2003 and 2004, respectively. In contrast, these values were of 2%, 13% and 8%, respectively, in the cover crop plot. These differences could be due to the fact that grapevines of the cover crop plot had less vigorous sprouts that produced smaller and less clustered bunches, less preferred by the moth. On the contrary, the infestation of Vine mealybug (Planococcus ficus) on bunches of the cover crop was about twice as high as it was in the tilled plot (28% vs. 12% of bunches damaged by colonies in 2004, respectively). This was probably caused by a more abundant population of ant species, which protect the mealybugs from their natural enemies, in the ground cover plot than in the tilled one. In particular, the prevalent ant species found in the cover crop plot were Tapinoma simrothi and Tetramorium spp., while Lasius niger was the most abundant one in the tilled plot.