Ground cover management in a Mediterranean vineyard: Impact on insect abundance and diversity

Sustainable agriculture requires the support of new tools for successful and low-impact management of pests and diseases at global and local scales. The implementation of cover crops is considered a promising alternative ecological structure for sustainable agriculture, because they provide refuge to natural enemies of pests. Specifically, we hypothesised that implementing cover crop vegetation in a vineyard can enhance populations of natural enemies as a measure to support conservation biological control. We analysed insect abundance and diversity on Vitis vinifera var. Tempranillo (clon RJ-26, rootstock "110-Richter") in a Mediterranean vineyard located in La Rioja, Spain from spring to autumn 2016-2017. Two types of sampling systems (pitfall traps and vacuum sampling) were used in each of the three evaluated ground cover management approaches (n=3): (i) tillage, (ii) spontaneous cover, and (iii) flower-driven cover. A total of 58 families that belonged to four functional subgroups of insects (predators, parasitoids, phytophagous insects, and pollinators) were found. Overall, differences among the three treatments were only detected for total abundance of insects collected in the ground traps, and the "spontaneous cover" treatment showed significantly higher predator richness and abundance. However, the higher Shannon-Wiener value was recorded for "flower-driven cover" at both the ground and canopy levels. In addition, the abundance of predators, parasitoids and phytophagous insects in the ground traps for both cover crop treatments was more than two times higher than that observed in "tillage" treatment. Several predator taxa, such as ants, ground beetles, earwigs, and vespoid wasps had significantly higher representation under spontaneous cover treatment. Moreover, for parasitoids, the "flower-driven cover" treatment revealed higher Hill numbers values (D-0, D-1, and D-2) at the canopy level, although no significant differences were observed. These results indicate that vegetation cover could be used to promote beneficial entomofauna in vineyards and thus be an effective conservation biological control tool.