Texture features explain the susceptibility of grapevine cultivars to Drosophila suzukii (Diptera: Drosophilidae) infestation in ripening and drying grapes.

Grapevine is a well-known host plant of the invasive pest Drosophila suzukii, but its susceptibility to pest oviposition and development greatly depends on the cultivar. To address environmental sustainability during viticultural zoning planning, new vineyard plantation and Integrated Pest Management programmes, it is essential to take pest pressure and cultivar susceptibility into account. To determine the different grapevine cultivars susceptibility to D. suzukii, we tested twelve widely spread cultivars during the ripening period. We also tested three cultivars during the drying period for raisin wine production. The infestation and emergence rates were consequently related to chemical and texture features of the berries to explain the role of skin and pulp characteristics in determining the nature of the susceptibility. Our results showed that susceptibility to D. suzukii infestation varies across cultivars. On ripening grapes, infestation is primarily influenced by skin and pulp firmness, elasticity and consistency. Suitability for egg development resulted mainly related to skin and pulp deformation. In a drying loft, infestation may also occur in relation to skin and pulp consistency. Lastly, we discuss the practical implication of the underestimated role of berry texture in D. suzukii oviposition and emergence success, in both ripening and drying grapes.

Non-crop plants used as hosts by Drosophila suzukii in Europe.

The invasive spotted wing drosophila Drosophila suzukii, a fruit fly of Asian origin, is a major pest of a wide variety of berry and stone fruits in Europe. One of the characteristics of this fly is its wide host range. A better knowledge of its host range outside cultivated areas is essential to develop sustainable integrated pest management strategies. Field surveys were carried out during two years in Italy, the Netherlands and Switzerland. Fruits of 165 potential host plant species were collected, including mostly wild and ornamental plants. Over 24,000 D. suzukii adults emerged from 84 plant species belonging to 19 families, 38 of which being non-native. Forty-two plants were reported for the first time as hosts of D. suzukii. The highest infestations were found in fruits of the genera Cornus, Prunus, Rubus, Sambucus and Vaccinium as well as in Ficus carica, Frangula alnus, Phytolacca americana and Taxus baccata. Based on these data, management methods are suggested. Ornamental and hedge plants in the vicinity of fruit crops and orchards can be selected according to their susceptibility to D. suzukii. However, the widespread availability and abundance of non-crop hosts and the lack of efficient native parasitoids suggest the need for an area-wide control approach.