Susceptibility of table grape varieties grown in south‐eastern Italy to Drosophila suzukii

Abstract

Since 2008, Drosophila suzukii, the spotted wing drosophila, has colonized most of the American and European continents, being able to adapt to very different climates. In Italy, this pest has been captured from northern Alpine to southern Mediterranean regions where it can infest a broad range of fruits, including wine grapes. Studies have shown that oviposition levels and developmental rates of D. suzukii on wine grapes are lower than on other berries, although recent observations indicate that grapes may become a suitable host plant in particular conditions. Here, we report, for the first time, the results of a series of no-choice oviposition experiments using berries of five table grape varieties sampled in the provinces of Taranto and Bari (Apulia region, south-eastern Italy) during 2013 from both organic and conventional farming systems.The sugar content (SC) and skin hardness of each sample were analysed to assess the influence of these physiological parameters on the susceptibility of table grapes to D. suzukii infestation. A negative correlation was found between the number of eggs laid and berry skin penetration force, whereas there was a positive one between the number of eggs and Brix values, as well as sampling date. In organic grapes, SC and skin hardness of two varieties ("Crimson" and "Scarlotta") were measured, respectively, higher and lower than in conventional grapes, thus making them more susceptible to pest infestation. The study hence shows that in laboratory conditions D. suzukii is able to heavily infest and develop on table grapes and that susceptibility to its infestation significantly depends on both variety and farming system. K E Y W O R D Salien invasive pests, conventional and organic farming, fruit flies, pest control

Influences of blackberry margins on population dynamics of Drosophila suzukii and grape infestation in adjacent vineyards

“…In viticulture, the landscape is often characterized by small and compartmentalized parcels, which can be surrounded by different semi‐natural habitats (Klick et al, ; Pelton et al, ). Risk assessment for D. suzukii in viticulture has been started only recently, and the few studies investigating the susceptibility of Vitis vinifera L. varieties revealed contradicting results so far (Baser et al, ; Ioriatti et al, ; Kim et al, ; van Timmeren & Isaacs, ). The prevailing uncertainty about the risk of damage arising for wine production has resulted in management strategies mainly based on prophylactic use of broad‐spectrum insecticides, which are known to seriously impact non‐target organisms across trophic levels (Cini et al, ; Müller, ; van Timmeren & Isaacs, ).…”

Management strategies against Drosophila suzukii: insights into Swiss grape growers choices

“…One such variety is the indigenous white variety Chasselas. In fact, white varieties are perceived to be less affected by D. suzukii than red varieties in our sample [Baser et al , Ioriatti et al , Linder et al and Saguez et al also mention that white varieties are less susceptible.] and given that infestation is low, grape growers seem to undertake fewer measures than with grapes perceived to be prone to infestation.…”

“…The percentage above is an estimate based on 160,000 berries from 600 Swiss vineyards between mid‐August 2016 and October 2016, and thus does not represent the real damage suffered by grape growers in their vineyards . Overall, we find that infestation pressure and damage to growers are heterogeneous over time and space, and might also depend on the cultivation system . Susceptibility to infestation is also variety specific and depends mainly on skin hardness, sugar content and acidity levels .…”

“…Most figures and literature on economic damage relate to red berries and cherry production . Grape susceptibility and the resulting economic damage is still moot . According to a ranking by Bellamy et al grapes are not the main host fruit for D. suzukii .…”

“…According to a ranking by Bellamy et al grapes are not the main host fruit for D. suzukii . However, grapes remain a crop where D. suzukii may feed, oviposit and develop further, thus representing an economic threat to growers . In fact, D. suzukii can occasionally be more troublesome in grapes since growers may be obliged to discard a whole bunch while berry growers can possibly sort infested fruit …”