Abstract
Spittlebugs (Hemiptera: Aphrophoridae) are the dominant xylem-sap feeders in the Mediterranean area and the only proven vectors of Xylella fastidiosa ST53, the causal agent of the olive dieback epidemic in Apulia, Italy. We have investigated the structured population phenology, abundance and seasonal movement between crops and wild plant species of both the nymphal and adult stages of different spittlebug species in olive groves. Field surveys were conducted during the 2016–2018 period in four olive orchards located in coastal and inland areas in the Apulia and Liguria regions in Italy. The nymphal population in the herbaceous cover was estimated using quadrat samplings. Adults were collected through sweep nets on three different vegetational components: herbaceous cover, olive canopy and wild woody plants. Philaenus spumarius was the most abundant species; its nymphs were collected from early March and reached a peak around mid-April, when the 4th instar was prevalent. Spittlebug adults were collected from late April until late autumn. P. spumarius adults were abundant on the herbaceous cover and olive trees in late spring, and they then dispersed to wild woody hosts during the summer and returned to the olive groves in autumn when searching for oviposition sites in the herbaceous cover. A relatively high abundance of P. spumarius was observed on olive trees during summer in the Liguria Region. The present work provides a large amount of data on the life cycle of spittlebugs within an olive agroecosystem that can be used to design effective control programmes against these vectors in infected areas and to assess the risk of the establishment and spread of X. fastidiosa to Xylella-free areas.
Highlights
Before the discovery of X. fastidiosa in several areas of the Palaearctic, Aphrophoridae were not regarded as relevant pests in Europe, and the studies on these insects were mainly focused on the taxonomy and the polymorphism of the dominant species, the meadow spittlebug P. spumarius[14,15,16,17,18,19,20]
The samplings of the spittlebug populations in four olive orchards located in two distant Italian regions, Apulia and Liguria, indicated the presence of three predominant species of Aphrophoridae: P. spumarius, N. campestris and Aphrophora alni, the latter only being found in the Ligurian olive groves
Philaenus spumarius was the predominant species in both regions, contributing by 77.9% and 83.1% to all the spittlebug nymphs and by 79.4% and 73.8% to the total spittlebug adults sampled during the 2016–2018 surveys in Apulia and Liguria, respectively
Summary
Before the discovery of X. fastidiosa in several areas of the Palaearctic, Aphrophoridae were not regarded as relevant pests in Europe, and the studies on these insects were mainly focused on the taxonomy and the polymorphism of the dominant species, the meadow spittlebug P. spumarius[14,15,16,17,18,19,20]. Other spittlebug species have basically been overlooked in the Old World, and little information on their biology and ecology is available[27,34,35,36,37,38,39] (see the recent review by Cornara et al.[40]). The aim of this study has been to fill the knowledge gaps on the phenology, abundance and dynamics of spittlebug populations in olive groves in the Mediterranean basin. For this purpose, multiannual surveys were conducted in two olive groves in Southern Italy and in two olive groves in Northern Italy. The different climatic and agroecological conditions of the sampling sites allowed us to monitor different populations of P. spumarius and of other potential vectors of X. fastidiosa in olive orchards in the Mediterranean basin and to analyse their within- and between-year variations
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