The global production of raspberries was approximately 950 thousand tons in 2022 (FAO, 2023) and the global import and export volume increased by 50% and 56% respectively, from 2012 to 2019 (Bojkovska et al., 2021). This indicates an increasing demand for raspberries. The annual production of raspberries in Norway is approximately two thousand tons, with ‘Glen Ample’ being the dominant cultivated variety (Akšić et al., 2022; FAO, 2023). The production of raspberries is consistently challenged by various pests and diseases, and thrips is one of them (Tan et al., 2022). Thrips in red raspberry, Rubus idaeus L., has been receiving more attention in Scandinavian raspberry production the last few years. They are more frequently observed in flowers and fruitlets, concurring with presumed thrips damage on the berries. In addition, thrips crawling in the lids of fresh market berry punnets lead to negative feedback from customers. The possible reasons for the increase in thrips abundance include less pesticide use during flowering as well as higher frequency of heat waves and higher average temperature across Europe during summer (Chapman et al., 2019; Sánchez-Benítez et al., 2022). In addition, altered growing techniques, such as plastic tunnels and black polyethylene mulch, could provide a better environment for overwintering thrips, increasing their survival rate and thus leading to more rapid resurgence of thrips populations during spring (Nielsen et al., 2021; Sampson et al., 2021). Changes in global climate are also predicted to promote migration of thrips, causing an invasion of new species (Mukherjee et al., 2023). These factors highlight the importance of studying and monitoring the species composition of thrips in economically important crops, such as raspberry.

Several species of thrips have been reported on raspberry, and among them are the cosmopolitan pests Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman. In addition, Tenothrips frici (Uzel), Thrips imaginis Bagnall, and Thrips fuscipennis Haliday, have been found in raspberry. Among these five species, T. imaginis is not present in Europe (Mound & Masumoto, 2005; CABI, 2023). In Norway, Thrips tabaci and T. fuscipennis are widely distributed in the southern part (Kobro, 2013, 2022), whereas F. occidentalis has only been reported as an indoor species (Gertsson, 2015) and Te. frici was found recently (Kobro & Ulitzka, 2021). In Portugal, several other polyphagous thrips species have been reported on sticky traps in greenhouse cultivated raspberry. These include Thrips major Uzel, Thrips flavus Schrank, Thrips angusticeps Uzel, Tenothrips discolor Karny, and Frankliniella tenuicornis (Uzel). In addition to these phytophagous species (suborder Terebrantia), thrips belonging to the predatory genus Aeolothrips (suborder Tubulifera)were also found on the traps (Mateus, 2016).

It is hypothesized that there are more species of thrips present on raspberry than those documented in the literature. To date, the thrips fauna of raspberry in Scandinavia has not been specifically investigated. The objective of this study was therefore to identify thrips present in the flowers of cultivated red raspberry in South Norway. Knowing the most common species present is important for further studies of damage potential and management of thrips in raspberry, including the possibility of virus vectoring.

A total of 213 adult female thrips were identified morphologically (Table 2). Five species of thrips were found: Thrips fuscipennis Haliday, Thrips major Uzel, Thrips flavus Schrank, Thrips vulgatissimus Haliday, and Thrips brevicornis Priesner. Among these five species, T. flavus was the most abundant, followed by T. fuscipennis and T. vulgatissimus. Thrips fuscipennis is the only species previously reported on raspberry (Raspudić et al., 2009; Bennison et al., 2020), but T. major and T. flavus have been found on sticky traps in greenhouse cultivated raspberry in Portugal (Mateus, 2016). All five species have been reported to be present in Norway (Kobro, 2013). In general, the thrips distribution concurred to that reported by Kobro (2022). Even though T. fuscipennis was the second most abundant species among the identified specimens, it was only found in Frogn. This matches its distribution, which is more concentrated in the south-eastern area of Norway where Frogn is located. Although T. tabaci and F. occidentalis are present in Norway (Gertsson, 2015) and have been reported on raspberry in other countries (Leach & Isaacs, 2018; CABI, 2023), they were not found in this study. This was probably because all the sampling sites were open field raspberry, and these two species tend to be most abundant in raspberry cultivated in tunnel (Gertsson, 2015; Mateus, 2016; Leach & Isaacs, 2018).

The presence of T. major and T. flavus in raspberry is well within expectation, as they are associated with a wide range of flowering plants in Europe, and are known to feed on many species of Rosaceae plants, including other species of Rubus, like blackberry and loganberry (Alford, 2014). Besides Rosaceae, T. flavus is also known to cause economic damage to a wide range of crops in other plant families, such as Gramineae, Solanaceae and Leguminosae (Sun et al., 2023). Thrips major is often found together with adults of other thrips in flowers, among them are T. fuscipennis, T. flavus, and T. vulgatissimus (Morison, 1957). To date, T. major is only regarded as minor pest in general (Velez-Gavilan, 2022). Thrips major and T. fuscipennis are quite common pests of strawberry, and their damage can result in malformed fruits, causing some economic losses (Alford, 2014; Nielsen et al., 2021). Besides strawberry, T. fuscipennis infests a wide range of other host plants that belong to the family Rosaceae (Bennison et al., 2020). Thrips vulgatissimus is found in flowers of many plants too, especially in small white flowers, such as certain species of Caryophyllaceae (Mound & Masumoto, 2005). It has also been reported on strawberry in Denmark, but only in small numbers (Nielsen et al., 2021). In Norway and Sweden, it is one of the most widely distributed thrips species (Kobro, 2013; Gertsson, 2015). Thrips vulgatissimus has been categorized as a relative important pest of barley, wheat and buckwheat in China and the United States (Reitz et al., 2011). The least common thrips in our study was T. brevicornis. It is described as a polyphagous thrips (Vierbergen et al., 2010) and is present in many flowers in Norway (Kobro, 2013). In addition to being flower-living, this species along with T. flavus and T. fuscipennis, are known as meadow-living and heliophilous (Masarovič et al., 2022). This implies that these thrips can also survive on alternative flowering plants in the surrounding of the orchards. The pest status of these species in raspberry is still unknown, and therefore, further investigation on their level of threat in this crop is important.

As a conclusion, only one out of the five species found in this study was previously documented on raspberry, thus confirming the hypothesis that more species of thrips were present on raspberry than currently documented. Although more evidence should be collected to investigate their pest status in raspberry, this study demonstrates the lack of information on thrips species occurring on this crop. Such records of species are also important because invasion of new species are occurring frequently and shift of thrips distribution has also been predicted due to climate change (Mukherjee et al., 2023). Therefore, the results will serve as an important thrips species reference in raspberry for future studies. Recommended further studies includes the pest status of these thrips, their potential as raspberry virus vectors, and to continue monitoring the thrips species composition in raspberry. Since all the sampling orchards were open-field, species composition in tunnel-cultivated raspberry should be studied to compare the species composition. Knowing more on the species composition can help to make better decision in thrips management especially after the adoption of the European Green Deal 2030.