Raspberry plants, valued for their fruits, are vulnerable to a range of viruses that adversely affect their yield and quality. Utilizing high-throughput sequencing (HTS), we identified a novel virus, tentatively named raspberry enamovirus 1 (RaEV1), in three distinct raspberry plants. This study provides a comprehensive characterization of RaEV1, focusing on its genomic structure, phylogeny, and possible transmission routes. Analysis of nearly complete genomes from 14 RaEV1 isolates highlighted regions of variance, particularly marked by indel events. The evidence from phylogenetic and sequence analyses supports the classification of RaEV1 as a distinct species within the Enamovirus genus. Among the 289 plant and 168 invertebrate samples analyzed, RaEV1 was detected in 10.4% and 0.4%, respectively. Most detections occurred in plants that were also infected with other common raspberry viruses. The virus was present in both commercial and wild raspberries, indicating the potential of wild plants to act as viral reservoirs. Experiments involving aphids as potential vectors demonstrated their ability to acquire RaEV1 but not to successfully transmit it to plants.

A novel negative-sense single-stranded RNA virus showing genetic similarity to viruses of the genus Rubodvirus has been found in raspberry plants in the Czech Republic and has tentatively been named raspberry rubodvirus 1 (RaRV1). Phylogenetic analysis confirmed its clustering within the group, albeit distantly related to other members. A screening of 679 plant and 168 arthropod samples from the Czech Republic and Norway revealed RaRV1 in 10 raspberry shrubs, one batch of Aphis idaei, and one individual of Orius minutus. Furthermore, a distinct isolate of this virus was found, sharing 95% amino acid identity in both the full nucleoprotein and partial sequence of the RNA-dependent RNA polymerase gene sequences, meeting the species demarcation criteria. This discovery marks the first reported instance of a rubodvirus infecting raspberry plants. Although transmission experiments under experimental conditions were unsuccessful, positive detection of the virus in some insects suggests their potential role as vectors for the virus.

The adoption of the European Green Deal will limit acaricide use in high value crops like raspberry, to be replaced by biological control and other alternative strategies. More basic knowledge on mites in such crops is then necessary, like species, density, and their role as vectors of plant diseases. This study had four aims, focusing on raspberry leaves at northern altitude: (1) identify mite species; (2) study mite population densities; (3) investigate mite intra-plant distribution; (4) investigate co-occurrence of phytophagous mites, raspberry leaf blotch disorder and raspberry leaf blotch virus (RLBV). Four sites in south-eastern Norway were sampled five times. Floricanes from different parts of the sites were collected, taking one leaf from each of the upper, middle, and bottom zones of the cane. Mites were extracted with a washing technique and processed for species identification and RLBV detection. Mites and leaves were tested for RLBV by reverse transcription polymerase chain reaction (RT-PCR) with virus-specific primers. Phytophagous mites, Phyllocoptes gracilis, Tetranychus urticae, and Neotetranychus rubi, and predatory mites, Anystis baccarum and Typhlodromus (Typhlodromus) pyri were identified. All phytophagous mites in cultivated raspberry preferred the upper zone of floricanes, while in non-cultivated raspberry, they preferred the middle zone. The presence of phytophagous mites did not lead to raspberry leaf blotch disorder during this study. RLBV was detected in 1.3% of the sampled plants, none of them with leaf blotch symptoms, and in 4.3% of P. gracilis samples, and in some spider mite samples, implying that Tetranychids could also be vectors of RLBV.

Red raspberry, Rubus idaeus, is known to be infested by at least six species of eriophyid mites. Among them, the raspberry leaf and bud mite, Phyllocoptes gracilis, (Figure 1, A–B) is the only known vector of a raspberry virus, namely the raspberry leaf blotch virus (RLBV) (Dong et al. 2016; McGavin et al. 2012; Tan et al. 2022). Raspberry leaf blotch (Figure 1, C), a leaf disorder displaying as leaf chlorosis, distortion and patchy necrosis, yellowing and thinning on lateral branches, has been attributed to the feeding of P. gracilis until RLBV was also found to be associated with these symptoms (McGavin et al. 2012). Previous sampling of eriophyid mites was often based on the presence of the leaf blotch symptom, and there is a reasonable doubt if the symptom was caused by RLBV infection or mite infestation. It could also be hypothesized that eriophyid mites are attracted to RLBV-infected plants as viruses could make host plants more attractive to vectors (Donnelly & Gilligan 2020; Shi et al. 2019). It is therefore important to improve the detection of both mites and RLBV to efficiently manage the virus. In addition, knowledge on the dominant infestation area of eriophyid mites on raspberry canes is essential to develop an effective pest management approach. Gordon and Taylor (1976) reported that P. gracilis on primocanes during late summer (mid-August) was dominantly found on the upper leaves, due to the presence of predatory mites on the lower and middle leaves. But mite behavior on floricanes is also important to study if the goal is to prevent mite migration and RLBV transmission to primocanes. This study aimed to investigate the population density of eriophyid mites on raspberry floricanes and the association of eriophyid mites, RLBV, and leaf blotch symptoms.