Mite Types, Numbers, and Plant Distribution on Red Raspberry

Jim Crocker
28th June, 2024

Mite Types, Numbers, and Plant Distribution on Red Raspberry

The RLBV-positive non-cultivated raspberry leaves found in this study displayed atypical symptoms like curling and yellowing (c, d) rather than the classic raspberry leaf blotch disorder (a), contrasting with a healthy, virus-negative cultivated leaf (b).

Image adapted from: Tan et al. / CC BY (Source)

Key Findings

  • The study, conducted in southeastern Norway, identified both plant-feeding and predatory mites on raspberry crops
  • Phytophagous mites preferred the upper zone of cultivated raspberries and the middle zone of non-cultivated raspberries
  • The presence of phytophagous mites did not cause raspberry leaf blotch disorder during the study period
The European Green Deal aims to reduce the use of acaricides in high-value crops like raspberries, promoting biological control and alternative strategies instead. This shift necessitates a deeper understanding of mite species, their densities, and their roles as disease vectors in these crops. A recent study by the University of South Bohemia[1] explored several aspects of mite populations in raspberry crops at northern altitudes. The study had four primary objectives: to identify mite species present on raspberry leaves, to study their population densities, to investigate their intra-plant distribution, and to examine the co-occurrence of phytophagous mites, raspberry leaf blotch disorder, and raspberry leaf blotch virus (RLBV). Sampling was conducted at four sites in southeastern Norway over five intervals. Floricanes from different parts of the sites were collected, with one leaf taken from the upper, middle, and bottom zones of each cane. Mites were extracted using a washing technique and processed for species identification and RLBV detection. The study identified both phytophagous (plant-feeding) and predatory mites. Phytophagous mites included Phyllocoptes gracilis, Tetranychus urticae, and Neotetranychus rubi, while predatory mites included Anystis baccarum and Typhlodromus (Typhlodromus) pyri. Interestingly, phytophagous mites in cultivated raspberries preferred the upper zone of the floricanes, whereas in non-cultivated raspberries, they preferred the middle zone. One of the significant findings was that the presence of phytophagous mites did not lead to raspberry leaf blotch disorder during the study period. This is noteworthy because RLBV is known to cause severe symptoms in raspberries, including yellow blotches on leaves and abnormal leaf hair development[2]. In this study, RLBV was detected in 1.3% of the sampled plants, none of which showed leaf blotch symptoms. Additionally, RLBV was found in 4.3% of P. gracilis samples and some spider mite samples, suggesting that Tetranychids could also serve as vectors for RLBV. The discovery that phytophagous mites did not cause leaf blotch disorder in this study contrasts with earlier findings where RLBV was associated with severe symptoms in raspberries[2]. This discrepancy highlights the complexity of plant-virus-vector interactions and suggests that other factors may influence the manifestation of symptoms. Moreover, the identification of predatory mites like Anystis baccarum, which are beneficial for controlling pest populations, aligns with previous research emphasizing the importance of conserving such predatory species in agricultural ecosystems[3]. The presence of these predatory mites offers a potential biological control method that could be integrated into pest management strategies, reducing the need for chemical pesticides. The study's findings contribute valuable insights into the ecology of mites in raspberry crops, particularly in the context of the European Green Deal's push for more sustainable agricultural practices. By understanding the distribution and impact of both phytophagous and predatory mites, researchers and farmers can develop more effective and environmentally friendly pest management strategies. This research underscores the importance of continued monitoring and study of mite populations and their interactions with plant diseases to ensure the health and productivity of raspberry crops.

AgriculturePlant ScienceAnimal Science

References

Main Study

1) The species, density, and intra-plant distribution of mites on red raspberry (Rubus idaeus L.).

Published 27th June, 2024

https://doi.org/10.1007/s10493-024-00930-7

Related Studies

2) First Report of Raspberry leaf blotch virus in Raspberries in Finland.

https://doi.org/10.1094/PDIS-04-12-0368-PDN

3) Anystis baccarum: An Important Generalist Predatory Mite to be Considered in Apple Orchard Pest Management Strategies.

https://doi.org/10.3390/insects5030615


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