Population dynamics, overwintering strategy, and cultivar-associated differences of Tuckerella japonica on tea in...

Tea, Camellia sinensis (Theaceae), is one of the most economically important industrial crops globally. The mite Tuckerella japonica (Trombidiformes: Tuckerellidae) has been reported as a pest on tea, yet information on its seasonal population dynamics and overwintering strategy in tea-growing regions remains limited. Moreover, comparative data on the population among different tea cultivars/clones are lacking. This study aimed to determine the population fluctuations, overwintering stage, and potential differences in susceptibility among tea cultivars. The study was conducted in Rize province, located in the Black Sea Region of Türkiye, during 2022 and 2023 under open-field conditions. Fieldwork was conducted in three tea gardens containing the cultivars Samidori and Saekari and the Muradiye-10 clone. During the vegetation period, sampling was performed at 20-day intervals from March to November. At each sampling date, 45 stems (15 cm long) were collected from lateral shoots, comprising 15 stems from each of the lower, middle, and upper canopy levels. Additionally, 60 leaves (20 per canopy level) were sampled, and when available, 25 flowers and 25 fruits were collected. During the winter period (December-February), monthly sampling was carried out using the same scheme. All samples were examined under a stereomicroscope, and the number of mites on stems, leaves, flowers, and fruits was recorded separately. Mites were mounted in Hoyer's medium, dried at 50 °C, and identified to species level using a phase-contrast microscope. Tuckerella japonica populations generally reached their peak densities on stems in July and October, while the highest densities on fruits were recorded in November. Population density decreased significantly during the winter months. In this period, only adult individuals were detected on stems, with no eggs or immature stages observed, indicating that T. japonica may overwinter as adults. Mite densities also varied among cultivars, with the Muradiye-10 clone showing lower infestation levels than the Saekari and Samidori cultivars. These findings enhance understanding of the seasonal biology of T. japonica in tea ecosystems and may aid in developing cultivar-based management strategies within integrated pest management programs.