Wi-Fi tethering using a mobile device (e.g., a smartphone or a tablet) as a hotspot for other devices has become a common practice. Despite the potential benefits of Wi-Fi tethering, the open source nature of mobile operating systems (e.g., Google Android) can be abused by a selfish device to manipulate channel-access parameters to gain an unfair advantage in throughput performance. This can cause serious performance problems within a well-planned Wi-Fi network due to an unauthorized selfish or misconfigured tethering device interfering with nearby well-planned access points (APs). In this paper, we demonstrate that the selfish behavior of a tethering node that adjusts the clear channel assessment (CCA) threshold has strong adverse effects in a multi-AP network, while providing the selfish node a high throughput gain. To mitigate this problem, we present a passive online detection scheme that identifies the network condition and detects selfish tethering nodes with high accuracy by exploiting the packet loss information of on-going transmissions. To the best of our knowledge, this is the first research to consider the problem of detecting a selfish tethering node in managed Wi-Fi networks.

Brown leaf spot disease caused by Alternaria spp. is among the most common diseases in potato crops. Typical brown spot symptoms were observed in commercial potato-cultivated areas of northern Korea during June 2021–2022. In total, 77 isolates were collected, and based on sequence analysis of the internal transcribed spacer (ITS) region, the collected isolates were identified as Alternaria spp. (83.1%). Phylogenetic analysis revealed that a majority of these isolates clustered within a clade that included A. alternata. Additionally, the ITS region and rpb2 yielded the most informative sequences for the identification of A. alternata. Pathogenicity tests confirmed that the collected pathogens elicited identical symptoms in the field. In the pathogenicity test performed on seven commercial cultivars, the pathogens exhibited strong virulence in both wound and non-wound inoculations. Among the cultivars tested, Arirang-1ho, Arirang-2ho, and Golden Ball were resistant to the pathogens. Furthermore, when testing effective fungicides in vitro, mancozeb and difenoconazole were found to be effective agents for inhibiting mycelial growth. In summary, our findings suggest that A. alternata plays a critical role in leaf disease in potato crop regions and emphasise the necessity for continuous monitoring and management to protect against this disease in South Korea.