Prevalence of Puccinia abrupta var. partheniicola and its impact on Parthenium hysterophorus in Kathmandu Valley, Nepal

Background Partheniumhysterophorus is a noxious invasive weed in tropical and subtropical regions of the world, including Nepal. Among 11 species of biological control agents released to control P. hysterophorus in Ausrtalia, winter rust Puccina abrupta var. partheniicola arrived fortuitously and has established in Kathmandu Valley, Nepal, nearly a decade back. However, the prevalence and effectiveness of this rust as a biological control agent in Kathmandu remain unknown. To address this knowledge gap, a roadside survey was done at an interval of 2 ± 0.25 km in Kathmandu Valley to assess the P. abrupta var. partheniicola incidence and its impacts on P. hysterophorus. Infested individuals of P. hysterophorus were further divided into four severity classes (very low, low, medium, and high), and rust incidence was calculated. The impact of the winter rust on the growth of P. hysterophorus was assessed by comparing biomass and seed output of infested and non-infested individuals. Results Among 81 locations where P. hysterophorus was present in the Kathmandu Valley, winter rust infestation was observed at 98% locations. At some locations within Kathmandu Valley such as Tinkune, Kirtipur, Chabahil, Buddha Chowk, and Dhobighat, the impacts of the rust on P. hysterophorus were medium to high. Aboveground biomass and seed output of P. hysterophorus were reduced by 47% and 73%, respectively, due to winter rust infestation. The study indicates that winter rust incidence is widespread in Kathmandu Valley with very low to high levels of damages to P. hysterophorus depending on the localities. Conclusion The rust has, therefore, a potential to reduce the growth performance of P. hysterophorus, and it can be used as a component of integrated management of P. hysterophorus by introducing to other suitable areas in Nepal.

Semi-Automated Roadside Image Data Collection for Characterization of Agricultural Land Management Practices

Land cover management practices, including the adoption of cover crops or retaining crop residue during the non-growing season, has important impacts on soil health. To broadly survey these practices, a number of remotely sensed products are available but issues with cloud cover and access to agriculture fields for validation purposes may limit the collection of data over large regions. In this study, we describe the development of a mobile roadside survey procedure for obtaining ground reference data for the remote sensing of agricultural land use practices. The key objective was to produce a dataset of geo-referenced roadside digital images that can be used in comparison to in-field photos to measure agricultural land use and land cover associated with crop residue and cover cropping in the non-growing season. We found a very high level of correspondence (>90% level of agreement) between the mobile roadside survey to in-field ground verification data. Classification correspondence was carried out with a portion of the county-level census image data against 114 in-field manually categorized sites with a level of agreement of 93%. The few discrepancies were in the differentiation of residue levels between 30–60% and >60%, both of which may be considered as achieving conservation practice standards. The described mobile roadside image capture system has advantages of relatively low cost and insensitivity to cloudy days, which often limits optical remote sensing acquisitions during the study period of interest. We anticipate that this approach can be used to reduce associated field costs for ground surveys while expanding coverage areas and that it may be of interest to industry, academic, and government organizations for more routine surveys of agricultural soil cover during periods of seasonal cloud cover.

Use of a rapid roadside survey to detect potentially invasive plant species along the Garden Route, South Africa

Early detection of emerging or sleeper weeds and monitoring of alien plant invasions forms the foundation of effective invasive alien plant management. Using a rapid roadside survey technique, we aimed to (1) establish a baseline of alien plant distribution and abundance along roads in the Garden Route, South Africa, and (2) identify priority species (particularly sleeper weeds) and priority areas to inform appropriate management action. We surveyed along 530 km of roads and recorded 109 alien and/or extralimital species across 1942 point locations. Of these, 35 species were considered to be sleeper weeds on account of displaying estimated dispersal distances distinctive of invasive plants and not being listed by the South African Plant Invaders Atlas (SAPIA) or regulated by South African legislation. Roads along natural forest and fynbos vegetation (often within the Garden Route National Park) displayed lower incidences of alien plants than those associated with degraded or transformed land, with roads along farmland associated with the highest incidences of alien plants. Roads in the Southern Cape region had more species and higher densities of alien plants than roads in the Tsitsikamma region, and a few species were exclusive to either.Conservation implications: Our inventory contributed significant new records and range extensions to SAPIA, while the identified sleeper weeds offered suggestions for species that may be considered for regulation under the National Environmental Management: Biodiversity Act of South Africa. We furthermore provided information to facilitate (1) timely management of emerging invasive alien plants, (2) prioritisation of species and areas for management action, and (3) future monitoring of alien plants in the Garden Route National Park and surrounds.