Search

Aim Invasive populations are often irregularly distributed due to sporadic dispersal events and patchy distribution of suitable habitat, making it difficult to recognize the population boundary and effectively target management. We designed a survey prioritization that addresses these irregularities and tested it on an invasive King Devil Hawkweed (Hieracium praealtum) population. Location Bogong High Plains, Victoria, Australia. Methods Our optimal design prioritized discovery of infestations beyond the known population boundary, while accounting for the diminishing likelihood of occurrence, plant detectability and the search resources available. Hawkweed management agencies implemented this design in the field. We evaluated its practicality and their progress towards delimitation. Results The survey design favoured locations outside the known population boundary with a relatively high likelihood of species occurrence and high capacity to detect individuals. Difficult-to-search sites were selected for intensive survey when the likelihood of occurrence was sufficiently high. The GPS tracks recorded by managing agencies during the survey corresponded well with the priority rankings, but did not include search effort information. In subsequent surveys, managing agencies have improved recording protocols and expanded their performance metrics. This will facilitate future evaluation of progress towards delimitation and eradication. Main conclusions Our optimization method effectively identified priorities for delimiting an invading population, accounting for the agencies' budget and the risk of detection failures. Probabilistic maps proved useful for communicating search priorities, and GPS track logs provided valuable spatial data for inferring where the species is likely to be absent. When comprehensive spatio-temporal data are available, survey findings can be used to update species occurrence models and thus our quantitative understanding of the population's extent. A probabilistic map provides a more nuanced view of delimitation than drawing a strict boundary around known infestations. Burgman et al.'s extended delimitation score is a promising summary statistic for reporting. [ABSTRACT FROM AUTHOR]

Grape phylloxera, Daktulosphaira uitifoliae (Fitch) (Hemiptera Phylloxeridae) is a damaging pest of grapevines ( Vitis spp.) around the world, and the management of this pest requires early detection of infestations. Here, we describe the development and validation of a sensitive DNA test for grape phylloxera that can be applied to soil. Species-specific primers were developed for grape phylloxera in the internal transcribed space region 2, and their specificity was confirmed after thorough screening by using a wide range of vineyard organisms and aphid genera. Preliminary testing of the detection limits of the grape phylloxera-specific primers was conducted using field-sourced soil types spiked with a known number of grape phylloxera. The assay was converted to a real-time polymerase chain reaction format (TaqMan MGB). This assay, in combination with DNA extraction from soil, can detect phylloxera crawlers added to soil. The assay was evaluated in the field at a recently detected grape phylloxera infestation site from the Yarra Valley in Victoria, Australia. The DNA assay proved to be substantially more sensitive than a standard ground survey for detecting grape phylloxera presence on vine roots in the infested vineyard. Moreover, unlike the ground survey, the assay provided quantitative information on grape phylloxera infestations, because grape phylloxera DNA concentrations in samples from vines closely matched the numbers of grape phylloxera crawlers collected with emergence traps placed at the base of vines. Unlike other detection techniques, the method can be applied at any time of the year, and it can be potentially modified to provide specific information on the virulence levels of the particular grape phylloxera genotypes responsible for any new infestations. [ABSTRACT FROM AUTHOR]