Reviewing research priorities in weed ecology, evolution and management: a horizon scan.

Weedy plants pose a major threat to food security, biodiversity, ecosystem services and consequently to human health and wellbeing. However, many currently used weed management approaches are increasingly unsustainable. To address this knowledge and practice gap, in June 2014, 35 weed and invasion ecologists, weed scientists, evolutionary biologists and social scientists convened a workshop to explore current and future perspectives and approaches in weed ecology and management. A horizon scanning exercise ranked a list of 124 pre-submitted questions to identify a priority list of 30 questions. These questions are discussed under seven themed headings that represent areas for renewed and emerging focus for the disciplines of weed research and practice. The themed areas considered the need for transdisciplinarity, increased adoption of integrated weed management and agroecological approaches, better understanding of weed evolution, climate change, weed invasiveness and finally, disciplinary challenges for weed science. Almost all the challenges identified rested on the need for continued efforts to diversify and integrate agroecological, socio-economic and technological approaches in weed management. These challenges are not newly conceived, though their continued prominence as research priorities highlights an ongoing intransigence that must be addressed through a more system-oriented and transdisciplinary research agenda that seeks an embedded integration of public and private research approaches. This horizon scanning exercise thus set out the building blocks needed for future weed management research and practice; however, the challenge ahead is to identify effective ways in which sufficient research and implementation efforts can be directed towards these needs.

Provisioning floral resources to attract aphidophagous hoverflies (Diptera: Syrphidae) useful for pest management in central Spain.

Noncrop plant communities present on the boundaries or within crop fields are essential for the maintenance of functional biodiversity, affecting beneficial insect numbers and ecological fitness. Habitat manipulation is an increasingly studied strategy aimed at enhancing natural enemies of agricultural pests by providing feeding and shelter resources. In this study, six plant species selected from preliminary work were tested for their potential attractiveness to four common aphidophagous hoverflies species. Potential attractiveness was evaluated through observation of hoverfly feeding visits to replicated flower plots distributed in a randomized design. The combination of the selected species covered a 2-mo full-bloom period. Sphaerophoria scripta L. and Sphaerophoria rueppellii (Wiedeman) were the dominant hoverflies present throughout the sampling period, whereas Eupeodes corollae (F.) and Episyrphus balteatus (DeGeer) visits were less abundant and appeared only in the early season. Potential attractiveness varied among plant species. Calendula arvensis L. and Coriandrum sativum L. were the most visited species. C. arvensis received a high number of visits throughout a long period, whereas the visits to Co. sativum were concentrated in a short blooming period. These results suggest that habitat management by using these plant species may increase the abundance of hoverflies and could improve the biological control of aphid pests typical of spring-summer crops in open Mediterranean environments.

Population cycles produced by delayed density dependence in an annual plant.

In contrast to insect and animal populations, little attention has been directed to the study of cycles in plant populations. It has been argued on theoretical grounds that plants present stable dynamics. Nevertheless, there are examples where plant populations appear to exhibit oscillatory dynamics, but the oscillatory signal is variable and comes from very short time series data. Using a combination of time series, models, and empirical results, we present evidence of population cycles for Descurania sophia in a 16-year field experiment. Endogenous and exogenous causal mechanisms were studied to identify processes underlying this temporal dynamic. Our results show a 4-year cycle produced by delayed density dependence. We suggest that high nutrient levels might be responsible for the observed dynamics of D. sophia. Our results suggest that although plant population dynamics may be stabilized by direct density dependence, delayed density dependence could destabilize dynamics.