Periodic Reporting for period 1 - FAB (Functional Agricultural Biodiversity : Optimising ecosystem service provision via functional agricultural biodiversity)
Reporting period: 2019-09-01 to 2021-08-31
The expansion of modern, chemical-intensive agriculture is regarded as the principal cause of widespread declines in the abundance and diversity of beneficial insects and the valuable ecosystem services they provide (e.g. crop pollination and pest control). Furthermore, as a consequence of warming winters, many beneficial insects are no longer entering into a winter diapause and are instead remaining winter active. This is rendering beneficial insects increasingly susceptible to winter conditions, particularly during a time when food sources are scarce. Such increased winter activity could lead to novel, potentially competitive, interactions between beneficial insects with implications for the beneficial ecosystem services they provide. If agriculture is to be sustainable into the future, it is imperative that agro-ecosystem biodiversity is supported, along with the natural processes provided by ecosystem services. Enhancing floral biodiversity in agricultural landscapes, particularly during winter months, is one way to reinstate beneficial biodiversity back into agricultural landscapes and to mitigate the loss of insect diversity. The FAB project investigated the spatial and temporal distribution patterns of key beneficial insects using cereal and flower fields in France. Ultimately, the project’s goal was to integrate the concept of functional agricultural biodiversity [the diversity of living organisms within agricultural landscapes that perform important roles] to help farmers restore key ecological services (biological pest control and crop pollination) to ensure biodiversity-friendly production. The overall objectives of the project were:
1. To determine the effect of floral cover on the provision of crops pest suppression (biological control).
2. To determine the effect of floral cover on the provision of pollination.
3. To determine potential synergistic or competitive relationships between key ecosystem service providing insects (biological control and pollination), resulting from specific floral mixes.
4. To propose composition matrices of Functional Agricultural Biodiversity and methods of management which can be applied in the field to maximise ecosystem service provision.
1. To determine the effect of floral cover on the provision of crops pest suppression (biological control).
2. To determine the effect of floral cover on the provision of pollination.
3. To determine potential synergistic or competitive relationships between key ecosystem service providing insects (biological control and pollination), resulting from specific floral mixes.
4. To propose composition matrices of Functional Agricultural Biodiversity and methods of management which can be applied in the field to maximise ecosystem service provision.
Two successive winter field trials were performed in the cereal fields of Brittany in north-western France in 2019/20 and 2020/21. During field trials, the abundance of aphid pests and their parasitoids wasps, as well as pollinators in cereal fields was studied in relation to winter flowering crops. No effect of winter flowering crops on parasitism rate was determined. Furthermore, there was no effect of pollinator abundance on the parasitism rate of aphids. Results thus suggest that, at least at present, there is no competition between bees (pollination) and parasitoids (biological pest control) over floral resources in winter in the temperate cereal fields of north-western France.
To further investigate potential competition between pollinators and biological control agents over floral resources, small-scale cage experiments were performed to investigate the effect of bee presence (Bombus terrestris) on the provision of biological control services of cereal aphid pests by Aphidius wasps. Cages were manipulated to vary the composition of winter flowering species available to the bees and parasitoids. Irrespective of floral mixture, the parasitism rate of aphids was lower in the presence of bees, suggesting the possibility of competitive interactions between parasitoids and bees over floral resources, although the result was not statistically significant. Furthermore, parasitism rate appeared higher in the presence of buckwheat (Fagopyrum esculentum), although the result was not statistically significant. Further work is thus required, although results hint at the potential for buckwheat to reduce competitive interactions between bees and parasitoids and, in doing so, enhance the natural biological control services provided by parasitoids.
Since many beneficial insects such as Aphidius parasitoids are becoming increasingly winter active as a consequence of warming winters, the project further investigated the potential for supplementary feeding of specific floral nectars to enhance the cold tolerance of parasitoid wasps. Preliminary results have suggested that supplementary feeding with faba bean (Vicia faba) nectar acts to increase the cold tolerance of Aphidius wasps. For this reason, the use of faba bean in winter flower strips and winter cover crops could aid the winter survival of this beneficial insect. Any measure to aid the winter survival of Aphidius wasps would act to boost the resultant spring population and thus contribute to enhancing the ecosystem service of biological control.
To further investigate potential competition between pollinators and biological control agents over floral resources, small-scale cage experiments were performed to investigate the effect of bee presence (Bombus terrestris) on the provision of biological control services of cereal aphid pests by Aphidius wasps. Cages were manipulated to vary the composition of winter flowering species available to the bees and parasitoids. Irrespective of floral mixture, the parasitism rate of aphids was lower in the presence of bees, suggesting the possibility of competitive interactions between parasitoids and bees over floral resources, although the result was not statistically significant. Furthermore, parasitism rate appeared higher in the presence of buckwheat (Fagopyrum esculentum), although the result was not statistically significant. Further work is thus required, although results hint at the potential for buckwheat to reduce competitive interactions between bees and parasitoids and, in doing so, enhance the natural biological control services provided by parasitoids.
Since many beneficial insects such as Aphidius parasitoids are becoming increasingly winter active as a consequence of warming winters, the project further investigated the potential for supplementary feeding of specific floral nectars to enhance the cold tolerance of parasitoid wasps. Preliminary results have suggested that supplementary feeding with faba bean (Vicia faba) nectar acts to increase the cold tolerance of Aphidius wasps. For this reason, the use of faba bean in winter flower strips and winter cover crops could aid the winter survival of this beneficial insect. Any measure to aid the winter survival of Aphidius wasps would act to boost the resultant spring population and thus contribute to enhancing the ecosystem service of biological control.
In summary, for agriculture to be sustainable into the future, agro-ecosystem biodiversity and ecosystem service provision must be supported into the future. To this end, cover crops and flowers strips offer a simple and effective method to reinstate beneficial biodiversity back into agricultural landscapes. Results of the FAB project contribute towards understanding the potential for floral mixtures to boost beneficial pollinating and pest control insects, all the while reducing competitive interactions that may act to undermine ecosystem service provision.