Project Overview:
Agricultural landscape heterogeneity can be broadly defined as the mixture (composition) and spatial arrangement (configuration) of crop fields, natural grasslands, forests, and other habitat types which surround an agricultural field. Managing agricultural heterogeneity is likely to represent an important means of promoting sustainable agriculture. Increasing the heterogeneity of farmed landscapes readily leads to a promotion of biodiversity within the area, including an increase in beneficial arthropods that carry out agro-ecosystem services. This increase in arthropod diversity facilitates the suppression of herbivorous insects through the increased abundance and activity of natural predators and parasitoids. However, the extent to which agricultural heterogeneity impacts the between- and within-species diversity of herbivorous insects is unknown. Species diversity is important from an agricultural perspective as some species are more virulent and represent a greater agricultural threat than others. Furthermore, the diversity within species, including genetic diversity and association with endosymbionts, can influence the biology and ecology of herbivorous insects. This can have wide ranging agricultural consequences such as conferring resistance against natural enemies and promoting pest proliferation. The research in this project will examine the extent to which agricultural heterogeneity influences the intra-species diversity in herbivorous insect species of agricultural importance.
Agricultural landscape heterogeneity can be broadly defined as the mixture (composition) and spatial arrangement (configuration) of crop fields, natural grasslands, forests, and other habitat types which surround an agricultural field. Managing agricultural heterogeneity is likely to represent an important means of promoting sustainable agriculture. Increasing the heterogeneity of farmed landscapes readily leads to a promotion of biodiversity within the area, including an increase in beneficial arthropods that carry out agro-ecosystem services. This increase in arthropod diversity facilitates the suppression of herbivorous insects through the increased abundance and activity of natural predators and parasitoids. However, the extent to which agricultural heterogeneity impacts the between- and within-species diversity of herbivorous insects is unknown. Species diversity is important from an agricultural perspective as some species are more virulent and represent a greater agricultural threat than others. Furthermore, the diversity within species, including genetic diversity and association with endosymbionts, can influence the biology and ecology of herbivorous insects. This can have wide ranging agricultural consequences such as conferring resistance against natural enemies and promoting pest proliferation. The research in this project will examine the extent to which agricultural heterogeneity influences the intra-species diversity in herbivorous insect species of agricultural importance.
Decreased sensitivity to pyrethroids in German cereal aphid populations
A key objective of this project was to sample aphid populations from the study sites in order to link any intra-species traits with specific phenotypes.
In summer 2021 over 30 cereal aphid populations were collected from 17 cereal fields in Northern Germany. These populations include 25 grain aphid populations and 7 bird cherry-oat aphid populations.
There are a range of experiments planned for these populations. The first of these experiments was to determine how effective pyrethroids are in controlling these aphid populations, with the aim to identify whether insecticide tolerance/resistance is absent, emerging, or established in these aphid populations. Pyrethroids were chosen as these are a standard class of insecticide that are routinely used to control aphid populations in field conditions.
In the grain aphid populations the response of the aphids to pyrethroids was highly variable, with the effective control at field concentration (i.e., the pesticide concentration used by farmers) ranging from 100% population control to <60% population control. This is not very surprising as tolerance and resistance to pyrethroids has been well described in grain aphid populations across Europe. However, the variation within the populations is interesting, with susceptible and tolerant populations collected from the same field; suggesting that fitness consequences might be associated with the pyrethroid tolerance phenotype. Additional work to identify any phenotypic traits that could result in these fitness consequences is planned.
In the bird cherry oat aphid populations the response of the aphids to pyrethroids was less variable, with six of the seven lines showing full control at the field concentration. However, one population showed a slight reduction in sensitivity to pyrethroids, with the field concentration only effectively controlling 96% of the aphid population. This indicates that resistance/tolerance to pyrethroids is starting to emerge in bird cherry-oat aphid populations, and follows recent reports of similar reductions in sensitivity to pyrethroids in bird cherry-oat aphid populations from Ireland, Australia, and China.
A key objective of this project was to sample aphid populations from the study sites in order to link any intra-species traits with specific phenotypes.
In summer 2021 over 30 cereal aphid populations were collected from 17 cereal fields in Northern Germany. These populations include 25 grain aphid populations and 7 bird cherry-oat aphid populations.
There are a range of experiments planned for these populations. The first of these experiments was to determine how effective pyrethroids are in controlling these aphid populations, with the aim to identify whether insecticide tolerance/resistance is absent, emerging, or established in these aphid populations. Pyrethroids were chosen as these are a standard class of insecticide that are routinely used to control aphid populations in field conditions.
In the grain aphid populations the response of the aphids to pyrethroids was highly variable, with the effective control at field concentration (i.e., the pesticide concentration used by farmers) ranging from 100% population control to <60% population control. This is not very surprising as tolerance and resistance to pyrethroids has been well described in grain aphid populations across Europe. However, the variation within the populations is interesting, with susceptible and tolerant populations collected from the same field; suggesting that fitness consequences might be associated with the pyrethroid tolerance phenotype. Additional work to identify any phenotypic traits that could result in these fitness consequences is planned.
In the bird cherry oat aphid populations the response of the aphids to pyrethroids was less variable, with six of the seven lines showing full control at the field concentration. However, one population showed a slight reduction in sensitivity to pyrethroids, with the field concentration only effectively controlling 96% of the aphid population. This indicates that resistance/tolerance to pyrethroids is starting to emerge in bird cherry-oat aphid populations, and follows recent reports of similar reductions in sensitivity to pyrethroids in bird cherry-oat aphid populations from Ireland, Australia, and China.