With the intent to enable others, please see my attached PhD thesis from 2015 below.
In the words of Prof Tor Wager, “the spirit of how science at its best is accomplished — with urgency, passion, inventiveness and collaboration.”
Landscape Composition, Wildflower Margins, and Their Interaction on Pest Control Services in Agricultural Systems
Thesis in a Nutshell
Landscape composition and crop field manipulations may be more important to natural enemies of crop pests, than pests.
There may be opportunity to enhance natural crop protection through:
- Reductions in crop field size
- Reductions in block cropping
- Increases to crop rotation diversification
- Increases in non-crop habitat e.g. wildflower margin establishments and maintenance of important grasslands
Natural pest control services can reduce the need for pesticides by suppressing pests through natural predators and parasitoids. Semi-natural habitats, such as grasslands, are central for the support of biodiversity in agricultural landscapes. Targeted management of semi-natural habitat to increase their area and/or quality, such as agri-environment schemes, can enhance biodiversity in agroecosystems. However, there is little research on how lowland calcareous grassland (LCG) extent and agri-environment schemes (AES), within intensive cereal landscapes, will affect pest regulation function. In this thesis, the impacts of wildflower field margins, semi-natural habitats and landscape composition on natural pest control services in UK cereal systems is investigated.
Large areas of LCG, and decreased cereal extent, supported increased densities of some generalist predators and higher aphid parasitism. Additionally, a decrease in interannual cereal area within the landscape was associated with an increase in aphid parasitism and generalist predator densities. While wheat fields with wildflower margins were found to support higher specialist predator densities with increased landscape proportions of cereal. However, wildflower margins, compared to grass margins, did not show any effect on natural enemy densities, richness, or aphid densities in wheat fields. Using fixed aphid bait trays to assess pest regulation services, wildflower margins were found to support increased canopy predation, though there was no indication of increased ground predation.
This study shows that fields with higher resource and semi-natural habitat availability can support natural enemy communities with higher species abundance and richness, and be more likely to suppress cereal aphids. Sustainable pest management requires further understanding of the processes acting across multiple spatial and temporal scales causing changes to the pest and natural enemy populations, communities and their interactions.