Detecting arthropod intraguild predation in the field

The process of biological control carries a distinct risk that an alien biological control agent (BCA) will become established as an invasive alien species with an associated threat to the local ecosystem biodiversity. It is imperative that a wide-ranging environmental risk assessment (ERA) is performed before the release of any BCA. This should include considering various potential but difficult to observe ecological interactions between the BCA and members of the native community, including disruption of intraguild relationships. Detection of intraguild predation (IGP) events involving predatory arthropods in the field can be done by analyzing their gut contents. Polymerase chain reaction (PCR) is a sensitive and specific tool to identify target prey DNA within a predator's gut. This paper reviews the efficiency of a DNA based approach for detecting IGP in the field, compared with detection by the use of monoclonal antibodies or gas chromatography. Prey specificity, detection times after prey consumption, capacity for quantification, multiple prey targeting and the time and costs involved in developing and using the different methods are considered

The spatial distribution of canopy- resident and ground-resident cereal aphids (Sitobion avenae and Metopolophium dirhodum) in winter wheat

We investigated, within two cereal fields in Southern England, the within-canopy spatial distribution of the aphids Sitobion avenae and Metopolophium dirhodum in relation to crop yield and plant nitrogen. We extended the study to investigate the spatial distribution of aphids that fell to, or returned from, the ground in order to estimate availability of the within-canopy aphid population to ground-active predators. We revealed that crop canopy aphid spatial pattern was associated with nitrogen or yield. Differences were evident between species: S. avenae was generally negatively associated with yield or plant nitrogen, whilst M. dirhodum exhibited positive association. For both aphid species, we observed strong spatial pattern for aphids falling to the ground and conclude that this could, in part, mediate the effectiveness of ground-active predators as pest control agents