The use of ELISA techniques to clarify predator/prey interactions in cotton.

The basis to understanding food webs is knowing which predators feed on which prey. This is particularly difficult to do with arthropods. To help solve this problem, sandwich enzyme-linked immunosorbent assays (ELISAs) have been developed in which prey are marked with an exotic vertebrate protein, and potential predators tested for that protein. However, it is unclear how effective the technique is with different prey species and different predators. This paper compares the effectiveness of marking two important emerging pests in Australian cotton: the cotton aphid and the green mirid, with marking of an established pest, cotton bollworm eggs; and the ability of predators to take up the mark from these prey.

The results suggest that although the eggs were the easiest prey to mark and had the longest retention of the mark, predators feeding on mirid prey were marked more strongly. Predators differed in their unmarked base absorbance levels, but this difference was slight compared to differences between different phylogenetic groups and their likelihood to assimilate the protein mark. For example, the three spiders tested were very likely to become marked, while the damsel bug was not. Differences in feeding techniques may contribute to this variability.

Sandwich ELISAs testing for the presence of exotic proteins are a very sensitive and effective way of identifying potential predators of marked prey, but caution must be taken when comparing predators from different phylogenetic groups using different foraging methods. In addition, some predators became marked without feeding on the prey, indicating that care must be taken regarding the release of marked animals into the field to minimise incidental marking of predators. Nevertheless, the technique has the potential to reveal cryptic predator/ prey interactions and therefore is a useful tool in the management of pests using conservation biological control.