How we measure biological control

A major focus of our lab is understanding the biological control supplied to agricultural systems by insects. Biological control is the amount of pest control accomplished by beneficial organisms called natural enemies. These organisms may be predators (such as lady beetles and spiders), pathogens (including fungi and bacteria), or parasitoids. Parasitoids are wasps or flies that lay one or more eggs in or on a host. The egg(s) hatch and consume the host, killing it.

We are interested in how farming practices influence the amount of biological control that is provided by these natural enemies, specifically insect predators. The way that we measure this is by putting out an insect prey and determining the amount of this prey consumed by predators. In the above picture, we have placed corn earworm eggs in two treatments: an open treatment where natural enemies can consume the eggs and a caged treatment which prevents predators from accessing the eggs but exposes them to environmental conditions. We leave these treatments in the field for 48 h and then re-count the eggs. We consider the difference in the proportion of eggs missing in the open and caged treatments to be amount of biological control provided to that site.

With this experiment we can compare the amount of biological control provided to different types of crops, crops which receive different amounts of agricultural inputs (such as pesticides) or crops which are embedded in different types of landscapes.