What happens to the biological control agents when the pest is gone – does it eat something else?
As the biological control agents cannot survive on any species other than the target, they will not eat anything else if their pest species goes into decline. With biological control the aim is control, not eradication. There will always been some of the pest plant or insect species left and as such there will always be small pockets of the biological control agent left. When biological control agent numbers decline, pest species numbers will increase. With the increase in pest species number the biological control agent numbers will start to increase until a balance is reached where the pest species number declines followed again by a decline in biological control agent numbers. It is this continuous oscillation of population numbers that keeps the system in balance.
