Modeling incomplete sterility in a sterile release program: interactions with other factors

Models were constructed for control of a pest species by the release of sterile insects and these models explored the consequences of incomplete sterility. This feature was then coupled with the lack of competitive ability of released insects, the immigration of insects from outside the control area, and the mode of population regulation (density- independent vs. density dependent). Using the density-independent models, it was seen that the limits on residual fertility of treated insects become much more stringent when incomplete sterilization is combined with a lack of competitive ability and immigration of insects into the control area. Strong density dependence in the system has a marked moderating effect on the requirements for sterility, competitive ability, and immigration. However, if the density-independent limits on these factors are exceeded, then suppression is possible, but collapse of the pest population is impossible using sterile releases alone. Even suppression might not be satisfactory if these three detrimental factors are prominent. It is suggested that one remedy is the use of the sterile release method in combination with other control methods.