| Abstrakt: |
A model of a two life-stage pest species is presented for determining the feasibility of control by means of predator release, habitat management and pesticide release. Only the effects on the population equilibria were determined. For the pest without predation, control by habitat management or pesticide release would always be effective against the stage attacked, and would also usually reduce the numbers of the stage not directly attacked. The release of predators without the other controls would always reduce the stage preyed upon and would usually reduce the other stage as well: the reduction of the two stages is by the same proportion if density dependence is only in the stage preyed upon. If predators are present, then the efficacy of using habitat management or releasing pesticides depends largely on whether or not the predators interfere with each other at high densities. If mutual interference is strongly density dependent then both the pest stages are likely to decrease if the control measures do not also affect predator mortality, but both are likely to increase if predator mortality is increased as a result of the additional control. If predators are present but are not crowded at high density, then neither habitat management nor pesticides are likely to be of much use in reducing the pest equilibria since these controls will usually just reduce the predators. [ABSTRACT FROM AUTHOR] |
