Complexities of determining total effects of pesticides on biological controls: the LC50 is not enough

The integration of pesticides and biological controls to control pest species is an important practice in IPM programs.  To successfully integrate pesticides and biological controls, a measure of toxicity for both biocontrol agents and pest species needs to be developed and compared.  Traditionally, this is accomplished by developing acute mortality estimates (LD/LC50s) for pest and beneficial species and comparing them using a ratio approach.  Another method is to use the IOBC method which involves a tiered approach moving from laboratory to semi-field and perhaps field data, if necessary.  If mortality is the only effect, then the above mentioned approaches may work.  However, exposure to pesticides can sometimes result in mortality and multiple sublethal effects resulting in unpredictable consequences at the population level. Furthermore, differential susceptibility to pesticides among life stages may result in a restructuring of populations that again may result in unpredictable impacts.  The population structure at the time of exposure can also influence pesticide impact.  In this talk, all of these issues will be discussed and a way to improve our understanding of pesticides impacts will be outlined.