Quantification of insect growth and its use in screening of naturally occurring insect control agents

In studies of the effects of allelochemicals or other factors on the development of different insect species, comparison of growth-inhibiting activities is difficult using the parameters currently employed. We introduce two new parameters, growth index (GI) and relative growth index (RGI), which can unify the quantification of insect development. This quantification can also eliminate the effects of different growth characteristics due to the genetic differences between insect species. By measuring growth-inhibiting effects of two phytochemicals, chaparrin and chaparrinone, on the tobacco budworm,Heliothis virescens, and the beet armyworm,Spodoptera exigua, bioassay procedures and GI and RGI calculations are demonstrated.