immunoassays useful for distinguishing between the insect pests heliothis virescens and helicoverpa zea are disclosed . these immunoassays employ either heliothis virescens - specific monoclonal antibodies which do not detectably cross - react with tissue of helicoverpa zea , or helicoverpa zea - specific antibodies which do not detectably cross - reict with tissue of heliothis virescens . thus , use of these antibodies in immunoassays conclusively demonstrates the presence of either heliothis virescens or helicoverpa zea organisms on crop plants tested . also disclosed are heliothis virescens - specific monoclonal antibody which does not detectably cross - react with tissue of helicoverpa zea , and helicoverpa zea - specific monoclonal antibody which does not detectably cross - react with tissue of heliothis virescens . these antibodies can be used in the disclosed immunoassays , and can be included in kits for conducting the disclosed immunoassays .