Second conference on test methods for resistance in insects of agricultural importance. Standard method for detection of insecticide resistance in Heliothis zea (Boddie) and H. virescens (F.). Tentative methods for detection in Diabrotica [spp.] and Hypera [variabilis (Hbst.) (postica (Gylh.)] College Park, Maryland. April 1-4, 1969.