Knockdown, mortality, and progeny production of lesser grain borers (Coleoptera : Bostrichidae) and rice weevils (Coleoptera : Curculionidae) exposedfor short intervals on wheat treated with cyfluthrin

Adult lesser grain borers, Rhyzopertha dominica (F.),and adult rice weevils , Sitophilus oryzae (L.), were exposed at bimonthly intervals for 2, 4, 8, and 24 h on wheat treated with 0, 1, 2, and 4 ppm cyfluthrin EC, then remov ed and held for 2 wk on untreated wheat. The percentage of lesser grain bor ers that were knocked down after they were exposed increased as exposure in terval and concentration increased, and was usually >90% at intervals >4 h for 8 mo after the wheat was treated. Mortality after 2 wk on untreated whe at generally decreased as residues aged, with no difference in mortality am ong exposure intervals. F-1 production of lesser grain borers was low in un treated controls, so effect of exposure could not be determined. The percen tage of lice weevils that were knocked down after exposure also increased a s exposure Interval and concentration increased; however, except for month 0, mortality after 2 wk on untreated wheat was usually <25% for all bioassa ys on wheat treated with 1 and 2 ppm cyfluthrin. Although the number of F-1 rice weevils was dependent on initial exposure interval and concentration, the exposure intervals were not sufficient to prevent oviposition. Progeny production also increased as the residues aged. Results of this study indi cate that lesser grain borers and lice weevils will survive if exposed For 24 h or less on wheat treated with cyfluthrin EC.