Host plant use ofHelicoverpaspp. (Lepidoptera: Noctuidae) in the Brazilian agricultural landscape

BACKGROUND The Old-World bollworm,Helicoverpa armigera(Hubner), was recently documented attacking cotton and soybean plants in Brazil; however, restricted basic knowledge on host plant interactions and landscape use in Brazil have limited the effectiveness of control measures. In this study, we evaluated the suitability of different crops commonly cultivated in Brazil as hosts forH. armigeraandH. zea, and examined their contribution to the establishment and size ofH. armigeraandH. zeafield populations. We also estimated the proportions ofH. armigeraandH. zeamoths that used cotton, noncotton C(3)plants, and C(4)plants as hosts in four regions in Brazil through the length of the cropping season. RESULTS Viability ofH. armigeralarvae was highest on cotton (46.1%), followed by millet (39.5%), sorghum (31.2%), soybean (24.2%), and maize (21.1%). Noncotton C(3)hosts served as the major source ofH. armigeramoths in all regions evaluated, and C(4)hosts were a source ofH. armigeramainly in regions where winter maize is typically cultivated.H. armigeramoths that used cotton plants as natal hosts were observed during the reproductive stage of the crop mainly in the state of Bahia. Only C(4)host plants were a consistent source ofH. zeamoths, primarily when maize was in the reproductive stage.H. armigeraindividuals were the main species infesting cotton and soybean fields whileH. zeaindividuals were the main species infesting maize ears. CONCLUSIONS Regional differences in the host use and population dynamics ofH. armigeraamong the regions evaluated may be attributed to variation in alternative host utilization (crops, noncrops, and weeds) and the possible occurrence of facultative diapause and or migration.