Comparison of the abundance of leaf-feeder insects in oilseed rape fields of lowlands and uplands

Diversity and density of leaf-feeder insects of oilseed rape in lowland (i.e. the preceding crop was rice) and upland (i.e. the preceding crop wasn’t rice) fields in Mazandaran province, Iran were compared in three region of the province during 3 years (2008-2010). In each region, one lowland and one upland field was selected and the insect pests were recorded using yellow water traps and quadrate (0.5m × 0.5m). In this study, one species of weevils, Ceutorhynchus picitarsis Gyllenhal (Col.: Curculionidae); 4 species of flea beetles, Phyllotreta atra (Fabricius), Psylliodes cupreus (Koch), Psylliodes persicus Allard and Chaetocnema hortensis (Geoffroy) (Col.: Chrysomelidae); turnip sawfly, Athalia rosae (L.) (Hym.: Tenthredinidae) and Spodoptera littoralis (Boisduval) (Lep.: Noctuidae) were collected in lowlands as well as in uplands. Therefore, there was no difference in species diversity in two kinds of fields. The results showed that no rice pest causes damage on oilseed rape in the lowlands, and these two crops have no common pests in the region. The density of flea beetles and weevils in upland fields was higher than those in lowlands. The kind of oilseed rape field (lowland or upland) had no significant effect on the larval density of S. littoralis and A. rosae.