Phyllophaga nitididorsis (Coleoptera: Melolonthidae), the first biennial melolonthid recorded in the Brazilian Cerrado

Abstract

AbstractPhyllophaga nitididorsis Frey, a species native to Brazil, has recently been recorded as a soil pest in soybean Glycine max (L.) Merr. fields in the north‐west region of Minas Gerais (MG), Brazil. Our study aimed to evaluate the phenology of P. nitididorsis in the Cerrado of Central Brazil. The study was conducted in a field (≈300 ha) in Buritis/MG where soybean is sown in October (spring) annually. Monthly (December 2012–November 2014) samples were collected by opening trenches (50 cm × 50 cm and 30 cm in depth), recording the developmental phases of all P. nitididorsis found. Specimens collected from the field were maintained in the laboratory at 25 (±2 °C), and their development was recorded at weekly intervals. Light traps were installed in the states of Minas Gerais, Goiás (GO), and the Federal District (DF) to verify species distribution. P. nitididorsis exhibited a biennial life cycle that lasted approximately 22 months, from egg to inactive adult, and 24 months from egg until the emergence of active adults. Eggs were found in the soil in November. The larval stage lasted about 20 months (≈607 days). Second‐instar and third‐instar larvae constructed chambers in the soil to overwinter during the dry season (March to September) during the first and second years of development, respectively. Pre‐pupae were observed between July and August and pupae between July and September. Inactive adults occurred in August and September, and the swarming period was between October and November. Adult P. nitididorsis were caught in all of the States where light traps were operated. The active phases of the insect (larvae and adults) were synchronised with soybean cultivation and the rainy season (October and March) in the Cerrado. To the best of our knowledge, our study is the first to report P. nitididorsis in the states of Goiás and the Federal District. Further, this species is the first biennial melolonthid observed in the Brazilian Cerrado.