Biology and Behavior of the Invasive Soil Pest Plectris aliena Chapman (Coleoptera:Scarabaidae) in North Carolina Agro-ecosystems and Implications for Management

Plectris aliena Chapman (Coleoptera:Scarabaeidae) is an invasive soil pest in North Carolina agro-ecosystems that began as a severe problem to sweetpotato growers in Columbus County, in 2006, causing unmarketable surface damage to the roots. Since its discovery, Plectris aliena has caused more than ;Studies on P. aliena larvae and adult populations were conducted to gather information on its abundance, distribution, and oviposition and larval depth in the soil profile. Flight intercept traps were used from 2008 to 2011 to capture P. aliena adults and revealed that peak emergence occurred the same time every year between 24 May and 10 June. Larval sampling and adult trap captures in fields planted to crops other than sweetpotato revealed that P. aliena completed development in fields planted to soybean, field corn, peanut, tobacco, and pasture. Egg deposition and late instar larval recovery in subterranean field cages occurred between 5.1 and 30.5 cm in the soil profile.;Experiments examined the cold hardiness of overwintering third instars and the oviposition biology of P. aliena adults. The temperature at which freezing caused mortality was an average of -5.1°C, which was much lower than the average winter soil temperature in regions currently affected by P. aliena and further north. Exposure of the grubs to temperatures below the average winter soil temperature (9.6°C) in Columbus County, but above 0.0°C, did not affect the behavior or development of grubs. Oviposition biology studies revealed that females oviposited an average of 21 more eggs in moist soil conditions (20% moisture) compared to dry soil (2%) and that one female could lay eggs over a period of up to three weeks.;A farmscape study in 2010 and 2011 showed that soil drainage and crop rotation had significant effects on the incidence of damage to roots in grower fields, with well drained soils having an average of 2% more damaged roots. Fields with soybeans planted the preceding year had as much as 15% more damage than other crops. The effects of habitats adjacent to grower fields where roots were sampled showed that as the location of the roots was closer to borders of soybean (planted the year before) or grass fields, the chance of damage to roots decreased.;Results from these studies contribute to a more complete understanding of P. aliena’s biology and behavior that could be useful towards grower management practices such as the application of insecticides at the appropriate depth and time of year. Winter climate is unlikely to affect the population abundance and development of P. aliena third instars for short periods of time based on temperature alone. Growers who use crop rotation and avoid planting sweetpotatoes the year after soybeans may reduce the incidence of P. aliena larval feeding on sweetpotato roots. Environmental conditions such as fields with poor drainage and certain border habitats may be avoided or selected in order to reduce risk of damage to roots by P. aliena..