Susceptibility of Cyclocephala immaculata (Coleoptera: Scarabaeidae) Eggs and Immatures to Heat and Drought in Turf Grass

Abstract

Eggs of the southern masked chafer, Cyclocephala immaculata Olivier, are laid under turf grass in the upper 3 cm of soil, where they are vulnerable to heat and desiccation. The ability of eggs to survive periods of drought was found to depend upon egg age, stress duration, and temperature. At 25°C, the minimum soil moisture level at which eggs developed was between 10.3 and 12.3%. Eggs surviving a stress period early in development required several days longer to hatch. In field tests, no eggs survived in desiccated turf, where afternoon soil temperatures exceeded 40°C and soil moisture dropped to <8%. Egg survival ranged from 55 to 73% in irrigated turf. Caged gravid females failed to lay eggs, and implanted 1st-instar grubs did not survive in desiccated turf.