Seasonal Emergence and Flight of Northern and Southern Masked Chafers 1 in Relation to Air and Soil Temperature and Rainfall Patterns 2

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Abstract
The southern masked chafer, Cyclocephala immaculata Olivier, and the northern masked chafer, C. borealis Arrow, are serious pests of turfgrass in central Kentucky. The temperature threshold for pupation of overwintering C. immaculata grubs was determined experimentally as 10.8°C. Trapping studies during 1979 and 1980 indicated that first emergence and peak flight of males occur approximately 1 to 2 weeks earlier for C. borealis than for C. immaculata . Thermal unit accumulations in air and soil were closely correlated with the first emergence of beetles, but they were less useful for predicting the date of 50 and 90% flight. Once emergence has begun, activity of masked chafers is more closely related to rainfall patterns than to temperature.