Forecasting model of spring hatch of overwintered eggs of Lycorma delicatula (White) (Hemiptera: Fulgoridae)

Lycorma delicatula (Hemiptera: Fulgoridae) is considered an invasive pest of grape vine in Korea. This study was conducted to develop a forecasting model to predict the spring hatch of overwintered eggs of Lycorma delicatula(White).We collected overwintering egg masses in the major grape growing area on 1st and 17th February, and 4th March in 2010. For eggs collected on respective sampling date, they were chilled at 5°C for 15 days, and them development was investigated 15, 19, 23, 27, 31, and 35°C and a photoperiod of 16:8(L:D)h. For each treatment, egg numbers range from 14 to 27. The hatching rate of eggs was highest at 15°C (92.08±8.72%) followed by 19°C (90.12±18.89%), 23°C (87.88±19.32%), 27°C (75.96±24.82%) and 31°C (30.92±24.81%). Eggs did not survive at 35°C. The developmental duration (Mean±SD) of eggs was 69.19±6.23, 39.47±2.24, 22.96±3.25, 17.56±1.58 and 12.15±6.29 days, at 15, 19, 23, 27 and 31°C, respectively. The relationship between egg developmental rate and temperature was described by a linear model (Y=0.0034X-0.036 (r2=0.988)),and a non-linear model of Gaussian equation (r2=0.998). The developmental variation of eggs was described by the three-parameter Weibull function (r2=0.958). The lower developmental threshold temperature was 10.73°C and effective accumulated temperature for egg development was 297.62 Degree days. The degree-day model using sine wave and the rate summation model were validated using field observation data for occurrence of the 1stinstar nymph. Both models predicted actual observed date for 50% hatch of overwintered egg masses very well.

Key words: Lycorma delicatula, egg development, forecasting model