Prediction of emergence of first-instar Ricania shantungensis (Hemiptera: Ricaniidae) in persimmons

An invasive species, Ricania shantungensis Chou & Lu 1977 (Hemiptera: Ricaniidae), poses a threat to persimmons in Korea. Pesticide application was the most effective when targeting newly hatched nymphs. Therefore, this study was conducted to develop a degree-day model to predict the emergence of first-instar R. shantungensis, the pesticide application timing, in persimmons. To estimate the lower developmental threshold, thermal requirement, and developmental rate, R. shantungensis eggs were collected from two locations and hatched at seven constant temperatures (12.4, 16.4, 20.4, 24.8, 28.3, 32.4, and 36.9 °C). The estimated lower developmental threshold and thermal constant were 12.0 °C and 159.9 degree-days, respectively. The developmental rates (the reciprocal of developmental times (days)) were 0.0264, 0.0526, 0.0818, 0.1001, and 0.1051 at 16.4, 20.4, 24.8, 28.3, and 32.4 °C, respectively. Based on these results, a degree-day model was developed and validated under field conditions. This model may increase the efficiency of R. shantungensis management in persimmon fields.