Potato Leafhopper (Homoptera: Cicadellidae) Oviposition and Development Under Cool Fluctuating Temperatures

Abstract

Two studies were conducted to provide information on the development of potato leafhopper, Empoasca fabae (Harris), eggs, male nymphs, and female nymphs under fluctuating temperatures, and on the ovipositional threshold of adult gravid females. Mean developmental times were measured for E. fabae eggs, male nymphs, and female nymphs under three fluctuating temperature regimes of 8–19, 10–21, and 13–24°C. These regimes were representative of January, February, and March daily temperatures in southern Louisiana, an overwintering site for E. fabae . Eggs developed in 34.9 ± 5.77 d, 28.8 ± 4.87 d, and 15.9 ± 2.09 d for the three regimes, respectively. Male nymphs developed in 47.8 ± 9.7 d, 39.1 ± 7.96 d, and 22.7 ± 3.3 d for the three regimes. Female nymphs developed in 47.0 ± 9.9 d, 39.4 ± 4.89 d, and 24.9 ± 3.11 d for the three regimes. A five temperature regimes database was created by combining these developmental times with developmental times reported by Hogg (1985) for similar but warmer fluctuating regimes. Logarithmic developmental rate equations, based on hourly temperature data, were developed from these data. The accuracy of these developmental equations was verified with independent data reported in the literature. Only females reared from eggs in the 13–24°C regime oviposited as adults. The constant temperature oviposition threshold for E. fabae was determined. Adult gravid females oviposited at 10°C, but not at 9°C. The estimated oviposition threshold was 9.5°C. Gravid females placed in the fluctuating regimes of 8–19°C and 10–21°C continued to oviposit. A factor inhibiting ovarian development in females reared from eggs under these two regimes was hypothesized.