Developmental periods of sweet potato whitefly, Bemisia tabaci(Gennaius) Q-biotype, were investigated on three host plants- sweet bell pepper (Capsicum annuum L.), eggplant(Solanum melongena L.) and oriental melon(Cucumis melo L. var. makuwa MAKINO). Egg and nymph development of B. tabaci were studied within temperature ranging of 15℃-35℃ by 2.5℃ under photoperiod 16:8(L:D). Egg period of B. tabaci was the shortest at 32.5℃ and nymphal period was shortest at 27.5℃ on sweet bell pepper. Nymphal period of B. tabaci on eggplant was the shortest at 27.5℃ as well. On the other hand, nymphal period of B. tabaci was shortest at 30℃ and 32.5℃. Lower temperature threshold and effective degree-day for completing egg development on sweet bell pepper were estimated as 13.11, 91.95, respectively. Lower threshold temperature of nymphal stage on sweet bell pepper, eggplant, oriental melon were estimated as 13.01, 13.39, 12.31,respectively. Degree-days required to complete nymphal stage on sweet bell pepper, eggplant, oriental melon were estimated as 191.22, 164.41, 190.34, respectively. The relationships between development rates of egg and nymph were well described by poikilothermal rate function and weibull function. The fitted curves will be used as input for a simulation model of the population dynamics of B. tabaci.

Resistance-breaking ability of wild brown planthopper (BPH), Nilaparvata lugens, on resistant rice cultivars has been reported in many Asian countries. To understand the development of resistance-breaking ability of wild BPH in Korea, we conducted the nymphal survivorship test and the electrical penetration graph (EPG) on susceptible and resistant rice cultivars with four different BPH populations, which were collected in the early 1980s (S-BPH), 2005, 2006, and 2007, respectively. The S-BPH showed low survival rates on resistant rice cultivars carrying Bph1 and bph2, respectively. On the other hand, recent(2005~2007) wild BPH populations seemed to have high resistance-breaking ability because they maintained elevated survival rates on most other resistant rice cultivars except Gayabyeo (Bph1 and bph2) and Rathu Heenati (Bph3). In the EPG monitoring, however, wild BPHs could not easily feed on the phloem sap of resistant rice cultivars, Cheongcheongbyeo (Bph1), ASD7 (bph2), and Gayabyeo. Wild BPHs spent more time on reaching the phloem sieve elements of resistant cultivars. Ph waveform duration and honeydew excretion amount of wild BPHs also decreased. From the results, we suggest that though recent wild BPHs collected in Korea have high resistance-breaking ability simultaneously on rice cultivars carrying Bph1 and bph2 through the increase of survivorship, they still have to pay some cost to feed on the phloem sap of resistant rice cultivars.