The rice leaf folder (RLF) Cnaphalocrocis medinalis (Güenée) is one of the most important insect pests which has caused large amounts of yield loss of rice in recent years. C. medinalis has many recorded host plants, but the fitness of C. medinalis on some main host plants, such as rice and maize, was unclear. Moreover, the biological response of C. medinalis reared on different host plants to high temperature was little known. In order to identify the temperature requirements of the rice leaf folder, the development, survival, fecundity and hatch rate of C. medinalis reared on rice and maize seedlings were measured under different temperatures (20-36℃) in this study.
The results showed that the duration from birth of larvae to emergence of adults on rice was 24.9, 20.1, and 19.4 days at 24, 27, and 30℃, respectively, whereas on maize seedlings, it was 28.3, 21, and 20.1 days, respectively. The developmental rate of C. medinalis reared on maize seedlings was 1-3 days slower than that on rice under 24℃ or 27℃, which mainly resulted from the lower developmental rate of the pupae stage. The average longevity of adults reared on maize seedlings at 24℃ and 27℃ was 10.4 days and 7.6 days, respectively, which was significant longer than that on rice. The development of larvae reared on rice was not inhibited at 33℃, and the larvae could grow into adults. However, the development of larvae on maize seedlings was significantly inhibited at 33℃, and none of the larvae developed into pupae. The survival of C. medinalis on rice was not significantly different between 27 and 33℃, whereas the mortality was very high when the temperature increased up to 36℃, and only a few larvae grew into prepupae. However, the survival of C. medinalis larvae on maize at 33℃ was lower than that at 21-30℃, and at 36℃ they failed to develop to the 2^nd instar.
Fecundity of C. medinalis was highest at 24℃ and 27℃: on rice, averages of 189 and 155 eggs per female, respectively, and on maize, 196 and 170 eggs per female, respectively. C. medinalis could lay a few eggs at 30℃ and 33℃ when reared on rice, and the average number of eggs per female was 35.6±2.6 and 15.6±3.8, respectively. However, no eggs were laid when the larvae were reared on maize seedlings at 30℃ and 33℃. Hatch rate of eggs was highest at 27℃, up to 75%, and there was no significant difference at this temperature between the rice and maize seedlings. At 33℃ and 36℃, no eggs hatched on maize seedlings, but about 25% and 7% of eggs on rice could hatch, respectively. The results of the present study indicate that C. medinalis can be reared well on both rice and maize seedlings, and the capacity of C. medinalis reared on rice to tolerate high temperature stress is higher than that on maize seedlings. The biological features of C. medinalis reared on maize seedlings at 24 and 27℃ were not significantly different from those on rice with the exception of slower development.