The Effects of Temperature and Host Age on the Fecundity of Four Trichogramma Species, Egg Parasitoids of the Cnaphalocrocis medinalis (Lepidoptera: Pyralidae).

The Cnaphalocrocis medinalis (Guenée) is one of the most important rice pests in Asia and is difficult to control by chemical insecticides due to its rapid development of resistance. To screen potential species for biological control of C. medinalis, we investigated the effects of temperature (20, 24, 28, 32, and 36 °C) and host age (1-, 2-, 3-, and 4-d-old) on the fecundity of four Trichogramma spp. on C. medinalis eggs. Our results indicated that C. medinalis eggs were acceptable to T. japonicum, T. chilonis, T. dendrolimi, and T. ostriniae, though no eggs were parasitized at 36 °C. There were no significant differences in parasitism among the four Trichogramma species under the tested temperature regions, except at 20 °C where parasitism by T. japonicum was significantly higher than that by T. chilonis and T. ostriniae. However, T. japonicum had significantly more progeny than the other three Trichogramma species at 32 °C. All four Trichogramma species performed well on 1-, 2-, and 3-d-old C. medinalis eggs, but parasitism on 4-d-old eggs was significantly reduced. Trichogramma japonicum parasitized the highest number of C. medinalis eggs on different aged hosts and had more progeny than the other Trichogramma species, especially on 3-d-old hosts. In conclusion, T. japonicum exhibited better performance on C. medinalis eggs than the other three Trichogramma species and could be considered as our most suitable Trichogramma candidate for control of C. medinalis.

[A banker plant system of 'Leesia sayanuka-Nlilaparvata muiri-Tytthus chinensis' to control rice planthoppers]. / "秕谷草-伪褐飞虱-ä¸­åŽæ·¡ç¿ ç›²è½"载体植物系统的可行性.

In order to clarify the feasibility of the banker plant system "Leesia sayanuka-Nlilaparvata muiri-Tytthus chinensis" to control rice planthooper, the effects of the combination of rice, L. sa-yanuka, N. lugen and N. muiri on the adult morphology, population growth, oviposition and feeding selectivity of T. chinensis were carried out in the present study. The results showed that the body size of male and female adults of T. chinensis rice population (feeding on N. lugens eggs) were significantly larger than those of T. chinensis population (feeding on N. muiri eggs). Population growth parameters including fecundity, net productive rate, innate capacity for increase, finite rate of increase of L. sayanuka feeding on N. lugens eggs were significantly higher than those of L. sayanuka feeding on N. muiri eggs. However, the population growth ability of L. sayanuka feeding on N. muiri was still high enough to expand the population. For the oviposition selection, both rice population and L. sayanuka population preferred laying eggs on rice than on L. sayanuka. Meanwhile, there was no significant difference in the predation of females, males and nymphs to N. lugens eggs or N. muiri eggs between rice population and L. sayanuka population. At last, based on our results, we discussed the feasibility of establishing the banker plant system "L. sayanuka-N. muiri-T. chinensis" in rice fields.