Rice Grain Damage by Combination and Sequence Infestations by the Rice Leaffolder, Cnaphalocrocis medinalis Guenee （Lepidoptera：Pyralidae）, and the White-Backed Rice Planthopper, Sogatella furcifera Horváth （Hemiptera：Delphacidae）

The rice leaffolder(RLF), Cnaphalocrocis medinalis Guenee(Lepidoptera: Pyralidae), and the white-backed rice planthopper(WBPH), Sogatella furcifera Horvath(Hemiptera: Delphacidae), are major insect pests in China and several other Asian countries. These two pests commonly occur simultaneously or in a temporal sequence. Thus, the investigation of the effect of complex infestations or temporal sequence infestations by these pests on rice yield has a practical significance for the control of these pests. The present study comprised experiments with the following four different variables in potted rice at the tillering stage: sin gle pest species infestation, complex infestation, complete combination infestation and temporal sequence infestation(C. medinalis infestation prior to S. furcifera and S. furcifera infestation prior to C. medinalis). The results showed that the four infestations resulted in a significant decrease in 1 000-grain weight(1 000GW) and rate of yield loss(RYL) but an increase in blighted grain rate(BGR), with a significant positive correlation with the infestation density. However, the influences of the complex infestation, complete combination infestation or sequence infestation on the 1 000 GW, BGR and RYL were greater than those of the single pest species infestations but did not have addition effects, i.e., the effects of the complex infestation and combination infestation or sequence infestation on the 1 000 GW, BGR and RYL were less than the additive effects of the two single pest species infestations at the same densities. In the condition of the same total infestation pressure, no significant differences in the 1 000 GW, BGR and RYL were found between C. medinalis infestation prior to S. furcifera and S. furcifera infestation prior to C. medinalis as well as between the sequence infestation and the complex infestation.