| Cicadulina bipunctella (Mats), belonging to the order Homoptera, the family Cicadellidae, the subfamily Euscelinae and the genus Cicadulina, is a kind of minute insect on maize with distribution in Sichuan, Chongqing and Guizhou province of china. It damages directly or indirectly maize in field and leads to great economic losses when the population occurs in abundance. Adopting comprehensively the knowledge and theory of population ecology and disease epidemics, by the field investigations and indoor trials, the bio-ecological characteristics and the pathogenicity of C. bipunctella, the seasonal dynamic of maize wallaby ear virus (MWEV) during the period of maize growth were studied systematically. The results are summarized below.1 The establishment of C. bipunctella experimental populationBy the field investigation, indoor trials and identification to the insect species on maize, the results indicated that C. bipunctella is a major vector insect transmitting MWEV, the non-pathogenetic population can't be established by collecting in field, separating from eggs, ecdysis and rearing individually.The experimental population was established. C. bipunctella, acquiring from the area of MWEV, could be reared on its host plants maize, wheat, millet and perennial grass family (gramineae) weeds, but maize with 5-7 leaves is the best host. Maintaining the host plants to survival long is the key factor to expand the population. The temperature inside range 25~28℃, the relative humidity 80 + 5% and the photoperiod 14L:10D are the suitable environmental factors for the growth and reproduction of C. bipunctella.2 The bio-ecological characteristics of C. bipunctella 2.1 The biological characteristicsC. bipunctella, adapting to gramineous crops and weeds, is a serious insect on maize. The adult has 1 pair big round black spots at the joint of the region of head and face, and the nymph has 2 symmetry black spots at the end of abdomen. There are 5 nymphal instars. The field investigations showed that it undergoes 3 generations during the period of maize in Nanchong Sichuan area, overwinters with adults in wheat and shows such behavior as high alertness, preference of illumination and preference of green leaves. In the early April of the next year, the overwinter adults start action, fetch, copulation and oviposition on maize.The development, survivorship, and fecundity of C. bipunctella reared on corn, wheat, sorghum, rice, millet, and barley were evaluated at 25℃ in laboratory, respectively. The results showed that the insect could develop and reproduce on corn, wheat, sorghum, rice, millet, and barley, except for Leptochloa panacea (Retz.) Ohwi. The development duration, survival rate, longevity and fecundity of C. bipunctella female adults varied significantly when reared on the six hosts. The development duration (24.1d) of the combined immature stage reared on sorghum was the shortest, then on corn (24.2d) and the longest on wheat (25.5d). The survival rate (40.8%) of immature stages, the longevity (12.2d) and oviposition per female (12.3 eggs) of female adults reared on rice were lower than the other five host plants. Based on the life-table parameters, the most suitable host plants for the development and reproduction of C. bipunctella were millet and corn, followed by sorghum, barley, wheat, and rice.2.2 The dynamic of the natural populationSystematic investigations were carried out on the dynamics of natural population of C. bipunctella. The results showed that the population quantity of the insect was obviously increased from the early April to the early May, them decreased till June, and increased again. There is a significant difference about the density on the three elevations, the density of the insect reached 3.5143 per maize in high elevation, 3.0114 per maize in middle elevation, and 1.0343 per maize in low elevation. The K value of negative binomial distribution less affected by density was chosen to describe the spatial and temporal patterns of the natural population of C. bipu...
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