Population dynamics of the whitebacked planthopper,Sogatella furcifera (Hemiptera: Delphacidae) with special reference to the relationship between its population growth and the growth stage of rice plants
A population census was conducted to describe the effects of the growth stage of rice on the population dynamics ofS. furcifera, in particular, on immigration, seasonal abundance, population growth rate, and wing-form expression. The number of immigrants was highest on rice plants 17 to 30 days after transplanting (DAT), which suggested that immigrants prefer to settle or remain more on rice plants at the tillering stage (approximately 20–30 DAT). Population growth rate from immigration to the 1st generation decreased with an increase in rice plant age. In contrast, population growth rate from the 1st to 2nd generation was not influenced by rice plant age and was negatively density-dependent. The percentage of macropters (flyers) was positively related to the growth stage of rice when rice was in the vegetative or early part of the reproductive stage, and reached 100% at about 10 days before heading (booting stage). Threafter, most adult females molted into macropters regardless of population density. The roles of host plant age and crowding effect on the population dynamics ofS. furcifera are discussed.
Population Seasonality: Will They Stay or Will They Go? A Case Study of the Sogatella furcifera (Hemiptera: Delphacidae)
The whitebacked planthopper Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is one of the most destructive pests of rice in East and Southeast Asia. It is also a long-distance migratory insect and population size fluctuates frequently in these rice regions along the middle and lower Yangtze River. We analyzed the population seasonality of S. furcifera based on field surveys, light trap catching, and meteorological factors. We found that many S. furcifera were retained in local late rice in 2012, due to continuous rain and slightly windy weather conditions during the migration period. These results suggest that a new pattern of population fluctuation may occur where resident S. furcifera are dispersed into a single medium rice during harvest period, then rebound and thrive in late rice when there are suitable temperatures in September. Although the residency of S. furcifera in late rice fields in 2012 seems to be a special case, our findings suggest that S. furcifera exhibit a type of facultative migration. Our research also illuminates studies of the migration events of S. furcifera and benefits our understanding of the dynamics of S. furcifera in Hunan Province.
Yellow Pan Water Trap for Sampling the Small Brown Planthopper, Laodelphax striatellus (FALLEN), a Vector of the Rice Stripe Virus
vector of the rice stripe virus, pan water traps of various colors were tested. Yellow pans which were set at the crop level attracted three times as many planthoppers as green or white pans, and black pans attracted about one tenth of those by yellow pans. Catching eMciency per area of pan decreased with increase of size of pan and pan of 60 cm in diameter seemed to be highest in eMciency and also convenient for handling. Yellow pans set at 1.5m height above the ground caught one tenth to one fourth as few planthoppers as pans set at the crop tevel. Sampling by yelTow pan water trap was compared with those by insect net sweeping and counting by eyes. At the beginning of the immigration season of the first generation or soon after the transplantation of riee plant, yellow pans showed higher eMciency than the other methods. Catching curves by yellow pan preceded those by counting. It was considered that yellow pan sampled planthoppers which were aetively flying at the crop level and counting estimated the density ef planthoppers sett!ed down on rice plants. Level of catching by a yellow pan corresponded to that of 5 hills by counting as a general trend. Sarnpling by sweeping much depended on the growth stage of rice plant, not necessarily with the density of planthopper. Catching by yellow pans showed the diurnal periodicity, bimodal curve of high catching ftom 5.00 to 11.00 in the morning and 15.00 to 19.00 in the evening. In 1963 and 1965 high catches were obtained in the season of the first generation but much less catches in 1964. Catch curves were composed of several minor peaks, synchronized among several