Inter-generational Changes in Relative Abundance of Insects Infected with Rice Dwarf Virus in Populations of Nephotettix cincticeps UHLER(Hemiptera : Deltocephalidae)

抄録

The generational changes in the relative abundance of rice dwarf virus (RDV)-infected insects in a population of the green rice leafhopper, Nephotettix cincticeps were studied in relation to the amount of the virus-infected rice plants as sources for feeding aquisition. Investigations were conducted in two localities in Kochi Prefecture : Nangoku and Ino. Nangoku represented an area where early and late rice crops are cultivated, while Ino is an area of single crop of middle-season rice. Surveys were carried out during the period 1964-69 in Nangoku and during 1968-69 in Ino.In Nangoku, changes in the percentage of infected insects from generation to generation formed a parabolic curve with its peak at the 1st generation. In Ino, on the other hand, the percentage of infected insects decreased from the overwintered to the 2nd or the 3rd generation and again increased toward the 5th generation. The proportion of infected insects (P) had no significant correlation with that of infected rice hills. However, P was closely related to the index of infected rice plants (I_v) which was derived from the proportion of the biomass of infected rice plants to the total biomass of the rice plants in the field. In Nangoku, the relationship between P and I_v can be representedas follows : log P=0.727 log I_v+0.106, or P=1.278 I_v^0.727.Whereas in Ino no relationship could be obtained because of insufficient data.