Abstract:

Eulecanium gigantea Shinji(Homoptera: Coccidae)is an important pest in the cities of Northern China in recent years. Experimental districts were selected in Taiyuan City and Taigu County from 1998 to 1999. Vitamin B₂(VB₂) was determined monthly in twigs and leaves of Sophora japonica, the most favorable host of the scale insect. The results showed that the population density and biological rhythm of the scale insect were contrasted with the content of VB₂ and the VB₂ content in the two pollution districts were significantly higher than that in the cleaning district. The more the city environment polluted, the more VB₂ content in the host tree was. A positive relativity between the density of the scale insect and the VB₂ contents was found. The regression equation was made out as Y=1507.76x-170.56, and the coefficient, r=0.839. From March to October, the two peaks of VB₂ content were corresponded to the two feeding and quick development stages of the scale insect. It was concluded that a higher VB₂ content in the host plant in some degree was benefit to the scale insect occurring greatly in the polluted city environment.

Key words: Eulecanium gigantea Shinji, Sophora japonica, VB₂, City pollution