Abstract:

Phenacoccus azaleae belonged to the family of Pseudcoccidae in Coccoidea. It is a new destructive pest in the Bunge Prickly-Ash forest, Zanthoxylum bungeanus in northern China. The host plant which was damaged attracting the natural enemy a ladybug, Harmonia axyridis was studied in Taihang Mountain Area of Shanxi Province during 1999—2001 The results showed as follow: The percentage of the numbers of the ladybug attracted to the damaged fresh twigs and leaves can reach 57.0%. Correspondingly, the percentage was 20 0% to the undamaged ones. The rates of the ladybug which were attracted to the extractive solution from the damaged twigs and leaves were 37.0%. However the rates of the check test only was 10.3%. The test results came to the conclusion that the volatiles of the host plant can be so greatly changed by the induction of the mealybug feeding that the attraction of the twigs and leaves was increased to the ladybug. And this kind of the volatiles could be extracted by hot water. Further more, the inductive activity released by the damaged host plant could persist for about two months after the mealybug stopped feeding. The inductive activities increased with the content of the damaged twigs and leaves in test. Through GC/MS analysis, it is found that some long chain ester compounds distinctly increased in damaged host tree. Some 15 kinds of the compounds are same between undamaged and damaged trees. However the contents are much higher in damaged host tree. Other new compounds are synthesized in the damaged host tree. Theses compounds might play the role to attract the natural enemies.

Key words: Pseudococcidae, Phenacoccus azaleae, Harmonia axyridis, Zanthoxylum bungeanus