Abstract:

The olfactory tendency preference was studied on the two predatory natural enemies, agreen lacewing, Chrysopa sinica and a ladybird, Harmonia axyridis, being attracted to the two kinds of trees, Diospyros kaki and Ziziphus jujuba that were damaged by a scale insect, Ceroplastes japonicus. The results showed that during around a year in the two stages, from May to June and from July to August, the two kinds of damaged host trees did not show the significant attraction to the two natural enemy insects. However, in the time from September to October, the attractive action showed strongly with a nocturnal and diurnal rhythm. In the midnight from 1:00 to 3:00 and in the afternoon from 13:00 to 15:00, the attractive effects reached significantly different level. Contrastively no attractive action was detected in the other two phases respectively in the morning from 7:00 to 9:00 and in the evening from 19:00 to 21:00. These effects as if related with the changes of temperature and humidity in one day. It was found that the source of volatile compounds come from the combination of the two host plants and Japanese wax scale,in which the former played the more important function than the later did. Compared with the volatile of undamaged persimmon, in the compositions of damaged persimmon trees, 6 components increased their contents, while 11 components appeared, including 3 kinds of terpenoids, 3 kinds of aromatic compounds, 3 kinds of hydrocarbons and 2 kinds of alcohols. Their function for attracting the predatory natural enemies was discussed.

Key words: Ceroplastes japonicus, Diospyros kaki, Ziziphus jujuba, Chrysopa sinica, Harmonia axyridis, Attraction, volatile