Abstract
Observations on the biology of the tea root borer, Xyleborus germanus, and the tea stem borer, Xyleborus compactus, were carried out. The preliminary tests on the artificial culture of the ambrosia fungi on which the larvae feed, and of the beetles were also undertaken. The results are summarized as follows:
1. Xyleborus germanus occurs twice a year, and overwinters as adult in tea root. The optimum temperature range for its development was assumed to be 21∼23°C. Larval growth of the first generation occurs from June to early July, the second generation from late August to September. They attack tea roots of 1.0∼1.5cm in diameter, at about 30cm in depth. Ratio of female to male is about 10 to 1. The outline of the life history is shown in Fig. 1.
2. Xyleborus compactus occurs twice a year, and overwinters as adult in tea twig. Larval growth of the first generation occurs from late July to late August, and that of the second from late August to September. They attack twigs of 5∼8mm in diameter. The surrounding tissues of their galleries are seriously injured, and the infestation by the beetles causes a die-back or a branch breackage of the tea bush. The optimum temperature range for the insect development was assumed to be 25∼27°C. Ratio of female to male was about 5 to 1.
3. The optimum temperatures for mycelial growth of the ambrosia fungus, Xyleborus germanus and Xyleborus compactus, were about 23°C, and about 26°C, respectively. The sporulations of the ambrosia fungi on agar based media were not so good, though the growth of mycelium was very good.
4. Xyleborus germanus could be successfully reared for one generation on wood material which had been autoclaved and inoculated with ambrosia fungus, and the succeeding generation is now in progress. However, the beetle could not complete one generation on the ambrosia fungus growing on agar based media.
