Abstract:

The effect of the different liliaceous host plants on the growth, development and reproduction of Bradysia odoriphaga Yang et Zhang was studied by feeding its larvae with four host plants, Allium tuberosum, A. fistulosum, A. sativum and A. cepa respectively in the laboratory. The main chemical constituents of garlicin and alcohol extracts from A. sativum, A. cepa and A. tubersoum were analyzed using gas chromatography and mass spectrometry. The results demonstrated that the effect of four host plants on the growth, development and reproduction of Bradysia odoriphaga was different. The most favorable food in the four host plants for the growth, development and reproduction of the pest was A. tubersoum. When the larvae were fed with A. sativum and A. cepa, the death rate of the larvae increased, the larval stage prolonged, the pupal weight decreased, and the average fecundity reduced. The insecticidal activities of the alcohol extracts from A. sativum and A. cepa, and the synthetic garlicin against its first instar larvae were different. When the first instar larvae were treated with the alcohol extract (2 g dry powder/mL) from A. sativum and A. cepa, which was diluted 100 and 200 times, their corrected mortality after 48 hours was 54.7% and 28.0%, and 49.4% and 22.7%, respectively. However, when the first instar larvae were treated with 10% garlicin, which was diluted 500 and 1 000 times, their corrected mortality  after 48 hours was 100% and 80.0%, respectively. Chemical constituent analysis showed that thioether compound might be one of insecticidal substances in A. sativum and A. cepa.

Key words: Bradysia odoriphagaYang etZhang, host plant, growth and development, insecticidal activity, chemical constituent analysis