Study on the oviposition preference of the litchi fruit borer, Conopomorpha sinensis Bradley (Lepidoptera: Gracillariidae)
DONG Yizhi
YAO Qiong
CHEN Bingxu
XU Shu
XU Haiming
Abstract：[Objective] The litchi fruit borer (LFB),Conopomorpha sinensis Bradley,is the most distructive pest of litchi and longan in China and causes severe damage and yield reduction during the litchi's fruit stage due to boring by larvae in the fruit.Control of LFB by spraying pesticides is hampered because the larvae live inside the plants.In addition,most pesticides kill a large number of beneficial natural enemies and result in pesticide residues.LFB is less harmful at the litchi shoot stage with its population rapidly decreases.The adults prefer litchi fruits over shoots for oviposition and lay fewer eggs on leaves than fruits under natural conditions.The purpose of the present study is to investigate the oviposition preferences of LFB.[Methods] In this study,factors such as litchi fruits,surface texture,color,shape and size,litchi young and old leaves,were conducted to test for their attractancy to ovipositon of LFB adults.The oviposition preference test design in the laboratory was used to examine the preference by observing the amount of eggs that were laid by the LFB on the different oviposition media.The cultivar of the litchi used to conduct the test was'Feizixiao'and it was collected from the Agricultural Scientific Experiment and Demonstration Farm,Guangdong Academy of Agricultural Sciences.With references to the experimental methods from former studies,the oviposition media made from litchi fresh and dried fruit,litchi young leaves and old leaves were used as the treatments in the test.To test the oviposition preference of the LFB to litchi fresh and dried fruits,two plastic cylinder containers were filled with a litchi fresh fruit and a dried fruit respectively and sealed with tissue paper to be used as the oviposition media.They were then put into the cage together to observe the amount of eggs laid by the LFB adults on their surface with a litchi fresh fruit and a dried fruit used as the control.To test the oviposition preference of the LFB to surface texture,seven litchi fresh fruits wrapped in 80,100,200,300,400 mesh screens,copy paper and tissue paper respectively were used as the oviposition media and were put into the cage together to observe the amount of eggs laid by the LFB adults on their surface with a litchi fresh fruit used as a control which was wrapped in tissue paper.To test the oviposition preference of the LFB to litchi young and old leaves,three plastic cylinder containers filled with a litchi fresh fruit,young leaves and old leaves respectively and all sealed with tissue paper were used as the oviposition media and put into the cage to observe the amount of eggs laid by the LFB adults on their surface.[Results] The fresh litchi fruit induced egg laying by the LFB adults,even when it was placed in a plastic cylinder container and there was no contact,adults still laid their eggs on the surface of the container,where the amount of eggs showed no significant difference from those that were laid directly on the fresh litchi fruit.But LFB adults did not lay any eggs once the fresh fruit was sealed with parafilm or replaced by the dried litchi fruit.It suggested that the oviposition stimuli were primarily from the volatiles of the fresh fruit.Surface texture affected ovipositon preference of the LFB adults as well.The adults laid many more eggs on the surface of 200,300 and 400 mesh screen than the surface of 80 and 100 mesh screen and copy paper.The pericarp of the litchi fruit presents intense protuberances between which small crack textures appear in the surface.Under natural conditions,LFB adults usually lay eggs in the crack texture on the surface of the litchi fruit.It suggest that LFB adults may prefer to lay eggs on a rough surface with a small crack texture and that egg laying was reduced when the surface became smooth or the crack texture was too large.However,surface texture did not directly induce egg laying.Without the stimuli from the volatiles of the host plant,LFB adults did not lay any eggs on the surface even when its texture was appropriate for egg laying.In addition,the volatiles of litchi young and old leaves induced egg laying as well as those of the fresh fruit.LFB adults laid eggs on the surface of the container used as the oviposition medium which had the same weight no matter if litchi young leaves,old leaves or a fresh fruit was placed in it.The amount of eggs laid on the above three containers had no significant differences.However,the LFB adults had no oviposition preference to visual factors,such as color,shape and size.[Conclusion]The odors of litchi fruit,young and old leaves can induce egg laying by LFB adults and the oviposition preference of the adults was influenced by the surface texture.That the surface of the leaves was too smooth was one of the reasons why the LFB adults laid significantly less eggs on leaves than fruits under their natural conditions.
Keywords：Conopomorpha sinensisOvipositon preferenceLitchiOdorSurface texture
Publication Date：2018-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 204-211 )