Repellency Of Volatile Oils From Non-host Plants On The Asiatic Citrus Psyllid(Diaphorina Citri Kuwayama)

The Asiatic citrus psyllid,Diaphorina citri Kuwayama(Hemiptera:Sternorrhyncha: Psyllidea)is most common and widely distributed vector of‘Candidatus Liberibacter asiaticus’(CLas)(α-Proteobacteria)the pathogen that caused the Asiatic form of huanglongbing,the most devastating disease of citrus which causes huge losses in the citrus industry.Synthetic pesticides are widely used to minimise the impact of the disease by reducing the incidence of the psyllid in orchards.However,the long-term use of synthetic pesticides leads to environmental pollution and the ‘3R’ problems(resistance,resurgence,residue).Therefore,there an urgent need to develop green and efficient prevention and control measures for the psyllid.In order to find efficient,green and environment friendly alternative to the synthetic pesticides,repellent effects of 23 non-host plant volatile oils and their chemical constituents were evaluated against male and female ACP adults.The evaluations were based on use of a Y-tube olfactometer,and potential active constituents were analyzed using gas chromatography-mass spectrometry(GC-MS)and gas chromatography-electrophysiological antennal detecting system(GC-EAD).The main contents and results are as follows:1.The repellency of 23 non-host plants volatile oils on D.citri(Mixed sex)were tested using a Y-tube olfactometer.Citronella oil,coriander oil and ginger oil at concentration of 100 μl/ml showed significant repellency: 68.5%,66.4%,and61.9%,respectively,can be used as an effective repellent.2.Repellency of the 23 non-host plants volatile oils were then tested separately against male and female D.citri adults and also using the Y-tube olfactometer.The results showed that citronella oil had significant repellency effects on females,with repellency rate of 57.1%.Although the repellency of males reached 50.0%,it did not differ significantly from the acetone control.Coriander oil repelled33.33% and 50% of female and male,respectively,but did not differ from the control and was differences in the response of males and females did not differ significantly.Ginger oil had a highly significant effect on female D.citri.It repelled 75.0% of females in contrast to 33.3% of males,the latter not differing significantly from the control.In general,females are more sensitive to citronella oil and ginger oil than males,for coriander oil,the differences in males and females repellent effect were not significant.3.The antenna potential response of D.citri to citronella oil,coriander oil and ginger oil were tested using GC-EAD.Twelve components from citronella oil caused antennae potential responses at males,while only four of them showed effects on females;There were 6 components in coriander oil that caused the females D.citri antenna potential responses,but only two of them caused male potential responses;There were 16 components in ginger oil that caused female D.citri antenna potential responses,and male D.citri antenna only responded to four of them.In general,the sensitivity levels from high to low were ginger oil,citronella oil,and coriander oil.Among them,both coriander oil and ginger oil contain linalool that can cause the potential change of D.citri antenna.4.GC-MS was used to analyze the chemical constituents in citronella oil,coriander oil and ginger oil.Fifty-four 54 chemicals were identified in citronella oil,mainly alcohols,esters and aldehydes.These three types of chemical composition accounted for 62.2% of the total substances.Fifty-one 51 chemicals were identified in coriander oil,mainly lipids and alcohols.They accounted for 45.8%of chemicals detected in coriander oil.Forty-seven substances were identified in ginger oil,mainly olefins and alcohols,which accounted for 53.6% of the total ingredients in ginger oil.Four chemical compounds,linalool,α-terpineol,decanal and geraniol were volatile components of each oils.5.The Y-tube olfactometer was also used to test responses of male and female D.citri to different concentrations of linalool(CAS Number: 78-70-6),α-pinene(CAS Number: 80-56-8),p-cymene(CAS Number: 99-87-6),2-hendecanone(CAS Number: 112-12-9)and camphene(CAS Number: 79-92-5).Linalool had no significant on male and female D.citri at 10 μl/ml 30 μl/ml and 60 μl/ml,and there was no significant difference between responses of males and females;α-pinene at 500 μl/ml had a significant effect on female D.citri,the repelling57.1% of females.However,there was no significant effect at other concentrations(100 μl/ml,1000 μl/ml),and no significant difference between responses of males and females;p-cymene had significant impacts on females at 100 μl/ml and 500μl/ml,repelling 57.14% and 69.56% of females,respectively.There was no significant effect at the concentrations of 10 μl/ml,and there was no significant difference between responses of males and females;2-hendecanone showed very significant repellency effects on females at 100 μl/ml,with a repellency rate of63.6%.But there was no significant effect at other concentrations(1 μl/ml,10μl/ml),and there was no difference between responses of males and females;When the concentration of camphene was 100 mg/ml,the repellency of females was 69.5%,which was very significant compared with control.Other concentrations(1 mg/ml,10 mg/ml)had no significant effects on males and females.