The Citrus Psyllid's Host Selectivity On Different Citrus Germplasm Resources

The citrus psyllid,Diaphorina citri Kuwayama,is not only one of the pests sucking juice from citrus plants directly,but also the only vector of citrus Huanglongbing(HLB)which causing serious destruction to the citrus production indirectly.This study was focused on the host selectivities of the psyllid on 70 cultivated varieties belonging to 8 citrus catergories in the fields during May-August,2012 in Fujian Academy of Agricultural Sciences,Fuzhou,China.The average number of the psyllid's adults on each citrus plant and the average number of its nymphae and eggs on each citrus shoot were chosen as its host selectivity indicators,and the systematic cluster analysis and variance analysis methods were used to evaluate its host selectivities as well.The preliminary results as follows:The psyllid's host selectivities were significant different within the 8 catergories of citrus plants investigated.In terms of the indicators used,Lemons and Pomelos were the most favourable and sensitive hosts for the psyllid,without significant difference between its suitable host,Murraya paniculata.Sweet oranges and Mandamus(Hybrids?Tangerines?Mandarins)were ranged to the second,while Kumquats and Sour oranges were the least favourable and insensitive hosts for the psyllid.But among the different citrus cultivated varieties,the psyllid's host selectivities were varied within different catergories.Those varieties in Mandarins?Tangerines and Sweet oranges were more selectable for the psyllid.Under laboratory conditions using different plants to detect the psyllid's host selective behaviours,it showed that after releasing the psyllid for 90 h,its distribution differences in either on Citrus and Murraya or on Murraya and Rhododendron,both reached to a significant level.The psyllid's host selective behaviours both on citrus hosts or on non-citrus hosts were without any relationships with the plant morphologies.In the same laboratory using the only Murraya seedlings to detect the psyllid's host selective behaviours,it showed that its number distributed on the shoots of Murraya was increased as its releasing time going on and its number percentage distributed on new shoots increased gradually.Its number distributed in the experimental position no.1 was the minimum,and those was the maximum in position no.9.The psyllid's distribution number on different length of the shoots of Murraya was no significant difference.Regardless of the Murraya seedlings in upright or inverted positions,the psyllid's number distributed on the top position of the shoots were more than that on the bottom position and with a significant different level.Further experiment by using Y-olfactometer had been conducted and the preliminary result also indicated that the psyllid's host selective behaviours had close relationship with the volatiles from its host plants.Many kinds of volatiles had been found from the psyllid's main host plants.Among them,mainly are:alkanes,alkenes,alcohols,acids,esters,aldehydes,ketones and phenols.