Las bacterium content of HLB-infected citrus trees was detected via the qPCR technology. The detection was carried out on a monthly basis throughout the whole year at the Huangyan district of Zhejiang Province. The results showed that the content of Las bacterium for HLB-infected citrus tree varied dramatically with time in a year. The highest value for the content of Las bacterium was observed in December, followed by November, but no significant difference (P＞0.05) was found between these two months. This was the case with the other months, whose values were lower (P＜0.05) than those detected in December and November.

　　Apart from the detection for the content of Las bacterium, the Las-holding ratio of Asian citrus psyllid (Diaphorina citri) captured from HLB-infected citrus tree was also detected. The highest ratio was found in December, which was not significantly different from that in January, but significantly higher than those detected in other months at P=0.05 level. Meanwhile, the pathogen quantity of Asian citrus psyllid showed that the average content of Las bacterium was highest during the period from December to the following January. This indicated that the Las-holding ratio of Asian citrus psyllid was directly affected by the content of Las bacterium for HLB-infected citrus trees. That is, the higher the ratio of Asian citrus psyllid, the more readily the spread of citrus HLB disease. Given that the spread of citrus HLB disease reached to peak in December and January, winter and spring would be the crucial period of controlling Asian citrus psyllid in order to prevent HLB disease.