Detection of Greening in Sprouts from Citrus Tree Stumps

摘要

A study was initiated to determine if stump sprouts from citrus trees that were removed because of visual citrus greening (huanglongbing, HLB) symptoms tested positive for Candidatus Liberibacter asiaticus (Ca. Las). The study was conducted in a commercial grove in DeSoto County, FL. All trees selected for the trial were visually determined to have HLB prior to removal. The 15 trees selected were removed using a standard tree shear mounted to a front-end loader. Remaining stumps were monitored on 30-day intervals to detect sprout formation from the stump or exposed lateral roots. Once sprouts appeared, the entire stump and exposed lateral roots were enclosed within a screen enclosure to exclude psyllids from feeding on new vegetative growth. At 160days after clipping, leaf and stem tissues from sprouts were tested for Ca. Las by the DNA-based quantitative PCR (qPCR) method. During the study, 12 of the stumps sprouted and produced 2 to 26 sprouts per stump. Two of 12 stumps that sprouted had insufficient vegetative plant material to test. Eight of the 10 stumps (80%) had one or more sprouts that were greening positive. The percentage of greening positive sprouts recovered from a positive stump ranged from 33% to 100%. The broad range in percent greening positive sprouts from an individual stump reflects the uneven distribution of Ca. Las in the roots and trunk of infected trees. Controlling root and stump sprouts after removal of greening infected trees is essential in its control and spread.