Determining HLB infection levels using multiple survey methods in Florida citrus

Abstract

A study was initiated to determine the effectiveness of various scouting methods within multiple blocks in a citrus grove in DeSoto County, FL. Surveys of the blocks were conducted by 5 different greening survey crews using multiple methods over a 2-week period in Jan. and Feb. 2009. Survey methods included walking, ATV, platform alone, and platform in combination with ATVs. Each crew flagged the trees that they determined to have HLB symptoms by visual detection methods. After flagging, the position of each tree was recorded and the fl ags were removed to allow other crews to survey the blocks unaided by previous surveys. After completion of scouting by all crews, each noted tree was tested using a DNA-based laboratory method (PCR) to determine if the tree actually contained the associated greening pathogen, Candidatus Liberibacter asiaticus. Survey results varied between survey methods as well as between crews. The combined average positive trees found by each survey method were calculated. Of all of the trees identified as being HLB infected during the survey process, walking and platform/ATV averaged 47% detection, ATVs averaged 61%, and platform without ATVs found 59% of the infected trees across all blocks and survey crews.