MATERIALS AND METHODSField sampling of citrus tissues. Leaves, stems and roots from40 trees were collected in March for three consecutive years (2016,2017, and 2018) from four different citrus orchards in Florida(Supplementary Table S1). Prior to sampling each year, trees wereassessed for HLB severity using a 1-to-5 disease rating (DR) scale,where 1 = vigorous with slight symptoms, 2 = slight decline, 3 =moderate decline, 4 = severe decline, and 5 = dead or dying, aspreviously reported (Ginnan et al. 2018; Rouse et al. 2010). Wedesigned our sampling time to coincide with maximum annual ‘Ca.L. asiaticus’ titers, which typically occurs in March (Blaustein et al.2017). Each tree was divided into four quadrants (north, south, east,and west) and stems with attached, fully expanded leaves were2collected from each of the quadrants and pooled. Feeder rootswere sampled from two sides of the tree approximately 0.5 m awayfrom the base of the trunk and sealed in a plastic bag. Gloves werechanged and clippers and shovels were sterilized with 30%household bleach between each tree that was sampled. All sampleswere immediately placed on ice in a cooler for transit to the lab-oratory, where they were placed at 4°C and processed within 24 haccording to Ginnan et al. (2018). Samples were stored at _80°Cand then lyophilized with a benchtop freeze dryer (LabconcoFreeZone 4.5L; Labconco, Kansas City, MO, U.S.A.) for 16 to 20 h.The lyophilized tissue was shipped to the University of CaliforniaRiverside (United States Department of Agriculture permit P526P-16-00352) on dry ice.