Herbal extracts: For green control of citrus Huanglongbing

Abstract Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus ( C Las), poses a substantial threat to global citrus agriculture. Current management strategies (planting disease-free nursery trees, implementing effective psyllid control, and removing all symptomatic trees) are inadequate for remedying diseased trees or alleviating economic losses. Therefore, new alternative methods for HLB control are urgently needed. In this study, the ethanol extracts from four traditional Chinese medicinal herbs: Sophora japonica (SJ), Lonicera japonica Thunb. (LJT), Taraxaci herba (TH), and Scutellaria baicalensis Georgi (SBG), were selected for the treatment assay of HLB. Analysis of flavonoid content revealed that SJ extract possesses the highest concentration, followed by LJT, TH, and SBG extracts. The potted studies demonstrated that all extracts reduced the C Las titers, with the SJ extract achieving the greatest significant reduction at a depletion rate of 79.05%. Field tests confirmed the remarkable efficacy of SJ extract, achieving a 99.1% reduction in C Las titers after 150 days. Physiological studies revealed that all extracts increased photosynthetic pigment concentrations, reduced starch/soluble sugar accumulation, and mitigated reactive oxygen species oxidative damage in HLB-affected plants, with SJ extract showing statistical significance relative to other treatments. Furthermore, herb extracts mitigated soil acidification, elevating pH beyond control levels, with SJ exhibiting the most prolonged effect. A comparative assessment of SJ extract and rutin, an established anti-HLB flavonoid, on HLB cure was performed, revealing no significant difference in efficacy. These findings establish SJ extract and flavonoid-rich botanicals as promising eco-friendly, environmentally sustainable alternatives for HLB management.