Submitted to: European Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/25/2013
Publication Date: 8/10/2013
Citation: Xu, M., Liang, M., Zheng, Z., Zhu, Q., Xia, Y., Chen, J., Deng, X. 2013. Preliminary research on soil conditioner mediated citrus Huanglongbing mitigation in the field in Guangdong, China. European Journal of Plant Pathology. 137:283-293. Interpretive Summary: Huanglongbing (HLB, also known as yellow shoot disease or greening disease) is devastating to citrus production worldwide. There are no known effective control measures for HLB. In China, management of HLB through nutrient applications has been used with varying results. This study evaluated effects of soil conditioner (SC), which contains natural compounds that improve nutrient levels and soil structure, on HLB-affected mandarin citrus in four orchards in Guangdong Province, China. After SC application, HLB-diseased trees grew more vigorously and reduced HLB pathogen level compared to the control treatment. SC-treatment benefited younger trees more than older trees. Fruit yield and quality (soluble solids and Vitamin C) from SC-treated citrus trees also were increased. Based on these results, SC treatments could be one component of a HLB-management program.
Technical Abstract: Huanglongbing (HLB, yellow shoot disease) is devastating to citrus production worldwide. No completely effective management measure is currently available. In China, HLB management through nutrient applications was used in the past, and now has renewed interest. Therefore, soil conditioner (SC) effects on HLB-affected mandarin citrus (Citrus reticulate Blanco) were evaluated in four orchards (three with cultivar Shatangju and one with cultivar Chuntianju) in Guangdong Province, China. HLB trees which received SC had greater growth and lower titers of the putative HLB pathogen “Candidatus Liberibacter asiaticus” than trees not receiving SC ten months post treatment. SC-treatment benefited younger trees more than older trees in that “Ca. L. asiaticus” titers in younger trees (two-years-old) were reduced more than those in older trees (eight-years-old). On four-year-old Chuntianju trees, the “Ca. L. asiaticus” titers were significantly lower in new leaves seven months after SC treatment (94.51% reduction or 2.59 times lower) than in new leaves sampled one or four months after SC treatment. Levels of P, N, K, Mn, and organic matter were greater in SC treated soil than non-treated soil when tested two months after application. SC applications also improved fruit yield and quality. Results from this study show that SC application could be a useful component for managing the impact of HLB in diseased orchards.