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The areca palm is one of the three important "trees" (hevea brasiliensis, areca palm, and coconut) of tropical agriculture in Hainan province, China. However, the areca palm is highly susceptible to yellow leaf disease—the mostcommon disease affecting the palm—which is highly destructive, spreads rapidly, andis difficult to control with comprehensive physical, chemical, and ecological measures. Eco-geochemical studies have focused on the elemental geochemical behavior and ecological effects of the soil-plant system, which may prevent yellow leaf disease in the areca palm. With the support of the People's Government of Wanning City, Hainan Province, an eco-geochemical study was conductedon the areca palm area of Wanning City. Thirty sets of geochemical samples were collected from the root soil, root system, and leaves of areca palms infected with yellow leaf disease, along with samples taken fromhealthy trees. Root soil samples were tested for 28 indicators—including Se, Cu, Pb, Zn, Cd, Hg, As, Cr, Ni, Fe, Mn, B, Mo, Cl, F, I, N, P, K, Ca, Mg, S, Co, Na, Si, Al, pH, and organic matter. Additionally, the plant samples were tested for 23 elements—including Se, Cu, Pb, Zn, Cd, Hg, As, Cr, Ni, Fe, Mn, B, Mo, F, I, N, P, K, Ca, Mg, S, Co, and Na. Binomial logistic regression analysisof whether areca palmswere infected with yellow leaf disease as the dependent variable showed that As, B, and Co in the root soil were the main characteristic elements for determining whether the areca palmwas infected. The coefficients of As were negative,while the coefficientsof B and Co were positive, indicatinga lower probability of areca palminfection when the As content is higher and the contents of B and Co are lower.N, Co, and Na in the rootsystemwere the main characteristic elements for determining whetherthe areca palmwas infected. The coefficients of As, N, and Na were negative, while the coefficients of Co were positive,indicating a lower probability of areca palmsbeing infected when the contents of As, N, and Na are higher, and the content of Co is lower. The elements Zn, Hg, Mg, and S in the leaveswere the main factors determining whether the areca palmswere infected. The coefficients of Zn, Hg, and S were negative, and the coefficientsof Mg were positive,indicating a lower probability of areca palminfection when the contents of Zn, Hg, and Sarehigher,and content of Mg content is lower.Statistical analysis also showed that the correct classification rate and chi-square test expressed leaf> root system> root soil, indicating that the differences in elemental contents in the leaveswere the most accurate reflection of whether the areca palmwas infected. Soil is the most important source of trace elements in leaves and roots.From an eco-geochemical perspective, changing the elemental composition of root soil can be prevented, and yellow leaf diseaseamong areca palmscan be controlled.The As indicator did not enter thestatistical model of leaves (but Hg did), indicating that As does not easily reach the leaves or even the fruit of the palm. As is well known,arsenic-containing pesticides and drugs are used for plant pest control and human disease treatment, which indicates that increasing arsenic elements in the root system may enhance the prevention of areca palm from developing yellow leaf disease. Thus, this study provides a new eco-geochemical approach for the prevention and control of yellow leaf disease in areca palms. However, arsenic, as a toxic element, is an important control indicator for soil environmental quality and agricultural food safety. Therefore, systematic field trial studies and evaluations of areca palm root soil and fruits should be conducted to avoid secondary contamination using As; this can prevent and control yellow leaf disease inareca palms. |
