Effects of Alkaline Calcareous and Magnesium Soil Amendments on the Incidence of Bacterial Wilt of Tomato

Abstract

Bacterial wilt of tomato caused by Ralstonia solanacearum is one of the major hindrances in tomato production. Previously, we demonstrated that increases of field soil pH up to the weakly alkaline condition at approximately pH7.5 using slag fertilizer led to the reduction of disease severity caused by bacterial wilt (Kadota and Imazaki 2016). However, the method was laborious and needed large quantities of slag fertilizer. Therefore, in this study, I develop a labor- and cost-effective method that can be used in integrated pest management (IPM) programs based on the previous knowledges. First, the effects of several alkaline minerals on the incidence of bacterial wilt were examined. As a result, only alkaline mineral did not cause a stable reduction of disease incidence. Then, the efficacy of the representative alkaline minerals calcium carbonate (CaCO3) and magnesium carbonate (MgCO3) against the disease were tested in the combination with supplemental minerals. In 2018, the disease incidences were reduced by the combined treatment “CaCO3 + a micronutrient fertilizer (MF) + iron (III) oxide (Fe2O3) + a silicon fertilizer (SF)” or “MgCO3 + MF + SF”. Furthermore, synergistic effects were detected among the alkaline and supplemental minerals. Thus, the combinations of CaCO3 or MgCO3 with the MF, Fe2O3, and/or the SF were synergistic against the disease and were labor- and cost-saving. However, in 2019, the disease incidences were not significantly reduced by each of the combined treatments, which suggests that more combinations with other IPM tools are needed for sufficient control of bacterial wilt.