Citrus bliss: potassium, sodium, and calcium silicates secrets for post-harvest diseases of fruit defense

Biotic stress significantly challenges the global citrus industry. Major post-harvest issues include diseases caused by <i>Penicillium digitatum, Penicillium italicum, Geotrichum citri-aurantii, Alternaria alternata</i>, and <i>Phytophthora citrophthora</i>. The negative impact of chemical fungicides on the environment and health necessitates eco-friendly alternatives. This study examines the effectiveness of sodium, potassium, and calcium silicates against common citrus diseases<i>. In vitro</i> tests evaluated mycelial growth inhibition using silicate concentrations from 0 to 10,000 ppm after 7 days at 25°C. Sodium silicate showed the highest efficacy, completely inhibiting <i>P. digitatum</i> and <i>P. italicum</i> at 2000 ppm. Potassium and calcium silicates achieved 100% inhibition against <i>Penicillium</i> spp. at a concentration of 1%. <i>In vivo</i> tests on Sidi Aissa clementines assessed the preventive and curative effects of 1, 2, and 6% silicate salt solutions. Sodium silicate prevented 41% of brown rot, 72% of sour rot, and 100% of green mold at 6%. Calcium silicate at 6% significantly reduced blue mold and black rot by 32% and 74%, respectively. Sodium silicate was most effective in curative treatments, suggesting its potential as a pre- or post-harvest spray to control <i>P. digitatum, P. italicum</i>, and <i>G. citriaurantii</i>.