Detection and management of soil-borne pathogens in citrus using non-inorganic control practices under greenhouse conditions

Citrus fruits are among the priority crops for Uganda. Government has invested significant resources to boost citrus production due to their potential to increase household income, nutritional security and national exports. However, soil-borne pathogens are among several biotic-factors significantly constraining production. Whereas inorganic chemicals have been applied in the past, they have potential detrimental effects. Therefore, an experiment was conducted in the greenhouse of National Forestry Resources Research Institute (NaFORRI) at Kifu - Mukono in 2020-2021 to determine dominant soil and Citrus pathogens and test efficacy of different non-inorganic citrus pathogen control practices. A randomized complete block design with five treatments replicated thrice was used. The treatments included; hot water, heated wet-soil, fumigated soil, solarized wet-soil, and untreated control. A total of 30 Citrus seeds per variety were treated with sodium-hypochlorite-solution (1:7) before being sown. Soils from above treatments were cultured on Potato and Sabouraud-Dextrose Agar (PDA and SDA) and de Man, Rogosa and Sharp (MRS) agar. Results indicated that Aspergillus niger was the dominant soil-borne pathogen identified in pure cultures. Others included A. flavus, A. fumigatus, A. viridinutans, Penicillium chrysogenum and Fusarium oxysporum. Ranking based on scores in: cost-effectiveness, leaf-health, chlorophyll-intensity and general-health of seedlings revealed solarization (35) as most effective technique for managing soil-borne pathogens, followed by boiling (33), heating (31), untreated control (27) and lastly fumigation (26). Identified pathogens induce aflatoxins in Citrus and lead to great losses during post-harvest handling; they also cause root and fruit-rots. Solarization creates solar-radiation in a miniature greenhouse that kills pathogens. There is a need to study non-inorganic control practices of citrus pathogens under field conditions for improved yields in Uganda.