Tomato bacterial wilt and canker disease caused by Clavibacter michiganensis subsp. michiganensis, is an important seed-borne pathogen that causes serious yield losses by damaging roots, stems, leaves, flowers and fruits of tomato plants both in greenhouse and open-field productions. Since it was first detected in tomatoes in 1909, several studies have been conducted in many countries on this disease agent. Since Cmm is a systemic spread disease agent, it is generally transmitted through infected seeds. It is also transferred to the next production season through diseased plant residues and contaminated soils, causing great crop losses. Since the disease agent is able to survive in different places, significant difficulties are encountered in control of tomato canker and wilt disease.
Vermicompost, obtained as a result of the vermiculture process and so called as black gold (Kangmin 2005; Patangray 2014), is the conversion of organic waste/wastes into fertilizer through digestive tracks of worms. It is used as a slow-release fertilizer and improves soil physical, chemical and biological properties (Yağmur and Eşiyok 2019). Vermicompost also provides soil aeration, increases water holding capacity and regulates soil microbial activity (Singh et al., 2003). Thus, an increase in product quality and quantity is ensured. Vermicompost is rich in microbial diversity and biomass. Therefore, it is also rich in enzymes and hormone-like chemicals produced by microorganisms. In addition, vermicompost ensures that plant nutrients can be used by the plant for a long time. This gives vermicompost a "slow-release fertilizer" feature (Şimşek-Erşahin 2013).
Vermicompost contains active substances like plant growth regulators. It is used as organic fertilizer, soil conditioner and in disease and pest control (Edwards and Bohlen 1996). Rich plant nutrients and microbial composition of vermicompost increase plant resistance against pests and diseases. With the aid of vermicompost, plants whose roots are covered by beneficial microorganisms are less affected by pathogens and population growth of soil pathogens and pests is limited. Thus, pathogens cannot cause disease or damage remains below the economic damage threshold.
It was proved in previous studies that vermicompost was quite effective in suppression of plant diseases and pests. Recently, studies on this subject have been gaining momentum. In present study, it was determined that vermicompost significantly suppressed bacterial canker and wilt disease. In pot experiments, different doses of vermicompost were used and the disease severity decreased the most in 40% vermicompost treatments and the disease was suppressed by 90%. The lesion size in vascular bundles also significantly decreased (66%). Parallel to pot experiments, vermicompost suppressed the disease significantly in the field experiments. Vermicompost suppressed the disease by 66% in field experiments. The disease remained at a limited level in the vascular bundles.
Present findings comply with the findings of earlier studies. In this sense, it was reported that compost tea prepared from the vermicompost supplied from Abbsfort (Canada) suppressed bacterial canker and wilt disease by 63%. In that study by Utkhede and Koch (2004), chemical and biological applications were made to tomato plants of Dombito variety. Cmm was applied to the plant in the form of spray through the applications made to the cotyledon leaves. Evaluations were made 42 days after inoculation, the infection rate was 71.6 in the plants to which the disease agent was applied, while a low infection rate (26.6) was determined in the vermicompost treatments. Yogev et al. (2009) studied the effect of compost consisting of tomato and pepper waste combined with poultry and cattle manure and reported that compost reduced Cmm disease intensity up to 100% in both natural infection and artificial inoculations and Cmm population of the compost decreased within 15–20 days. Tutar (2013) indicated that chloroform extracts of vermicompost had a strong effect against Pseudomonas syringae, Xhantomonas carotae, Sclerotinia sclerotiorum, Fusarim oxysporum, Aspergillus humicola, A. fumigatus and a weak effect against Erwinia chrysanthemi, Pseudomonas fluorescens and Penicillium brevicompactum. On the other hand, ethanol extracts had a strong effect against Pseudomonas syringae, Xhantomonas campestris and Aspergillus fumigatus and a weak effect against Erwinia herbicola, E. chrysanthemi and S. sclerotiorum. It was reported that vermicompost products obtained from some organic residues or wastes suppressed plant fungal diseases of Phythium, Fusarium, Rhizoctonia ve Phytophthora spp., Plectosporium tabacinum, Botrytis cinerea, Verticillium wilt, Sclerotonia rolfsii (Szczech 1999; Edwards and Arancon, 2004; Şimsek-Erşahin et al. 2008).