Current applications of soil for the control of soilborne pathogens in plastic houses or in open field cultivations

• Published in: Phytopathologia mediterranea Vol. 48; no. 2; p. 343
• Main Authors: Tjamos, E C, Antoniou, P P, Tjamos, SE
• Format: Journal Article
• Language: English
• Published: 01-08-2009
• Subjects: Citrullus lanatus; Clavibacter michiganensis; Cucumis sativus; Dahlia; Fusarium oxysporum; Lycopersicon esculentum; Sclerotinia minor; Solanum tuberosum; Verticillium; Verticillium dahliae
• ISSN: 0031-9465

Watermelon plants grafted on rootstocks resistant to Fusarium oxysporum f. sp. niveum are able to avoid Fusarium wilt. However, this protection is not extended to Verticillium dahliae infections. Indeed watermelon cultivations established in fields previously cultivated with potato or cotton (both susceptible to Verticillium wilt) cause widespread infections of watermelons regardless of the use of Fusarium resistant rootstocks. In July 2007, strip soil solarization was applied in 10 hectares sandy loam field previously cultivated with potatoes. A strip of 2 m wide was covered mechanically by impermeable transparent plastic films (actual width 2.80 m) while an intermediate zone of 1.50 m wide was left uncovered. Mechanical application of the plastic film was carried out by a specifically regulated tractor in dry soil while irrigation tubes 1 m apart were also inserted during covering to be used to extensively water the soil. Two months after the application of soil solarization the plastic film was teared in the middle to allow rain to water the field during winder. In February 2008 the soil was cultivated with a riper without soil mixing while the plantation was established in March 2008 and transparent plastic tunnels covered the plants. Enumeration of Fusarium oxysporum propagules in solarized or unsolarizad control strips revealed that soil solarization for two months almost destroyed all Fusarium oxysporum propagules. Regarding symptom development in unsolarized strips up to 50-60% of the plants developed brown vascular discoloration indicating vascular wilt diseases. Laboratory examinations and pathogen isolation revealed that almost 80% of symptomatic plants were infected by Verticillium dahliae. On the contrary neither vascular wilt symptoms nor Verticillium dahliae was isolated form watermelon plants grown in solarized strips proving the effectiveness of the root stocks against Fusarium wilt. Preliminary calculations of the effect of solarization on the number of produced watermelon fruits per plant with commercial value showed that the difference between treated and untreated plots was not significant (the corresponding figures were 2.5 to 3.2). However, the mean weight of watermelon fruits from the untreated was per 8-10 Kg compared to 14-16 Kg from the solarized plots. This significant difference in th total production and the size of fruits justified the low cost extensive machine application of soil solarization in the Amaliada region of Helia county in Peloponnesus Greece (Cost of application 750 Euro per ha). Various examples of succesful soil solarization application refer to globe artichoke, lettuce, tomato and cucumber against several soilborne pathogens. In Iria region, soil solarization has beem applied to control Verticillium dahlias and Sclerotinia minor for the last 25 years as well as in the region of Lechaina (Helia) and Lapa (Achaia) for the control of Sclerotinia minor and other soilborne pathogens of lettuce. Soil solarization is also applied in Preveza county for the last 30 years for the control of Pyrenochaeta lycopersici, F. oxysporum f.sp. cucumerinum and Clavibacter michiganensis subsp. michiganensis. Solarization is a useful alternative of methyl bromide for the control of soilborne pathogens in Greece.