Soil solarization and control of vascular wilts in plastic houses.
polymnia P. antoniou AND E. C. TJAMOS
Agricultural University of Athens Department of Plant Pathology
75 Iera odos Votanikos 11855, ATHENS ,GREECE
introduction
Application of soil solarization has shown to be very effective against several soilborne pathogens and even bacteria in Greece (1-12 ). The technique was also efficient when was combined with polyethylene and low doses of methyl bromide (2, 3). However, the duration of its effective application has restricted the use of the method so far. In this work we demonstrate effective control of Fusarium oxysporum f.sp. cucumerinum of cucumber and Clavibacter michiganensis subsp. michiganensis of tomatoes in plastic houses by reduced doses of methyl bromide fumigation, soil solarization and impermeable plastics.
materials and methods
The effect of reduced doses of methyl bromide with common polyethylene or impermeable plastics (Plastopil Hazorea) was evaluated in plastic house cucumber cultivations of W. Greece. Plastopil plus 35 g/m2 or polyethylene plus 35 or 70 g/m2 of methyl bromide were applied. Furthermore, solarization with impermeable plastics for 15 days plus 35 g/m2 or for 30 days without fumigant were also tested. Chlamydospores of a pathogenic isolate of Fusarium oxysporum f.sp. cucumerinum were formed after mixing with 5 g of sterile soil and inserted into the appropriate nylon mesh envelopes. The envelopes were incorporated into highly Fusarium infested soil prior to treatment at 20 cm soil depths at two different sites of the experimental plot. To evaluate disease incidence and final yield sixteen cucumber plants of the susceptible hybrid Palmera were planted in each of the 4 experimental plots per treatment.
Similarly the effect of reduced doses of methyl bromide with common polyethylene plus 35 or 70 g/m2 of methyl bromide fumigation or solarization with impermeable plastics Plastopil for 30 days, solarization for 15 days plus 35 g/m2 or solarization for 30 days plus 35 g/m2 were evaluated against Clavibacter michiganensis subsp. michiganensis in plastic house tomato cultivations of W. Greece. Furthermore, tomato stem segments infested by infiltration with a bacterial suspension of antibiotic resistant mutants of Clavibacter michiganensis subsp. michiganensis containing 108 cells per ml were covered with cheese cloth envelopes. The infested stem segments were added prior to treatment at two different soil depths of 20 and 30 cm and at two different sites of naturally infested experimental plots. Twenty tomato plants per plot and four experimental plots per treatment with two replicates per plot were used.
results and conclusions
Laboratory tests to quantify the inocula after fumigation by using V8, a Fusarium oxysporum selective medium, showed that Plastopil plus 35 g/m2 of methyl bromide is more effective than polyethylene plus 35 or 70 g/m2 of methyl bromide in drastically destroying the pathogen. Solarization for 15 days and 35 g/m2 or solarization for 30 days are the most effective treatments able to almost eliminate the pathogen at 20 cm soil depth. All polyethylene or plastopil treatments were effective in decreasing significantly the disease incidence. The effect of various treatments on the diseased incidence showed that polyethylene plus 35 or 70 g/m2 of methyl bromide, plastopil plus 35 g/m2 and solarization and plastopil are equally effective in reducing symptom development. Data on yield showed that the final yield reached an average of 21 tn. / he in the control plots in comparison with 31-39 tn. / he in the treated plots (Table 1.).
Table 1. Effect of soil treatments with various doses of Methyl Bromide and types of plastics on Fusarium oxysporum f. sp. cucumerinum inocula, disease incidence of diseased cucumber plants and final yield.
Treatment / log cfu / g εδάφουςFusarium oxysporum f. sp. cucumerinum / Final disease incidence as % of diseased cucumber plants / Final Yield
(tn/he)
Control / 5 / 53 / 2
NB / 5 / -- / --
PE 35 / 3 / 8 / 3
PE 70 / 3 / 8 / 3
V 35 / 2 / 10 / 4
V35S(15d) / 2 / 7 / 3,5
VS(30d) / 1 / 6 / 3,9
* Four experimental plots per treatment and two replicates per plot
** 16 cucumber plants per plot four experimental plots per treatment
NB: Not Buried P: Polyethylene V: Plastopil Hazorea impermeable plastic
ControlNB: Not Buried
P35: Polyethylene plus 35 g/m2 methyl bromide
P70: Polyethylene plus 70 g/m2 methyl bromide
V35: Plastopil plus 35 g/m2 methyl bromide
V35S15: solarization with Plastopil for 15 days plus 35 g/m2 methyl bromide
VS30: solarization with Plastopil for 30 days
As for the quantification of bacterial cell survival at the site of chemical exit and at the 20 cm soil depth it was demonstrated that all applied doses and plastic film combinations are entirely ineffective in reducing the inocula of the bacterium in tomato stem segments It is also shown that 15 days solarization plus 35 g/m2 methyl bromide was ineffective compared to 30 days solarization with or without methyl bromide with Plastopil which was partially effective in reducing bacterial inoculum of the pathogen. However, solarization either 15 or 30 days affected significantly the level of the disease incidence and increased significantly the final yield (Table 2).
Indeed the percentage of the diseased plants ranged between 32-55% with all treatments involving methyl bromide fumigation with both types of plastics and solarization with plastopil for 15 days. However, both approaches of solarization for 30 days were effective in reducing symptom development down to 10%. Data on yield showed that the final yield was average of 30 tn. / he in the control plots and reached 50-70 tn. / he in the treated plots (Table 2. ).
Table 2. Effect of soil treatments with Methyl Bromide , two types of plastics and solarization on infiltrated Clavibacter michiganensis subsp. michiganensis disease incidence of diseased tomato plants and final yield.
Treatment / log. cfu / g soilClavibacter michiganensis subsp. michiganensis / Final disease incidence as % diseased tomato plants / Final yield
(tn/he)
Control / 7 / 47 / 30
NB / 6 / -- / --
PE 35 / 6 / 49 / 50
PE 70 / 6 / 55 / 50
V 35S(15d) / 7 / 32 / 60
V35S(30d) / 5 / 10 / 70
VS(30d) / 4 / 10 / 70
* Four experimental plots per treatment and two replicates per plot
** Twenty tomato plants per plot and treatment
NB: Not Buried P: Polyethylene V: Plastopil Hazorea impermeable plastic
Control: / ControlNB: / Not buried
PE 35 : / Polyethylene plus 35 g/m2 methyl bromide
PE 70: / Polyethylene plus 70 g/m2 methyl bromide
V 35S(15d) / Solarization with Plastopil for 15 days plus 35 g/m2 methyl bromide
V35S(30d): / Solarization with Plastopil for 30 days plus 35 g/m2 methyl bromide
VS(30d): / VS30: Solarization with Plastopil for 30 days
literature cited
1. Tjamos, E.C. & Faridis, A., 1980
Control of soil-borne pathogens by solar heating in plastic houses in Greece, pages 82-84. In the Proceedings 0f 5th Congress of the Mediterranean Phytopathological Union, Patras, Greece.
2. Tjamos, E.C., 1983
Control of Pyrenochaeta lycopersici by combined soil solarization and low dosage of methyl bromide Acta Horticulturae 152: 252-258
3. Tjamos, E.C., Paplomatas, E.J & Foundas, D., 1987
Control of Verticillium wilt of artichokes by solar heating or combination of solar heating with a reduced dose of methyl bromide 239-242. In the Proceedings of the Integrated and Biological Control in Protected Crops. P. Cavalloro Editor A.A. Balkema Publisher
4. Tjamos, E.C., Karapapa, Vaso & Bardas, D., 1989
Low cost application of soil solarization in covered plastic houses for the control of Verticillium wilt of tomatoes in Greece. Acta Horticulturae 255:139-150
6. Tjamos, E.C. and Makrynakis, N., 1990
Control of fungal wilt diseases of melon by application of soil solarization in the field. Proceedings of the 8th Congress of the Mediterranean Phytopathological Union-Agadir Morocco (pages 423-425).
7. Tjamos, E.C., Biris, D.A. & Paplomatas, E.J., 1991 Recovery of Verticillium wilted olive trees after individual application of soil solarization in established olive orchards Plant Disease, 75: 557-562.
8. Tjamos, E.C., 1991
Soil solarization in Greece. In Soil Solarization pp. 205-214. Katan J. & decay J. Editors
9. Helena, K. & Tjamos, E.C., 1992
Evaluation of soil solarization singly or in combination with fungal or bacterial biocontrol agents to control Fusarium wilt of carnation pp. 75-78. In Biological Control of Plant Diseases: Progress and Challenges for the Future. Athens, Tjamos, Papavizas and Cook Editors
10. Tjamos, E.C., Antoniou Polymnia & Panagopoulos C.G., 1992
Control of Clavibacter michiganensis subsp. michiganensis after application of soil solarization in tomato plastic houses. Phytopathology, 82: 1076 (abstract).
11. Antoniou Polymnia, Tjamos E.C. & Panagopoulos C.G., 1995
Use of soil solarization for controlling bacterial canker of tomato in plastic houses in Greece. Plant Pathology 44:438-447
12. Antoniou Polymnia, Tjamos E.C. & Panagopoulos C. G., 1997
Sensitivity of propagules of Fusarium oxysporum f.sp. cucumerinum, Verticillium dahliae, Clavibacter michiganensis subsp. michiganensis to reduced doses methyl bromide fumigation in combination with impermeable plastics Phytopathologia Mediterranean.