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
E-MAIL ect@auadec.aua.ariadne-t.gr
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/m 2 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/m 2 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.
log cfu / g εδάφους
Treatment
Final Yield
Final disease incidence as % of
diseased cucumber plants
Fusarium oxysporum f. sp.
(tn/he)
cucumerinum
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
* 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
3,9
Control
NB: 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 soil
Final disease incidence as
Final yield
Clavibacter michiganensis subsp. michiganensis
% diseased tomato plants
(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
* 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
70
Control:
Control
NB:
PE 35 :
Not buried
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 44:438447
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.