6. Effect of soil solarization on nematodes

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Effectiveness of sol solarization for control of plant parasitic nematodes
Soil solarization and control of plant parasitic nematodes
Soil solarization for control of pratylenchus thornei on Chickpea in Syria.
The role of sol solarization in the scope of meloidogyne spp. integrated control under sandy soil conditions

Effectiveness of sol solarization for control of plant parasitic nematodes

F. Lamberti and N. Greco
Istituto di Nematologia Agraria, C.N.R., 70126 Bari, Italy

Introduction

Control of plant parasites is the ultimate objective of plant protectionists. A control method should be effective, cheap, safe and easy to operate and to apply. Most of the available methods to control plant pathogens do not fully meet these requirements. Some of them, such as steaming and the use of chemicals, are very effective but costly and require specialized machinery and well-trained personnel. Chemicals may also cause pollution and residues may remain in edible parts of plants in high concentration at harvest. The use of crop rotations is effective and safe, but control is limited to a few nematodes, such as Heterodera spp. and Globodera spp., that have narrow host ranges. They may also require changes of the farm crop planning. Resistant cultivars are available only for a few crops and their continued use may induce selection of new nematode pathotypes.

Soil solarization is a rather recently developed technique, which has shown promise for the control of several soilborne pathogens and weeds in warm areas (10, 11). Its effectiveness against nematodes was first demonstrated in Israel and later, attempts to control nematodes by soil solarization were also made in Australia (15), USA (12, 17), Italy (7), and South Africa (1). The use of soil solarization for control of nematodes has received increasing attention in recent years.

Effects of Soil Solarization on Nematodes

The efficacy of soil solarization is based on the sensitivity of nematodes to relatively high temperatures. Hot water treatment is still suggested as a method to kill nematodes within plant parts. Soaking narcissus bulbs for 3-4 hours in hot water at 44-45°C. is suggested for the control of Ditylenchus dipsaci. The same temperature is also effective in disinfesting chrysanthemum cuttings from Aphelenchoides ritzema-bosi, but in this case a 30 minute treatment is enough. The soaking treatment can be reduced to 5 minutes by raising the water temperature to 50°C Endo (6) demonstrated that the time required to kill 100 percent juveniles within cysts of Heterodera gIycine is temperature dependent. He found that I second, 8 minutes, and 8 hours were required to inhibit egg hatch of the nematode at 63, 52, and 44, respectively. Similar lethal temperatures (5 min exposure at 55°C) are reported for Globodera rostochiensis (13). Notwithstanding that under clear plastic mulch, temperatures higher than 50°C can be reached only in the lop 5 cm of the soil, temperatures of 40-50°C have been reported up to 10-15 cm depth in hot seasons in several countries (1, 7, 11,15,17).

Moreover, temperatures of 36-40°C can be reached at 20-30 cm depth in warm areas. Such temperatures, if prolonged, can be lethal to nematodes or at least may reduce their infectivity because of energy reserve depletion. Such weakened nematodes may also be more vulnerable to biotic and abiotic stresses. Further, nematode antagonists may prevail in the soil after solarization or they may colonize the solarized soils much faster than the non-solarized soils when incorporated artificially. These possible long lasting effects have not been investigated for nematodes, but they are known to exist for other soilborne pathogens. In deeper soil profiles (30-40 cm) lethal or sublethal temperatures usually are not attained, where the temperature increases only 3-4°C. However, this may render nematodes more active, which in turn increases nematode infection by Pasteuria penetrans (18) or nematode capture by some trapping fungi. Because of soil biotic and abiotic changes following solarization, the suppressing effect on nematodes may not become evident or can last for several months. Walker and Wachtel (18) found that infection of Meloidogyne javanica juveniles by P. penetrans increases for ten months after soil solarization and Stapleton and DeVay (17) observed a reduction of Helicotylenchus digonicus populations only three months after solarization treatment.

The beneficial effect of nematode control is further enhanced because of the lack of or the reduced interaction of nematodes with soilborne diseases, such as those caused by Verticillium spp. and Fusarium spp.

Present Knowledge on Nematode Control By Soil Solarization

The effectiveness of soil solarization on nematode control has been ascertained by several investigators in different areas. In fields heavily infested with Ditylenchus dipsaci in Israel, soil solarization protected garlic bulbs throughout the growing season resulting in a greater yield increase compared with EDB and methyl bromide applications (16). In Italy, control of D. dipsaci in a sandy soil increased with solarization periods and only 10, 6 and 2 percent nematodes were still viable after four, six, and eight weeks solarization, respectively (7).

Satisfactory control has also been obtained against cyst forming nematodes. In New York State, the hatch of Globodera rostochiensis from solarized soil was nil, 32, and 41% of that in non-treated soil at 5, 10, and 15 cm depth, respectively (12). Better control was achieved in Italy, where only 24-38% of eggs survived in cysts of Heterodera carotae from the top 30 cm soil solarized for four to eight weeks (7). In another trial the yield of carrots from plots solarized for eight weeks was 4.6 kg/m, compared with 5.5 kg in plots treated with 400 1/ha DD and only 2.3 kg in the control (Greco et al., unpublished).

Root-knot nematodes, Meloidogyne spp., are widespread throughout the world and the most damaging nematode group. Although in some solarization experiments control of these nematodes was inconsistent (1, 7), other investigations have demonstrated that excellent control is achieved by soil solarization under greenhouse conditions (2, 3, 4, 5). Here, soil temperatures in the top 30 cm of mulched soil can be 3-5°C higher than in mulched soil in open air and, therefore, higher nematode mortality can be expected. In Spain (5), nematode control in solarized soil was slightly less than in soil treated with methyl bromide, but yields were similar in both treatments. In Italy, several solarization experiments have been undertaken to control pathogens of solanaceous crops in the greenhouse. Tomato roots were heavily galled and rotting by the end of the growing season in control plots, while they were nearly free of nematodes in plots treated with methyl bromide. In solarized plots root infestation was intermediate because of the late nematode attack, but no rotting of the root was observed (3). Moreover, alternating methyl bromide with solarization treatments inhibited root infestation as did soil treated with methyl bromide for two consecutive years. In the same solarized plots, yield increases averaged 60 percent over the control and were similar to those obtained with methyl bromide treatments.

In other experiments in Sicily (2, 3, 4), aimed at the control of soilborne pathogens of pepper in greenhouse culture, yield and fruit size from solarized soil averaged 12.2 and 2.3 times, respectively, over those in controls. Higher yield was obtained with soil solarization, alone or in combination with reduced dosages of methyl bromide, and with methyl bromide alone (6 times over control) than with DD (5.4 times the control).

Interesting results have also been reported using soil solarization to control the reniform nematode, Rotylenchulus reniformis. Heald and Thomas (9) observed that the development of cowpea in plots solarized for six weeks was greatly enhanced as was the subsequent yield of lettuce. Nematode densities at the harvest of the cowpea crop were 47 specimens/100 g soil in solarized plots and 14 400 in the controls. Satisfactory control was also similarly obtained by McSorley and Parrado (14), even though nematode population densities increased during the following tomato crop.

Observations on other nematodes, occasionally occurring along with the targeted soil pathogens, have demonstrated that soil solarization is also promising for the control of several other plant parasitic and free-living nematodes.

Conclusions

Results achieved so far clearly demonstrate that soil solarization can profitably be used to control nematodes. However, nematodes develop in the rhizosphere, which reaches 40-50 cm depth in annual plants. Usually soil temperature in solarized plots never approaches lethal or sub-lethal levels at more than 30 cm depth. Therefore, nematodes in the deeper soil profile may survive solarization and still cause some damage when plants with deep root systems are cultivated. As a result, in heavily infested soil, and especially with cyst forming nematodes, the beneficial effect of soil solarization, is practical and may be as effective as high fumigant rates alone, even in heavily infested soil (4). Moreover, alternating fumigants with solarization for soil disinfestation nearly eradicates nematodes as does consecutive fumigation with methyl bromide. This makes soil solarization a very promising technique for limiting the amount of nematicides required in agriculture. Therefore, we feel that soil solarization must also be investigated under less favourable climatic conditions and be considered in integrated nematode management programmes.

Reference

1. Barbercheck, M. E. and S. L. Von Broembsen. 1986. Effects of soil solarization on plant-parasitic nematodes and Phytophthora cinnamoni in South Africa. Plant Disease 70:945-950.

2. Cartia, G. and N. Greco. 1987. Effetti della solarizzazione del suolo su una coltura di peperone in serra. Colture Protette 16(5):61-65.

3. Cartia, G., N. Greco, and G. Cirvilleri. 1988. Solarizzazione e bromuro di mettle nella difesa dai parassiti del pomodoro in ambiente protetto. Proc. Giornate Fitopatologiche, Lecce, Italy. 16-20 May, 1:437488.

4. Cartia, G., N. Greco, and T. Cipriano. 1989. Effect of soil solarization and fumigants on soil-borne pathogens of pepper in greenhouse. Acta Horticulturae 255:111-116.

5. Cenis, J. L. 1984. Control of the nematode Meloidogyne javanica by soil solarization. Proc. 6th Congr. Union Phytopath. Mediterr., Cairo, Egypt, 1-6 October, p. 132.

6. Endo, B. Y.. 1962. Lethal time-temperature relations for Heterodera glycines. Phytopathology 52:992-997.

7. Greco, N., A. Brandonisio, and F. Elia. 1985. Control of Ditylenchus dipsaci, Heterodera carotae and Meloidogyne javanica by solarization. Nematol. Medit. 13:191-197.

8. Grinstein, A., D. Orion, A. Greenberger, and J. Katan. 1979. Solar heating of the soil for the control Verticillium dahliae and Pratylenchus thornei in potatoes. In: Soilborne Plant Pathogens. Schippers. B. and Gams W. Eds., Academic Press, London, pp.431-438.

9. Heald, C. M. and C. E. Thomas. 1983. Nematode control by soil solarization. J. Nematol. 13:114-115.

10. Katan, J. 1987. Soil solarization. In: Innovative Approaches to Plant Disease Control. I. Chet, Ed., J. Wiley and Sons, New York, pp.77-105.

11. Katan, J., A. Greenberger, H. Alon, and A. Grinstein. 1976. Solar heating by polyethylene mulching for the control of diseases caused by soilborne pathogens. Phytopathology 66:683-688.

12. LaMondia, J. A. and B.B. Brodie. 1984. Control of Globodera rostochiensis by solar heat. Plant Disease 68:474476.

13. Mai, W. F. and W. H. Lautz. 1953. Relative resistance of free and excysted larvae of the golden nematode Heterodera rostochiensis Wollenweber to D-D mixture and hot water. Proc. Helminthol. Soc., Washington, D. C., 20:1-7.

14. McSorley, R. and J. L. Parrado. 1986. Application of soil solarization to Rockdale soils in a subtropical environment. Nematropica 16:125-140.

15. Porter, 1. J. and P. R. Merriman. 1983. Effect of solarization of soil on nematode and fungal pathogens at two sites in Victoria. Soil Biol. Biochem. 15:39-44.

16. Siti, E., E. Cohn, J. Katan, and M. Mordechai. 1982. Control of Ditylenchus dipsaci in garlic by bulb and soil treatments. Phytoparasitica 10:93-100.

17. Stapleton, J. J. and J. E. DeVay. 1983. Response of phytoparasitic and free-living nematodes to soil solarization and 1, 3 - dichloropropene in California. Phytopathology 73: 1429-1436.

18. Walker, G. E. and M. F. Wachtel. 1988. The influence of soil solarization and non-fumigant nematicides on infection of Meloidogyne javanica by Pasteuria penetrans. Nematologica 34:477-483.

Soil solarization and control of plant parasitic nematodes

M.M. Satour, F.W. Riad and A.S. Abdel-Hamied,
Plant Pathology Research Institute,
Agricultural Research Center, Ministry of Agriculture, Giza, Egypt

Abstract

Solar heating of soil by means of polyethylene mulching during hot season for the control of a variety of soilborne pathogens was tested. In this study, solarization reduced the reproduction factor (RF) of nematodes on broad bean from 4.44 to 0.027 after treatment. The RF on onion, strawberry and tomato was 0.37, 0.0 and 0.0. in solarized soil. The corresponding values from non-solarized soil were 0.6, 1.07 and 1.5 on the same crops. Effects of solarization for six weeks were more pronounced than those from four weeks of treatment.

Introduction

Soil solarization as a method for the control of soilborne pathogens was evaluated through the Tri-national project programme in Egypt. Solarization is a unique method of mulching that integrates pest control, soil and water conservation, and increased growth response of crops (11). In recent years, this new method for controlling soilborne pathogens and weeds by means of solar heating of the soil was developed in Israel (4, 5) and in California (6). Additional control depends upon the properties and specificity of materials used, as well as other physical, chemical and biological aspects of the ecosystem (1, 7). Soil and root densities of beneficial fungi and bacteria sometimes increase after solarization (2, 10). Field experiments compared pesticides with solarization, alone and in combination, for effects on plant growth. Severity of Verticillium wilt of potatoes is increased by the nematode, Pratylenchus thornei (Krikun and Orion, unpublished data). The efficiency of solarization in controlling V. dahliae and Pratylenchus thornei on potatoes was tested in a naturally infested field and compared to a nematicide mixture of ethylene dibromide and chloropicrin. Solarization of soil killed microsclertia of V. dahliae, reduced diseased plants by 96-99 percent and the P. thornei population by 80-100 percent, controlled weeds, and increased the yields of potatoes by 35 percent (3).

In the present work, the efficiency of soil solarization on control of fungi, nematodes and weed flora was tested. The subsequent indirect effect on crop yield of varieties under different field conditions was also studied.

Material and Methods

Field experiments in Egypt were conducted to study the effect of mulching for nematode control, either singly or in combination with recommended herbicides. Naturally infested soils in Giza, Fayoum, Ismailia, Qualyobia and Gharbia governates were selected to represent different soil types. Heavy textured clay soils in Fayoum, Qualyobia and Giza governorates, versus sandy soils in Ismailia were compared. Solarization was done according to Katan(5). The following crops were planted in September, after four or six weeks of solarization tomato, onion, strawberry, potato, rape, broad bean and corn. Extraction of nematodes was made from 200 g soil sample, using sieves and the Baermann funnel technique (9). Nematode determination and identification were effected under a microscope using the Hawksley counting slide. The reproduction factor (RF) assessment was made according to the formula Pf/Pi where Pf = final population, Pi = initial population. Treatments were carried out throughout the seasons 1985-1986 and 1986-1987. All experiments involved two main treatments, non-solarized (NS) and solarized (S) and were planted with the same crops. Data were taken every two months after covering the soil with polyethylene sheets (PE) (1985-86 season), and every month after covering (1986-87 season). Four samples per plot were taken for extraction of nematodes. Soil samples were taken to a depth of 15-20 cm. The soil was irrigated and tightly mulched with 50 mm-thick transparent PK. Soil solarization was carried out for six weeks during July and August of 1985 and 1986. Timing and mulching period were tested in Fayoum (Tamya Experimental Farm), which used treatments of two durations, four and six weeks.

Results and Discussion

Experiments during 1985-1986

1. Fayoum (Tamya experimental farm): Data revealed that solarization resulted in reductions of nematode populations. Table I shows that all treatments gave RF = 0, except the treatments of June (four weeks) and July (four weeks), while RF of non-solarized control plots was 2.35. Data in Table 2 show that solarization gave good control for nematodes. The RF in solarized treatments ranged from 0 to 0.47, while in non-solarized plots, reductions ranged from 0.98 to 1.57.

2. Ismailia. A. - Fayed experimental farm: Table 3 clearly shows the effect of solarization on the control of nematodes on onion, broad bean, and rape, with RF's of 0.03, 0.0 and 0.14 for Tylenchorhynchus and Trichodorus spp. The corresponding RF values in non-solarized soil were 1.44, 0.51 and 1.45 on the same crops and the same nematodes. These data confirmed those of E. Siti et al. (8), who obtained excellent control of Ditylenchus dipsaci by treating the soil with solar heating with transparent polyethylene sheets prior to planting.

B. Manaef private farm: Table 3 indicates that the RF in the solarized treatment was 0 on tomato plants for TyIenchorhynchus spp., Meloidogyne spp., and Trichodorus spp. The corresponding RF value in non-solarized soil was 0.89 on the same crop and the same nematodes.

Experiments during 1986-1987

The Giza experiment was conducted to study the effect of solarization and herbicides, either singly or in combination, in a soil naturally infested with Rotylenchulus reniformis Tylenchorhynchus spp. Praylenchus spp. and Heterodera spp. where broad bean was cultivated. Non-solarized control treatments were used. Data in Table 4 show variation in RF between the treatments. Generally, the RF in solarized treatments was 0.027, while in nonsolarized it was 4.44. Solar heating of the soil by means of polyethylene mulching during hot seasons controlled nematodes in all localities. Solarization was tested in a soil with Meloidogyne, Pratylenchus. Helicotylenchus, Tylenchorhynchus and Hoplolaimus spp. in Beni-Sweif, Fayoum, Qalyobia and Ismailia localities (Table 5). In general, combinations of solarization and herbicides gave good control of nematodes and healthy plants, compared with non-solarized plots.

References

1. Avidov, E., N. Aharonson, J. Katan, B. Rubin, and Q. Yarden. 1985. Persistence of terbutryn and atrazine in soil as affected by soil disinfestation and fungicides. Weed Science 33:457461.

2. Elad, Y., J. Katan, and I. Chet. 1980. Physical, biological, and chemical control integrated for soilborne diseases in potatoes. Phytopathology 70:418422.

3. Grinstein, A., D. Orions, A. Greenberger, and J. Katan. 1979. Solar heating of the soil for the control of Verticillium dahliae and PratyIenchus thornei in potatoes. pp. 431-433. In: Soilborne Plant Pathogens. B. Schippers and W. Gams (eds.). Academic Press, New York. 686 pp.

4. Grinstein, A., J. Katan, Razik-Abdul, C. Zeydan, and Y. Elad. 1979. Control of Sclerotium rolfsii and weeds in peanuts by solar heating of the soil. Plant Dis. Reptr. 63:1056.

5. Katan, J., A. Greenberger, H. Alon, and A. Grinstein. 1976. Solar heating by polyethylene mulching for the control of diseases caused by soil borne pathogens. Phytopathology 66:683-688.

6. Pullman, G. S., J. E. DeVay, R. H. Garber, and A. R. Weinhold. 1981. Soil solarization effect on Verticillium wilt of cotton and soil-borne populations of Verticillium dahliae, Pythium spp., Rhizoctonia solani and Thielaviopsis basicola. Phytopatholgy 71:954-959.

7. Rubin, B. and A. Benjamin. 1983. Solar heating of the soil: Effect on weed control and on soil incorporated herbicides. Weed Science 31:X19-825.

8. Siti, E., E. Cohn, J. Katan, and M. Mordechai. 1982. Control of Ditylenchus dipsaci in garlic by bulb and soil teatments. Phytoparasitica 10 (2):93100.

9. Southey, J. F. 1970. Laboratory Methods for Work with Plant and Soil nematodes. Tech. Bull. 2, 148 pp. HMSO, London.

10. Stapleton, J. J. and J. E. DeVay. 1984. Thermal components of soil solarization as related to changes in soil and root microflora and increased plant growth response. Phytopathology 74:255-259.

11. Stapleton, J. J. and J. E. DeVay. 1986. Soil solarization: A non-chemical approach for management of plant pathogens and pest. Crop Protection 5:190-198.

Table 1. Effect of solarization and timing on the control of nematodes on onion at Fayoum, 1985/1986

1 Pi = Initial nematode population; Pf = Final nematode population; RF = Pf/Pi.

Table 2. Effect of solarization on the control of nematodes on onion and broad bean at Fayoum (Tamya farm) 1985/1986

1 Pi = Initial nematode population; Pf = Final nematode population; RF = Pf/Pi.

Table 3. Effect of solarization on the control of nematodes on onion, bean, and rape (rayed farm); and tomato (Manaef farm) at Ismailia, 1985/1986

Pi = Initial nematode population; Pf = Final nematode population.

Table 4. Effect of polyethylene mulching of soil and herbicide treatments on broad bean in soil naturally infested with nematodes at Giza, 1986/1987

Table 5. Effect of solarization for control of nematodes on onion and strawberry at Beni-Sweif, Fayoum, Qalyobia and Ismailia localities

1 Pi = Initial nematode population; Pf = Final nematode population; RF = Pf/Pi

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