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In this article we will discuss about:- 1. Symptomatology of Sclerotinia Sclerotiorum 2. Pathogenicity Test of Sclerotinia Sclerotiorum 3. Morphological & Cultural Characters 4. Germination of Sclerotia of Pathogen 5. Environmental Factors 6. Screening of Varieties/Germplasm 7. Soil Solarization 8. Soil Amendments 9. Biological Control 10. Chemical Control.
Contents:
- Symptomatology of Sclerotinia Sclerotiorum
- Pathogenicity Test of Sclerotinia Sclerotiorum
- Morphological & Cultural Characters of Sclerotinia Sclerotiorum
- Germination of Sclerotia of Pathogen
- Environmental Factors of Sclerotinia Sclerotiorum
- Screening of Varieties/Germplasm against Sclerotinia Sclerotiorum
- Soil Solarization of Sclerotinia Sclerotiorum
- Soil Amendments of Sclerotinia Sclerotiorum
- Biological Control of Sclerotinia Sclerotiorum
- Chemical Control of Sclerotinia Sclerotiorum
1. Symptomatology of Sclerotinia Sclerotiorum:
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The most important fungal disease is stem and pod rot caused by Sclerotinia sclerotiorum (Lib.) de Bary, a comparatively new disease observed for the first time in Assam.
A search for the literature revealed that, so far a little work has been done on this devastating disease, except for report of its occurrence, no information is available on etiology, mode of perpetuation, source of resistance, chemical and biological control of the disease, so the information available for the management of Sclerotinia sclerotiorum causing diseases in the different plants have been cited.
Morris and Swingle (1921) reported that the symptom on the sunflower produced by Sclerotinia sclerotiorum as development of scaly lesion on stem at soil level and rotting of root and back around the crown. The leaves become yellow and the infection spread up to stem and ultimately entire plant died.
The symptoms of the disease on the lettuce crop caused by Sclerotinia sclerotiorum as wilting of outer leaves only giving the plants as one sided appearance of stress. A soft watery decay followed and subsequently white mycelium produced in and around the affected plants. Harter and Zaumayer (1977) observed symptom on bean infected by Sclerotinia sclerotiorum in the form of irregular, water-soaked spots on the stem followed by formation of similar spots on branches and leaves.
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Naito (1986) observed the symptom on sugar-beet caused by Sclerotinia sclerotiorum as dark green to light brown discoloration with irregular soft rot on flower, stem and leaves.
According to Ahmad and Mouscler (1987) yellowing, defoliation and drying of lentil occurred when infected with Sclerotinia sclerotiorum in southern Syria.
Mirza and Ahmad (1988) observed that the head of affected cabbage plants in the experimental field at Islamabad were covered with a white mycelial growth associated with large black sclerotia. On the basis of cultural and sclerotial characters of the pathogen, it was identified as Sclerotinia sclerotiorum.
Symptoms on Ajowan infected with Sclerotinia sclerotiorum appeared as wilt in entire root system showed extensive rotting. The infection results in death and decay of plants, numerous sclerotia of different size produced by the pathogen were found in pith region of dead plants. Infection occurred on the stem at the soil level and on the foliage at their bases or on the foliage that came in contact with soil.
Verma and Verma (1993) observed the symptoms of disease on safflower caused by Sclerotinia sclerotiorum as infected plants showed wilting, brown discoloration and rotting at the base of capsule. Dense white mycelia growth and black sclerotia were observed inside infected plants, a whitish mycelia.
Curd rot and different types of symptoms of appeared on cauliflower plants infected with Sclerotinia sclerotiorum.
Upadhyay (1994) observed a severe wilt disease on Amni majus plants. Affected plants showed wilting of inflorescence and yellowing of leaves, a whitish mycelia growth appeared at ground level, black sclerotia were observed at soil level also on plant and root.
Symptoms on stem and fruit rot caused by Sclerotinia sclerotiorum in pepper plants were observed for first time by Yanar (1996).
Ram Palat (2001) observed the symptoms of the disease on Rajmash crop caused by Sclerotinia sclerotiorum as the infected parts of the plants became water-soaked, turned brown and finally straw colored followed by appearance of thick white mycelia mat on the affected surface and discoloration of underlying tissues at the soil level or at little higher above the soil.
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Dense white growth of fungus with sclerotia were seen. On splitting of affected parts a number of sclerotia could be seen and finally affected plants wither- off.
Kumar (2003) observed symptom of disease on sunflower caused by Sclerotinia sclerotiorum as water-soaked spots on the affected portion followed by discolouration of tissues leaves, turned yellow and finally plants wither away. On splitting the affected portion a number of sclerotia may be noted. The grains either not developed or under developed due to infection.
Molinero Ruiz and Melero Vara (2003) studied the symptoms on sunflower due to stem and root rot and wilt diseases caused by Sclerotinia minor as light brown, water-soaked lesion developed on the collar of infected and extended along the stem, affecting the pith and causing early and sudden wilt. White mycelia and sclerotia (5-2 mm long) formed in the pith of stem.
Brinjal plants infected with Sclerotinia sclerotiorum showed tissues necrosis, wilting, shedding of affected stem, yellowing and dropping of leaves. On fruit, formation of water- soaked spots and then the white mycelia growth and sometimes sclerotia formation may be seen.
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2. Pathogenicity Test of Sclerotinia Sclerotiorum:
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Neledu (1998) described pathogenicity of isolates of S. sclerotiorum on soybean and amaranthus. They observed that isolates with small sclerotia (3-5 mm) were more virulent than those with large sclerotia (10-15 mm).
Yanar (1996) demonstrated the pathogenicity of S. sclerotiorum isolates by artificial stem inoculation of 8 weeks old pepper with mycelia grown on autoclaved agar medium.
Garibaldi (2001) observed for the first time, sudden wilt in commercial planting of hybrid Gazania sp. Initial symptoms included stem necrosis at the soil level and yellowing and tan discolouration of leaves. As stem necrosis progressed, infected plants wilted and died.
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Wilt followed by soft rot occurred within a few days on young plants. Necrotic tissues became covered with white mycelia that produced dark spherical sclerotia. Sclerotinia sclerotiorum was consistently recovered from infected stem of Gazania.
Bag (2003) reported Schizantlius wisetonensis (butter fly flower) showing symptoms of wilt and dry stem rot was associated with Sclerotinia sclerotiorum. This is the first report of this pathogen on Schizanthus wisetonensis.
3. Morphological & Cultural Characters of Sclerotinia Sclerotiorum:
Narasimhan and Thirumalachar (1959) noted that Sclerotinia sclerotiorum grew rapidly on potato dextrose agar (PDA), Czapek’s (Dox) agar and Standard nutrient agar media. On other solid media such as wheat, peanuts, meal alone or in combination with agar, the mycelia development was dense and greater number of sclerotia was produced than those on Potato dextrose agar.
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In Richard’s agar medium, growth of fungus was dense development in white floccose mat. While describing the structure of apothecia of the fungus, Kosaik and Willet (1975) found that hymenium is made of asci and paraphyses.
The asci measured 119-162 x 6.5-10.9 µm in size. They were inoperculate, cylindrical, narrow, round at the apex with 8 ascospores in each ascus, each ascospore being hyaline, ellipsoid, smooth walled and measuring 10.2 -14 x 6.4-7.7 pm in size. Paraphyses were about 100 pm long, 1-2 pm in diameter multinucleate, sparsely septate and occasionally branched at base.
Willet and Wong (1980) studied the morphological characters of Sclerotinia sclerotiorum. Mycelium measuring 9-18 pm in diameter with lateral branches had the diameter less than the main hyphae. Mycelial growth rate on solid media was fast and formed moderate to abundant amount of aerial mycelium.
The sclerotia were black, round or semi-spherical in shape measuring 3-10 mm in size. The sclerotia could be easily detached from stalked apothecia and several apothecia grew from single sclerotium
Gangopadhyay (1984) observed that large and smaller sized sclerotia were in Corn meal agar. Sclerotia production showed that cauliflower agar contained all the necessary compounds in the available form for its optimum multiplication from sclerotia to sclerotia.
Singh (1998) reported that the natural media from seed extract of the host supported good growth and development of Sclerotinia sclerotiorum as compared to synthetic growth substrate. Addition of dextrose sugar in seed decoction enhanced the process of growth and development of the fungus.
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4. Germination of Sclerotia of Pathogen:
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Sclerotial germination and formation of mature apothecia were best in pure sand. Of mixture, sand and clay at 3:1 gave the best results, sclerotia germination decreased with increase in the proportion of clay. Sclerotia germination was well on the surface of all the soil types, germination decreased with increase in depth.
Tores and Moreno (1987) applied substrates like earth, peat, sand and filter paper and found abundant apothecia production on it (filter paper). Mylchreest and Wheeler (1987) grew an isolate of S. sclerotiorum isolated from oilseed rape on sterilized wheat grain for 3 weeks at 20°C, followed by 4 weeks at 4°C. Harvested sclerotia were buried 1 cm deep in compost and kept at 10°C until apothecia stipes appeared.
Singh (1991) in his study found that physic-chemical properties and ion exchange capacity of soil sample influenced apothecial germination of sclerotia of S. sclerotiorum. Carpogenic germination was reduced in soil having higher level of organic carbon. pH had no effect on germination.
Percentage germination enhanced with increasing amount of sand in the soil samples and was reduced with increasing amount of silt and clay.
Uniform and non-aggregated sclerotia of S. sclerotiorum were produced in large numbers in a medium consisting of wheat grain and perlite. Sclerotia of 5 out of 7 isolates germinated and produced fertile apothecia when incubated in moist perlite under near U.V. radiation. Kopmans (1993) noted that sclerotia of S. sclerotiorum when buried in sand and clay soil and were exposed to different irrigation schedules, most rapid germination occurred after 30 days in continuously irrigated soil.
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A break in irrigation delayed the apothecia formation for about the same period as the length of the break. Huang and Kozub (1994) studied the germination of immature and mature sclerotia produced on Potato dextrose agar medium at 20°C. Immature sclerotia rapidly germinated myceliogenically producing hyphae but mature sclerotia germinated carpogenically with the production of apothecia directly.
Singh (1995) studied the carpogenic germination of sclerotia of Sclerotinia sclerotiorum in soil samples collected from different places in U.P, India. The percentage germination was reduced in soils that contained high concentration of Na+, Ca++, Cl– and SO4– and very low concentration of Mg++ and HCO3–. There was no effect of pH.
Host-Range of Pathogen:
Butler and Bipsy (1931) reported 24 plant species as the hosts of Sclerotinia sclerotiorum and some of them were Brassica spp., Eureca sp., Capsicum sp., Sesame, Coriander, Hibiscus sp., Chickpea, Sunflower and Tomato.
Roy (1973) studied the host range of Sclerotinia sclerotiorum and listed 27 hosts, of which 13 were new records for India. Kumar (2003) conducted host range study with 24 plant species from 9 families (chenopodiaceae, compositae, Brassicaceae, cucurbitaceae, euphorbiaceae, leguminoceae, malvaceae, solanaceae and umbelliferae) including field crop and weed species also, inoculated with mycelia suspension of Sclerotinia sclerotiorum.
The result showed that Sclerotinia sclerotiorum was not host specific but had a wide host range. The infected plants belonging to Brassicaceae, Leguminoceae and Umbeliferae developed the inoculums before and after sowing of broccoli plants, thus facilitating the secondary infection. A number of plant species were reported as host of Sclerotinia sclerotiorum from time to time by many workers.
5. Environmental Factors of Sclerotinia Sclerotiorum:
Adam (1975) conducted a laboratory experiment and showed that normal soil temperature (10-30°C) did not adversely affect the survival of sclerotia but a constant soil temperature of 35°C for weeks reduced the survival of sclerotia of Sclerotinia sclerotiorum.
Sharma and Sharma (1985) reported that the temperature of 20-25°C and RH of 90-95% were congenial for disease development in cauliflower caused by Sclerotinia sclerotiorum and three independent variables (temperature, rainfall and humidity) were of significance for disease development in 1977-79 crop season.
Sigvald and Wearn (1992) observed that the low temperature during spring and summer and considerable rainfall in early summer favoured the Sclerotinia stem rot. Temperature between 0-30°C followed by intermediate relative humidity was responsible for production of apothecia in Sclerotinia spp.
Despande (1995) observed that in semi-arid regions, the wetness of leaves or other plant parts is essential for development of white mould disease caused by Sclerotinia sclerotiorum in dry edible beans.
The leaf wetness period in the dense canopy exceeded than that of open canopy by 14%, corresponding to higher white mould severity. The respective white mould severity for dense and open canopies was 93 and 30% in 1990 and 73 and 10% in 1991. Boland (1997) studied that in white mould, apothecia appeared within the crop in late June.
During two weeks apothecia occurred in the field soil when temperature were in the range of 15-30°C and metric potential were generally more than 5 bars. Li (1997) found that sclerotia germination was satisfactory at temperature between 25-28°C where as it was reduced at other temperatures tried in experiment.
6. Screening of Varieties/Germplasm against Sclerotinia Sclerotiorum:
Sharma (1982) screened 8 genotypes of cauliflower by applying 50 ml of a homogenized suspension adjacent to the stem of 52 month old plant of each genotype and also dry leaf inoculation. Master Osena and Avans showed least plant infection and minimum leaf lesion size.
From 1981-83, 70-80 commercial cultivars/breeding lines and plant introduction lines of Phaseolus vulgaris L. were screened for resistance against Sclerotinia sclerotiorum in experimental plot in Ontario, Canada, of which 5-5 were found to be moderately to highly resistance.
Jao (1994) evaluated more than 800 cultivrars of soybean in the field for resistance against Sclerotinia sclerotiorum and found most resistant as Dong, Mong 37, Dong Mong 39 No. 30 and 9 others.
Disease incidence was recorded at harvesting time. Singh and Kalda (1995) screened 69 cauliflower lines for resistance to Sclerotinia rot caused by Sclerotinia sclerotiorum. Under artificial screening the leaf tissue of susceptible lines began rotting at the site of inoculation, only four winter cultivars i.e. Janovan, EC 103576, EWAWH and EC 177283 were resistant.
Miao (1995) conducted an experiment on evaluation of 365 accessions of soybean for resistance against Sclerotinia sclerotiorum and found 24 resistant and 15 moderately resistant accessions. Middleton (1995) conducted field test for resistance to infection by Sclerotinia sclerotiorum on selection of Phaseolus vulgaris.
They confirmed the relative resistance of accessions Rico 23, Ex Rico 23, NY 5223 and HY 5268, new source of resistance were identified in accession PER 257, Bat 447-1C, BC 17, Xan 170, A 480, Pad 22, Flair, Pearly, Wongi, Shim, Uribe Redondo and P 1263958. Akem and Khabbabeh (1999) evaluated 15 chickpea genotype against Sclerotinia sclerotiorum causing stem rot of chickpea.
Out of 15 genotype 5 exhibited some resistance to sclerotinia stem rot and this was shown by delayed initial infection, restricted lesion development and no sclerotia production. Yanar and Miller (2003) conducted an experiment to determine the level of resistance on 12 commercial pepper cultivars and 110 Capscicum spp. accessions to Sclerotinia sclertiorum by using limited term and ascospore inoculated method.
None of the commercial cultivars tested was resistant to Sclerotinia sclerotiorum. Stem rot incidence among Capsicum spp. accessions tested by ascospore inoculation ranged from 0-100%. Fifty-eight accessions has significant less stem disease than the susceptible commercial cultivar, Marengo.
7. Soil Solarization of Sclerotinia Sclerotiorum:
Katan (1976) conducted two field experiments with eggplant and one with tomato and found that mulching with polythene sheets prior to planting reduced Verticillium wilt by 25 to 95%, controlled weeds, improved plant growth and stand and increased yield. The method considered was less costly than fumigation and non-hazardous.
Chen and Wu (1990) observed that Sclerotinia. sclerotiorum was completely killed at 4°C after 3-4 hours, at 35-40°C after 10-14 hours and was unaffected at 35°C when soil moisture was 40% maximum water holding capacity, sclerotia were treated in.45, 40 or 35°C for 4 hours/ day. The treatment killed all the sclerotia in 4 days.
Phillip (‘1990) studied that the soil solarization reduced the population of Sclerotinia sclerotiorum in soil and reduced the ability of the surviving sclerotia to form apothecia. The greatest reduction occurred in the top 5 cm layer of soil but significant effects were seen at 10 and 15 cm depth.
Deshpande and Tiwari (1991) conducted an experiment in pots to study the effect of soil solarization during summer on Sclerotinia rolfsii, the collar root pathogen of betelvine. All the betelvine cuttings planted in solarized pots were found free from collar rot disease (mortality 0.0%).
Cartia (1994) also conducted an experiment in the laboratory and field to investigate the effect of temperature on the viability of sclerotia of Sclerotinia sclerotiorum and found that the recovery, and myceliogenic germination of sclerotia on Potato dextrose agar buried in the soil at depth of 5, 15 and 30 cm were reduced after 15 and 30 days of soil solarization.
High mortality of sclerotia was achieved after 30 days as soil temperature increased 6-7°C above that of the control. Similar results were obtained in the laboratory.
Solarization for 30 days and 15 days affected recovery and viability of sclerotia in relation to depth of sclerotia burial in the soil. Krishna Rao and Krishnappa (1995) observed the effect of soil solarization for the control of Meloidogyne incognita and Fusarium oxysporum f. sp. ciceri. complex pathogen to chickpea.
Solarization by covering the soil with clear transparent polythene sheet for 6 weeks during hot summer months showed an increase in soil temperature (8°C) and conservation of moisture (5%) when compared to unsolarized control.
Increased soil temperature coupled with soil moisture resulted in a significant reduction in population density of M. incognita (58.1%), F. oxysporum f. sp. ciceri (80.80%), weeds (80.60%) and their dry weight (90.50%).
Soil solarization with transparent polythene mulch (25 micro meter) was effective to control damping off pathogens of different vegetable crops in the nursery. Mulching with polythene resulted in 13.5°C higher temperature at 8 cm soil depth with an average maximum temperature of 49.7°C.
Swaminathan (1999) in their study found that soil solarization reduced the viability of sclerotia of Sclerotinia sclerotiorum which were buried in the soil at a depth of 10 cm, solarization for 8 weeks had a greater effect than for 4 weeks.
Sclerotial viability in solarized plots were reduced by 52, 8 and 0% as compared to 95, 53 and 89% for non- solarized plots, respectively. Average maximum temperature recorded for solarized plots over the trial period ranged from 33 to 35°C, temperatures were approximately 8-10°C lower in non-solarized plots.
8. Soil Amendments of Sclerotinia Sclerotiorum:
It has been observed that disease caused by Sclerotinia sclerotiorum and number of sclerotia per plant can be lowered down by the application of 10-40 tonnes of FYM/acre cauliflower seed crop. The use of higher dose of nitrogen (60-100 kg/ha) enhanced the incidence of stem rot of sunflower caused by S. sclerotiorum while higher phosphorus and normal nitrogen level reduced the disease incidence.
Singh (2000) observed that soil amendments like pyrite, gypsum at the rate 2.0 tonnes/ ha and mustard cake, castor cake, neem cake, paddy straw and wheat straw at the rate 20.0 tonnes/ ha were effective against Sclerotinia stem rot of bishop weed and maximum disease reduction was obtained by pyrite followed by neem cake, mustard cake and gypsum.
An indoor study was conducted to assess the potential of organic residues with or without biological control agents, as soil amendments for control of carpogenic germination of sclerotia of Sclerotinia sclerotiorum and production of apothecia.
Of the 87 organic residues tested including crop straws, animal manures and processed by-products, 46 inhibited carpogenic germination of sclerotia when applied to soil at the rate of 1% and three were effective at 5%.
Organic soil amendments combined with biological agents such as Coniotliyrium minitans and Trichoderma virens enhanced the control of apothecia of Sclerotinia sclerotiorum of killing of sclerotia through mycoparasitism.
Date of Sowing:
Singh and Singh (1984) sown the seeds of Cicer arietinum in Sclerotinia sclerotiorum sick field at weekly interval on 15th October to 10th December. It was noted that yield was higher in November sown crop. Similarly Singh (1995) reported that early sowing (October, 21) of pea resulted in highest incidence of disease followed by November, 2 and November, 14.
Sowing in last week of November resulted in minimum disease development and increased yield. Late sown crop after November resulted in no disease development with reduced yield.
The disease of Trifolium alaxandrium controlled by sowing crop in November rather than in late September-October. Singh and Tripathi (1995a) observed a significant reduction in disease severity caused by Sclerotinia sclerotiorum in late sown crop of sunflower. It suggested that a sudden increase in temperature might be responsible for the increase in disease.
Evaluation of Botanical Products:
Kurucheve and Padmavati (1977) selected five plant products and assayed for fungitoxicity against Pythium aphanidermatum, the causal organism of damping off of chillies. Among them, extract from Allium sativum bulb (1.0%) recorded the minimum mycelia growth (176.00 mg) followed by Law son ia inermis leaf extract.
Maximum per percentage of germination, growth and vigour of chilli seedlings were also observed with garlic bulb. Moore and Atkins (1977) observed that garlic extract was shown to have fungicidal and inhibitory action against several fungal species including some that caused mycoses.
The effect of aqueous leaf extract of garlic on the two pathogens viz. Sclerotinia sclerotiorum and Fusarium oxysporum f. sp. ciceri on Cicer arietinum studied by Singh (1979) and found that the growth of pathogen reduced greatly at 7000 and 5000 ppm, respectively. Seeds treated with garlic extract before sowing produced wilt free seedlings.
Singh (1994) isolated seven alkaloids and tested against germinating ascospores of Sclerotinia sclerotiorum, stem rot pathogen of chichpea. All were inhibitory to some extent but protopine nitrate from Fumaria indica at the rate 2000 µ litre/m was the most effective.
Dohroo and Gupta (1995) studied that neem oil has fungicidal properties that were inhibiting to Sclerotinia, Rhizoctinia and Sclerotium. Chattopadhyay (2002) conducted an experiment on evaluation of efficacy of 10 plant extracts against Sclerotinia sclerotiorum causing sclerotinia rot of Indian mustard and found that among the botanicals, bulb extract of Allium sativum yielded the best results.
9. Biological Control of Sclerotinia Sclerotiorum:
Zazzerini (1987) reported that Bacillus subtilis isolated from rhizoshere of sunflower plant infected with Sclerotinia sclerotiorum gave good result in inhibiting the sclerotia formation. Sesan and Csep (1994) found that soil treated with Coniothyrium minitans gave similar disease control as seed treatment with Trichoderma viride (isolate Td 50) and Trichodex 25 WP (T harzianum) T-39 or chemical treatment.
The biological agents like Coniothyrium minitans and Gliocladium virens were assayed by Budge (1995) against Sclerotinia sclrotiorum and found that C. minitans was most effective in controlling the disease.
Expert and Digat (1995) demonstrated that a significant protection of sunflower against the Sclerotinia wilt caused by Sclerotinia sclerotiorum could be obtained by seed bacterization with some Pseudomonas fluorescens and Pseudomonas putida strains. A total 14.8% of strains examined, clearly exhibited mycelia growth of Sclerotinia sclerotiorum in vitro and 44% produced Cyanide in vitro.
Strain GL 92 and T 1-5 of P. fluorescens and P. putida, respectively gave satisfactory level of root colonization. Gerlagh (1995) also conducted a five year experiment on biocontrol of Sclerotinia sclerotiorum with the mycoparasite Coniothyrium minitans.
Application of the mycoparasite, C. minitans to bean, carrot, chicory and potato crops grown in rotation in soil infested with sclerotia of Sclerotinia sclerotiorum led to reduction of upto 90% in the number of the apothecia of the pathogen. 90% reduction in disease incidence in carrot crop was also reported.
Mc Laven (1996) found that application of Coniothyrium rninitan to soil at seedling time reduced apothecia production of sclerotia of Sclerotinia sclerotiorum under the canopies of bean, rape, wheat and barley. The application of Talaromyces flavus was also effective and combination of C. minitans and T. flavus as effective or less effective than C. minitans alone.
Jones (2000) observed that Coniothyrium minitan isolate Conio when applied as maize meal pertile solid substrate, soil incorporation at full application rate (1012 cfu m-2) gave significant control of Sclerotinia disease of lettuce crop caused by Sclerotinia sclerotiorum.
It significantly reduced sclerotial germination and apothecial production compared with the control. Huang (2000) evaluated the effectiveness of 5 indigenous bioagents (Coniothyrium minitan, Talaromyces flavus, Trichothecium roseum, Trichoderma virens and Epicoccum perpurascens) in the field for the control of white mould, Sclerotinia sclerotiorum of Phaseolus vulgaris.
The incidence of white mould in dry bean had significantly reduced by all five biological control agents. Among all these, C. minitans and E. perpurascens were the most effective agents and they reduced the incidence of white mould by 56 and 43%, respectively.
Similarly, Singh (2003) also evaluated four bioagents namely Coniothyrium minitan, Trichoderma viride, Gliocladium virens and Bacillus subtilis against Sclerotinia sclerotiorum causing stem rot of Ajowan in the pot experiment and found that all the bioagents inhibited the growth of Sclerotinia sclerotiorum in Ajowan plants, maximum decrease in percentage incidence was observed in C. minitans followed by T. viride.
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10. Chemical Control of Sclerotinia Sclerotiorum:
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Pegg (1972) tested five fungicides for the control of Sclerotinia sclerotiorum in French bean. Among them, benomyl (1.0 g/1) gave effective control when applied at both full bloom and petal stage. Bean field sprayed with benomyl did not develop Sclerotinia rot in the storage. Spraying of 0.1% vitavax at 10 days interval gave almost complete control of white rot disease of seed crop of cauliflower caused by S. sclerotiorum (Singh and Gangopadhyay, 1984).
Kochman and Langdon (1986) stated that sunflower seed lots infested with the sclerotia of Sclerotinia sclerotiorum provided a means of dispersal of the fungus.
When sclerotia were dusted or dipped with 19 formulations, benomyl 50% + lindane 1%, thiobendazole wettable powder, thiobendazole 45% water based flowable, iprodione 50%, thiophanate 70% and omadion 50% completely inhibited germination when in direct contact with organism.
Nagy and Ratkos (1986) reported that germination was improved and disease incidence during germination reduced by ultrasonic treatment.
TMTD (thiram)+ agrocit was most effective fungicide combination for seed dressing while in pots infected with Sclerotinia sclerotiorum, rovral (iprodione), thiram and chemical containing copper and zinc gave best results. Yarden (1986) reported that combined application of benomyl and thiram for control of Sclerotinia sclerotiorum in soils.
The effect of the combined fungicidal treatments was expressed by a reduction of sclerotial germination, rate of apothecial production and delay in apothecial emergence. Herd and Phillips (1993) observed the best control of curd rot of cauliflower caused by several fungi including Sclerotinia sclerotiorum by the application of captafol, mancozeb, chlorophenical streptocycline and boric acid under natural condition.
Singh (1994) observed that Sclerotinia rot of mustard could be managed by seed treatment with benomyl and carbendazim when sprayed alone or in combination with other fungicides. Seed treatment followed by spraying with benomyl or carbendazim was recommended practice.
Fayalle (1995) conducted an experiment on stem rot of sunflower caused by Sclerotinia sclerotiorum and found that spraying of vitavax, topsin-M, indofil M-45 and thiram could minimize the disease to a greater extent.
Singh and Kapoor (1996) studied the effect of 9 systemic and non-systemic fungicides on mycelial growth, sclerotial production, ascospore germination and myceliogenic and carpogenic germination of sclerotia of Sclerotinia sclerotiorum from pea.
Carbendazim (25 micro gram/ml) gave complete inhibition of mycelial growth on Richard’s agar. No sclerotia were produced with carbendazim (50 micro gram, 37 micro gram/ml), captan (250 micro gram/ml) and metalaxyl + mancozeb (50 micro gram/ml). All the test fungicides significantly reduced sclerotial germination.
Soil application of carbendazim (500 micro gram/ml) resulted in 15 per cent myceliogenic and 20.7% carpogenic sclerotial germination, captan ranked second.
Sharma and Kapoor (1997) conducted an experiment in vitro for evaluation of carbendazim, triadimefon, trimorphine, iprodione, mancozeb, dinocap and elemental sulphur for inhibition of mycelial growth, sclerotial germination and ascospore germination of Sclerotinia sclerotiorum from pea, and reported the most effective one was ipridione followed by triademefon.
The maximum inhibition was at 0.5% concentration of iprodione, triademefon and dinocap. Pathak and Godika (2002) studied the fungicidal efficacy of different fungicides as a seed dressing. The mustard seeds (var. Varuna) were inoculated with conidia then dressed at the rate 2 g/kg with one of six fungicides viz. carbendazim, mancozeb, thiram, ridomil MZ (Mancozeb + Matalaxyl) apran SD and bayleton.
All fungicides performed better than the untreated control but ridomil MZ gave maximum germination (44%) with zero post emergence mortality, carbendazim showed 40% germination and 60% post emergence mortality.
