|Archived at http://orgprints.org/00001122|
Anders Borgen, PhD. student.
Department of Agricultural Sciences.
Royal Vet.- and Agricultural University.
Agrovej10, 2630 Taastrup,
Denmark. (E-mail: anders(at)ecoweb.dk).
Mehrnaz Davanlou, Green guide,
Kongens Enghave Bydel, Wagnersvej 19,
2450 Copenhagen SV,
Denmark. (E-mail: md.kgse(at)ipost.kk.dk).
Common bunt (Tilletia tritici syn. T. caries) is a
significant seed borne plant disease in organic agriculture. General measures in
ecological crop protection like crop rotation and manuring practice has in
practice failed to control this disease, and direct seed treatment therefore
seems to be necessary to ensure yield and food quality. Current study indicate
that biological control can give successful control without negative effects on
seed germination vigour. A combination of biocontrol agents and milk powder
improves the effect of the biocontrol. Application of compost to the soil
increases the frequency of this disease. The potential role of biocontrol within
the principles of ecological disease management is being discussed.
Keywords: Tilletia caries, Tilletia tritici, common
bunt, stinking smut, Effective microorganisms, seed treatment, compost,
biocontrol, ecological agriculture
Common bunt (Tilletia tritici syn. T. caries) is potentially one of the most devastating plant diseases. The fungus grows systemically in infected wheat plants (Triticum aestivum) and develop ovaries filled with fungal spores (bunt balls). During threshing, the bunt balls break and the spores attach to the healthy seeds during seed handling. When spore-contaminated seeds are sown, the spores germinate synchronously with the seeds and infect the germinating plants.
Simple nitrogen components like tri-methyl-amine evaporate from the fungal spores (Ettel and Halbsguth, 1963), giving bunt-infested grain a smell like rotten fish. This is also the reason for the disease to be called stinking smut. Only a small number of infected heads in the field will reduce the quality of the wheat because of the stench of the bunt spores. Control of common bunt is therefore crucial for the production of quality wheat. In a Swedish experiment, 50% of the people could smell the presence of only 1000 spores per gram of seeds (Johnsson, 1991). This level can occur with a field frequency of less than 0.1% infected heads (Borgen et al, 1992). Ingestion of contaminated grain may also be hazardous to human health as it is for some animals (Westermann et al, 1988).
Common bunt is an ancient plant disease. Spores have been found on 4000 year old seeds from the ancient Mesopotamia (Johnsson, 1990), and it is likely that the disease has been a problem for wheat production ever since its domestication. Since then, the disease has been one of the most intensively treated in plant protection (Woolman and Humphrey, 1924; Buttress and Dennis, 1959; Sharvelle, 1979). Since cheap and effective seed treatments with organic mercury started in the 1920s, research in this disease has been limited. Mercury is now banned in most industrialized countries for environmental reasons, and modern synthetic pesticides have taken its place in the control of bunt.
The multiplication of bunt frequency from year to year will, in untreated seeds, depend on wheat variety and meteorological conditions especially during germination, but is often about 100 fold under Danish weather conditions in susceptible varieties (Borgen et al, 1992). In order to prevent multiplication of the bunt infections from year to year, the sum of all involved control measures must therefore have an efficiency of more than 99%. In conventional agriculture this control level is exclusively reached by seed treatments, and at least in Denmark almost all seed lots of winter wheat are seed treated with pesticides mainly because of this disease (Nielsen et al, 1998). In organic agriculture seed treatment with synthetic pesticides are excluded. Common bunt is therefore potentially a very serious disease for wheat production in organic cropping systems (Piorr, 1991; Borgen et al, 1992 ).
Research in alternative regulation of common bunt is going on in Europe, mainly focussing on different seed treatments like uses of plant extracts, cereal flour, milk powder and other organic compounds, hot water and hot air treatments and antagonistic bacteria and fungi (Heyden, 1997; Spiess and Dutschke, 1991; Becker and Weltzien, 1993; Bergman, 1996; Borgen et al, 1995; Borgen and Kristensen, 1996; Gerhardson et al., 1997; Knudsen et al, 1995). In the tradition of research in organic agriculture, the use of compost and EM (Effective Microorganisms) have played a central role in plant protection, since these products simultaneously attempt to improve soil fertility and create a beneficial microbial soil flora, and thereby prevent development of some plant diseases (Sangakkara et al, 1999; Tränkner, 1993). Furthermore, one of the negative effects of seed treatments is often that seed vigour in terms of germination speed is reduced. Low doses of EM have been shown to improve germination speed (Sangakkara and Attanayake, 1993). Fast and even germination is essential for yield potential also in conventional agriculture, but in organic agriculture the influence is likely to be higher since it also influences the competition with weeds and some pests and pathogens which can not as easy be regulated without pesticides.
Our current experiment aimed to investigate different biological methods for
their potential in control of common bunt in organic agriculture.
MATERIALS AND METHODS
Trials were conducted over three years to screen different biological material and products for their effect on bunt infection and for side effect on germination vigour.
In the first year (1994-5) two field trials were conducted. Seeds of winter wheat (Triticum aestivum, cultivar 'Kosack') were contaminated with dry spores of T. tritici at a dose of 5 g per kg resulting in a spore contamination of 2,291,000 spores per gram seed tested by the ISTA Haemocytometer Method (Kietreiber, 1984). The contaminated seeds were treated either with liquid manure in a dose of 30 ml/kg, or with 130 g milk powder per kg or with both. Seed treatments were done in a spinning-wheel seed-dresser (Hege no. 11). In the second experiment in year 1994-5, seeds were treated with 21,7 g/kg of the commercial product Mycostop containing Streptomyces griseoviridis stain K61 which contains 108 CFU/gram (Lahdenperä, et al 1991). 26 ml/kg water was used as carrier.
Field trials were conducted at Højbakkegård, an experimental farm of the
Royal Veterinary and Agricultural University and located 18 km east of
Copenhagen, Denmark (55º40' N, 12º18' E, 28 m above mean sea level). The soil
type is moreanic sandy loam, and common bunt had not been recorded in the
experimental area on beforehand. Untreated seeds were sown in 8 replications,
and each seed treatment were sown in four replications in 1.25x5 m plots. Heads
in the first and second row in each plot were diagnosed for bunt infection. An
average of 2392 heads were diagnosed for each treatment.
In the second year (1996-7) a field trial was also conducted in which seeds of winter wheat (cultivar 'Pepital') were contaminated with spores of T. tritici at a dose of 5 g per kg resulting in a spore contamination of 1,975,000 spores per gram seed tested by the ISTA Haemocytometer Method (Kietreiber, 1984). Where nothing else is noted, seed samples of 100 g were treated after contamination in a spinning-wheel seed-dresser (Hege no. 11) with milk powder and the biological agents listed below .
A bacterial suspension containing 109 spores per ml of Pseudomonas chororaphidis strain MA 342, were used in a dose of in 300 ml water per kg seed for two hours in a closed plastic bag and afterwards dried with cold air (Gerhardson, 1997). We compared this treatment with the application of lower doses of 150 ml/kg and 40 ml/kg of the same suspension applied in the seed dresser, the last dose both with and without 20g milk powder per kg seed.
EM (Effective Microorganisms) is a commercial product containing 80 microorganisms, the major part being yeast and lactic acid bacteria. EM was applied in a dose of 40 and 150 ml per kg seed, and the lower dose was applied with and without 20g milk powder per kg seed.
To see the effect of metabolites and growth media in the suspensions the doses of 150 ml/kg of both water, EM and the Pseudomonas-suspension were also applied after the suspensions had been autoclaved for 20 minutes at 120 ºC at 0.2 MPa.
'Symbioplex' is a commercial product which according to the list of ingredients contains 5*108 spores per gram of each of the lactic acid bacteria Lactobacillus acidophilus, Bifidobacterium bifidus and Streptococcus thermophillus. This product was applied with and without 20g milk powder per kg seed in a dose of 5g + 20ml H2O per kg seed (total 7.5*109spores/kg).
One strain of Trichoderma harzianum in the commercial product Supresivit, containing 109 bacterial spores per g, was tested in the dose of 2 g/kg. The bacterial powder was added with 30 ml water/kg.
The isolat of Gliocladium roseum IK726 was applied in a lower dose of 2.5*109 CFU per kg seed, and a higher dose at 4.5*109 CFU per kg. 3 ml of inert water was in both cases used as carier. The lower dose was applied with and without milk powder.
Two samples of compost were used. One type was composted garden waste which had been stored for more than one year; the other compost type was from a fresh compost heap of cattle manure and straw. The temperature in the cattle compost heap was about 60ºC at the time of collection, which was three days before seed treatment. Compost extracts were made by mixing the compost with water to give a thick paste ( 50% D.M.) which was filtered through a sieve with ½ mm holes. The concentrations and compositions of active microorganisms in the compost extracts were not measured.
Rumen juice was taken from a cow through a rumen fistulat and was applied at a dose of 40 and 150 ml/kg to the seeds. The lower dose was applied with and without milk powder.
After treatment, seeds were dried in the open air at room temperature, and where more than 40 ml/kg liquid had been added, the treatment was divided into a series of treatments with each application of no more than 20 ml water. The seeds were then dried with the help of a cold air stream. After treatment the seeds were stored at 5 Cº in paper bags. Samples were taken out for a field test which took place 2-6 days after seed treatment. Germination tests were conducted 1-3 months there after.
After sowing, 100g of compost was put into each row of an untreated control, equivalent to 6 t/ha. The compost was placed by hand directly into the rows in close contact with the seeds in the rows.
Germination tests were done as a cold sand tests in plastic plates containing 1.5 kg sand with water (65ml H2O/kg quartz sand). 100 seeds were sown in each of three replicates at a depth of 1.5 cm and at temperature of 10 Cº. Emerged plants were counted over 3 consecutive days.
Each treatment was sown in rows of 1.25 m with 10 replicates at Højbakkegård.
In each treatment, an average of 1869 heads in each treatment were diagnosed for
bunt infection based on visible macro-symptoms after heading.
In 1998-9 a container experiment was conducted using combinations of seed and
soil treatments with EM. l ml EM was applied on the 18th August 1998 to 30x40 cm
boxes (=83 l/ha) containing 18 l prefertilized peat soil (Pinstrup Whole Mixture
no. 2). Application was repeated on the 26th of August. EM was applied in a
1:500 water solution; the rest of the treatments receiving only water. The 21th
of September seeds of the spring wheat cultivar 'Cadenza' contaminated with
951,000 spores per gram seed, were treated with EM, and two days after here sown
with 16 seeds in each of 20 boxes for each treatment. Seed treatment included
concentrated fresh EM at a dose of 20ml/kg and a water-diluted solution of 1:200
at the same dose. The boxes were placed in open air from the 18th August when
the first soil application was done until the end of November, when the boxes
were brought into a greenhouse. Plants were then grown to the heading stage and
were then diagnosed for bunt infection. The same germination test was conducted
as in the field trial.
RESULTS AND DISCUSSION
Results from the field experiments are presented in Table 1 and 2. In addition to the presented results in Table 2 the recommended dose of Pseudomonas MA 342 of 300 ml/kg gave a reduction in bunt infection of 96.2% and the autoclaved treatment 150ml/kg a reduction of 58.1%. The autoclaved treatment of EM 150 ml/kg resulted in a reduction of 76.5%. All these effects were statistically significant (p<0.001 when tested against untreated controls by a Generalized Linear Model (GENMOD-procedure in SAS ver. 6.12. ), as was a decrease in germination vigour for the seed treatments above when tested by the Generalized Linear Mixed Model (GLIMMIX procedure in the software SAS ver. 6.12).
Results from the container experiments are presented in Table 3. Both seed
treatments resulted in a minor, but statistically non-significant decrease in
The principles of organic agriculture are driven by an attempt to promote beneficial life forms, rather than directly to kill damaging ones. Killing organisms always creates a biological vacuum, which may be the basis for migration of other possibly damaging organisms. The killing of pathogens also often includes killing of beneficial organisms which may help in protecting the plants from pathogens (Neergaard, 1977). Hence, the fundamental principles of ecological disease control is to optimize growth conditions for the plants rather than to kill the pathogens. This principle includes adequate crop rotation, resistant varieties, mixed cropping, balanced plant nutrition and the aerobic composting of manure (IFOAM, 1998). However, these principles only have a limited potential in the control of common bunt.
Being a seed borne disease, crop rotation only has a very limited effect against common bunt. Spores can survive in the soil for an extended period of time and infect wheat later in a rotation (Johnsson, 1990; Borgen and Kristensen, 1997). Crop rotation is therefore important to prevent uninfected crops from being infected, but it has no influence in preventing the multiplication of the disease from year to year in an already infected seed lot. Being a systemic disease, plant nutrition has very limited effect on the disease once the plant is infected. Breeding for resistant varieties has a potential, but for the time being, the variety Stava is the only variety available in Denmark known to be fully resistant, and this variety is not optimal for Danish meteorological conditions. In many regions of the world the situation is the same. Wheat grown for baking purpose also sets strong limitations for the choice of varieties and the possibilities for crop mixing.
The use of biological control of pathogens in organic agriculture implies a dilemma. On the one hand it is a pesticide-free control measure that promotes beneficial life-forms rather than actively kills pathogens. On the other hand there may be problems connected to the use of some biological control forms parallel to problems related with pesticides. In organic agriculture e.g. plants juices can be used in plant protection, but single chemical compounds isolated from plants or copies hereof are unwanted because they are not used in the concentration and in a chemical and organic environment of which they naturally occur. In the same way the use of a single or a very limited number of microorganisms may disturb the existing balance in the soil flora, and the use of non-indigenes species not already present in the local soil is certainly questionable in organic agriculture. If a biological agent is cheap, easy and effective against a specific problem, the use of this agent has the same problem as synthetic pesticides; it removes the problem, but does not resolve the cause of the problem. If problems are treated rather than prevented, they are likely to show up in another form. If for example a problem with a disease related to mono-cropping is removed by a treatment, other problems related to the mono-cropping system will remain. In the case of common bunt, the mono-cropping system has been still more intensive with narrower crop rotations and less focus on resistance in the period where pesticide seed treatments have been used. Now, where the sustainability of the pesticides are in question, we are 70 years behind in development of sustainable control methods against this disease. With a few exceptions, the use of specific microorganisms in biocontrol of pathogens is therefore excluded in the national standards of the Association for Organic Farming (LØJ, 1999) and many other organic standards, although the international minimum standards which apply in Denmark are open for the possibility (IFOAM, 1998; European Union, 1991). The claim for a specific biological control agent to be included in the organic standards is being discussed among organic farmers in Denmark and in IFOAM. Beside the existing risk assessment from the authorities the discussion centers around the following principles
1) the problem to be treated is significant for the production,
2) the use of biocontrol is necessary in control, meaning that the problem can not be prevented with known methods or be substituted by less critical methods
3) the microorganisms are natural occurring in the local soil already in the actual form. Any use of GMOs are excluded
4) the microorganisms are non toxic for higher organisms including the farmer
5) the use will not irreversible change the balance of the soil micro flora
Even seed treatment is not an optimal way to control plant diseases according to the principles of organic agriculture, it may be necessary until more resistant varieties have been bred and marketed. Our current study shows that seed treatments with biological agents may have a potential against this pathogen in organic agriculture.
The frequency of infections by common bunt are affected by some of the treatments presented in this study, others not. The most promising results are obtained by a combination of milk powder and some of the specific microorganisms, of which Pseudomonas strain MA342 gave almost full control without significant reduction of germination vigour. Pseudomonas MA 342 alone had a significant effect on bunt even at the low dose of 40*109 spores/kg, and the effect was improved considerably in combination with milk powder and came out with a result better than the recommended high dose of 300 ml/kg (300*109 spores/kg) and without significant negative effect on germination vigour.
Pseudomonas MA 342 has been shown in previous studies to control bunt fully at the full dose (300 ml/kg) and with 92,3-98,0% in half dose (Gerdhardson 1997). Considering the small amount of bunt infection in the uncontaminated control plots in 1997 which indicates a minor background infection from soil or machinery, the result confirms previous studies. For commercial purposes the formulation used in this study is now exchanged in favour of an oily suspension using only about 6 ml/kg. This product is sold in many European countries as "Cedomon". However, this product is not approved for winter cereals today (1999), since problems with germination vigour are observed with this formulation. This study indicates that a combination of PseudomonasMA 342 with milk powder may lead to a solution of the problems with germination vigour in the product. Pseudomonas MA 342 is isolated from cereal roots in a Swedish soil and have been found in many other European soils as well (Gerdhardson pers. comm.).
Gliocladium roseum isolate IK726 reduced the bunt frequency in the higher dose of 4.5*109 CFU per kg, but did not significantly do so at the lower dose. In neither doses were negative side effects on germination observed. This indicates that the dose could be increased further and thereby possible improve the effect of the product. This experiment can therefore not exclude the potential of this isolate of Gliocladium roseum as a control agent against common bunt, and further experiments are planned to evaluate this. The current isolat of Gliocladium roseum IK726 is isolated from barley roots a Danish field soil (Knudsen et al, 1995).
Streptomyces griseoviridis strain K61 in the product Mycostop reduced the bunt frequency at the dose of 2.2*109 CFU/kg tested, but this was inadequate to give full control. There might therefore be a potential for this product, but further studies with higher doses or combinations with other treatments are needed to determine the full potential.
Trichoderma harzianum in the product Supresivit did not show any effect on bunt frequency or germination vigour. The dose of 2*109 spores/kg may be too low for the purpose. Further studies with higher doses or combinations with other treatments are needed to determine whether this product has a potential as seed treatment in control of common bunt.
EM1 reduced the frequency of common bunt, but only in concentrations where germination vigour was also reduced. The effect of the product can therefore not be improved by increasing the dose. The product has a low pH, about 3.5 and contains various other metabolites from the microbial activity. The treatment with the high dose of fresh EM only gave an insignificant improvement in effect as compared with autoclaved EM. Lactic acid bacteria are the major group of organisms in EM. The results with Symbioplex containing only lactic acid bacteria shows that this group of bacteria has no effect on bunt infection at least in the concentration of 7.5*109 spores/kg used here. This indicates that the major effect of EM as seed treatment in this study is not biological, but probably chemical.
The container experiment with EM basically confirms the results from the field experiment that common bunt cannot be fully controlled by EM used as a seed treatment, even it has a significant reducing effect in this experiment when used in the half dose of the field trial. The EM used were in both year produced recently and delivered directly from the producer. Whether the difference in effect was an expression of differences in composition of the product or caused by other reasons can not be stated.
Seed treatment with diluted EM in the container experiment seem to have no influence on bunt frequency or on germination speed. In this study it increased mean germination time, but this effect was not statistically significant. In previous studies on the effect of diluted EM on germination, EM has been applied to the water used in the germination test. In this study it has been used as an application to the seed, and fresh water is applied in the germination test. The dose applied in this study is therefore not comparable with previous studies on the effect of EM on germination of seeds which may explain the contradictory results (Sinqueira et al, 1993; Sangakkara and Attanayake, 1993). The use of EM as a soil application seems to have no influence on bunt infection of the seedlings. The microorganisms in the EM product is formulated in Japan, and information on the occurrence of the same strains of organisms in other regions are limited, which makes the use questionable in organic agriculture elsewhere. In Denmark both organizations for organic farming ( Demeter Association and Association for Organic Farming) has decided to ban the use among their controlled members.
Milk powder can reduce infection of common bunt, but full control is often related to problems with field emergence (Winter et al, 1997; Borgen et al, 1995; Becker and Weltzin, 1993; Tränkner, 1993). Tränkner (1993) concluded that even the effectiveness of the milk powder in control of the disease could be improved by mixing with compost extracts as shown by Becker and Weltzin (1993), the effect is limited and could be better obtained by an increase of the amount of milk powder. This conclusion is generally confirmed by this study. Compost and rumen juice used as seed treatment had a very limited effect on bunt infection. Microorganisms growing in the fresh compost at 60 ºC must be thermofillic. Soil temperature under Danish conditions at the start of October is about 5-10 ºC, and the bacteria in the fresh compost may therefore not be well-adapted to this environment. The same can be expected for the rumen juice, where the microorganisms are mainly obligate and facultatively anaerobic and selected for growth at 39 ºC in the cow rumen (Van Soest, 1982). The well-composted garden waste had no effect when used alone, but had a tendency to improve the effect of the milk powder. A higher concentration of organisms in this treatment may have improved the effect.
Liquid manure has been used for centuries in Europe as a seed treatment against common bunt (Buttress and Dennis, 1959). Also modern research has included treatments with liquid manure (Borgen et al, 1995; Heyden, 1993), but in these trials seeds has been washed in liquid manure. The effect of the treatments were therefore a combination of the washing and the biological/chemical effect of the liquid manure. In the current experiment the seeds have not been dipped in the liquid, but only added as a surface amendment. This treatment seems to have no effect on bunt infection which indicates that the effect shown in previous experiments are mainly a washing effect.
The application of compost to the soil significantly increased the infection of common bunt. This confirms previous field trials by Rabien (1928), even it could not be confirmed in green house experiments by Voss (1938). Rabien explained the effect of compost by the fact that oxygen in the seed-surface environment is a liming factor for the infection of bunt, and compost increases the air volume in the soil compared with normal mineral field soil. Even application of compost to the soil has many beneficial effects on plant production, including the increasing effect of air volume, it may therefore have a negative side effect on bunt infection in cases where seeds or soil are contaminated with bunt spores. In the current experiment the compost was deliberately put into the row close to the seeds, while in normal farming practice the physical distance between seeds and compost are likely to be higher. On the other hand, 6t compost per hectare as used in this experiment is relatively low compared with the manuring practice for cereal production on many organic farms. Whether the normal use of compost will have practical implication of bunt infection can not be decided by this experiment.
Among the well characterized products in this screening test,
Pseudomonas MA 342 is the only product previously tested against common
bunt. The high effect of this product as compared with the others must be seen
in relation to the 10-20 fold higher number of organisms applied to the seeds in
the treatments. The doses chosen to test the effect of the other treatments are
therefore not qualified, but must be characterized as preliminary screenings.
"No effect" for a product does therefore not necessary mean "no potential
effect", but may indicate that the dose tested was too low for the control of
this pathogen. Evaluation of the products at this stage must therefore be seen
in combination with the side-effect on seed vigour.
In organic agriculture infections by plant pathogens should if possible be
prevented by general means to improve growth conditions for the plants. In the
case of common bunt (Tilletia tritici) these general means are at the
present stage inadequate to control the disease, and other control measures are
therefore necessary. The current study shows that the selected general
substances with high concentration of microorganisms like liquid manure, compost
extracts, rumen juice and EM (Effective Microorganisms) have a limited potential
in the control of common bunt. The application of compost to the soil even
increases the infection of common bunt. Some selected microorganisms used for
biological control of other seed pathogens seems to have a potential also in the
control of common bunt. Pseudomonas MA 342 can give full control of
common bunt in combination with milk powder with no negative effect on
germination vigour of the seeds, while further studies on Trichoderma
harzianum, Streptomyces griseoviridis and Gliocladium
roseumare needed to evaluate the potential of these fungi. Combinations of
active biological agents with milk powder indicates that this combination can
improve the potential of the biological treatment i.e. in cases where physical
limitations hinders the application of the dose needed to obtain adequate
control of the pathogen.
We thank sponsors and the companies who delivered the products knowing that
the purpose was not to promote or deprecate any specific product or method, but
only to screen the agents not previously tested with this disease. We specially
thank Erik Nielsen (Sonnerup Eco-advisors) and Berndt Gerhardson (SLU) also for
information about EM and Pseudomonas and Birgit Jensen and Inge Knudsen
(Depart. Plant Biology, KVL) for help with application of Gliocladium
and other support. We thank the staff of the Depart. Agricutultural Sciences,
KVL for practical assistance in the experimental process.
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Table 1. Results from two field trials with treatments of
biologically based products in control of common bunt (Tilletia
tritici). Treatments statistically tested against untreated control. Bunt
frequency in the control was 53.2% for the first five treatments, and 35.2% for
the last treatment.
dose Reduction of bunted heads
Control 0 0%
Milk powder 130 g/kg 95,8% ***
Milk powder +
Liquid manure 130 g/kg +30 ml/kg 94,5% ***
H2O 30 ml/kg 13.1% *
Diluted liquid manure 15 + 15 ml/kg 13.4% *
Liquid manure 30 ml/kg ÷2.3% (n.s.)
+H2O 2.2*109 CFU/kg+30ml/kg 45.7% ***
Table 2. Control of common bunt with biological agents in
combination with a low dose of milk powder. The doses (low and high) are not
based on previous trials or recommendations for this disease, and the
effectiveness and potentials of the products are therefore not comparable.
Treatments statistically tested against untreated control. Bunt frequency in the
control was 27.4%. Germination time is calculated from estimates generated by a
Generalized Linear Mixed Model.
low dose (1) higher dose (2) low dose(*)
control + H2O Reduction of bunted heads 0% 9.6% n.s ~42% (3)
Days for 50% germination 9.08 8.81 n.s
uncontaminated seeds Reduction of bunted heads 97.4% ***
Days for 50% germination 8.85 n.s.
Compost in field Reduction of bunted heads -61.1% ***
Pseudomonas MA342 Reduction of bunted heads 63.7% *** 87.6% *** 97.2% ***
Days for 50% germination 9.19 n.s. 9.68 ** 9.16 n.s.
Thricoderma harzianumReduction of bunted heads 0.4% n.s.
Days for 50% germination 8.70n.s.
Gliocladium roseumReduction of bunted heads 14.7% n.s. 45.9% ** 86.6% ***
Days for 50% germination 8.50 * 8.68 n.s. 8.77 n.s.
Lactic acid bacteria Reduction of bunted heads 3.0% ns 59.3% ***
Days for 50% germination 9.05 n.s. 9.02 n.s.
EM Reduction of bunted heads 0.9% n.s. 87.6% *** 72.8% ***
Days for 50% germination 9.11 n.s. 9.83 *** 9.35 n.s.
garden compost Reduction of bunted heads 8.6% n.s. 10.3% n.s. 64.7% ***
Days for 50% germination 8.73 n.s. 8.93 n.s. 9.03 n.s.
Thermo compost Reduction of bunted heads 0.1% n.s. 40.8% *** 45.3% ***
Days for 50% germination 9.04 n.s. 9.09 n.s. 9.13 n.s.
Rumen juice Reduction of bunted heads 3.9% n.s. 76.3% *** 47.0% ***
Days for 50% germination 9.01 n.s. 9.13 n.s. 9.16 n.s.
(1)low dose is for Gliocladium roseum=2.5*109 CFU/kg, for Symbioplex=7.5*109 spores/kg , for Thricoderma harzianum2*109 spores/kg and for Pseudomonas MA342 40*109 spores/kg. For the rest of the treatments the microbial content was not estimated and they were dosed by 40 ml/kg seeds except for the control, where nothing was applied.
(2) High dose is for Gliocladium roseum=4.5*109, CFU/kg, for Pseudomonas MA342 150*109 spores/kg. For the rest of the treatments 150 ml/kg seeds.
(3) Result for milk powder and water are extrapolated from a logistic
dose-response curve. 1% milk powder application reduced the bunt infection by
12,2% (n.s.) and 3% applied reduced attack by 74,1%(***) (Borgen and Kristensen,
Table 3. Semi field trial with control of common bunt with
EM as seed treatment and as soil amendment. Bunt infection in the untreated
control was 67.7%. Seed treatment caused minor statistical insignificant
reductions in germination speed. Treatments statistically tested against
Reduction of bunted heads
1 x soil treatment (83 l/ha) 5.0% n.s.
2 x soil treatment (2 * 83 l/ha) -10.2% n.s. (p=0.08)
2 x soil treatment +
Seed treatment (20ml/kg diluted EM 1:200) 8.6% n.s.
Seed treatment (20ml/kg diluted EM 1:200) -1.4% n.s.
2 x soil treatment +
Seed treatment (20ml/kg concentrated EM) 42.4% ***
Seed treatment (20ml/kg concentrated EM) 49.8% ***