Fra Anders Borgens Publikationsliste

A. Borgen 1997: Effects of seed treatments with EM in control of common bunt (Tilletia tritici). Proceedings of The 5th International Conference on Kyusei Nature Farming and EM technology. Bangkok 23-25/october 1997.


Effect of seed treatments with EM (Effective Microorganisms) in control of common bunt (Tilletia tritici) in wheat

Contribution to the proceedings of the 5th International Scientific Conference on Kyusei Nature Farming in Bangkok 23-25 October 1997

By Anders Borgen



Abstract

Common bunt is one of the most important diseases in winter wheat, and one of the most intensively pesticide treated diseases in regions, where this pathogen occurs. When pesticides are not used in seed propagation, i.e. in organic agriculture, this disease is normally a serious problem. EM1 (Effective Microorganisms) is a product used in Kyusei Nature Farming, containing a bunch of different microorganisms against various fungal plant diseases. In order to develop methods to diminish pesticide use, and to improve organic agriculture, the potential of EM to regulate this pathogen was investigated. In 1996 seeds contaminated with teleutospores of Tilletia tritici were treated with two levels of EM1, two levels of acetic acid and two levels of milk powder. A combination of EM1 and milk powder were tested as well.

EM1 had a significant effect on disease rate (87.6% reduction) when applied in high dosages (150ml/kg seed), but in this dose germination vigour and field emergence were also negatively affected. The use of the same dose of autoclaved EM1 had almost the same effect on disease rate and germination vigour. This might indicate, that the causative agent in the EM1 product are not the effective microorganisms themselfs, but the metabolites of the organisms, most probably lactic acid. Using acetic acid (1.22M, 30ml/kg) it was possible to get a better control of the pathogen with no significant harm to germination. Based on these trials it can be concluded, that EM1 is not an optimal control agent against common bunt. However the use of EM1 did reduce the disease rate, and this can therefore be a positive side-effect if EM1 is used as a seed treatment for other reasons.



Introduction

Common bunt is one of the most damaging plant diseases known in agriculture. The fungus (Tilletia tritici syn. T.caries) grows systemically in wheat plants (Triticum aestivum). Instead of normal kernels in the spikes, the kernels develops into bunt balls filled with fungus spores. During harvest, the bunt balls breaks, and the spores attach to the healthy seeds. The spores stink due to the release of simple nitrogen components like tri-methyl-amin, and this has given the disease the synonym stinking smut. When contaminated seeds are sown, the spores will germinate in synchrony with the kernels and infect the germinating plants systemically and thereby close their life cycles.

Common bunt is an old plant disease. Spores are found on seeds from the ancient Mesopotamia 4000 years ago (Johnsson 1990), and it is likely, that the disease has been a problem to wheat production ever since the domestication of this plant species. Since then, the disease has been one of the most intensively treated diseases in the history of plant protection (Woolman & Humphrey 1924, Buttress & Dennis (1959), Sharvelle (1979)). Since seed treatments with organic mercury started in the 1920s, research in this disease has been limited, since this treatment was both cheap and effective. Mercury is now banned in most industrialized countries for environmental reasons, but other synthetic pesticides have taken its place in the control of bunt.

In organic farming, seed treatments with pesticides are not used. Common bunt is therefore, in this cropping system, a significant threat to wheat production. Research in ecological regulation of this disease are going on in Europe, mainly focusing on different seed treatments like plant extracts, organic compounds, hot water treatment and antagonistic bacteria (Heyden et al 1997, Spiess & Dutschke 1992, Becker, J & H.C. Weltzien 1993, Bergman, S 1996, Borgen, A. and Kristensen, L 1996, Gerhardson, B, M.Hökeberg and L.Johnsson 1996).

Kyusei Nature Farming is an organic cropping system mainly differing from other ecological systems by the intensive use of the product EM (effective microorganisms). Among other purposes like plant nutrition, the EM is used in plant protection against various fungal diseases. In Kyusei Nature Farming the question is therefore straightforward: Can EM be used in the control of common bunt?



Materials and Methods

Seeds of wheat, variety Pepital, were abundantly contaminated with teleutospores of Tilletia tritici in a rate of 1.975.000 spores per gram seed. Pepital is a winter wheat variety known to be very susceptible to common bunt with no known resistance genes. Samples of 100 g of this contaminated seed lot were treated with different applications in a laboratory spinning wheel seed dresser (Hege no. 11). Among the applications were two levels of EM, 40ml/kg and 150ml/kg. The formulation EM1 was used in this trial. These treatments were compared with two levels of 1.22M acetic acid 20ml/kg and 30ml/kg. In order to develop the method and to determine the working mechanism, EM1 were autoclaved for 20 min at 120 C, and a seed lot were treated with 150ml/kg. One sample were treated with a combination of 40ml EM1/kg and 20g skimmed milk powder pr. kg. This treatment was compared with two levels of milk powder 10g/kg and 30g/kg.

The treated seed lots were sown in a randomized field block-trial in small plots of aproximately 125 seed pr. plot in 10 replications the 11th of October 1996. After tillering all heads were diagnosed for bunt infection, and the frequency of bunted heads was calculated.

The different treatments were tested for side-effects on germination vigour. This was done by germinating 100 seeds in quartz sand and water (65ml/kg), and the number of sprouts in each sample were counted three consecutive days. This germination test was replicated tree times at low temperatures (10-12 *C). Because of the differences in temperature in the different replications in the germinations test, it was necessary to express the germination vigour as an applied germination index. This is done by this formula:

(n1/N1+0.9*n2/N2+0.8*n3/N3)*100/C

were n is the number of sprouts on the day 1, 2 or 3, N is the average of number of sprouts on that day in the test. This equation is in each replication divided by the average of the replication, C and multiplied by 100. This transformation gives a good description of the relative germination vigour of the seed sample, and thereby the eventual phytotoxic side effect of a seed treatment.

The statistical calculation in Figure 1 is done by a Ryan test on the transformed data (ln(x)+1) using the GLM option REGWQ in the software SAS ver. 6.12.





Results

The results of the experiement are presented in Figure 1. The low doses of EM1 and milk powder had no significant effect on either bunt rate or germination vigour. The higher dose of milk powder, the low dose of acetic acid and the combination of milk powder and EM1 reduced the bunt rate significantly with no significant effect on germination vigour. The reduction in germination vigour due to EM1+ milk powder had a p-value of 0.14. The high dose of EM1, both regular and the autoclaveted, reduced bunt rate, but reduced also the germination vigour significantly. The differences between the autoclaved and the regular EM1 had a p-value of 0.62. The high dose of acetic acid had the best effect on bunt disease, significantly better than even the highest dose of EM1. The reduction of germination vigour of the seeds was in this trial not significant with a p-value of 0.30.













Discussion and Conclusion

The control of common bunt is crucial for the production of quality wheat. 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. 50% of the people in a Swedish experiment could smell the presence of only 1000 spores pr gram of seeds (Johnsson 1991). This level can be obtained by a field frequency of less than 0.1% infected heads (Borgen, unpublished). The multiplication of bunt frequency from year to year will depend on wheat variety and climate conditions especially during germination, but is often about 100 times under Danish climate conditions in susceptible varieties (Borgen 1992, Borgen unpublished). In order to prevent a multiplication of the bunt rate from year to year, the sum of control measures must therefore have an efficiency of more than 99%.

It has been possible to give a significant reduction in bunt rate in the field trial by the treatment with EM1. The reduction in bunt rate seems to be proportional with the amount of EM1 applied to the seed sample. However the treatment also causes a significant reduction in germination vigour proportional to the dose applied. A better control of the bunt can therefore not be obtained by an increase of the dose, because it would also increase the phytotoxic effect on germination. An efficiency of 99% can therefor not be obtained by seed treatment alone with EM1 without an unacceptable decrease in germination vigour.

Seed treatment with autoclaved EM1 (150ml/kg) resulted in a control of the bunt frequency almost as good as with the same amount of fresh EM1. Even the autoclavation at 120 C for 20 minutes may not have killed all microorganisms in the formulation, the concentration is likely to be radically reduced. This indicates, that the working mechanism of the EM1 on the bunt is not primarely an biological effect, but rather a physical or chemical effect of the metabolites in the product. This meight be lactic acid, since EM1 is declared to contain 80% lactic acid bacteria with a pH about 3.5. This is confirmed by the treatment with acetic acid, which also gives a significant reduction in bunt rate. With acetic acid 30ml/kg it is possible to obtain a significanly better effect on bunt control with no decrease in germination vigour. Acetic acid is as such a better control agent against common bunt than EM1. The acetic effect on bunt spore germination is known (Hahne 1924), but has never before been used as control agent in the field.

The treatment with milk powder gives a significant control of the bunt without reduction in germination vigour. This effect is related to bacterial activity, using the milk powder as a nutrient source (Becker and Weltzien 1993). The combination of milk powder and EM1 gives a better control, than EM1 or milk powder alone. The effect on germination vigour was not significant compared with control (p=0.15). It can not from this experiment be explained, whether this effect is caused by the bacteria in the EM1 product or it is the acetic effect, that increases the efficiency of the milk powder on the bunt control in the combined formulation. From this experiment there seems to be no argument for the use of this combined formulation compared with 30 g milk powder or 2 ml acetic acid, since they have the same effect on the disease, but without a tendency to reduce germination vigour.

In this study, only the effect of seed treatment on common bunt and seed vigour has been investigated. The environmental impact of the use, or the effect on yield due to increased release of nutrients from the humus fraction in the soil, has not been studied. The chosen experimental design is developed for seed treatments with pesticides, biological antagonists, organic nutrients a.o. This design seems not to fit EM. EM is in other studies used due to a principle of creating disease supressive soils. In this study it has not been investigated, whether long term soil treatments with EM (activated EM or bokashi (EM compost)) can create disease supressive soils adequate to control common bunt.

On this background it can be concluded, that EM1 is not an optimal seed treatment against common bunt, since other treatments like acetic acid or milk powder gives the same or better disease control with less harm to germination vigour. If however EM1 is used as a seed treatment in Kyusei Nature Farming for other reasons, i.e. to increase nutrient availability in the soil, the EM1 can in combination with other measures contribute to the regulation of common bunt.







References

Becker, J & H.C.Weltzien 1993: Bekämpfung des Weizensteinbrandes (Tilletia caries(D.C.)Tul. & C.Tul.) mit organischen Nährstoffen. (Control of common bunt (Tilletia caries (D.C.)Tul. & C.Tul.) with organic compounds). Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz 100(1):49-57.

Bergman, S 1996: Värmebehandling mot utsädesburne svampsjukdomar. (Heat treatment of seed borne diseases). Forskningsnytt om øekologisk landbruk i Norden 2:6-7.

Borgen, A., C.Markussen og L.Kristensen 1992: Frøbårne svampesygdomme på byg og hvede i økologisk jordbrug - udbredelse og betydning i 1990. (Seed borne diseases in barley and wheat in ecological agriculture). Msc thesis, KVL 131 sider

Borgen, A and Kristensen, L 1996: Stinkbrand må reguleres. (Common bunt must be regulated). Forskningsnytt om øekologisk landbruk i Norden 2:9-11.

Gerhardson, B, M.Hökeberg and L.Johnsson 1996: Biologisk utsädessanering för konventionel og ekologisk odling. (Biological control of sowing material in conventional and ecological agriculture). Forskningsnytt om øekologisk landbruk i Norden 2:8-9.

Hahne,J 1924: Untersuchungen über die Keimingsbedingungen von Tilletia-Sporen. (Investigations on the germination conditions of Tilletia-spores). Kühn-Archiv 9:157-263

Heyden, B 1997: Mitteilungen aus der Arbeit des Johanna und Carl Graf Keyserlinck Institut. (Report from the work at Johanna und Carl Graf Keyserlinck Institut). Ed: B.Heyden.

Johnsson,L 1990: Brandkorn i Bibeln, stinksot i vetet och Tilletia i litteraturen - en kortfattad historik från svensk horisont. (Bunt in the bible, wheat bunt and Tilletia in litterature - a short historic review from a swedish view point). Växtskyddsnotiser 54:76-80

Johnsson,L 1991: Dvärgstinksot (Tilletia controversa) og vanligt stinksot (Tilletia caries) i svenskt vete. (Dwarf bunt (Tilletia controversa) and common bunt (Tilletia caries) in swedish wheat). Växtskyddsrapporter. Jordbruk 6:1-19

Spiess,H and J.Dutschke 1992: Bekämpfung des Weizensteinbrandes (Tilletia caries) im biologisch-dynamischen Landbau unter experimentellen und praktischen Bedingungen. (Treatment against common bunt (Tilletia caries) in biodynamic farming under expierimental and practical conditions). Ökologie und Landbau 81:7-9