Effect of seed treatment with acetic acids in control of seed
borne diseases
From: Proceedings from BCPC Symposium No. 76, 2001: “Seed Treatment: Challenges &
Opportunities”, eds. A. J. Biddle. BCPC, Farnham, 135-140.
Anders Borgen(1)
Bent Nielsen
DJF-Flakkebjerg, 4200 Slagelse, Denmark, email:Bent.Nielsen@agrsci.dk
ABSTRACT
In field trials, seed treatment with acetic acid has reduced common bunt (Tilletia
tritici) in winter wheat by 91.5-96.2% and by 83% in spring wheat without negative
effects on germination vigour of the seeds. Leaf stripe (Pyrenophora graminea) in
spring barley was reduced by 93,4%. Acetic acid is a cheap and environmental friendly
fungicide with a possible scope of application especially in organic agriculture, where
conventional pesticides are prohibited.
INTRODUCTION
Lime has been used as a seed treatment against common bunt since the 1700th century
(Olsen 1792). The effect of lime as a seed treatment against common bunt is likely to be
an effect of water-reaction (pH) since lime is a strong base. The opposite effect of a
very low pH has never been studied as a seed treatment, but already Hahne (1925) showed
that acetic acid has a strong effect on bunt-spore germination. However, the use of acetic
acid as a seed treatment against common bunt must relay on a combination of the effect on
the pathogen and the side-effect especially on seed germination. The effect of lime
against common bunt is not complete, and the use has been limited since the development of
more effective seed treatments like copper (Kühn 1866) and hot water treatment (Jensen
1888a, 1888b). Since the development of organic mercury seed treatment (Riehm 1913) common
bunt has been controlled almost exclusively by synthetic pesticides in the industrialised
world.
In the past decades, increasing focus has been put on the environmental side-effects of
the synthetic pesticides and a wish to reduce the amount of pesticides used, or to replace
them with naturally occurring substances (Nielsen et al. 1998). In organic
agriculture normal pesticides are not used, and here seed borne diseases has become a
severe problem. The aim of this study is to investigate whether seed borne diseases can be
controlled by seed treatment with acetic acid.
MATERIALS AND METHODS
Field trials were conducted at three sites on Zealand, Denmark: Common bunt at
Højbakkegård in 1997 and '98, leaf stripe in barley at Flakkebjerg in 1999 and both leaf
stripe and common bunt at Mørdrupgård in year 2000.
The effect of different doses and concentrations of acetic acid was tested by applying
increasing doses to seeds of wheat and barley. For the test of the effect on common bunt (Tilletia
tritici syn. T.caries) at Højbakkegård in 1997 and '98 the winter wheat
variety 'Pepital' was used and at Mørdrupgård in 2000 the spring wheat variety Dragon
was used. The spring wheat seed used had a very low germination ability in order to
increase the possibility to get a high infection in the field and to detect possible side
effects on germination from the seed treatment. The seeds were contaminated with 5 g
spores per kg seeds, which resulted in a contamination between 1.7 to 2.0 mill spores per
gram seeds when tested by the ISDA haemocytometer method (Keitreiber 1984).
Test for the effect on leaf stripe (Pyrenophora graminea syn. Dreschlera
graminea) were in both years done in seed lots of the variety Alexis which
by a blotter test was tested to be heavily infected.
In 1997 and '98 normal fermented 5% vinegar for household use was used (FDB
Lagereddike). In 1999 and 2000 the different concentrations were made by adding
increasing volumes of inert water into concentrated acetic acid (99.9%). After treatment
the seeds were stored at 5 Cº. Samples were taken out for field test 2-6 days after seed
treatment. Germination tests were conducted 1-3 month later at Højbakkegård and
Mørdrupgård. At Flakkebjerg the effect on germination were tested by the number of
emerging plants in the field.
Germination tests in lab were done as a cold sand test in plastic plates containing 1.5
kg sand with water (65ml H2O/kg quartz sand). Sowing depth was 1.5 cm and
temperature was 10 Cº. The emergent number of seedlings were counted every day for 5 days
after first emergence. The number of replicates were 3-4.
In the field trials at Højbakkegård and Mørdrupgård, treatments were sown in rows
of each 1.25 m in 8 or 10 replicates. Total number of diagnosed plants in these trials was
1-2000 on average in each treatment. Trial at Flakkebjerg were sown in rows of 4 meter
with 100 seeds pr. meter in 4 replicates After heading the ratio of infected ears (common
bunt) or plants (leaf stribe) were counted based on visible macro-symptoms.
Data of diseased plants and germination speed was analysed by a generalised linear
model (GENMOD in SAS ver. 6.12).
RESULTS
Common bunt
At the estimated optimal dose of 20 ml/kg the experiment at Højbakkegård in 1997
resulted in a reduction of bunt infection of 96.2% (Figure 1). Highest dose (3 ml/100g)
reduced the time for 50% germination at 10 Cº by 34.5% *** in lab. At the lower doses no
tendensy of decreased germination vigour was recorded.
| Table 1: Effect of different combinations of acetic acid as a seed treatment. Percent reduction in disease frequency of spring wheat infected by common bunt (Tilletia tritici) tested against treatments with inert water. Grey cells indicating treatments with a significant reduction in germination vigour. Experimental year 2000 at Mørdrupgård. Average infection in control plots was 8.0%. | |||||||
Dose of acetic acid, ml/kg |
|||||||
 |
5 | 10 | 20 | 30 | 40 | 50 | |
| 5% | 20 n.s. | 49 | 79 | 62 n.s. | 54 n.s. | 63 | |
| 10% | 35 | 59 n.s. | 83 | 70 | 63 | 70 | |
| 20% | 4 | 39 | 75 | 54 | 45 | 55 n.s. | |
| 30% | 30 | 55 | 30 n.s. | 67 | 60 n.s. | 67 n.s. | |
| 99.9% | 46 | 66 | 86 n.s. | 74 | 69 n.s. | 75 n.s. | |
In 1998 at Højbakkegård (Figure 2), the application of a 5% solution of acetic acid
reduced the frequency of common bunt by more than 91,5% at a dose of 20 ml/kg or higher.
The negative effect on seed vigour seems to be proportional to the dose applied (Figure
3). When more than 40 ml/kg was applied, the effect was statistical significant according
to the contrast test.
Even low vitality seeds were used in a very susceptible spring wheat variety Dragon at
Mørdrupgård in year 2000, the bunt frequency was very low in all plots. The use of low
vigour seeds resulted in a low field germination in both treated and untreated plots. The
average number of ears were only 37 per plot. As it is appears in Table 1, the effect of
many treatments were statistical insignificant because of a low number of plants,
especially infected plants. However, the same optimal dose can be found to be about 20
ml/kg in a concentration between 5% and 20%.
Barley leaf stripe
At Flakkebjerg 1999, the infection of barley leaf stripe was significantly reduced
proportional to the dose of 5% acetic acid applied (Figure 4). However, at the highest
dose of 50 ml/kg the number of emergent seedlings in the field was significantly reduced
(p<0.0001). The highest reduction recorded without significantly reduction in
germination was at the dose of 40 ml/kg, where leaf stripe was reduced by 55,9%.
In spring barley at Mørdrupgård the infection of leaf stripe was reduced by 93,4% at
the dose of 20 ml/kg of concentrated acetic acid with no significant effect on field
emergence (Table 2).
| Table 2: Effect of different combinations of acetic acid as a seed treatment in barley. Percent reduction in disease frequency of barley leaf stripe (Pyranophora graminea) tested against untreated control. Grey cells indicating treatments with a significant reduction in germination vigour. Experimental year 2000 at Mørdrupgård. Average infection in control plots was 17.4%. | |||||||
|
|||||||
 |
5 | 10 | 20 | 30 | 40 | 50 | |
| 0% | 28,6 n.s. | 4,2 n.s. | 6,4 n.s. | 8,3 n.s. | -1,6 n.s. | 7,2 n.s. | |
| 5% | -7,8 n.s. | 10,4 n.s. | 26,9 n.s. | 32,9 n.s. | 54,5 | 84,8 | |
| 10% | -6,2 n.s. | 12,7 n.s. | 67,8 | 82,4 | 95,8 | 84,5 | |
| 20% | 8,1 n.s. | 26,7 n.s. | 84,3 | 96,1 | 93,3 | 50,6 n.s. | |
| 30% | 29,2 n.s. | 36.0 n.s. | 90,3 | 91 | 99,5 n.s. | 48,8 n.s. | |
| 99.9% | 12,7 n.s. | 68,5 | 93,4 | 99,7 n.s. | 99,7 n.s. | 94,4 | |
DISCUSSION AND CONCLUSION
Acetic acid is a natural occurring substance with a high biodegradability and a very low oral toxicity to humans, game birds and others who normally come in contact with seeds treated with fungicides. However, acetic acid is an acid and evaporates from the seeds during seed treatment. Precautions should therefore be takes to insure human health and safety at work. Substituting conventional fungicides with acetic acid is believed to reduce general environmental impact of seed treatments. Seed treatment with acetic acid would be cost effective, since it is a cheap substance and unsold treated seeds could be used for feeding, while seeds treated with more eco-toxic fungicides most be incinerated under controlled conditions.
In the winter wheat experiments, the infection of common bunt was high as was the
reduction of infection by 91.5-96.2% when treated with 20 ml/kg of acetic acid with out
affection the germination vigour of the seeds. In spring wheat the infection was lower and
a reduction of only 75-83% was recorded. The differences in effect between the experiments
in winter wheat and spring wheat can not be concluded from these experiments. It may be
caused by the differences in crop, in differences in infection level or the fact that the
spring wheat was grown from very low vitality seed which may have made the seeds more
sensitive to the treatment.
The experiments with spring barley shows that barley leaf stripe can be effectively
controlled by a high concentration of acetic acid in a dose of 20 ml/kg. In the first
experiment only a low concentration of 5% was tested and in this concentration the results
are equivalent with the second experiment.
Common bunt is a very devastating plant disease since only a few plants can give the
hole crop an odour of rotten fish. The sum of treatments must therefore have a very high
effect against this disease (Borgen 2000a). Even the effect of 91.5-96.2% as shown in this
experiments are not adequate in cases with a high spore load in susceptible varieties as
used in these experiments. Seed treatments with acetic acid can therefore not stand alone,
but must be combined with other measures in an integrated strategy. This could be physical
removal of spores or only used according to thresholds depended on the susceptibility of
the varieties (Borgen 2000a).
Barley leaf stripe is an important seed borne disease, but the effect of the disease is
only significant to the yield. The need for effective control is therefore less than for
common bunt in wheat. A control effect of 93.4% as achieved in this experiment is
therefore believed to be sufficient in most cases.
In resent years, soil borne infection of common bunt has been of increasing importance
in wheat production (Borgen 2000b). Some systemic pesticides are effective also against
soil borne infection, and has a higher effectivity also against seed borne infection of
near to 100%. In organic agriculture, conventional fungicides are prohibited and acetic
acid could therefore be an interesting alternative to the current practice of discarding
all infected seed lots or to be used in combination with other treatments (Spie 2000).
REFERENCES
Hahne, J. 1925: Untersuchungen über die Keimungsbedingungen von Tilletia-sporen. Kühn.Archiv 9:157-263.
Jensen, J.L. 1888a: Nye Undersøgelser og Forsøg over Kornsorternes Brand (Første Meddelelse). Wilhelm Priors Boghandel, Kjøbenhavn. 18 p.
Jensen, J.L. 1888b: Om Kornsorternes Brand (Anden Meddelelse). Triers Bogtrykkeri, Kjøbenhavn. 72 p.
Keitreiber, M. (1984): ISTA Handbook on Seed Health Testing: Working Sheet no. 53. Bundesanstalt für Pflanzenbau, Wien, Austria.
Kühn J.C. 1866: Einbeizen des Weizens. Ztschr. Landw. Cent. Ver. Prov. Sach., 23(4):86-87
Nielsen, B.J., A.Borgen, G.C.Nielsen and C.Scheel 1998: Strategies for controlling seed-borne diseases in cereals and possibilities for reducing fungicide seed treatments. The Brighton conference - Pest and Diseases, p.893-900.
Olsen, A. 1791: Tilforladelig Underretning hvorledes man paa bedste Maade skal behandle Hveden førend den saas, at den skal blive fri for den skadelige Brand. Kiøbenhavn 1791
Riehm, E. 1913: Prüfung einiger Mittel zur Bekämpfung des Steinbrandes. Mitt. K. Biol. Anst. Land- u.Forstw., 14:89
Spiess, H. 2000: Aktuelle Versuchergebnisse zur Weizensteinbrandbekämpfung. Lebendige Erde 5:41
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