Determination of Optimum Timing of Fungicides Application Based on Growth Stages for Controlling of Wheat Tan Spot

Document Type : Research Article


1 Etka Research and Innovation Center

2 Etka organization

3 Assistant Professor, Department of Plant Protection Research, Agricultural and Natural Resources Research Center of Golestan Province, Gorgan

4 Mazare Novin Iranian Holding, Mazrae Nemone Joint Stock Company, Gorgan


Introduction: Tan spot )Pyrenophora tritici-repentis( is one of the most destructive leaf diseases that causes significant damages to wheat during epidemic periods. The application of fungicides is a rapid control practice of the disease during epidemic periods. Under the Integrated Management of Diseases (IDM), fungicides application for controlling leaf diseases is recommended based on disease level (disease pressure), plant growth stages, and only for susceptible cultivars. Several fungicides have been proposed for controlling tan spot, but the efficiency of recommended fungicides is effective when they are used to reduce the disease pressure on important plant leaves especially flag leaf. According to growth stages, four timing have been recommended to fungicides application including, T0 (early stem elongation to node forming 1), T1 (node formation 2-3), T2 (the full flag leaf emergence) and T3 (flowering). The results of fungicides application at different growth stages of wheat are inconsistent and also there is no comprehensive study about the timing of fungicides application for controlling this disease in Iran. Therefore, the present study was carried out to determine the appropriate timing of fungicides application at four wheat growth stages.
 Materials and Methods: A field experiment was conducted in a split plot design with four replications. The main and sub-main factors of the experiment were cultivars (Karim and Koohdasht) and the spraying treatments, respectively, and common fungicides (such as Tilte, Folicur, Falcon, and Rexduo) were sprayed at four timings including, T0 (early stem elongation to node forming 1), T1 (node formation 2-3), T2 (the full flag leaf emergence) and T3 (flowering). The spraying treatments were as follows: one, two, three and four spraying times. The efficiency of spraying treatments was evaluated one week after the last spraying by determining the disease index (incidence, severity and area under the disease progress curve; AUDPC) and also comparing the yield and yield components.
 Results and Discussion: The results showed that spraying treatments from the full flag leaf emergence to flowering stages (Tr3, Tr5, Tr6, Tr8 and Tr9) decreased the values of AUDPC-I by 42.1 to 80.5% and 33 to 76.6% for Koohdasht and Karim cultivars, respectively, whereas the values of AUDPC-S decreased by 30.7 to 47% and 33 to 58% in Koohdasht and Karim cultivars, respectively. The effect of spraying treatments on damage reduction showed that the damage reduction ranged between 1.4-30.8% and 1.1-29.7% in Koohdasht and Karim cultivars, respectively. The highest damage reduction was observed at the full flag leaf emergence to flowering stages. The highest yield increase was observed at the full flag leaf emergence to flowering stages, which was more than 36% (1071.2 to 1298.9 kg/ ha) and 34% (1054.5 to 1313.8 Kg/ ha) in Koohdasht and Karim cultivars, respectively. The spraying treatments at the node formation stages had the least effect on the yield improvement, which were, respectively, 2.1-7.1% and 1.5-5% in Koohdasht and Karim cultivars. In both cultivars, the comparison of economic profit showed that treatment of Tr3 (flag leaf emergence stage), in addition to decreasing the disease severity and yield increase, and reduction of spraying costs had the highest economic profit compared to other spraying treatments (Tr6, Tr8 and Tr9). Spraying prior to the appearance of flag leaf stage (node formation) was not effective for reducing tan spot severity.
Conclusions: The treatment of Tr3 (spraying once at the full flag leaf emergence stage), was the best timing of fungicide application for the disease pressure reduction, and the yield and economic profit increase. In addition to the timing and spraying frequency, the disease pressure reduction rate and yield enhancement, economic profit should be also considered to decide on spraying application.


1. Abbasi A. 2011. Chemical control of tan spot disease of wheat in Mazandaran province. Thesis of MS, Agriculture Faculty, Azad University of Damghan.
2. Abbasi A., Forutan M., and Pirnia M. 2010. Study of the effect of some fungicides recorded on control of wheat tan spot. Proceedings of the 19th Iranian plant Protection Congress, 31-3 Jul. – Aug. 2013, Tehran, Iran.
3. Aghajani M.A. 2013. Guide to identifying and managing wheat diseases in Golestan province. Norozi press. 124 p.
4. Aghajani M.A., Bagherani N., and Mottaki A. 2010. Chemical control of tan spot in golestan province. Proceedings of the 19th Iranian plant Protection Congress, 31-3 Jul. – Aug. 2013, Tehran, Iran.
5. Aghajani M.A., and Talie F. 2007. Technical Journal of Tan Spot of Wheat. Technical Publishing and Scientific Group of Research Center Agriculture and Natural Resources of Golestan Province. 20 pp.
6. Addaghi M., Abbasi A., and Pirnia M. 2016. Study of the effect of some fungicides recorded on control of Tan Spot of Wheat. Applied research in Plant Potection, 5(2):81-93. (In Persian with English abstract)
7. Bailey K.L., Gossen G.P., Watson P.R., and Derkson D. A. 2001. Effect of tillage and crop rotation on root and foliar diseases of wheat and pea in Saskatchewan from 1991 to 1998: univariate and multivariate analysis. Canadian Journal of Plant Science, 81: 789-803.
8. 8-CABI. 2013. Pyrenophora tritici-repentis (leaf spot ofwheat). CBI Crop Protection Compendium, 57 p.
9. Dehghan M.A. 2010. Investigation on the emergence and spread of wheat tan spot disease in Golestan province and evaluation of resistance of different wheat genotypes to it. Proceedings of the 19th Iranian plant Protection Congress, 31-3 Jul. – Aug. 2013, Tehran, Iran.
10. De Wolf E., Effertz R.J., Ali S., and Francl L.J. 1998. Vistas of tan spot research. Canadian Journal of Plant Pathology, 20: 349-370.
11. Duczek L.J., and Jones-Flory L.L. 1994. Effect of timing of propiconazole application on foliar disease and yield of irrigated spring wheat in Saskatchewan from 1990 to 1992. Canadian Journal of Plant Science, 74: 205–207.
12. Edwards J.T., Hunger R.M., and Payton M.E. 2012. Agronomic and economic response of
hard red winter wheat to foliar fungicide in the southern plains. Crop Management, 11(1): 1-10.
13. Forutan A., Dalili A., and Shayegan J. 1995. Isolation of Drechslera tritic –repentis from wheat leaf infected in Mazandaran Province. Proceedings of the 12th Iranian plant Protection Congress, 11-16 Sep. 1995, Karaj, Iran.
14. Harvey I.C, Craigie R.A., and McCloy B.L. 2015.The control of tan spot of wheat (caused by Pyrenophora tritici-repentis: a possible emerging disease in New Zealand. New Zealand Plant Protection, 68: 428-433.
15. Heger M., Oerke E.C., Dehne H.W., and Hindorf H. 2003. Evaluation of an action threshold-based IPM wheat model in Rheinland (Germany) in 1999/2001. OEPP/EPPO Bull, 33:
16. Jørgensen L.N., and Thygesen K. 2006. Should strobilurins still be used in wheat? Danish andforeign experience. Proceedings of the 3th Danish Plant Congress, 10–11 Jan. 2006, Denmark.
17. Kelley K.W. 2001. Planting date and foliar fungicide effects on yield components and grain traits of winter wheat. Agronomy Journal, 93(2): 380-389.
18. MacLean D. 2016. Evaluating fungicide timing for leaf spot diseases of wheat and Fungicide Resistance in Pyrenophora tritici-repentis. Thesis of MS, University of Saskatchewan.
19. Lopez J.A., Rojas K., and Swart J. 2015. The economics of foliar fungicide applications in
winter wheat in Northeast Texas. Crop Protection, 67: 35–42.
20. Ransom J.K., and McMullen M.P. 2008. Yield and disease control on hard winter wheat
cultivars with foliar fungicides. Agronomy Journal, 100: 1130-1137.
21. Saari E., and Prescott J.M. 1975. A scale for appraising the foliar intensity of wheat diseases. Plant Disease, 59: 377–380.
22. Wegulo S.N., Breathnach J.A., and Baenziger P.S. 2009. Effect of growth stage on the
relationship between tan spot and spot blotch severity and yield in winter wheat. Crop Protection, 28: 696-702.
23. Wegulo S.N., Stevens J., Zwingman M.V., and Baenziger P.S. 2012. Yield response to foliar fungicide application in winter wheat. p. 227-244. In D. Dhanasekaran, N. Thajuddin, and A Paneerselvam (ed.) Fungicides for Plant and Animal Diseases. InTech press, Croatia.
24. Wiersma J.J., and Motteberg C.D. 2005. Evaluation of five fungicide application timings for
control of leaf-spot diseases and Fusarium head blight in hard red spring wheat. Canadian Journal of Plant Patholology, 27: 25-37.
25. Zadoks J.C., Chang T.T., and Konzak C.F. 1974. A decimal code for the growth stages of cereals. Weed Research, 14: 415-421.