Abstract

Field data is given on the plant sanitary situation in grain-growing areas of six regions of European Russia over the period 1988-2003. The composition of rusts complexes and the population structure of wheat, rye and barley are examined and average crop losses are estimated.

Introduction

The principal grain producers in Russia, where 75% of the grain-growing area is concentrated, are: North Caucasus, Central Chernozem, Central, Povolzhski, Volgo-Vyatski and Uralski regions. The regions differ in their composition of cultivated crops. Winter wheat and spring barley prevail in North Caucasus, Central Chernozem and Central regions; winter rye, spring wheat and barley in Volgo-Vyatski; and spring wheat, rye and barley in the Uralski and Povolzhski regions. The plant sanitary situations in these grain-growing areas, the frequency of outbreaks and their severity, are determined by the agroecological specificity of each region: climate, types of soil and their fertility, structure of sowing areas and economic factors. The composition of rust complexes, correlations of different species in populations, intensity of their development, and resulting damage to the crops follow different time courses even within an agroecological region.

Materials and Methods

Throughout the growing season, starting from the tillering stage (10EC) to maturation (92EC), at intervals of 15-20 days data-collecting tours were made of fields of winter and spring wheat, winter rye, and winter and spring barley, in the areas of 6 administrative regions of the Russian Federation. The areas were: North Caucasus, Central Chernozem, Central, Povolzhski, Volgo-Vyatski and Uralski. Plant sanitary monitoring was carried out in 15-20 fields of each crop in 2-3 districts of each region. Disease severity was assessed according to the International Scale (Peterson et al., 1948, Sanin et al.,1988, Sanin et al.,1992). The compositions of pathogen complexes were determined. The plant pathogens reported are characterised by the average percentage of their occurrence in the fields of the region. The crop losses caused by each disease and pathogen complex as a whole were assessed with the help of some mathematical models (Stepanov et al.,1978, Terechov et al.,1982, Stepanov et al.,1984, Sanin et al.,1984).

Results and Discussion

North Caucasus region.
Due to climatic and other natural conditions this region is exceptionally favorable both for cultivation of cereal crops and for development of plant pathogens. It occupies a variety of climatic zones ranging from arid to moderately-moist and subtropical. The main cereal crops are winter wheat and winter barley which occupy 4.3 million ha, or 74.2% of the grain producing area. The annual production of the area is more than 14 million tons or about 28% of the gross yield of grain in Russia. The high concentration of grain crops, along with favorable weather conditions, tend to predispose to frequent and destructive outbreaks of plant pathogens which result in substantial reductions of yield. In recent years the rust complex of winter wheat has consisted of brown rust (Puccinia triticina) and yellow rust (Puccinia striiformis). Brown rust (Puccinia triticina) spreads everywhere in this region. It was dominant in populations until 1992-93. In last years its share of the population structure increased from 47 to 65%. Epiphytotics of brown rust have occurred in 2-3 years out of 10; the severity of the disease has reached 70-80% at the epiphytitotic stage, and crop losses 30-35%. In recent years a marked increase in yellow rust (P. striiformis) development has been observed. It was in a depressed state in the previous 30 years. Its share of the population structure has increased from 10% to 39%.

Central Chernozem region.
Due to its climatic and agricultural conditions this region is favourable for the cultivation of cereal crops. The main crops are winter wheat and spring barley which occupy 3.2 million ha, or 80% of the grain producing area. The gross yield of grain is 5.5 million tons, or 10.5% of the general harvest. The region is characterized by high temperatures and moderate humidity which favour frequent and strong development of diseases. Brown rust of wheat (P. triticina) spreads over the entire region. Its share is 22% of the population structure. The most substantial outbreak of the disease was observed at the beginning of the '90s. Epiphytotics of P. triticina have occured in 3-4 years out of 10. Infection of wheat plants reached 70-80%, crop losses 15-20%. Dwarf rust (P. hordei) has been found in recent years.

Central region.
The climatic and agricultural conditions of this region divide it into northern, central and southern zones. The central and southern zones are most favorable for cultivation of cereal crops. The leading crops are spring barley, winter wheat, winter rye, and oats which occupy 4.2 million ha, or 77% of the grain producing area. The gross yield of grain is 6.1 million tons, or 12% of the total harvest. The climate is characterized by moderate temperatures and sufficient humidity which determine the complex of diseases. Brown rust of wheat (P. triticina) spreads absolutely everywhere. Its share in the population structure has decreased from 55% to 36% in recent years. In epiphytotics, which have occurred in 5-7 years out of 10, the infection of wheat reached 80-100%, and crop losses were 20-30%. The rust complex of winter rye in the Central Region consists brown rust (P. dispersa) and stem rust (P. graminis). Brown rust of winter rye (P. dispersa) occurs annually and spreads over the entire area. Its share of the population structure is 49%. Epiphytotics have occurred in 5-7 years out of 10. Leaf infection reaches 80-90% in an epiphytotic year, and crop losses 20%. In some years stem rust (P. graminis) has been observed in rye. Its share of the population structure is 12%. Epiphytotics have occurred in 2-3 years out of 10. In these years the plants infected amounted to 70-80%, and crop losses up to 40%. Dwarf rust of barley (P. hordei) amounts to 15% of the pathogen complex; leaf infection has not been higher than 10-12%. Oats are predominantly attacked by crown rust (P. coronifera). Epiphytotics have occurred in 1-2 years out of 10, with leaf infection 40-50% and crop losses up to 20%.

Povolzhski region.
The climatic and agricultural conditions of this region divide it into two zones. The northern part is characterized by moderate temperatures and sufficient humidity, and central and southern parts by higher temperatures and low humidity. The main crops here are: spring and winter wheat, spring barley, and winter rye, which occupy 8.8 million ha, or 91% of the grain producing area. The gross yield is 8.7 million tons, or 17% of total grain production. Wheat occupies more than 50% of the crop producing area. In recent years the total grain producing area in the region has increased; the area sown with winter wheat has increased, but that of spring wheat has decreased. Brown rust of wheat (P. triticina) appears annually and virtually everywhere in the region. Its share of the population structure amounts to 55%. Epiphytotics of this disease have occurred in 6-7 years out of 10; plant infection reached 80-90%, and crop losses 20-30%. In winter wheat most outbreaks have occurred at the end of the growing season, while in spring wheat it is at the ripening stage. Crop losses are 20-30%. Winter rye is grown in the northern part of the region. Its rusts complex consists of brown rust (P. dispersa) and stem rust (P. graminis). Brown rust (P. dispersa) occurs annually all over the area. Its share of the population structure is 67%. Epiphytotics have occurred in 5-6 years out of 10 with up to 60-80% of plants infected, and crop losses 20-25%. Stem rust (P. graminis) have shown weak or moderate development.

Volgo-Vyatski region.
The climatic and agricultural conditions of this region are notable for low temperatures and sufficient humidity. The grain producing area is 2.7 million ha, giving a gross yield of 3.1 million tons, or 6% of total production. The main crops are: winter rye, spring wheat, spring barley and oats. Weather conditions may be favorable to one or other of the pathogens. The frequency and scale of severe outbreaks are limited by cold winters and short growing seasons. Brown rust (P. triticina) of spring wheat occurs annually. Its share of the population structure amounts to 41%. Epiphytotics have occurred in 3-4 years out of 10, with crop losses of 15-20%. The rust complex of winter rye in this region consists of brown rust (P. dispersa) and stem rust (P. graminis). Brown rust (P. dispersa) of rye also occurs annually in some degree, amounting to 49% of the population structure. Epiphytotics have occurred in 4-6 years out of 10, with crop losses of 15-20%. The share of stem rust of rye (P. graminis) in the population structure reaches 22%. Epiphytotics have occurred in 4-5 years out of 10 with up to 60-80% of plants infected, and crop losses can be as much as 50%.

Uralski region.
The climatic conditions of this region divide it into two contrasting zones. The northern part is characterized by moderate temperatures and sufficient humidity, similar to the Volgo-Vyatski region. The southern part differs in having a hot, dry climate with high temperatures and a rain deficit. The producing area is 8.8 million ha, the gross yield of grain 8.9 million tons, or 17.2% of total grain production.
The main crops are spring wheat, which occupies about 60%, and spring barley which occupies 25% of the grain producing area. There are also winter rye and oats. Brown rust (Puccinia triticina)of wheat is the main disease; its share of the population structure is 66%. Outbreaks occur annually, showing moderate development with 30-40% of plants infected. Winter rye is grown in the northern part of the region. Its rust complex consists of brown rust (P. dispersa) and stem rust (P. graminis). Brown rust (P. dispersa) of rye occurs annually; its share of the population structure amounts to 50%. Epiphytotics have occurred in 4-5 years out of 10, with crop losses of 20-25%. Stem rust (P. graminis) has occurred in some fields; its share is as small as 8%. At the end of the growing season the infection of plants can each 30-40%. Results of the generalized data on frequency of epiphytotic occurrence and crop losses in different regions are submitted in Table 1 and Table 2.

References

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Sanin SS, Pyzhikova GV, Neklesa NP, Bistritskaya VN, Ibragimov TZ, Lebedev SA , 1988. Practical suggestions on diagnosis, recording and control of brown rust, blotch and powdery mildew of wheat. Moscow, pp. 26.

Sanin SS, Nazarova LN., Dimchenko AM, Politiko PM, Strizhekozin YuA, Zhochova TP, Phochenkova TV, Korneva LG, 1980. Diagnosis, recording and control of stem and brown rust of wheat under intensive cultivation. Moscow, pp. 30.

Stepanov KM, Nazarova LN, Pyzhikova GV, Strizhekozin YuA , 1978. Methods for calculating damage due to stem and yellow rust of wheat and stem rust of rye. Mycological Phytopathology 12, 516-520.

Terechov VI, Kaidash AS, Kaidash AS, Granin EF, Bessmeltsev VI, 1988. Suggested methods for forecasting and control of brown rust of wheat, pp. 27.

Sanin SS, Pyzhikova GV, Strizhekhosin YuA, Nazarova LN, Agaev AA, 1984. Mathematical modeling of epiphytotics of stem rust of wheat, of endemic and exotic origin. Vestnik Selskokhozaistvenoi  Nauki N3, 85-89.

Stepanov KM, Nazarova LN, Strizhekhosin YuA,  Agaev AA, 1984. Mathematical modeling of the development of stem rust on barley. Selskokhoziastvenaya  Biology N5, 116-120.