One of the important tasks of agricultural production is an opportunity to predict changes in the pathogenic complex of grain crops. It is important not only to identify presence of certain pests, but also to estimate a degree of pathogen development, a role of the host varieties, their immunological potential. The species S. tritici occupies a leading position among the pathogenic complex of septorious spots. Most commonly the species S. tritici was identified on the winter varieties “Moskovskaya 39” and “Severodonetskaya Yubileynaya” with a frequency of occurrence of 90%. The same situation was identified among spring wheat varieties. The species S. nodorum occupies the second position in the distribution of septorious spots in the pathogenic complex. The species S. avenae was significantly inferior to the first two. For each variety being tested, the degree of damage made by a separate type of septoria was calculated according to the frequency of occurrence of each type of pathogen (a species composition) and the plant incidence of septoria. Among the spring soft wheat varieties, there can be identified “L 503”, “Favorit”, “Tulaykovskaya 10”. The septoria incidence degree of these varieties was 27.9%, 23.6%, and 29.3% respectively. Since the S. tritici occurrence in these varieties was more often compared to others (84%, 78%, and 83%, respectively), these varieties can be classified as poorly susceptible to the pathogen. The spring durum wheat varieties are more resistant to Septoriosis. The variety “Orenburgskaya 10” is found the best in this trait with only 17.1% incidence degree. The variety “Krasnokutka 10” showed the largest incidence degree (37.9%). Using the F-test (Fisher test) and the multiple comparisons (Bonferroni-Holm method), there has been shown a significant effect of the agroclimatic year conditions, a life form and the species on the formation of the species composition of Septoria spots. At the same time, the ratio of the species S. tritici, S. nodorum, S. avena throughout all years of study remains stable.

Currently, septoria is the basis of the pathogenic complex on wheat crops in Russia, occupying the predominant position among harmful fungal diseases. In case of severe wheat damage, the crop loss caused by the fungus Z. tritici, makes up from 10–25 to 40–60%. The crop loss caused by the fungus P. nodorum parasitizing is from 10–20 to 30–50% during the years of epiphytoty. The question of the economic significance of P. avenae has not yet been examined completely. However, depending on the area of wheat cultivation and the year of observation, its part in the septorian population may reach up to 76.9%. It was of interest to study in detail the influence of conditions of the specific year, life form, and species of wheat on the formation of the species composition of Septoria in the pathogenic complex of wheat. Among the complex set of factors included in the concept of the environment, a significant role belongs to its abiotic components, namely, climate and weather, but the variety as an environment-forming factor has a decisive role. Our studies were carried out during 2010–2017. During the research period, the weather conditions varied significantly over the years and were not always favorable for the development of plants and formation of a good wheat crop. During the study, deviations in the amount of precipitations during the vegetation period, and, in general, over the year from the long-term average annual values, were noted. The years of 2012, 2014 and 2015 were characterized by the highest moisture supply during the vegetation season. It has been predicted that cooler days of April and May will promote the better development of P. avenae and P. nodorum. P. nodorum receives its predominant development during the years with wetter weather within the vegetation period of wheat, in contrast to Z. tritici more resistant to low humidity. These data demonstrate adaptation of the pathogen to conditions of an increased temperature regime and reduced rainfall amount.