DEPENDENCE OF BROWN RUST ON WINTER WHEAT AND RYE ON A NUMBER OF DAYS WITH DEFINITE WEATHER FACTORS

Nowadays the primary task is to find a general formula of predicting development of brown rust on winter wheat and rye. The existing methods allow making predictive formulas and the regression equation only for those regions, where a long-year study of disease and weather has been carried out. When we try to predict brown rust on a greater area, it’s rather expensive and it needs a wide range of research posts. One of the methods to make a general formula was based on studying weather factors effecting on pathogen development. It’s well-known that dripping moisture is necessary for rust spore germination. It usually appears on plant surface as a result of precipitations and dew. A substantial increase in humidity is characteristic for the period. Temperature has also a significant effect on pathogen development. When it lowers, moisture stays on the plant for a longer time and postpones a period of infection. Thus, we found two factors (air humidity and its temperature), which influence a lot on development of brown rust pathogen. Due to calculations we ascertain the ratio of the number of days with minimum air humidity (40% or more) to the number of days with an average daily temperature of 15°С or more, which shows the effect of these factors on brown rust development. The period for which is to ascertain the ratio is May of this year. The figures received according to the formula are a summary index of the weather (XЧД). In the conditions of the Tambov region heavy or medium development of brown rust on winter wheat and rye is possible when XЧД is 1,40 or more.