REGIONAL FORECAST OF WHEAT AFFECTION WITH LEAF RUST. DA YUSUPOV 1 , VB LEBEDEV l l Research Agricultural Institute for South-East Region, 7 Tulaikov str., Saratov, 410020, Russia Background and objectives Leaf rust caused by Puccinia recondite f.sp.tritici occurs in all regions where wheat is cultivated, Russia including. Each regional weather conditions exert various effect on development of leaf rust. Taking this into consideration one should pay special attention to weather conditions of the region on the process of affection when making computer forecasts. The goal of our study is the developing of crop protection system with the use of fungicides in Saratov region. Resuits and conclusions As a result of our studies the frequency of degree affection of leaf rust in wheat was established. Mathematical models of the forecast of affection with respect to phases of wheat growth have been developed and calculation of possible losses of grain during harvest caused by leaf rust was performed as applied to regional application. These models have a good knack for high-forecast capacity. Adequacy of the models has been tested with the use of independent experimental data. The average relative error of the forecast varies between two samples (variants of experiments) within 1,9-19 %. Forecast models have been loaded into computer and recommended for practical application in regional Plant Protection service.