Agroecological importance of the protective forest plantings in Lower Volga region

The positive role of protective forest plantings in maintaining the stability of biotic communities and ensuring stabilization of a phytosanitary situation in the agricultural and woodland landscape of steppe and semiarid zones of Lower Volga region is established. The analysis of long-term data testifies that in general, the number of a harmful complex on fields of winter wheat (Triticum) and brown mustard (Brassica juncea) in the system of forest strips is lower than in opened agrocoenosis in average by 20,6 % and 16,2 %, respectively. The regularities of distribution of harmful and useful insects in corn and mustard agrocoenosis are noted. The obtained data on distribution of harmful insects and their concentration in a forested field gives the grounds to include regional processings of agrocoenosis of agricultural and woodland landscape in the system of protective measures. It is established that the existence of fields afforestation in Volgograd region creates the favorable conditions for development and accumulation of entomophages in fields. It leads to restriction of mass reproduction of harmful insects and to the decrease in their injuriousness. The essential distinctions in distribution and development of diseases in the agrocoenosis protected by forest plantings and the treeless fields are revealed. The maximal values of development of a complex of diseases on winter wheat are observed in zones, adjacent to forest strips (I and III), minimum - in the middle of a field. The estimated values of development of diseases in forested field is less, and in certain cases it slightly differs from the data obtained in a treeless field.