EN
The results of performed studies showed that migration of Rhopalosiphum padi on secondary hosts in Eastern Poland took place in the second half of May. While the aphid population developed on the primary host a constant decrease in the nitrogen compounds content was observed. During spring migration, individuals of bird cherry-oat aphid colonized secondary hosts that contained a higher amount of total nitrogen and free protein amino acids. Therefore changes in the content of basic nutrients within host plant tissues may be one of the most important factors affecting the host plant alternation by R. padi.