Observations over the Population Dynamics of the Pests of Generative Organs of Spring Rape in the Moscow Region
The studies were aimed at recording and analyzing the population dynamics of pests of the generative organs of spring oilseed rape, as well as the colonization of the plants in the Moscow region. The observations were conducted in 2008-2009 and in 2011-2013 on the plants of Ratnik variety in a plot of about 0.4 hectares; the forecrops in different years were vegetable crops and potato. Additional surveys were conducted in an area of 2-4 ha, as well as on rape crops in different areas of the Moscow region. Weather conditions with a few exceptions were normal. In most seasons, rape buds and flowers were colonized by eggs and larvae of bronzed blossom beetle (Meligethes aeneus Fab.), diamontback moth caterpillars (Plutella xylostella L.) and eggs and larvae of swede midge (Contarinia nasturtii Kieff.). The annual colonization of rape flowers and buds with bronzed blossom beetle exceeded 10%, while its maximum number in the experiment was noted in 2012. It was 2409 pcs/m2, which was most likely due to the accumulation of the pests in the site. In the budding and flowering phases, some diamontback moth caterpillars damaged the generative organs, while, in the experiment, their maximum reached 80 pcs/m2 in 2013. The rape buds colonized by swede midge larvae swelled and became 3-4 times larger. They did not bloom and did not yield fruits and seeds. Swede midge larvae were first recorded on the rapeseed study plot in 2009. Then their number increased annually and in 2013 reached 1720 pcs/ m2 with 10% of generative organ colonized by the pests. The correlation between the dynamics of the number of studied insects and weather conditions (average daily temperature and precipitation) turned out to be insignificant. Entomophages and diseases significantly affecting the populations of these pests were not recorded.