In the years 2003–2005 studies were conducted in the area of Lublin the aim of which was to study the population dynamics of aphids colonizing the trees of Juglans regia L. in the street and the park sites against the course of weather conditions. The weather in spring probably had no effect on the date of hatching of the larva of fundatrix, which was usually observed in the third 10-days’ period of May. On the other hand, the dry period, heat waves (above 30°C) and stormy rainfalls affected the break in the aphid population observed in July and August. The maximum population of P. juglandis was found in the second 10-days’ period of June, while that of Ch. juglandicola – at he turn of June and July. The highest number of P. juglandis was observed in 2004, while that of Ch. juglandicola in 2003. In 2003 the dominating species in both sites was Ch. juglandicola, while in the other years of studies it was P. juglandis.

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