In 2007–2009, studies on the number of pear sucker and its parasitization degree by the hymenopteran Sectiliclava cleone were carried out on two plots of pear orchard, differing in terms of applied protection strategy (without and with insecticide treatment). The presence of parasitoids was only recorded in case of single insect pests from the summer generations. A parasitization degree of wintering insects was higher in the plot without insecticide treatment comparing to the one with chemical protection (5 insecticide treatments during a season). After the first season the presence of the parasitoids in host’s abdomines was stated in 22–67% of female and 9–37% of male pear suckers on the first plot, and 3–14% of female and 2–15% of male pests on treated plots. After the second season, the percentage values were higher and amounted to 32–60% for female and 20–30% for male pear suckers in the untreated plot, and 16–26% of female and 6–14% of male pests on the second plot, depending on the date of spring observations. The number of the pest on both experimental plots varied in subsequent years and insect generations. In general, pear suker occurred at a low intensity, causing no visible damage. After the first season the number of wintering pest on untreated plot was initially twice higher, however, after overwintering it lowered 1.5 times comparing to treated plot. Following the second year of research, the number of pests from the summer generation was 3–4 times higher. The number of wintering insects on untreated plot was 5 times lower comparing to treated plot. In the last season (2009) on untreated plot the number of individuals shaked off from 25 branches amounted to 12.2 and 193.6 respectively during the spring and autumn. On treated plot with insecticides, the number of pests shaked off from 25 branches varied on average 40.6 in the spring and 65.4 in autumn.
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