The impact of brick (Agrochola circellaris Hufn.) and owlet moths (Lepidoptera: Noctuidae) on the health of seeds of field elms (Ulmus minor Mill.) in the landscape parks of the Świętokrzyskie Province

Abstract In the period of 2012-2013, a research was conducted to investigate the insects damaging the seeds of field elm (Ulmus minor Mill.). The aim of the research was to specify the damages to field elm seeds caused mainly by the brick (Agrochola circellaris) and to indicate the possible dependence between the number of damaged seeds by the caterpillars of this moth and stand density. The research was conducted in the areas of Cisów-Orłowiny Landscape Park (C-OLP) and Nida Landscape Park (NLP) in the Świętokrzyskie Province. In both parks, there were two test stands situated, each of which covered the material collected from the trees. The number of field elms ranged from four to six. Furthermore, a sample of 300 seeds were randomly collected from each tree. The elms in Cisów-Orłowiny Landscape Park were observed in full density stands (fully stocked stands); however, these trees in Nida Landscape Park were growing in loose density stands (under-stocked stands). In total, there were 12,000 seeds collected from 20 trees. The analysis of the collected research material demonstrated that 436 seeds from the field elms (Ulmus minor) were damaged by the brick (Agrochola circellaris). It constituted 3.6% of the total number of collected samples (Table 1). In the seed samples collected from the test stands in Cisów-Orłowiny Landscape Park, the damages caused by the caterpillars of the brick moth ranged between 0.8% and 2.9%. In the case of seed samples collected from Nida Landscape Park, the damages caused by the caterpillars of the brick moth were greater and ranged between 4.1% and 6.5%. The percentage of undamaged seeds ranged between 94.4% in Cisów-Orłowiny Landscape Park and 84.7% in Nida Landscape Park, which constituted, on an average, 89.5% for both parks. The 6.8% of the seeds were also damaged by other insects. The results of the research showed the dependence between the number of field elm seeds damaged by the brick Agrochola circellaris and the stand density (Table 2). The seeds collected from trees growing in the Nida Landscape Park in loose density stands (under-stocked stands) were twice as frequently damaged than those collected from the trees growing in Cisów-Orłowiny Landscape Park in full density stands. Also, the damages caused by other insects were greater among the seeds collected from trees growing in loose density stands than in full density stands (Table 1).