Entomologia Research Papers - Academia.edu (original) (raw)

Part I. Characteristics of ecological requirements of cambio- and xylophagous insects in chosen oak stands in southern Poland Abstract. The study was carried out in the years 1991–1993 and 2006–2008 (complementary observations) within... more

Part I. Characteristics of ecological requirements of cambio- and xylophagous insects in chosen oak stands in southern Poland

Abstract. The study was carried out in the years 1991–1993 and 2006–2008 (complementary observations) within selected oak stands or those with oak dominance – located in southern Poland, where increased oak decline has been observed (Forest Districts Niepołomice and Dębica, as well as the urban forest situated in Kraków – Uroczysko „Las Wolski”). The main objective of the study was to perform comprehensive ecological research on oak cambio- and xylophagous insects, with the aim to determine their participation and role in the decline of oak stands and to develop more effective methods of forecasting the occurrence and limiting excessive abundance of oak cambio- and xylophagous insects. Field studies were conducted on 26 permanent and temperature observation plots. For detailed qualitative and quantitative entomological analyzes, there were selected weakened, dying and dead oak trees colonized by cambio- and xylophagous insects and their entomophages. Entomological analyzes were carried out over the entire length of trees – within 1-meter sections. The field experiments were supplemented by laboratory cultures of tree sections with feeding cambio- and xylophagous larvae. On the basis of detailed entomological analyzes of 220 weakened, dying and dead oaks, 40 cambio- and xylophagous insect species were found, including 19 secondary pest insect species, that played an important role in the process of breaking weakened oak trees, as well as fragments of oak stands of various age classes. They were characterized by high values of ecological indices (stability, domination and density of occurrence, the synthetic index Q, Agrell’s index, indicator of trunk length colonization and density of feeding sites) and significant size of damage caused as well as leading position in micro-succession chains on weakened trees.It was found that as the age of oak stands increased, there changed the species composition and quantitative structure of communities and micro-environmental-trophic associations of cambio- and xylophagous insects. There was demonstrated the dependence of some cambio- and xylophagous species on the type and condition of breeding material, tree age, height and DBH, as well as tree trunk diameter and thickness of the bark. Among the factors limiting the population size of the most frequently and numerously occurring secondary pest insects, parasitoids from the Ichneumonidae family (Hymenoptera, Ichneumonidae) and woodpeckers were the most important. There were listed the species that played a critical role in the process of breaking weakened oaks and/or in the depreciation of wood (Leiopus spp., Saperda scalaris, Scolytus intricatus, Agrilus biguttatus, A. angustulus, A. sulcicollis, Plagionotus arcuatus, P. detritus, Phymatodes testaceus, Rhagium mordax, Pogonocherus hispidulus, Elateroides dermestoides, Xyleborus monographus, Xyleborus dispar, Xyleborinus saxesenii, Trypodendron domesticum). In order to limit the size of damage caused by secondary pest insects, and thus, the intensity of dieback of the studied oak stands and mixed stands with oak predominance, prophylactic and protective measures were proposed.

Part II. Biology, forecasting and limiting the excessive occurrence of jewel beetles in oak stands

Abstract. The aim of the study was to investigate the biology and ecology of jewel beetles Agrilus spp. (Coleoptera: Buprestidae), specifically to fill gaps in knowledge about their habitat requirements. A particularly important issue was the determination of the role of these insects in the decline of oak stands and the evaluation of possibilities to control their populations. An attempt was also made to develop methods for forecasting the threat to oak stands due to jewel beetle mass occurrence, and also for using feeding and/or sexual attractants to control these pests. Data on the use of attractants and traps for trapping the oak buprestid beetle Agrilus biguttatus (Fabr.), its habitat preferences, tree colonization and killing, as well as on the methods of pest control was collected on permanent research plots and during numerous field inspections carried out in the forest districts from which jewel beetle effects were reported. In the years 2006–2009 and earlier, the following Forest Districts were inspected: Białowieża, Browsk, Brzeg, Chojnów, Czarna Białostocka, Hajnówka, Jabłonna, Jarocin, Karczma Borowa, Krotoszyn, Łochów, Piaski, Pińczów, Puławy, Pułtusk, Rudka, Wołów and Żmigród. Based on the results obtained, the causes of oak dieback were determined, above all – the role played by jewel beetles in this process. Dispensers containing compounds derived from bark and leaf extracts as well as eucalyptus oil were tested in the context of their suitability for attracting adult jewel beetles. Different types of traps designed for catching adult jewel beetles were also tested. The analysis of feeding sites performed in forest stands and the observations carried out under laboratory conditions (on colonized oak bark and wood cuttings) enabled the determination of jewel beetle species composition and population numbers as well as the species of accompanying insects, including other pest insects, parasitoids and predators. In the stands with visible effects of jewel beetle damage, the possibility to efficiently control pest populations by the removal of colonized trees was evaluated. Due to the fact that the greatest difficulty is the identification of colonized trees, an attempt was made to verify the features that confirm tree colonization by jewel beetles. During field inspections, about 200 trees with various symptoms considered characteristic of colonization by jewel beetles were checked. Recommended prophylactic methods contributing to oak jewel beetle control include: limiting the activity of foliophages and fungal pathogens; improving site water conditions; maintaining appropriate stand density and structure, as well as sustaining natural enemies, such as woodpeckers, insect parasitoids and insect predators. Summing up the crucial research results, it was found that the oak jewel beetle is the most important pest of oak stands, causative to mass oak dieback when its population reaches outbreak level. Then this species starts colonizing not only so far preferred old, weakened oak trees growing in sunny sites, but may cause the decline of oak trees (even several-year-old), growing in sunny and shadowed sites, on the edges and inside stands, both dominant and those in regression. The increase in oak jewel beetle population density is observed more than ever in the stands on fertile forest sites, in the years following the prolonged periods of drought for several successive growing seasons.

Part III. Habitat preferences of jewel beetles from the genus Agrilus Curtis (Coleoptera, Buprestidae) in oak stands of the Krotoszyn Forest District

Abstract. Research on jewel beetles (Agrilus spp.) associated with oak stands were carried out in 2008–2009, in the Krotoszyn Forest District – both in a managed forest stand and in that with restricted forest management activities, situated in the buffer zone of the Smoszew Nature Reserve. The aim of the study was to examine the habitat preferences of species from the genus Agrilus, as well as the comparison of the structure of their communities in the studied stands. Moericke (yellow pan) traps, installed in oak crowns at the height of 20–25 meters, were used to catch jewel beetle adults. In total, 2338 adults of six Agrilus species were collected. The comparison of the structure of jewel beetle communities in the two studied stands did not show any significant differences. However, there were clear differences in the preferences of individual species. Excluding A. sulcicollis Lac., all the observed species preferred the forest stand growing in the buffer zone of the Nature Reserve. Based on the observation of jewel beetle phenology, it was found that adult activity may begin as early as the second decade of April and end even in September (e.g. A. olivicolor Kies.). Among the jewel beetle species caught in oak crowns, there were distinguished two main groups, characterized by different dates of adult emergence. The first phenological group comprised the so-called early spring species: A. sulcicollis, A. laticornis (Ill.) and A. angustulus (Ill.). The remaining observed species, i.e. A. olivicolor, A. obscuricollis Kies. and A. graminis Kies. were included in the group of the so-called late spring jewel beetles. The culmination of the occurrence of all the jewel beetle species observed in the canopy of oak stands ranged from the beginning of June to the end of July, which coincides with the duration of A. biguttatus (Fabr.) swarming.