Entomopathogenic fungi (EPF) in Croatian forests are known only from observations of insect cadavers that show obvious signs of disease. To date, their presence in soils has not been investigated. ...The aim of this study was to investigate their occurrence, diversity, and distribution, and to assess their density in tested soils. Soil samples were collected during 2018, 2019, and 2020 at different localities throughout the country, and analyzed by using a method of isolation of fungi on selective culture media. To assess the density of EPF in tested soils, colonies of individual fungal species were counted and recorded; the results were expressed as the number of colony-forming units (CFU) per gram of dry soil. After morphological and molecular analysis, five entomopathogenic fungal genera were identified: Beauveria spp., Metarhizium spp., Purpureocillium spp., Lecanicillium spp., and Paecilomyces spp. Results also showed that the range of a total EPF colony density in the soil varies from 4 × 103 to 27.4 × 103 CFU g−1. The most common were EPF of the genus Beauveria, which were recorded at four of five locations, and at 16 of 25 sampling points, but the highest average number (density) of colonies belonged to the genus Metarhizium. Since this type of research was never conducted in Croatia previously, this is the first evidence that insect pathogenic fungi are present in soils of different natural forest habitats. Such research can be useful in selecting and utilizing entomopathogens that are suitable for biological pest control in certain target areas.
Research highlights: The pine-tree lappet moth, Dendrolimus pini, can cause serious needle defoliation on pines with outbreaks occurring over large geographical areas. Under laboratory conditions, ...the promising potential of the naturally occurring entomopathogenic fungus Beauveria bassiana was tested against D. pini larvae as a biological control method. Background and objectives: The aim of this study was to investigate the most effective concentration and treatment dose of B. bassiana conidial suspension and how it affected the survival and feeding behavior of the pest. Materials and methods: The first experiment applied the fungal suspension directly on the back of selected larvae, and in the second experiment, sporulating cadavers obtained in the first experiment were placed into Petri dishes with healthy individuals. Different doses per larvae µL and spore suspension concentration spores/µL) were used. The second experiment was designed to investigate the horizontal transmission of fungi by exposing individual caterpillars to a cadaver covered in B. bassiana mycelia. Mortality rates were analyzed by Chi-squared tests using absolute values for total mortality and B. bassiana- attributed mortality. The lethal time and feeding-disruption speed were analyzed with parametric and non-parametric tests with the aim to determine whether statistically significant differences were observed between treatments. Results: Analysis of lethal time revealed that the 20 µL dose and 7.9 × 104 concentration yielded highest mortality, but also the average dieback rate of 9.4 days was significantly faster compared to all other treatments. In order to see whether insects stopped feeding after infection with B. bassiana, larvae weight loss was examined. Results showed that effective treatments induced change in the feeding behavior of infected larvae. The feeding disruption caused by the 20 µL treatment occurred on average 5.5 days after exposure or 3.9 days before the final dieback of larvae.
Phoretic mites use bark beetles for transportation to new, suitable habitats. Some phoretic mites act as predators and parasitoids of the bark beetles’ immature stages, especially egg and early ...larval stages, and are potential agents for the biological control of scolytine forest pests. Mites live very frequently in relationships with other invertebrates. Many are found in association with various species of bark beetles. Here, a total of 41 specimens of different bark beetles of the genus Ips (Ips acuminatus, Ips sexdentatus and Ips typographus) were studied for presence, species composition, and abundance of phoretic mites. The beetles were collected on dead wood and parts of tree bark of Pinus nigra, Pinus sylvestris and Picea abies in the Black Sea Mountains in Kastamonu and Artin Province of Turkey. A total of nine mite species were found, including Dendrolaelaps quadrisetus, Ereynetes sp., Histiostoma piceae, Paraleius cf. leontonychus, Pleuronectocelaeno barbara., Proctolaelaps hystricoides, Schizostethus simulatrix, Trichouropoda lamellosa and Uroobovellaipidis. All species are identified for the first time within Turkish fauna.
Background and Purpose: The pine-tree lappet moth, Dendrolimus pini, is a widely distributed pest in Europe that can cause serious needle defoliation on pines, with outbreaks occurring over large ...geographical areas. In Croatia the presence of D. pini was recorded only in the continental part, but not in a high level of abundance, and the outbreak of the population has never been recorded so far.
Materials and Methods: In autumn 2014 an unexpected and complete defoliation on Aleppo pine (Pinus halepensis Mill.) occurred in the vicinity of Skradin, near Šibenik, and was followed by defoliation in summer and autumn 2017 in Telašćica Nature Park, Dugi otok. Infested areas were inspected and overwintering larvae in soil surface were counted in order to estimate the population and assess whether the critical number of the population has been exceeded. Specimens were collected and transferred to the Laboratory for Entomological Analysis in the Croatian Forest Research Institute for further laboratory analysis.
Results: Since more than 10 larvae per m² of soil surface were found, it was concluded that an outbreak occurred at both localities. In both cases natural antagonists played an important role in lowering the pest population. In Skradin, entomopathogenic fungus Beauveria bassiana that occurred on the overwintering larvae broke the pest population, and in Dugi otok it was recorded, but to a much lesser extent and in combination with Drino inconspicua parasitoid. In both cases pines recovered very well in the following spring, with some bark beetle attacks mostly at the edge of the forest.
Conclusions: The outbreaks of D. pini resulting with a total defoliation of Aleppo pine stands, and the fact that they occurred in the Mediterranean region which is not an optimal area for its appearance, makes these events unusual. Also, this is the first record of D. pini population breakdown by some antagonist.
Mediterranean pine engraver, Orthotomicus erosus was never considered as a significant pest in Croatia and did not appear in high population densities until 2017, when it reached outbreak level in ...Aleppo pine stands. The beetle was first detected in Marjan Forest Park, Split, and was soon recorded in other parts of the Dalmatian coast. Soon after the outbreak occurred, we observed that all of the attacked trees exhibit severe blue staining in the sapwood which indicated fungal infection caused by the Ophiostomatales group of fungi. This raised the need to investigate their relationship with O. erosus and the pine decline, and the main aim of this study was to isolate and identify them. Isolates were obtained from adult O. erosus beetles, their galleries, and blue-stained sapwood, and identified according to the morphological characteristics and DNA sequencing. A total of six Ophiostomatales (Ophiostoma ips, O. piceae, Graphilbum cf. rectangulosporium, O. floccosum, Sporothrix pseudoabietina and Ceratocystiopsis cf. minuta) were identified in the study. This is the first record of Ophiostomatales as organisms associated with the pest O. erosus and pine species in Croatia.
The oak lace bug (OLB), Corythucha arcuata (Hemiptera: Tingidae), was first identified as an invasive pest in Europe in northern Italy in 2000 and since then it has spread rapidly, attacking large ...forested areas in European countries. The OLB is a cell sap-sucking insect that is native to North America, with Quercus spp. as its main host. Its rapid expansion, successful establishment in invaded countries, and observations of more damage to hosts compared to native areas are most likely due to a lack of natural enemies, pathogens and competitors. In its native area, various natural enemies of OLBs have been identified; however, little is known about the occurrence and impact of OLB pathogens. None of the pathogenic fungi found on OLBs in natural conditions have been identified until now. In this study, we provide evidence of four entomopathogenic fungi that are naturally occurring on invasive OLBs found in infested pedunculate oak forests in eastern Croatia. On the basis of their morphology and multilocus molecular phylogeny, the fungi were identified as Beauveria pseudobassiana, Lecanicillium pissodis, Akanthomyces attenuatus and Samsoniella alboaurantium. The sequences generated for this study are available from GenBank under the accession numbers MT004817-MT004820, MT004833-MT004835, MT027501-MT27510, and MT001936-MT0011943. These pathogenic species could facilitate biological control strategies against OLBs.
Various biotic and abiotic factors are the cause of the decline of coniferous forests throughout Europe. Trees weakened by unfavorable weather conditions create an ideal environment for a possible ...outbreak of bark beetles. The damage caused by bark beetles costs billions of dollars worldwide every year. Extreme climate events are responsible for the enormous forest losses in Tara National Park in the last ten years, leading to a massive bark beetle infestation. The understanding of the diversity and role of mites as biological control agents is still insufficient. In this study, we summarize the current knowledge on the diversity of mites associated with Ips typographus L. in Europe and provide information on the diversity of these mites in Serbia. Paraleius leontonychus, Uroobovella ipidis, Dendrolaelaps quadrisetus, Histiostoma piceae, and Trichouropoda polytricha were detected for the first time in Serbia. Moreover, the occurrence of Paraleius leontonychus represents the southernmost occurrence of this species.
Background and Purpose:
Orthotomicus erosus
, Mediterranean pine engraver, is widely distributed across the Mediterranean and southern Europe, Asia and North Africa. It is considered as secondary ...pest found on recently dead or felled trees, but can also attack weakened living trees. In high population levels this species can attack healthy trees and cause their dieback. Severe outbreaks occur after dry periods, or after fire in adjoining stands in warmer parts of the Mediterranean region, while this scenario has never happened in Croatia up to now. Bark beetles are important forest pests which have already been researched and discussed in relation to climate change, indicating that the predicted increase in temperature would lead to higher survival rates and faster development, thus directly influencing their population dynamics. Increase in temperature may stimulate changes in insects’ rate of development, voltinism, population density, size, genetic composition, extent of host plant exploitation, longitudinal and latitudinal distribution. Since climate conditions might have changed in the last few years as predicted in the Mediterranean region, the aim of our research is to document the first outbreak with high population levels of
O. erosus
in Croatia.
Materials and Methods:
The extent of dieback was evaluated by counting trees with dieback symptoms on diagonal transects plotted through each of 33 forest management sections of Marjan Forest Park (Split). Trunk sections from several trees with early stage symptoms were collected for further laboratory analysis, which consisted of incubation phase and subsequent morphological identification. During regular yearly surveys in forests of Croatia, the pest was observed on several sites and damages were recorded for both years 2017 and 2018. The records were entered into a map using QGIS version 3.2.1-Bonn. Spatial data was downloaded from DIVA-GIS server. Monitoring efforts were initiated in affected areas where 13 flight barrier pheromone traps (Theyson®) equipped with pheromone lure Erosowit® (Witasek, Austria) were set-up in late March in state-owned and privately owned forests across Dalmatia. Catches in the traps were collected and
O. erosus
adults were counted on a weekly basis in order to identify the abundance of the pest in monitored sites, as well as to obtain the first information about population dynamics and to assess voltinism.
Results:
On-site survey and the evaluation of dieback extent included sampling of 5% of all trees in Marjan Forest Park ,and the results showed that 23% of all trees in the forest park were affected by dieback symptoms. Visual examination of trunks, branches and bark showed symptoms of bark beetle infestation, while preliminary on-site examination of the observed adults pointed out to
O. erosus
. After two weeks in controlled conditions, bark beetle adults started to emerge from trunk sections which were placed in several mesh cages for incubation. Morphological identification by using stereomicroscope and the key for European bark beetles resulted in identification of
O. erosus
species. Over the course of the year 2017 one more site was reported to be infested with
O. erosus
, and eight additional sites were reported over the course of year 2018. In total, 446 ha were reported as infested, varying in intensity, in several different management units of state-owned and privately owned forests. The total number of trapped beetles in pheromone traps varied largely among sites. Our data indicate that several generations (at least 5 generations per year) were present in the year 2018.
Conclusions:
Sudden surge in observed damages, as well as the number of beetles trapped during monitoring, in years 2017 and 2018 throughout Aleppo pine forests in Dalmatia are the first record of
O. erosus
outbreak in Croatia.
O. erosus
is native to Croatia and so far it has been considered only as a minor pest whose outbreaks have never been recorded. Drought intensity and frequency and aridification trends in the research area (Dalmatia, Croatia) cause cumulative stress to trees and have increased
O. erosus
occurrence.
O. erosus
is expected to exhibit increased voltinism, better overwintering performance and earlier spring flights. Our first results confirm this epidemic stage of
O. erosus
with high abundances in Dalmatia in 2018 and at least 5 generations per year, which alter the population level of this pest. Finally, with high dispersal abilities of
O. erosus
through active flight and easy transportation with infested material (logs and branches with bark),
O. erosus
has the potential to become an important forest pest in Croatia. Thus, extensive studies on its biology, ecology, natural enemies and interaction with ophiostomatoid fungal species are needed in order to predict further spread and suggest viable and effective management measures.
As part of the research, the population of the eight-toothed spruce bark beetle in different types of forests in five protected areas in Bosnia and Herzegovina was analyzed. The study focused on the ...protected areas of Sarajevo Canton, specifically the secondary forests of fir and spruce, as well as the mixed forests of beech and fir (containing spruce). Pheromone traps were used as the research sample, and they were placed within PA Bijambara, PA Trebević, and PA Skakavac. The objective was to investigate the influence of forest type and climatological factors on the number of captured Ips typographus bark beetles from 2018 to 2021. The average number of captured I. typographus bark beetles during that period ranged from 491.39 to 901.68 individuals in secondary fir and spruce forests, and from 201.88 to 701.54 individuals in beech and fir forests (including spruce).
The aim of this study is to identify plant lice
Cacopsylla pulchella
as a new alien insect in the fauna of Albania. In order to assess the potential of this insect as a pest causing damages on trees, ...infestation level assessment was used. In the first decade of June 2020 samples were collected at three locations in Albania, where
Cercis siliquastrum
is grown. Samples were collected and brought to the laboratory for further analysis. Field research was performed to assess distribution and infestation intensity across various localities. The intensity of infestation was assessed by visual examination and was categorized according to previously determined categories.
C. pulchella
was confirmed on
C. siliquastrum
in three localities in Albania. Most of the infested trees had a moderate or high intensity of infestation. Compared to the results of other countries, it seems that the Judas trees are under heavy attack in Albania. Librazhd and Elbansn districts had the highest recorded infestation level. Infested trees found in this study should be inspected in the following years and this alien insect should be further monitored in order to estimate its potential of becoming an invasive pest in this country.
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