A model is presented to predict sanitary felling of Norway spruce (
Picea abies) due to spruce bark beetles (
Ips typographus,
Pityogenes chalcographus) in Slovenia according to different climate ...change scenarios. The model incorporates 21 variables that are directly or indirectly related to the dependent variable, and that can be arranged into five groups: climate, forest, landscape, topography, and soil. The soil properties are represented by 8 variables, 4 variables define the topography, 4 describe the climate, 4 define the landscape, and one additional variable provides the quantity of Norway spruce present in the model cell. The model was developed using the M5′ model tree. The basic spatial unit of the model is 1
km
2, and the time resolution is 1 year. The model evaluation was performed by three different measures: (1) the correlation coefficient (51.9%), (2) the Theil's inequality coefficient (0.49) and (3) the modelling efficiency (0.32). Validation of the model was carried out by 10-fold cross-validation. The model tree consists of 28 linear models, and model was calculated for three different climate change scenarios extending over a period until 2100, in 10-year intervals. The model is valid for the entire area of Slovenia; however, climate change projections were made only for the Maribor region (596
km
2). The model assumes that relationships among the incorporated factors will remain unchanged under climate change, and the influence of humans was not taken into account. The structure of the model reveals the great importance of landscape variables, which proved to be positively correlated with the dependent variable. Variables that describe the water regime in the model cell were also highly correlated with the dependent variable, with evapotranspiration and parent material being of particular importance. The results of the model support the hypothesis that bark beetles do greater damage to Norway spruce artificially planted out of its native range in Slovenia, i.e., lowlands and soils rich in N, P, and K. The model calculation for climate change scenarios in the Maribor region shows an increase in sanitary felling of Norway spruce due to spruce bark beetles, for all scenarios. The model provides a path towards better understanding of the complex ecological interactions involved in bark beetle outbreaks. Potential application of the results in forest management and planning is discussed.
O nalazu hrastove mrežaste stjenice (
Corythucha arcuata
) u parku dvorca Lužnica kod Zaprešića, Hrvatska, 6 km od slovenske granice, obavijestio nas je prof. Boris Hrašovec sa Šumarskog fakulteta ...Sveučilišta u Zagrebu u jesen 2016. godine. 17. 11. 2016 obavili smo potragu za štetnikom na sedam lokacijama u jugoistočnoj Sloveniji (Mokrice, Obrežje, Rigonce, Dobova, Mostec, Zakot i Bukošek). Pričvršćeno i djelomično zeleno lišće, kao i otpalo lišće
Quercus robur
je bilo na terenu pomno pregledano i sumnjivi uzorci su stavljeni u plastične vrećice i donijeti u laboratorij za daljnju analizu. Morfološka identifikacija je provedena na uzorku jajnih grupa na donjoj strani lišća i svlakova ličinki (exuviae) koje su bile prisutni na otpalom lišću
Q. robur
. Izvršeno je mjerenje broja jaja u 9 jajnih grupa i dužina i širina 30 jajnih čahura. Jajne ljuske (čahure) i svlakovi ličinaka na otpalom lišću
Quercus robur
bile su na pretraženom području nađene samo u hrastovoj šumi kod sela Zakot u blizini Brežica (E, 45°54’48“ N), koji je 14 km od najbližjeg nalaza u Hrvatskoj kod dvorca Lužnica. Jajne grupe sadržale su od 12 do 61 jajnih čahura. Jajne čahure su bile vretenastog oblika i crna s apikalnim otvorom i rubnim zadebeljenjem, duge 560 μm (475-596 μm) i široke 196 μm (183-196 μm). Ličinke su bile uglavnom tamne sa prozirnim žućkastim dijelovima na obje strane tijela. Imale su brojne bodlje. Brojne katranasto crne mrlje izmeta (faeces) hrastove mrežaste stjenice nalazile su se ravnomjerno na donjoj površini hrastovog lišća na kojem su bile prisutne jajne čahure i svlakovi ličinki.
C. arcuata
najvjerovatnije se proširila u Sloveniju iz Hrvatske, gdje je bila opažena kod dvorca Lužnica, ili kao autostoper sa željezničkom transportom, jer sjevernu granicu šume kod sela Zakot predstavlja željeznička pruga koja vodi od balkanske regije prema srednjoj Europi. U početku srpnja 2017. ustanovili smo namnoženje
C
.
arcuata
na lokaciji prvog nalaza i širjenje vrste na područje Krakovske hrastove šume, udaljeno 17 km zračne linije od sela Zakot.
Here we report the discovery of
Corythucha arcuata
in Slovenia in autumn 2016. Egg shells and molts of oak lace bug were found on the fallen leaves of
Quercus robur
in an oak forest in the village of Zakot near Brežice in the southeastern part of Slovenia.
C
.
arcuata
most likely spread to Slovenia from Croatia, where it was previously reported from the park at Lužnica Castle near Zaprešić, 14 km from the find in Slovenia, or as a hitchhiker on rail traffic running along the northern edge of infested forest. Further spread of
C. arcuata
to Krakovo oak forest was detected in the beginning of July 2017.
•A phenology model of Pityogenes chalcographus was developed.•The model quite accurately simulates the seasonal dynamics of P. chalcographus.•Sensitivity analysis revealed the most influential ...parameters.•CHAPY was calibrated and validated for Slovenia.•Development of the model revealed several knowledge gaps.
The purpose of the study was to develop, calibrate and validate a comprehensive phenological model for the spatiotemporal simulation of the seasonal development of the six-toothed spruce bark beetle, Pityogenes chalcographus (CHAPY). The validation dataset was acquired through monitoring of the bark beetle's phenology at eight sites in Slovenia in 2017 and 2018, along with air and bark temperature measurements. The predictions were made using air temperature from the INCA system (Integrated Nowcasting through Comprehensive Analysis), which is used to calculate the effective bark temperature for beetle development. Since the biology of P. chalcographus is poorly studied, a sensitivity analysis was used to pinpoint the most important model parameters. The first order (main) effect was the highest for the lower developmental threshold (DTL), while the second order (interaction, total) effect was the highest for the optimum temperature (TO). DTL was calibrated with an iterative procedure, and the best result with the lowest mean absolute error (MAE) was achieved at 7.4°C. Effective temperatures in the range between TO and the upper developmental threshold were calculated with a nonlinear function whose parameters were appropriately calibrated. The spring date threshold when the model calculation starts was calibrated with an iterative procedure and set at 9th March, which had the minimum MAE. The onset of Norway spruce infestation in spring was estimated using a lower threshold of 15.6°C for flight activity and a mean thermal sum of 216.5 degree-days (dd) from 9th March onward. The observed mean thermal sum required for total development of filial beetles was 652.8 ± 22.7°C, while the predicted mean thermal sum was 635.4 ± 31.4°C. Re-emergence of parental beetles occurred when 52.7% of the minimum thermal sum for total development was reached. The relative duration of the egg, larval and combination of the pupal and teneral adult developmental stages was 9.4%, 58.2% and 32.4%, respectively. Mass swarming concluded in the end of August when daylength was lower than 13.6 h, which was determined with the independent dataset of 1,017 pheromone traps. The diapause initiation at a daylength < 13.6 h is included in the model as an assumption. Successful hibernation of established broods is predicted by assessing the developmental stage of initiated generations at the 31st December. For validation, we compared the timing of phenological events in the field with predicted events using both 30-minute recorded data at study sites in the field and hourly data from the INCA. The time of spring swarming was estimated with a MAE of 5.6 days. The onset of infestation was predicted with a MAE of 6.0 days. The predicted onset of emergence of filial beetles was estimated with a MAE of 2.1 days. Additionally, CHAPY simulates the number of generations. CHAPY was successfully incorporated into two publicly available web applications. Development of the model revealed several knowledge gaps in P. chalcographus phenology, thus providing opportunities for further research of the second most damaging bark beetle of Norway spruce in Central Europe and for further improvement of the CHAPY model. Potential applications of the model for monitoring and management of P. chalcographus are discussed.
•A phenology model of Ips typographus in Slovenia was developed (RITY-2).•The model is based on PHENIPS and was validated and calibrated for Slovenia.•RITY-2 quite accurately simulates the ...spatiotemporal dynamics of I. typographus.•Two publicly available web applications were developed.•The model is used for the timely deployment of pheromone traps and trap trees.
We developed the RITY-2 phenology model for the spatial and temporal simulation of the seasonal development of Ips typographus based on the PHENIPS model and the data of Integrated Nowcasting through Comprehensive Analysis (INCA). Many parts of PHENIPS were improved with innovative approaches and a new model was developed. European spruce bark beetle phenology was monitored at eight study sites in 2017 and 2018, along with air and bark temperature measurements. RITY-2 predictions are based on air temperature from the INCA system, which is used to calculate the effective bark temperature for beetle development. An innovative procedure was introduced which finds most appropriate spring threshold from which calculation of the phenological model initiates. The onset of Norway spruce infestation in spring was estimated using a lower threshold of 14.5 °C for flight activity and a mean thermal sum of 53.0 degree-days (dd) from 7th March onward. The rate of brood development was calculated from the cumulative effective thermal sum of 30-min temperature data using upper and lower temperature thresholds of 38.9 and 8.3 °C, respectively, and a nonlinear function. For validation, we compared the timing of phenological events in the field with predicted events using both 30-minute recorded data from trap logs in the field and hourly data from INCA. The onset of spring swarming was estimated with a mean absolute error of 2.4 days. The onset of infestation was predicted with a mean absolute error of 4.7 days. The observed onset of emergence of filial beetles was estimated with a mean error of 0.5 dd. The model is calculated according to three scenarios that simulate different stand conditions. RITY-2 explicitly considers the strong effects of regional topography and can be used for precise monitoring of the actual state of bark beetle development at the specific model cell with a spatial resolution of 1 km × 1 km. Additionally, RITY-2 simulates the number of generations, which is necessary to assess the potential impact of bark beetle outbreaks at the regional scale. The model was successfully incorporated into two web applications that serve as tools for the timely deployment of pheromone traps and trap trees for European spruce bark beetle monitoring. The possible application of the RITY-2 model for the whole of Central Europe using data from the INCA system is discussed.
The North American oak lace bug feeds on leaves of ‘white oaks” in its native range. In Europe, it was first discovered in northern Italy in 2000. In recent years, it has subsequently spread rapidly ...and population outbreaks have been observed in several European countries. In the present study, we summarize the steps of its expansion.
To predict its potential host range, we checked 48 oak species in 20 sentinel gardens in seven countries between 2013 and 2018.
In total, 27 oak species were recorded as suitable hosts; 13 of them are globally new ones, 23 out of the 29 in section Quercus (∼ white oaks, an intrageneric taxonomic unit within genus Quercus), including Asian oaks, native to Japan, Korea and China, and four out of five in section Cerris (another intrageneric unit of the same genus), were accepted as hosts. None of the species in section Lobatae (red oaks) or in the Ilex group was accepted.
Host records were also collected in forest stands of 10 countries. We found 11 oak species that were infested. Outbreak populations were most commonly found on Quercus robur, Quercus frainetto, Quercus petraea and Quercus cerris, comprising widespread and outstandingly important oaks species in Europe.
Based on our findings, we conclude that suitable hosts for oak lace bug are present in most of Europe and Asia. This means that a lack of hosts will likely not restrict further range expansion.
The East Asian ambrosia beetle (Xylosandrus germanus - Blandford 1894) is an invasive species that has become successfully established in Europe and North America. In Slovenia, X. germanus was first ...recorded in 2000 in the western part of the country, and since 2008 the species has also been identified in other parts of Slovenia. The first economic damage was recorded in 2016 after a massive attack on recently felled logs of different tree species, spurring research into this non-native invasive species. To examine the distribution and abundance of X. germanus compared to other ambrosia beetles and to determine voltinism and the flight period of the species in our climatic conditions, we deployed 19 ethanol-baited traps from March to November 2017 in oak-, beech- and fir-dominated forest stands in central Slovenia. To verify the vertical distribution of X. germanus, traps were installed at altitudes ranging from 303 m to 941 m a.s.l. Furthermore, the impact of the ice storm that hit Slovenia in 2014 on the abundance of X. germanus was also studied. Non-native X. germanus represented 71.8% of the total catch and was significantly more abundant than the other five most common species: Xyleborinus saxesenii (20.0%), Xyleborus monographus (3.6%), Anisandrus dispar (2.5%), Trypodendron domesticum (1.2%) and Trypodendron signatum (0.6%). X. germanus was most abundant in beech-dominated stands, but the differences between forest types were not significant. The species was found along the entire altitudinal gradient. Our results indicate that the swarming of X. germanus in lowland forests may already occur by the middle of March. Maximum flying activity was observed in May and early June in forests below 600 m a.s.l. and at the end of May and in June in forests above 700 m a.s.l. Only one generation per year was observed. The ice storm positively affected the abundance of X. germanus, especially in areas where sanitary logging was delayed. Xyleborinus attenuatus was detected for the first time in Slovenia.
From 2007 to 2008, a study of presence of the lime leafminer (Phyllonorycter issikii) in Slovenia and an attack of different species of the genus Tilia in six ecological regions at 22 sites in urban ...areas was carried out. The aim of the study was to determine the extent of lime leafminer in Slovenia and investigate whether the localities, ecological region, hosts species and years affect the moth population density, the damage to the leaves, and the number and surface of mines in the leaves of different host plants. This paper also gives recent data on the range and hosts of the lime leafminer; in Asia, it is indigenous in three countries, while in Europe it has expanded in 20 countries. In natural distribution, its hosts are local species of linden (Tilia spp.); in Europe its hosts are also linden hybrids, as well as exotic species of limes.
Parasitoids are known to be an important factor in the population density regulation of bark beetles. In our study of the parasitoid complex of spruce bark beetles in 2011 and 2012, we collected bark ...samples from trees infested with
I. typographus
from spruce stands in the altimontane belt of Slovenia. The samples were taken at different altitudes: 450, 700 and 1230 m above sea level. A total of 9 bark beetle species and 12 parasitoid species was found.
Ips typographus
was most abundant, with 93% of all species of scolytids. The parasitoid species that were found belonged mainly to the Pteromalidae and Braconidae families. By far the most abundant and frequent species was
Roptrocerus xylophagorum
, which represented 84% of all parasitoids and was present in all study samples. Differences in species composition, parasitoid species diversity, species abundance and parasitism rate were confirmed between locations and also between both years of our study.
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