| Abstract | Kada se govori o potkornjacima razlikujemo dva različita pristupa. Prvi uključujepotkornjake u kategoriji štetnika, a drugi uključuje potkornjake u kategoriji insekata s veomavažnom ekološkom ulogom u šumskim ekosustavima. Smrekov pisar (Ips typographus L.) išesterozubi smrekov potkornjak (Pityogenes chalcographus L.) najvažniji su štetnici smreke uEuropi. Oluje, snjegolomi, šumski požari i dugoročna razdoblja suše najvažniji su okidačiepidemija smrekovih potkornjaka. Fiziološki oslabljena stabla s narušenim sustavom obranebivaju prva kolonizirana. Ako su dostupne dovoljne količine materijala populacijapotkornjaka raste iznad praga epidemije i zdrava dubeća stabala mogu biti uspješno napadnutai kolonizirana. Iz tog razloga pogodan materijal treba ukloniti iz sastojina ili uhrpati odmahnakon sječe ili prorjede. To uvijek nije moguće dijelom zbog ljudskih resursa ili nepovoljnihterenskih uvjeta.Cilj istraživanja obuhvaćenih ovim radom bio je problematici zaštite smrekovih šumaod nepovoljnog utjecaja potkornjaka pristupiti prema načelima integriranog pristupa. U tusvrhu istraživanje je provedeno u smrekovim šumama Like u gorskoj Hrvatskoj na područjušumarije Perušić u periodu od 2013. do 2015. godine. Postavljene su dvije pokusne plohe narazličitim nadmorskim visinama, jedna u smrekovoj kulturi na nadmorskoj visini od 500metara, a druga u prebornoj prirodnoj sastojini smreke na nadmorskoj visini od 1100 metara.Istraživanje je obuhvatilo više različitih aspekata biologije i etologije dvije najvažnijevrste smrekovih potkornjaka. Istraživana je fenologija smrekovih potkornjaka pomoću lovnihstabala u smrekovim šumama na različitim nadmorskim visinama; prostorna distribucija vrstapotkornjaka po sekcijama lovnih stabala; mogućnost primjene Phenips modela za predviđanjenapada i razvoja smrekovog pisara; povezanost gustoće napada s uspjehom reprodukcije;utjecaj brojnosti predatora na mortalitetom populacije; niše zimovanja; markiranje jedinki iprostorna distribucija označenih jedinki na granici nacionalnog parka Sjeverni Velebit iokolnih gospodarskih šuma; mogućnost monitoringa populacija smrekovih potkornjakamokrim i suhim tipom najraširenije naletno barijerne crne Theysohn feromonske klopke temogućnost monitoringa s različitim tipovima naletno barijernih feromonskih klopki;mogućnost uspostave higijene sastojine nakon sječe ili prorjede pomoću dvije metodeslaganja grana te potreba i opravdanost otkoravanja panjeva kao mjere integrirane zaštitešuma od napada potkornjaka.
U razvoju moguće je razlikovati razvojni stadij jaja, ličinke, kukuljice i odraslog imaga.Tri larvalna stadija uočena su kod obje vrste potkornjaka.Smrekov pisar je bivoltna ili polivoltna vrsta u smrekovim šumama na nižimnadmorskim visinama, a na višim nadmorskim visinama univoltna ili bivoltna vrsta, ovisno ovremenskim prilikama. Kod osnivanja glavnih generacija razvija barem jednu sestrinskugeneraciju. Hodnici sestrinskih generacija su jednokraki, vertikalni bez bračne komorice.Početak proljetnog rojenja zabilježen je od sredine svibnja do sredine lipnja. Sredinomsrpnja ili početkom kolovoza zabilježeno je ljetno rojenje ove vrste.Stadij jaja traje relativno kratko, uglavnom oko tjedan dana. Stadij ličinke na nižojnadmorskoj visini traje od 14 do 30 dana, najčešće između 21 i 25 dana. Na višoj nadmorskojvisini stadij ličinke traje nešto duže od 22 do 36 dana. Stadij kukuljice bez obzira nanadmorsku visinu u pravilu traje jedan do dva tjedna.Razvoj od jaja pa sve do izlaska novih kornjaša trajao je između 42 i 68 dana na nižoj nadmorskoj visini, a na višoj nadmorskoj visini između 50 i 72 dana.Šesterozubi smrekov potkornjak je univoltna ili bivoltna vrsta u smrekovim šumama ina nižoj i na višoj nadmorskoj visini. Broj uspješno razvijenih generacija u jednoj godiniuglavnom ovisni o vremenskim prilikama.Proljetno rojenje šesterozubog smrekovog potkornjaka na nižoj nadmorskoj visiniodvija se uglavnom od sredine svibnja do sredine lipnja, a na višim od kraja svibnja dosredine lipnja. Proljetno rojenje u pojedinim godinama evidentirano je dva tjedna ranije nanižoj nadmorskoj visini. Od sredine srpnja do sredine kolovoza zamijećeno je ljetno rojenješesterozubog smrekovog potkornjaka na nižoj nadmorskoj visini, dok na višoj nadmorskojvisini nije zabilježen razvoj ljetne generacije šesterozubog smrekovog potkornjaka na lovnimstablima. Kod osnivanja proljetnih generacija šesterozubi smrekov potkornjak osniva baremjednu sestrinsku generaciju. Hodnici sestrinskih generacija su jednokraki bez bračnihkomorica.Ukoliko su tijekom prvog pregleda lovnih stabala zamijećena jaja kod sljedećegpregleda za tjedan dana već su uočene prve ličinke. Može se zaključiti da je razvojni stadijjaja jako kratak. Stadij ličinke na nižoj nadmorskoj visini traje od 14 do 49 dana, dok na višojizmeđu 20 i 48 dana. Stadij kukuljice traje između jedan i dva tjedna na obje nadmorskevisine.Potpuni razvoj šesterozubog smrekovog potkornjaka od jaja do izlaska novih kornjašatraje između 35 i 70 dana na nižoj nadmorskoj visini, a na višoj nadmorskoj visini od 50 do 84 dana.
Smrekov pisar uglavnom kolonizira dijelove debla s debljom korom, dok šesterozubismrekov potkornjak kolonizira gornje dijelove debla s tanjom korom. Između debljine kore ibroja ulaznih rupa smrekovog pisara uočena je statistički signifikantna pozitivna korelacija,dok je između debljine kore i broja ulaznih rupa šesterozubog smrekovog pisara uočenastatistički signifikantna negativna korelacija.Šesterozubi smrekov potkornjak je satelit vrsta smrekovog pisara koja se prilagodilana različite načine: vjerovatno detektira feromone agregacije smrekovog pisara ili pojedinukomponentu kao kairomon; feromonima agregacije djeluje repelentno na smrekovog pisara;zbog male veličine tijela iskorištava dostupan materijal koji zbog tanke kore i floemasiromašnog šećerima ne može iskoristiti smrekov pisar te koristi lenticele kao otvorene ulazekroz deblju koru stabala.Na temelju podataka temperature kore promatrana fenologija smrekovog pisara nalovnim stablima i fenologija dobivena Phenips modelom uvelike se poklapaju. Razlike suvidljive u očekivanom vremenu početka infestacije gdje model predviđa početak razvoja 4 do5 dana ranije ukoliko se koristi temperatura kore ili 16 do 18 dana ranije ukoliko se koristitemperatura zraka. Do ubrzavanja ili usporenog razvoja potkornjaka može doći zbog efektazasjenjivanja ili izloženosti pojedinog dijela lovnog stabla direktnom utjecaju sunčeveradijacije.Model predviđa početak razvoja sestrinske generacije od 5 do 12 dana ranije ili 4 do 17dana kasnije. Nedostatak modela je što ne može predvidjeti gustoću napada o kojoj uvelikeovisi početak osnivanja sestrinske generacije.Reprodukcija smrekovog pisara prema modelu prestaje kada dužina fotoperioda padneispod 14,5 sati. Dok je temperatura zraka visoka, a u vezi s time i temperatura floema ženkesmrekovog pisara odlažu jaja u galerijama. Moguće je da se dijapauza nakon skraćivanjafotoperioda očituje u smanjenju broja odloženih jaja jer je na lovnim stablima uočenoodlaganje jaja i nakon skraćivanja fotoperioda.Unatoč odstupanjima koje Phenips model ne može predvidjeti (efekt zasjenjivanja,izloženost kore sunčevoj radijaciji, početak razvoja sestrinskih generacija koji je uvjetovangustoćom napada i temperaturom floema te temperatura floema i temperatura zraka u vrijemeskraćivanja fotoperioda) model se može primjeniti za predviđanje napada i razvoja smrekovogpisara, pogotovo u sastojinama u kojima se može očekivati povećanje voltinizma i povećanirizik od epidemija smrekovog pisara jer su podignute izvan optimalnog područja rasprostranjenosti smreke.
Većina markiranih jedinki smrekovog pisara leti na male udaljenosti (do 200 m), a tekmanji dio (manje od 5 %) je sposoban za let na udaljenosti veće od 1 km, vjerovatno uzpomoć vjetra.Povećani opseg ljudskih aktivnosti u gospodarskim šumama (uklanjanje vjetroizvala,snjegoloma, stabala stradalih od gljiva uzročnika truleži korijena te stabala oštećenihdjelovanjem ostalih biotskih i abiotskih čimbenika) te smanjenje ljudske aktivnosti (u viduuklanjanja stabala pogodnih za razvoj) unutar nacionalnog parka vjerovatno utječu namigracije i prostornu disperziju jedinki smrekovog pisara između gospodarskih šuma i šumaposebne namjene, a samim time i na dužinu leta.Uočene su dvije niše zimovanja smrekovog pisara - pod korom napadnutih stabla i ušumskoj stelji. Sniženjem nadmorske visine povećava se udio zimujućih imaga pod koromnapadnutih stabla - od vršne zone Zavižana (50 %), preko Štirovača (60 %) do najniženadmorske visine sa smrekovim sastojinama u g.j. Žitnik (76-94 %).Niska gustoća napada smrekovog pisara odnosno mali broj galerija po m2 kore nužno neznači veliki uspjeh reprodukcije izražen brojem kćeri u odnosu na majku (/). Uspjehreprodukcije kretao se od 0,51 do 4,17 /, dok se gustoća galerija kretala od 27 do 117galerija po m2 kore.Visoki mortalitet populacije smrekovog pisara (imaga do 42 %, ličinki i kukuljicaizmeđu 70 i 100 %) kod niske gustoće napada posljedica je nemogućnosti prezimljavanjepredadultnih stadija (L3 ličinka, kukuljica), ali i velike brojnosti ličinki predatora. Većinamužjaka smrekovog pisara (74 %) kopulira s dvije ženke što je svojevrsna prilagodbaizbjegavanju unutarvrsne kompeticije između ličinki.Sanitarnu sječu kao mjeru sanacije žarišta napada smrekovog pisara potrebno jeprovoditi u ranu jesen na višim nadmorskim visinama, odnosno tijekom zime ili rano uproljeće na nižim nadmorskim visinama. U pravilu osnova zaštite šuma od potkornjaka jedobro poznavanje biologije. Lovna stabla koriste se u zaštiti šuma od potkornjaka veći dužiniz godina. Zrela stabla smreke posjeku se u proljeće i ostave u sastojini dok traje rojenjepotkornjaka. Kada su debla kolonizirana uklanjaju se iz sastojine prije razvoja mladihkornjaša. Nakon razvoja sintetičkog feromona lovna stabla su u većini slučajeva zamijenjenaferomonskim klopkama. Feromonske klopke opremljene s feromonom koriste se u sustavuintegrirane zaštite šuma za monitoring populacije potkornjaka, ali i za masovni izlov i prekidinfestacije. U posljednja dva desetljeća šumarska operativa u Hrvatskoj uglavnom koristiticrnu naletno barijernu Theysohn feromonsku klopku za monitoring populacija smrekovihpotkornjaka u smrekovim šumama
Mokre i suhe naletno barijerne crne Theysohn feromonske klopke mogu se s gotovojednakom učinkovitošću (broj ulovljenih jedinki potkornjaka) i selektivnošću koristiti umonitoringu populacija smrekovih potkornjaka. Potvrđeno je da niti smrekov pisar nitišesterozubi smrekov potkornjak ne mogu pobjeći iz suhih feromonskih klopki makon štoupadnu u lovnu posudu na dnu klopke.Predatorska vrsta Thanasimus formicarius L. može pobjeći iz lovnih posuda suhihferomonskih klopki, dok mogućnost bijega nije uočena kod predatorske vrste Nemozomaelongatum L. Mokre i suhe naletno barijerne crne Theysohn feromonske klopke na sve tritestirane pozicije (sastojina, rub sastojine, čistina) pokazale su jednaku učinkovitost lovljenjajedinki obje vrste potkornjaka.Monitoring populacija smrekovih potkornjaka (smrekovog pisara i šesterozubogsmrekovog potkornjaka) moguće je provoditi s testiranim naletno barijernim feromonskimklopkama (crna Theysohn, smeđa WitaTrap, multi funnel WitaTrap), dok bijeluWitaTrap i cross Witaprall Ecco feromonsku klopku treba izbjegavati zbog signifikantosmanjene učinkovitosti. Najselektivnija feromonska klopopka u ovom istraživanju bila jecross Witaprall Ecco, vjerovatno zbog mreže koja ima ključan utjecaj na selektivnostklopke. Signifikantno najnižu selektivnost za predatorsku vrstu T. formicarius pokazala jemulti funnel WitaTrap feromonska klopka, dok je istodobno isti tip klopke bio najvišeselektivan prema predatorskoj vrsti N. elongatum što je posljedica reducirane učinkovitostiklopke jer su predatori u klopku privučeni količinom svoga plijena.Uvid o razini gustoće populacije je od velike važnosti, posebice kada vremenski uvjetikao dugogodišnje suše i oluje mogu biti uzrok porasta populacije. Feromonske klopkeopremljene s feromonima ključan su faktor u monitoringu populacija i procjeni rizikanastajanja šteta uzrokovanih potkornjacima. Stoga je mnogo važnije osim efikasnostiferomonske klopke utvrditi prag epidemije za svaku agresivnu vrstu potkornjaka na temeljubroja ulovljenih jedinki u feromonskoj klopki.Cilj uspješne kontrole potkornjaka je suzbijanje potkornjaka u svim stadijima razvoja. Upravilu sve metode bi se trebale primjenjivati zajedno kao jedan integrirani sustav. Sječu iproredu sastojina najbolje je provoditi u mjesecima rujan i listopad jer će se ostatci sječe(grane, ovšci stabala i drugi ostatci) isušiti do proljeća i potkornjaci se neće moćirazmnožavati u takvom materijalu, pogotovo u prirodnim prebornim smrekovim sastojinamagdje se ostatci sječe ne koriste za biomasu zbog nepovoljnog terena.Prilikom proreda ili dovršene sječe u kulturama, odnosno preborne sječe u prirodnimsastojinama smreke potrebno je uspostaviti šumski red slaganjem grana u hrpe s debljim dijelom grane prema centru hrpe. Najčešća vrsta potkornjaka u hrpama granama bio ješesterozubi smrekov potkornjak. Metoda slaganja grana s debljim dijelom grane prema centruhrpe imala je signifikantno manji broj bračnih komorica od suprotne metode slaganja grana.Atraktivni materijal postat će neprikladan za napad potkornjaka zbog visoke vlažnosti usredini hrpa grana. Uhrpavanjem grana reducira se broj ubušenih potkornjaka, grane i ovršciposječenih stabla ne ometaju razvoj mladog naraštaja, stvara se povoljno stanište zasaproksilične kukce i povećava se bioraznolikost. Mnogo veće hrpe pogodnog materijala kojese u Švedskoj koriste kao izvor energije i ostavljaju da se isuše tijekom ljeta nisu uzrokovaleznačajni mortalitet stabla, posebice mlađih stabla uzrokovanih napadom šesterozubogsmrekovog potkornjaka.Otkoravanje panjeva kao mehanička mjera suzbijanja napada potkornjaka unutarsustava integrirane zaštite šuma provodi se u hrvatskome šumarstvu duži niz godina.Nije ju potrebno provoditi jer mali broj potkornjaka kolonizira panjeve i uspijevadovršiti svoj razvoj. S druge strane ovom mehaničkom mjerom direktno se povećava opasnostod truleži korijena ostalih neposječenih dubećih stabala u sastojini te se nepovoljno utječe nastanište saproksiličnih kukaca.U smrekovim sastojinama gdje uvjeti terena ne ograničavaju kretanje strojeva savdostupni drvni materijal kao što su nedavno vjetrom izvaljena stabla na rubovima sastojina,veliki prelomljeni ovršci stabala i ostali pogodni dijelovi drveta trebaju biti uklonjeni izsastojina jer predstavljaju pogodan materijal za razmnožavanje. Smrekovi trupci trebaju sečim prije ukloniti iz sastojina ili ukoliko je potrebno duže skladištenje preporučeno jeotkoravanje trupaca ili navodnavanje i održavanje trupaca vlažnima.Šumska higijena nakon redovne sječe ili prorjede i uklanjanje stabala oštećenih vjetrom,snijegom, udarom groma i nekim drugim biotskim i abiotskim čimbenicima najvažniji je diointegrirane zaštite šuma od napada potkornjaka. |
| Abstract (english) | When somebody speaking about bark beetles it is necessary to distinguish two differentapproaches. First one include bark beetles in category of a pests, and second one include barkbeetles in category of insects with important ecologic role in forests ecosystems. Eighttoothed spruce bark beetle (Ips typographus L.) and six toothed spruce bark beetle(Pityogenes chalcographus L.) are the most important pests of spruce in whole Europe.Storms, snow breaks, forests fires and long term drought periods are most important outbreaktriggers of spruce bark beetles. Weakened trees with poor defense system are colonized first.If this kind of breeding material becomes abundant bark beetles populations may increasebeyond epidemic threshold and healthy standing trees can be successfully attacked andcolonized. Because of this reason all suitable material need to be removed or pilled just afterthe felling or thinning. It is not always implemented, due to either shortage in manpower orlimited site accessibility.The aim of research encompassed in this work was to approach the issue of protectionspruce forests from the adverse impact of bark beetles in accordance with the principles of anintegrated pest management. For this purpose research was conducted in spruce forests ofLika in Croatian mountain region inside the territory of Perušić forestry office in period from2013. to 2015. Two experimental plots were set up on different elevations, first one in spruceculture at the elevation of 500 meters, and second one in natural uneven aged spruce stand atthe elevation of 1100 meters.The research included different biology and ethology aspects of two most importantspruce bark beetle species. This study includes the bark beetle phenology using trap trees inspruce forests on different elevations; spatial distribution of bark beetle species on trap treessections; using possibility of Phenips model for attack prediction and development of eighttoothed spruce bark beetle; interconnection of eight toothed spruce bark beetle attack densitywith breeding success; impact of natural enemies abundance on populations mortality;overwintering niches; spatial distribution using marked beetles in mark/recapture experimentson the border between the national park North Velebit and surrounding management forests;comparing wet and dry type of widely used flight barrier black Theysohn pheromone trapand monitoring possibility with different types of flight barrier pheromone traps; possibility ofsetting up a forests hygiene strategy after thinning or felling using two different methods ofbranches pilling; validation of stump debarking as an integrated forests protection measureagainst bark beetles attack.
The development stage of egg, larvae, pupae and adult beetle can be easily separated inboth bark beetle species. Three larvae instar by both bark beetle species was confirmed.Eight toothed spruce bark beetles is bivoltine or polyvoltine species in spruce forests onlower elevation, and univoltine or bivoltine species on higher elevation with cooler climate. Ineach season both species develop at least one sister brood generation. Sister brood galleriesare longitudinal uniramous without mating chamber.Start of spring swarming was observed in mid May to mid June, while in the period ofmid July to the beginning of August summer swarming was observed.The egg instar is very short, less then one week. The larval development lasted between14 and 30 days, mostly between 21 and 25 days on lower elevation, and lasted longer,between 22 and 36 days in higher elevation. Pupal stage lasted between one and two week onboth elevation.Full development period, egg to emerged adult beetle lasted between 42 and 68 days onlower elevation or between 50 and 72 days on higher elevation.Six toothed spruce bark beetle is univoltine or bivoltine species in spruce forests on bothelevations. The number of fully developed generations in one year mostly depend on weatherconditions.Spring swarming of six toothed spruce bark beetle was observed in the period of midMay to the middle of June on lower elevation, and between end of May and middle of June onhigher elevation. In some years spring swarming on lower elevations was observed two weeksearlier. In the period of mid July to the beginning of August summer swarming was observedon lower elevation, while summer generation development of this species was not observedon trap trees on higher elevation. During the spring swarming period this species developingat least one sister brood generation. Sister brood galleries are uniramous without matingchamber.While the eggs were observed during the first trap trees check at the following trap treescheck for one week first larvae were hatched. It was concluded that the egg developmentperiod is very short, mostly 7 days. The larval development lasted between 14 and 49 days onlower elevation or between 20 and 48 days on higher elevation. Pupae development lastedbetween one and two week on both elevations.Full development period egg to emerged adult in six toothed spruce bark beetle lastedbetween 35 and 70 days at lower elevation or between 50 and 84 days at higher elevation.Trunk segments with thick bark were mainly colonized by eight toothed spruce bark beetle,while six toothed spruce bark beetle colonized mostly upper trunk parts with thinner bark
There was a statistical significant positive correlation between bark thickness and thenumber/density of entrance holes in eight toothed spruce bark beetle, while for six toothedspruce bark beetle statistical significant negative correlation was observed.Six toothed spruce bark beetle is satellite species of eight toothed spruce bark beetlewhich had been adapted with different tools: probably detecting eight toothed spruce barkbeetle aggregation pheromones or some component as kairomon; effective aggregationpheromones acts as repellent on eight toothed spruce bark beetle; because of small body sizethis species is capable to colonize very thin material which is not suitable for eight toothedspruce bark beetle because of bark thickness and phloem pour with sugars; this species usinglenticels as a open entrance hole trough thicker bark.According to bark temperature observed phenology of eight toothed spruce bark beetleon trap logs and phenology obtained with Phenips model are overlapping very good. There isdifferences in onset of infestation, where model predict onset 4 or 5 days earlier if the barktemperature were used, or 16 to 18 days earlier if air temperature were used. Exposure of barksurface to direct sun light or shading effect can result with acceleration or developmentretardation.Model predict start of sister brood development 5 to 12 days earlier, or 4 to 17 dayslater. Model imperfection is impossibility to predict attack density which is main trigger ofsister brood onset.According to model reproduction of eight toothed spruce bark beetle is aborted whenphotoperiod decreased below the threshold of 14,5 hours. While the air and phloemtemperature are high enough the females hatching the eggs in galleries. It is possible thatdiapause is reflected in decreasing number of hatched eggs after shortage of photoperiod.Despite deviations which could not be predicted by the model (shadowing effect,exposure of bark surface to direct sun light, onset of sister brood conditioned with attackdensity and phloem temperature, temperature of air and phloem in time of photoperiodshortage) can be used for prediction of attack and development of eight toothed spruce barkbeetle, specially in stands raised outside optimal distribution areal of spruce where increasingnumber of successfully developed generations and enlarged epidemic risk can be expected.Most of the eight toothed spruce bark beetle marked individuals were caught within less200 meters, and only five percentage were caught more then one kilometer away. Beetlesdispersed in all directions. The dispersal of longflying beetles was probably aided by wind.Increase range of human activities in intensive management forests (removing windfelled, snow breaks, root rot damage trees or trees damaged with some other biotic and abiotic factor) and decreased human activities inside the national park probably influence themigration, spatial distribution and flight duration of eight toothed spruce bark beetles betweenthese two kind of forests.Two overwintering niches of eight toothed spruce bark beetle were observed - under thebark of attacked trees and in the littler. With decreasing of elevation percentage ofoverwintering adults under the bark of attacked trees increasing from peak mountain zoneon Zavižan (50 %), across Štirovača (60 %) to the lowest elevation with spruce stands inŽitnik management unit (76-95 %). Sanitation felling as a hot spot recovery measure isnecessary to implement in early autumn on higher elevations or during the winter and earlyspring on lower elevations.Low attack density of eight toothed spruce bark beetle expressed as a number ofgalleries per square meter of bark does not mean always a high breading success expressed asa number of daughters per mother (/). While the gallery density was between 27 and 117per square meter of bark reproduction success was 0,51 to 4,17 /.High mortality rate (up to 42 % of callow adults and in pupae and larvae between 70 to100 %) which had been observed at low attack density is a consequence of preadult instarsoverwintering inability and high abundance of predator larvae. Majority of eight toothedspruce bark beetle males (74 %) copulating with two females as a adaption to avoidintraspecific competition between larvae.The basic of forest protection against bark beetles is knowledge of bark beetle biology.Trap trees as a part of forest protection had been used for long period of time. Mature sprucetrees felled in spring and left in the stands until the swarming period ends. When the trunkshave been colonized they were removed from the stands before the young beetles completethe development. After development of the synthetic pheromone in most cases trap trees hadbeen replaced with pheromone baited traps. Pheromone traps equipped with pheromone luremay be used in integrated forests protection for monitoring bark beetle populations or masstrapping and possible disruption of beetle infestation. In Croatia, as a part of integrated forestprotection strategy classical black Theysohn flight barrier pheromone traps are used formonitoring I. typographus populations in spruce forests.Wet and dry flight barrier black Theysohn pheromone traps can be applied in sprucebark beetle monitoring with approximately equal efficiency (expressed as a number of caughtbark beetles individuals) and selectivity to two main predator species ant beetle(Thanasimus formicarius L.) and Nemozoma elongatum L.
It had been confirmed that neither eight toothed spruce bark beetle or six toothed sprucebark beetle can escape from dry pheromone traps after they fall down in collecting box at thetrap bottom.Ant beetle can easily escape from collecting box of dry pheromone traps, while theescape abilities for N. elongatum was not observed. In all three positions which had beentested (stand, stand edge, clear area without forest tree inside a forest complex) wet and dryTheysohn pheromone traps had shown the same trapping efficancy for both bark beetlespecies.Monitoring of spruce bark beetle populations can be implemented with different type oftested flight barrier pheromone traps (black Theysohn, brown WitaTrap, multi funnelWitaTrap) with approximately the same efficency (expressed as a number of caught barkbeetles individuals), while the white WitaTrap and cross Witaprall Ecco pheromone trapsshould be avoid because of significant reduced efficency. The most selective pheromone trapin this research was cross Witaprall Ecco probably because of net which had a crucialinfluence on selectivity. Significant lowest selectivity to ant beetle had shown the multi funnelWitaTrap pheromone trap probably because bottle shape of hunting container. For predatorspecies N. elongatum the most selective traps in reserach were multi funnel traps, but that wasprobably consequence of reduced efficency because predators are atracted in pheromone trapswith the quantity of prey.Knowledge about population abundance level is therefore of great importance, speciallywhen the weather conditions like long-lasting drought and storm felling can trigger populationincrease.Traps baited with pheromone can be used for monitoring and assessing the risk of damagecaused by bark beetles. Because of that it is important to define epidemic threshold for eachaggressive bark beetle species based on the number of speciments caught in pheromone traps.The aim of successful bark beetle control is to reach the beetle in all stages of itsdevelopment. In principle all methods should be used together as a integrated system. Themonths September and October are the best time for harvesting and thinning because loggingresidues (branches, tops, and other waste) will dry and will be unattractive to the beetles untilfollowing spring, especially in nature uneven aged spruce forests stands where the usinglogging residues as a energy source is limited with terrain conditions.If felling or thinning in spruce culture or natural uneven aged spruce stands need to beconducted in warmer part of year, it is recommended to set up a forest hygiene with pilling ofsuitable material, mostly branches with thicker branches part oriented to center of pile. The most abundant species in piles was six toothed spruce bark beetle. Branches pilling withthicker part oriented to pile center had shown a significant lower number of mating chamberscompared to opposite branches pilling method with thicker branches part oriented to pileedge. On this way attractive material will become unsuitable for bark beetle attack because ofhigh moisture in center of piles. With branches pilling number of entrance holes will bereduced, branches and tops dont disturbed the development of new spruce saplingsgenerations, creating suitable habitat for saproxylic beetle and increasing the biodiversity offorests ecosystems. The much bigger piles of suitable material in Sweden which are mostlyused as a fuel and had left during the summer to dry out did not influence the significant treemortality, specially of younger trees caused by six toothed spruce bark beetle.Stump debarking as a mechanical measure against bark beetle attack in integrated forestprotection management had been applied in Croatian forestry for long period of years.It is not necessery to conduct because of low bark beetle attack density and very few ofthem are successful. This method possibly increase the risk infection of root rot which canoccure on left standing trees in stands and make a negative impact on saproxylic beetleswhich need a bark layer for egg hatching.In spruce stands where terrain conditions doesn't influence machines moving allavailable wooden material as recent edge blowdowns, large broken tops and other suitablepiece of wood should be removed out of stands because it's suitable breeding material. Sprucelogs have to be removed out of stands as soon as possible or if logs storage should to be long,debarking the logs is recommended or keeping the logs wet with irrigation.Forest hygiene establishment just after regular felling or thinning and removing of tressdamaged by wind, snow, highlight or some others biotic and abiotic factors are mostimportant part of integrated forest protection against bark beetle attack. |
