| Abstract | Entomopatogene gljive roda Beauveria spadaju u najpoznatije i jedne
su od najistraživanijih uzročnika bolesti kukaca. To svojstvo čovjek
nastoji iskoristiti u suzbijanju i regulaciji populacija štetnih
organizama. U zaštiti šuma još ne nalaze veliku primjenu, a u Hrvatskoj su općenito vrlo malo istraživane. Prisutne su u kopnenim ekosustavima diljem svijeta, a predstavljaju prirodne neprijatelje brojnim vrstama kukaca. Do danas su zabilježene kao uzročnici bolesti na preko 700 vrsta u 15 različitih redova domaćina, uključujući redove Hemiptera, Coleoptera, Lepidoptera, Thysanoptera i Orthoptera u koje spadaju štetni kukci koji se komercijalno najviše suzbijaju. Primjerice, od bioloških preparata na tržištu kojima su entomopatogene gljive djelatna tvar njih gotovo 40% pripada gljivama roda Beauveria. Osim što su sposobne regulirati populacije štetnih kukaca, mogu biti i antagonisti biljnih patogena, endofiti u biljkama, promotori biljnog
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rasta, te mogu štititi korijenski sustav biljaka od različitih štetnih kukaca u tlu. Brojna istraživanja dokazala su njihovu sposobnost da endofitski koloniziraju biljke te se javljaju prirodno ili su uspješno introducirane u brojnim biljnim vrstama kako bi štitile biljke domaćine od štetnih kukaca. Iz roda Beauveria poznato je više vrsta, no dugo se govorilo uglavnom o vrsti Beauveria bassiana (Balsamo) Vuillemin (Ascomycota, Hypocreales, Cordycipitaceae), koja se koristi kao sredstvo biološke kontrole poljoprivrednih štetnika diljem svijeta, a njezina patogenost dokazana je i na različitim štetnim šumskim kukcima. Zbog sve većeg postrožavanja mjera uporabe kemijskih sredstava u šumarstvu, i sve učestalijeg okretanja biološkim metodama kontrole štetnih kukaca i u šumama, otkrivanje novih vrsta i sojeva entomopatogenih gljiva i istraživanje metoda njihove primjene predstavlja potencijal za biološku kontrolu različitih ekonomski važnih i/ili invazivnih vrsta štetnika.
Svrha ovog istraživanja bila je odgovoriti na određena fundamentalna pitanja o entomopatogenima u šumskim ekosustavima Hrvatske, a posebno su obrađivane gljive roda Beauveria. Kroz laboratorijske pokuse istraživala se mogućnost njihove upotrebe u terenskoj aplikaciji, posebice za tretiranje štetnih kukaca koji trenutno predstavljaju problem u šumarstvu. Odabrana su dva vrlo različita ciljana štetna organizma: invazivna vrsta hrastova mrežasta stjenica Corythucha arcuata (Say) (Hemiptera: Tingidae) i domaća vrsta borov prelac Dendrolimus pini L. (Lepidoptera: Lasiocampidae). Obje vrste pokazale su veliku štetnost na većim ili vrlo velikim površinama. Za izolaciju, analizu i identifikaciju gljiva korištene su morfološke, molekularne i filogenetske metode (bioinformatičke analize), a neke metode (primjerice endofitska detekcija Beauveria gljiva) modificirane su i/ili razvijene u samom istraživanju. Provedeno je više desetaka laboratorijskih pokusa u kontroliranim uvjetima temperature, vlage i svjetla gdje se ispitivao učinak primjene izolata Beauveria gljiva na navedene ciljane organizme u različitim dozama i koncentracijama suspenzija spora (u nekim pokusima i u kombinaciji s
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insekticidima), da bi se definirao optimalan učinak.
Rezultati ovog istraživanja potvrdili su prirodnu prisutnost vrsta roda Beauveria na našem području na različitim vrstama kukaca i utvrdili njihovu distribuciju u tlu u različitim šumskim zajednicama u Hrvatskoj. Nadalje je utvrđeno kako B. bassiana ne može biti inokulirana kao endofit u biljnom tkivu hrasta lužnjaka te ga tako štititi od napada štetnih kukaca jer za razliku od zeljastih vrsta biljaka za drvenaste vrste vjerojatno postoji prejaka prodorna barijera. U eksperimentalnom dijelu istraživanja utvrđena je patogenost i efikasnost domaćih sojeva gljiva B. bassiana i B. pseudobassiana, te dobar potencijal u biološkoj kontroli borovog prelca i hrastove mrežaste stjenice. Dobivene su optimalne doze i koncentracije suspenzija te uvjeti temperature i vlage kojima se može postići željeni efekt u laboratorijskim uvjetima, stoga se u budućnosti može istraživati i njihova terenska primjena. U pokusima gdje su te gljive kombinirane s konvencionalnim insekticidom (u malim, ekološki prihvatljivim 'ultra low' dozama) pokazalo se da insekticid ne inhibira njihov rast i klijavost i nema štetan učinak na njihovu virulentnost što ukazuje na mogućnost takve kombinirane primjene. Dobivene spoznaje predstavljaju temelj za razvijanje i uključivanje biološke kontrole entomopatogenim gljivama kao komponente u integriranoj zaštiti šuma, te pokazuju njihov potencijal kao ekološki prihvatljivije i održivije alternative. Primjenom ovih gljiva podizao bi se prirodni inokulum već prisutan u određenom području, što bi značilo dugotrajniju kontrolu populacije ciljanog štetnika a time dugoročno i smanjenu upotrebu kemijskih insekticida i manje negativnog utjecaja na neciljane vrste, što se uklapa u sam kocept integrirane zaštite šuma. Cilj je ujedno i potaknuti razvoj entomopatologije kao znanstvene grane koja se bavi patologijom (bolestima) kukaca u Hrvatskoj i otvoriti mogućnosti za provedbu novih, sličnih istraživanja. |
| Abstract (english) | Entomopathogenic fungi from the genus Beauveria are one of the most common and most-studied insect pathogenic fungi. This feature man seeks to use in the control and regulation of pest populations. In forest protection, they still haven't been extensively applied, and in Croatia they have generally been very little researched. They are present in terrestrial ecosystems around the world and represent natural enemies to many insect species. To date, those fungi have been reported to cause disease on over 700 species in 15 different orders, including Hemiptera, Coleoptera, Lepidoptera, Thysanoptera, and Orthoptera, which include commercially most controlled insect
pests. From mycoinsecticides available on market almost 40% are
based on Beauveria fungi. Besides being able to regulate pest
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populations, they can also be antagonists of plant pathogens, endophytes in plants, plant growth promoters, and can protect plant root system from various harmful insects in the soil. Numerous studies have proven their ability to endophytically colonize plants, and they occur naturally or are being successfully introduced into numerous plant species. Today, many Beauveria species are known, but for a long time it was thought this genus contains only several species, including most common Beauveria bassiana (Balsamo) Vuillemin (Ascomycota, Hypocreales, Cordycipitaceae), which is used for biological control of agricultural pests around the world. Its pathogenicity has been proven on forest insects as well. Due to the increasing tightening of measures for the use of chemicals in forestry, and the increasing use of biological methods to control forests pests, discovery of new species and strains of entomopathogenic fungi and research of their application methods represents the potential for biological control of various economically important and/or invasive pests. The purpose of this study was to answer fundamental questions about entomopathogens in Croatian forest ecosystems, with special reference to the genus Beauveria. Through laboratory experiments, the possibility of their use in field application was investigated, especially against insect pests that currently present a problem in forestry. Two very different target pests were selected: the invasive oak lace bug Corythucha arcuata (Say) (Hemiptera: Tingidae) and the native pine pest Dendrolimus pini L. (Lepidoptera: Lasiocampidae). Both species have shown great harmfulness over larger or very large areas. Morphological, molecular and phylogenetic methods (bioinformatics analysis) were used for isolation, analysis and identification of fungi, and some methods (e.g. endophytic detection of Beauveria fungi) were modified and/or developed in the study itself. Dozens of laboratory experiments were performed under controlled temperature, humidity, and light conditions to investigate the effect of applying Beauveria isolates to these target organisms at different
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doses and concentrations of spore suspensions (in some experiments in combination with insecticides), to determine optimal effect. The results of this study confirmed the natural presence of Beauveria species on different insect species and determined their distribution in the soil in different forest communities in Croatia. It was further found that B. bassiana cannot be inoculated as an endophyte in pedunculate oak and thus protect it from harmful insects, because unlike herbaceous plant species for woody species a penetrating barrier is probably too strong. In the experimental part of the research, the pathogenicity and efficacy of native strains of B. bassiana and B. pseudobassiana were determined, and their potential in the biological control of pine-tree lappet moth and oak lace bug was proven. Optimal doses and concentrations of suspensions, as well as temperature and humidity conditions that can achieve the desired effect in laboratory conditions have been obtained, so their field application can be investigated in the future. In experiments where these fungi were combined with a conventional insecticide (in small, environmentally friendly ‘ultra low’ doses) it was shown that the insecticide does not inhibit their growth and germination, and has no detrimental effect on their virulence indicating the possibility of such combined application. The obtained knowledge represents the basis for the development and inclusion of biological control with entomopathogenic fungi as a component in integrated forest protection, and shows their potential as environmentally friendly and sustainable alternative. Application of these fungi would raise the natural inoculum already present in a certain area, which would mean longer-term control of the target pest population and thus long-term reduction of chemical insecticides use and less negative impact on non-target species, which fits into the concept of integrated forest protection. The aim is also to encourage the development of entomopathology as a scientific branch that deals with pathology (diseases) of insects in Croatia and open opportunities for the implementation of new, similar research. |
