Virulence of Different Entomopathogenice Fungi Species and Strains against the Hazel Longhorn Beetle _Oberaa linearis_ (Coleoptera: Cerambycidae)  
[PERSON]  
1 Department of Agriculture, University of Ioannina, 45100 Ioannina, Greece 12 ELGO-Demeter, Plant Protection Division of Patras, 26442 Patras, Greece; [EMAIL_ADDRESS]  
[PERSON]  
2 Laboratory of Plant Physiology, Department of Biology, University of Patras, 26504 Patras, Greece; [EMAIL_ADDRESS]  
[PERSON]  
3 Laboratory of Plant Physiology, Department of Biology, University of Patras, 26504 Patras, Greece; [EMAIL_ADDRESS]  
[PERSON]  
4 Laboratory of Plant Health Management, Department of Agrotechnology, University of Thessaly, Geopolis, 45100 Larissa, Greece; [EMAIL_ADDRESS]  
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))  
The adult _O. linearis_ has a very narrow body, with length size 11-16 mm. It is colored black with pale yellow legs. In the male, the antennae are slightly shorter than the body, whereas in the female they are even shorter. The larvae are apodous, with the characteristic shape of the Cerambycidae. They can reach a final length of 20-25 mm and are white to yellowish, with a brownish prothoracic plate [4]. The complete life cycle of _O. linearis_ commonly lasts two years, although it can be prolonged to three years in areas exhibiting lower temperatures. However, [PERSON] [4] claimed that in Greece the insect completes one generation in a year in walnut trees [4; 13]. The females lay eggs separately near the tip of young shoots. On walnut trees, females may lay eggs on the pedicel of the fruit. The larvae hatch and create a gallery, which causes the apical part of the shoot to wither. As the tunnel elongates, the larvae open small holes to remove excrement. Galleries on hazel trees are longer than those on walnut trees. After overwintering for two years, the larvae pupate and adults emerge (May-June) and feed on the lateral veins of young leaves and mate. Affected twigs exhibit wilting, desiccation, and splitting at the level of egg-laying scars. Consequently, on walnut trees, there can be fruit depletion and loss of dormant floral buds and certain foliage sections. The severity of damage increases with a higher population density of the insects, potentially causing significant harm. In hazelnuts, damage is typically confined to shoots and twigs, usually not warranting control measures. Nevertheless, economic damage to the hazelnut crop may still occur in cases of excessively high insect population densities [12; 13]. In response to the growing demand, from consumers and farmers, for alternative, non-chemical methods of pest management, the utilization of entomopathogenic fungi (EPF) has been a promising option for the replacement or reduction of the excessive use of chemical insecticides [14; 15; 16]. These are naturally occurring microorganisms that are harmless to the environment and mammals [17]. Apart from that, they regrow on the dead insect bodies, thus introducing more inoculum into the ecosystem [18; 19]. Various species of EPF have been successfully employed for pest control, not only for beetles [20] but also for other insect orders like moths and whiteflies [21; 22]. Among the most commonly used species are _Beaureria bassiana_ ([PERSON]) Vuillemin (Hypocreales: Cordycipitaceae) and _Metathizium anisopliae_ ([PERSON].) Sorokin (Hypocreales: Calvicipitaceae), which have already been applied as biological products for pest control in the commercial sector [23; 24]. Despite the plethora of published studies on the insecticidal effects of many EPF, there is scarce data on their action against xylophagous beetles. Notable mortality rates of 51.1-86.3% and 69.6-81.8% were observed in _Hedypathes betulinus_ ([PERSON]) (Coleopterara: Cerambycidae) when infested by _B. bassiana_ and _M. anisopliae_ isolates, respectively [25].