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The invasive ambrosia beetle, Xylosandrus germanus Blandford (Coleoptera: Curculionidae: Scolytinae), is one of the most significant pests in hazelnut orchards in Turkey. Chemical control of the beetle is very difficult, because it spends the majority of its life in the sapwood of host trees. In this study, entomopathogenic fungi (EPF), Metarhizium anisopliae (TR-106 isolate), and Beauveria bassiana (TR-217 isolate) were tested against the female adults of X. germanus under laboratory conditions by two different methods. In the first method, conidial concentrations (1 × 10 6 and 1 × 10 8 conidia ml −1 ) of the fungal isolates were directly applied to the beetles in Petri dishes (2 ml per dish), using a Potter spray tower. In the second method, the same conidial concentrations were applied on a sterile hazelnut branch placed in the Petri dishes, and then, beetles were released in dishes. The Petri dishes were incubated at 25 ± 1°C and 75 ± 5% RH, 16:8-h light:dark photoperiod. Lethal time values (LT 50 and LT 90 ) for the isolates were calculated, using Probit analysis. As a result, LT 50 and LT 90 values of M. anisopliae isolate at 1 × 10 8 conidia ml −1 were 4.43 and 6.01 days, respectively, at the beetle application method and 3.97 and 5.68 days, respectively, at the branch application method. LT 50 and LT 90 values were 6.03 and 10.80 days, respectively, at 1 × 10 8 conidia ml −1 , when B. bassiana was applied directly on the beetles and 5.96 and 11.79 days at the same concentration, when it was applied on the branch application method. M. anisopliae at 1 × 10 8 conidia ml −1 caused 100% mortality rate at the end of the 8th day in the two application methods. The mortality rates when applying 1 × 10 8 conidia ml −1 of B. bassiana recorded 64% and 80% by the end of the 8th day on branch and insect application methods, respectively. The efficiency of 1 × 10 6 conidia ml −1 of the isolates was lower than 1 × 10 8 conidia ml −1 against X. germanus in both application methods. This study showed that the isolates of TR-106 and TR-217 had a significant potential as biological control agents against X. germanus.

Hazelnut, a very important cash crop in Turkey, is frequently colonized by bark and ambrosia beetle species (Scolytinae). Some scolytine species may cause economic damage while other species do not; therefore, proper identification is important in orchard management. Extensive sampling demonstrated that the most common pest species in Turkey’s hazelnut orchards are Anisandrus dispar, Xylosandrus germanus, and Xyleborinus saxesenii. Hypothenemus eruditus can also be common, but only colonizes branches that are already dead. Lymantor coryli, Hypoborus ficus, Taphrorychus ramicola, and Taphrorychus hirtellus are rare and do not causes damage to live plants. Xyleborinus saxesenii appears to have been frequently misidentified and misreported as either L. coryli or Xyleborus xylographus. The former is rare, and the latter probably does not occur in Turkey. To avoid future misidentifications, a dichotomous identification key is provided for bark and ambrosia beetles of hazelnut orchards in Turkey.

The efficacy of the native entomopathogenic fungus, Isaria fumosorosea TR-78-3, was evaluated against females of the bark and ambrosia beetles, Anisandrus dispar Fabricius and Xylosandrus germanus Blandford (Coleoptera: Curculionidae: Scolytinae), under laboratory conditions by two different methods as direct and indirect treatments. In the first method, conidial suspensions (1 × 10 6 and 1 × 10 8 conidia ml −1) of the fungus were directly applied to the beetles in Petri dishes (2 ml per dish), using a Potter spray tower. In the second method, the same conidial suspensions were applied on a sterile hazelnut branch placed in the Petri dishes. The LT 50 and LT 90 values of 1 × 10 8 conidia ml −1 were 4.78 and 5.94/days, for A. dispar in the direct application method, while they were 4.76 and 6.49/days in the branch application method. Similarly, LT 50 and LT 90 values of 1 × 10 8 conidia ml −1 for X. germanus were 4.18 and 5.62/days, and 5.11 and 7.89/days, for the direct and branch application methods, respectively. The efficiency of 1 × 10 6 conidia ml −1 was lower than that of 1 × 10 8 against the beetles in both application methods. This study indicates that I. fumosorosea TR-78-3 had a significant potential as a biological control agent against A. dispar and X. germanus. Further studies are necessary to evaluate the efficacy of the isolate on the pests under field conditions.