Biodiversity Data Journal : Taxonomy & Inventories
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Taxonomy & Inventories
New parasitoid (Hymenoptera, Chalcidoidea) records of bark beetles (Coleoptera, Curculionidae, Scolytinae) in pine plantations in Bulgaria
expand article infoSevdalin Belilov‡, Ivaylo Todorov§, Margarita Georgieva‡, Georgi Georgiev‡
‡ Forest Research Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria
§ Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria
Corresponding author: Margarita Georgieva (margaritageorgiev@gmail.com), Georgi Georgiev (ggeorgiev.fri@gmail.com)
Academic editor: Simon van Noort
Received: 10 Jul 2023 | Accepted: 19 Sep 2023 | Published: 29 Sep 2023
© 2023 Sevdalin Belilov, Ivaylo Todorov, Margarita Georgieva, Georgi Georgiev
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Belilov S, Todorov I, Georgieva M, Georgiev G (2023) New parasitoid (Hymenoptera, Chalcidoidea) records of bark beetles (Coleoptera, Curculionidae, Scolytinae) in pine plantations in Bulgaria. Biodiversity Data Journal 11: e109325. https://doi.org/10.3897/BDJ.11.e109325
 Open Access

Abstract

Background

In 2020 and 2021, chalcidoid parasitoids (Hymenoptera, Chalcidoidea) of bark beetles in pine (Pinus spp.) plantations were studied in Bulgaria. Samples (cuttings of stems and branches) of pine trees infested by bark beetles were collected from seven plantations of Pinus sylvestris and P. nigra in Bulgaria. From each sampling plot, five cuttings were collected and placed in photoeclectors in laboratory conditions (18-22ºC). Emerged bark beetles and parasitoids were regularly gathered and fixed in ethanol.

New information

Six parasitoid species - Dinotiscus colon, Metacolus azureus, M. unifasciatus, Rhopalicus quadratus, R. tutela (Chalcidoidea: Pteromalidae) and Heydenia pretiosa (Chalcidoidea, Heydeniidae) were reared from five bark beetle hosts (Ips acuminatus, Pityogenes bistridentatus, Pityophthorus pityographus, Tomicus piniperda and T. minor). Amongst them, three species (H. pretiosa, M. azureus and R. quadratus) are recorded as new for Bulgarian fauna.

Keywords

bark beetles, parasitoids, Pteromalidae, Heydeniidae, new records, Bulgaria

Introduction

In the 1950s and 1960s, intensive forest planting has been developed under the process of afforestation on degraded and deforested lands in the lower forest belt in Bulgaria. Pinus nigra Arn. and Pinus sylvestris L. have been the main species used in forest plantations in this region. Increasing the age of plantations in the habitats has led to an increase in moisture deficit, deterioration of the physiological condition of plants and a reduction of their resistance to abiotic and biotic effects (Mirchev et al. 2016). These factors had an adverse effect on forests, especially on the pine monocultures in the lower forest belt (Yangyozov 2010).

In recent decades, forest mortality has increased for many tree species in the countries in the Mediterranean Region due to dry and warm conditions (Allen et al. 2010). In Bulgaria, the tendency for decreasing precipitation during the vegetation period had an adverse effect on forests reducing their resistance to biotic and abiotic factors. This creates a prerequisite for increased development of population density of biotic agents, such as bark beetles or fungal pathogens, especially in pine plantations created outside of their natural range (Yangyozov 2011).

A total of 121 species of bark beetles have been established in Bulgaria and about half of them are associated with pines (Pinus spp.) (Doychev 2014). Some of them, mainly representatives of the genera Ips and Tomicus, appear as destructive pests in pine plantations weakened by various abiotic factors (Mirchev et al. 2016). Their ecology is not well studied, especially with regard to trophic associations with chalcidoid parasitoids (Chalcidoidea, Hymenoptera).

The present study reports new chalcidoid parasitoids of bark beetles for the Bulgarian fauna and information about their impact on host abundance.

Materials and methods

Our studies of parasitoids (Hymenoptera, Chalcidoidea) of bark beetles were conducted during the years 2020-2022 in seven plantations of Pinus sylvestris L. and Pinus nigra Arn. growing in five localities in Bulgaria. The main characteristics of the studied areas are presented in Table 1.

Table 1.
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Main characteristics of the studied areas.

№

Locality

Geographical coordinates

Altitude, m a.s.l.

Tree species

Origin

Age, years

Year of study

1

Golema Rakovitsa

N 42.615944, E 23.784333

651

Pinus sylvestris

Plantation

40

2020

2

Krushovitsa

N 42.590466, E 23.657520

697

Pinus sylvestris

Plantation

55

2020

3

Mechkovtsi

N 42.556080, E 23.747801

939

Pinus sylvestris

Plantation

45

2021-2022

4

Venkovets

N 42.436282, E 23.668128

828

Pinus sylvestris

Plantation

50

2022

5

Dolni Pasarel 1

N 42.424683, E 23.616527

831

Pinus sylvestris

Plantation

55

2022

6

Dolni Pasarel 2

N 42.437758, E 23.649787

889

Pinus sylvestris

Plantation

55

2022

7

Dolni Pasarel 3

N 42.418542, E 23.617609

833

Pinus nigra

Plantation

55

2022

Samples (cuttings of stems and branches of approximate length 30-35 cm and diameter 12-30 cm for stems and 5-10 cm for branches) of trees attacked by bark beetles were collected in May-August. In each plantation, five trees were examined and sampled.

The material was transported to the Forest Research Institute in Sofia where each cutting was kept in a separate photoeclector at room temperature (18-22ºC). The samples were observed weekly for the emergence of adult hosts or parasitoids.

The emerged bark beetles were identified using the keys of Karaman (1971) and Grüne (1979). Parasitoids were identified following Graham (1969), Gibson (2003) and Tselikh (2010).

The biological material was deposited in the entomological collections of the Forest Research Institute and Institute of Biodiversity and Ecosystem Research in Sofia.

Checklist

Dinotiscus colon (Linnaeus, 1758)

Material   Download as CSV 
  1. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Krushovitsa
    ; verbatimElevation:
    697 m
    ; verbatimLatitude:
    42.590466
    ; verbatimLongitude:
    23.65752
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    23/07/2020
    ; sex:
    1 male
    ; establishmentMeans:
    Rearing from Ips acuminatus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    C7ED67B3-F891-54F3-9BB7-B797E14D58CA
Native status: 
native

Metacolus azureus (Ratzeburg, 1844)

Material   Download as CSV 
  1. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Krushovitsa
    ; verbatimElevation:
    697 m
    ; verbatimLatitude:
    42.590466
    ; verbatimLongitude:
    23.65752
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    05/08/2020
    ; sex:
    4 males, 6 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Pityogenes bistridentatus, Pityophthorus pityographus, Tomicus piniperda, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    54F1A671-E15F-525B-9F25-4CB56D1C60C1
Native status: 
native

Metacolus unifasciatus (Foerster, 1856)

Materials   Download as CSV 
  1. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Krushovitsa
    ; verbatimElevation:
    697 m
    ; verbatimLatitude:
    42.590466
    ; verbatimLongitude:
    23.65752
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    05/08/2020
    ; sex:
    11 males, 15 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Pityogenes bistridentatus, Pityophthorus pityographus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    10BEBAA0-9021-59A5-98EB-45A2B0DCEB98
  2. country:
    Bulgaria
    ; municipality:
    Ihtiman
    ; locality:
    Mechkovtsi
    ; verbatimElevation:
    939 m
    ; verbatimLatitude:
    42.55608
    ; verbatimLongitude:
    23.747801
    ; startDayOfYear:
    29/06/2022
    ; endDayOfYear:
    05/07/2022
    ; sex:
    2 males, 3 females
    ; establishmentMeans:
    Rearing from Ips acuminatus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    899EC99C-99D5-50B7-8790-25FC081F2981
Native status: 

native

Rhopalicus quadratus (Ratzeburg, 1844)

Materials   Download as CSV 
  1. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Golema Rakovitsa
    ; verbatimElevation:
    651 m
    ; verbatimLatitude:
    42.615944
    ; verbatimLongitude:
    23.784333
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    02/09/2020
    ; sex:
    13 males, 11 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Tomicus piniperda, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    CCF09913-6DDD-57E8-9035-635C44EDAE2C
  2. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Krushovitsa
    ; verbatimElevation:
    697 m
    ; verbatimLatitude:
    42.590466
    ; verbatimLongitude:
    23.65752
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    02/08/2020
    ; sex:
    46 males, 27 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Pityogenes bistridentatus, Pityophthorus pityographus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    33D856DE-18EA-50C7-847D-344904C26DD3
  3. country:
    Bulgaria
    ; municipality:
    Ihtiman
    ; locality:
    Mechkovtsi
    ; verbatimElevation:
    939 m
    ; verbatimLatitude:
    42.55608
    ; verbatimLongitude:
    23.747801
    ; startDayOfYear:
    18/06/2021
    ; endDayOfYear:
    01/07/2021
    ; sex:
    5 males
    ; establishmentMeans:
    Rearing from Tomicus piniperda, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    8A07ACFC-6FF9-57FA-982D-FA938C3F726F
  4. country:
    Bulgaria
    ; municipality:
    Sofia, Pancharevo region
    ; locality:
    Dolni Pasarel
    ; verbatimElevation:
    889 m
    ; verbatimLatitude:
    42.437758
    ; verbatimLongitude:
    23.649787
    ; startDayOfYear:
    11/07/2022
    ; endDayOfYear:
    21/07/2022
    ; sex:
    10 males, 18 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    DBF82BC2-E5AF-5816-9C8B-74B09D14EB97
  5. country:
    Bulgaria
    ; municipality:
    Ihtiman
    ; locality:
    Venkovets
    ; verbatimElevation:
    828 m
    ; verbatimLatitude:
    42.436282
    ; verbatimLongitude:
    23.668128
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    01/07/2020
    ; sex:
    5 males, 7 females
    ; establishmentMeans:
    Rearing from Ips acuminatus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    2F261A1F-BFE9-5010-84EA-71D08C3C11A4
Native status: 

native

Rhopalicus tutela (Walker, 1836)

Materials   Download as CSV 
  1. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Golema Rakovitsa
    ; verbatimElevation:
    651 m
    ; verbatimLatitude:
    42.615944
    ; verbatimLongitude:
    23.784333
    ; startDayOfYear:
    11/07/2022
    ; endDayOfYear:
    01/08/2022
    ; sex:
    3 males, 1 female
    ; establishmentMeans:
    Rearing from Tomicus piniperda, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    DA9884E5-C355-527C-B4F8-B23A190DC204
  2. country:
    Bulgaria
    ; municipality:
    Sofia, Pancharevo region
    ; locality:
    Dolni Pasarel
    ; verbatimElevation:
    833 m
    ; verbatimLatitude:
    42.418542
    ; verbatimLongitude:
    23.617609
    ; sex:
    3 males, 3 females
    ; establishmentMeans:
    Rearing from Ips acuminatus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    6F8E5C68-164A-563E-8A71-EF2AFD81ECCB
Native status: 
native

Heydenia pretiosa (Förster, 1856)

Materials   Download as CSV 
  1. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Krushovitsa
    ; verbatimElevation:
    697 m
    ; verbatimLatitude:
    42.590466
    ; verbatimLongitude:
    23.65752
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    31/07/2020
    ; sex:
    2 males, 18 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Pityogenes bistridentatus, Pityophthorus pityographus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    92C41B55-3328-50C3-997D-14A77D564FDF
  2. country:
    Bulgaria
    ; municipality:
    Elin Pelin
    ; locality:
    Golema Rakovitsa
    ; verbatimElevation:
    651 m
    ; verbatimLatitude:
    42.615944
    ; verbatimLongitude:
    23.784333
    ; startDayOfYear:
    06/06/2020
    ; endDayOfYear:
    31/07/2020
    ; sex:
    1 female
    ; establishmentMeans:
    Rearing from Tomicus piniperda, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    32F813A2-A298-563E-B2F5-25FCA7EF9A43
  3. country:
    Bulgaria
    ; municipality:
    Ihtiman
    ; locality:
    Venkovets
    ; verbatimElevation:
    828 m
    ; verbatimLatitude:
    42.436282
    ; verbatimLongitude:
    23.668128
    ; startDayOfYear:
    11/07/2022
    ; endDayOfYear:
    21/07/2022
    ; sex:
    1 male, 1 female
    ; establishmentMeans:
    Rearing from Ips acuminatus
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    9A29ABAA-EE82-59E5-B617-7465E323CA9D
  4. country:
    Bulgaria
    ; municipality:
    Sofia, Pancharevo region
    ; locality:
    Dolni Pasarel
    ; verbatimElevation:
    831 m
    ; verbatimLatitude:
    42.424683
    ; verbatimLongitude:
    23.616527
    ; startDayOfYear:
    11/07/2022
    ; endDayOfYear:
    01/08/2022
    ; sex:
    2 males, 2 females
    ; establishmentMeans:
    Rearing from Ips acuminatus, Tomicus minor
    ; recordedBy:
    S. Belilov leg. [SB]
    ; occurrenceID:
    35FB0428-21CA-5C9A-B4E5-EFF0E84F07E2
Native status: 
native

Analysis

Six parasitoid species from two chalcidoid families were found to emerge from the tree samples: Dinotiscus colon Linnaeus, 1758, Metacolus azureus Ratzeburg, 1844, Metacolus unifasciatus Foerster, 1856, Rhopalicus quadratus (Ratzeburg, 1844), Rhopalicus tutela (Walker, 1836) (Chalcidoidea, Pteromalidae) and Heydenia pretiosa Förster, 1856 (Chalcidoidea, Heydeniidae) (Table 2).

Table 2.
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Number and relative abundance of different species in the parasitoid complex.

Species

Host

Locality

Date of collection

E mergence

period

Parasitoid number

Relative share, %

♀♀

♂♂

Ʃ

Dinotiscus colon

I. acuminatus

Krushovitsa

05.06.2020

06.06.-23.07.2020

1

0

1

0.4

*Heydenia pretiosa

I. acuminatus

Krushovitsa

05.06.2020

06.06.-31.07.2020

11

1

12

12.6

D. Pasarel 1

11.07.2022

11.07.-01.08.2022

1

0

1

Venkovets

11.07.2022

11-21.07.2022

1

1

2

P. bistridentatus

Krushovitsa

05.06.2020

06.06.-31.07.2020

5

1

6

T. piniperda, T. minor

G. Rakovitsa

05.06.2020

06.06.-31.07.2020

1

0

1

I. acuminatus, P. bistridentatus, P. pityographus

Krushovitsa

05.06.2020

06.06.-02.08.2020

2

0

2

T. minor

D. Pasarel 1

11.07.2022

11-21.07.2022

1

0

1

D. Pasarel 3

11.07.2022

11.07.-01.08.2022

1

2

3

*Metacolus azureus

I. acuminatus

Krushovitsa

05.06.2020

06.06.-05.08.2020

1

0

1

4.5

P. bistridentatus

Krushovitsa

05.06.2020

06.06.-23.07.2020

3

0

3

I. acuminatus, P. bistridentatus, P. pityographus

Krushovitsa

05.06.2020

06.06.-05.08.2020

2

3

5

T. piniperda, T. minor

Krushovitsa

05.06.2020

06.06.-05.08.2020

0

1

1

Metacolus unifasciatus

I. acuminatus

Krushovitsa

05.06.2020

06.06.-05.08.2020

6

4

10

14.0

Mechkovtsi

29.06.-05.07.2022

3

2

5

P. bistridentatus

Krushovitsa

05.06.2020

06.06.-23.07.2020

7

5

12

P. bistridentatus, P. pityographus

Krushovitsa

05.06.2020

06.06.-02.08.2020

0

1

1

I. acuminatus, P. bistridentatus, P. pityographus

Krushovitsa

05.06.2020

06.06.-02.08.2020

2

1

3

*Rhopalicus quadratus

Ips acuminatus

G. Rakovitsa

05.06.2020

06.06.-02.09.2020

5

2

7

64.0

Krushovitsa

05.06.2020

06.06.-05.08.2020

14

15

29

D. Pasarel 1

11.07.2022

11.07.-01.08.2022

2

0

2

D. Pasarel 2

11.07.2022

11-21.07.2022

9

5

14

Venkovets

11.07.2022

11-21.07.2022

7

5

12

P. bistridentatus

Krushovitsa

05.06.2020

06.06.-23.07.2020

10

29

39

I. acuminatus, P. bistridentatus, P. pityographus

Krushovitsa

05.06.2020

06.06.-02.08.2020

3

1

4

T. piniperda, T. minor

G. Rakovitsa

05.06.2020

06.06.-01.07.2020

6

11

17

T. piniperda, T. minor

Krushovitsa

05.06.2020

06.06.-05.08.2020

0

1

1

T. minor

Mechkovtsi

16.06.2021

18.06.-01.07.2021

2

0

2

D. Pasarel 1

11.07.2022

11-21.07.2022

7

5

12

T. minor, T. piniperda

Mechkovtsi

16.06.2021

18.06.-01.07.2021

3

0

3

Rhopalicus tutela

T. piniperda, T. minor

G. Rakovitsa

05.06.2020

06.06.-01.07.2020

1

3

4

4.5

I. acuminatus

D. Pasarel 1

11.07.2022

11.07.-01.08.2022

0

1

1

I. acuminatus

D. Pasarel 2

11.07.2022

11-21.07.2022

3

2

5

Total

120

102

222

100.0

The parasitoids emerged from five species of bark beetles (Coleoptera, Curculionidae, Scolytinae): Ips acuminatus (Gyllenhal, 1827), Pityogenes bistridentatus (Eichhoff, 1878), Pityophthorus pityographus (Ratzeburg, 1837), Tomicus piniperda (Linnaeus, 1758) and Tomicus minor (Hartig, 1834).

In this study, three species (H. pretiosa, M. azureus and R. quadratus) were newly recorded for the Bulgarian fauna.

During the study period, R. quadratus (64.0%) was the most abundant species in the total number of the emerged parasitoids, followed by M. unifasciatus (14.0%), H. pretiosa (12.6%), Metacolus azureus (4.5%) and Rhopalicus tutela (4.5%), whereas Dinotiscus colon was represented by 0.4%.

The parasitism varied widely in individual species and groups of bark beetles and in different localities: in I. acuminatus from 47.8% (Krushovitsa loc.) to 90.5% (Dolni Pasarel loc.); in T. piniperda and T. minor from 2.1-2.8% (Mechkovtsi loc.) to 91.7% (Rakovitsa loc.); in P. bistridentatus and P. pityographus from 7.7 to 89.6% (Krushovitsa) (Table 3). It should be emphasised that, in individual cases, both more than one host and more than one parasitoid were isolated from the photoeclector samples.

Table 3.
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Parasitism of bark beetles in studied localities.

Locality

Year

Parasitoid species

Bark beetle host

Parasitism, %

Golema Rakovitsa

2020

Rhopalicus quadratus

Ips acuminatus

53.8

Heydenia pretiosa, Rhopalicus quadratus, Rhopalicus tutela

Tomicus piniperda, Tomicus minor

91.7

Krushovitsa

2020

Dinotiscus colon, Heydenia pretiosa,

Metacolus azureus, Metacolus unifasciatus, Rhopalicus quadratus

Ips acuminatus

47.8

Heydenia pretiosa, Metacolus azureus, Metacolus unifasciatus, Rhopalicus quadratus

Ips acuminatus, Pityogenes bistridentatus, Pityophthorus pityographus

58.3

Heydenia pretiosa, Metacolus azureus, Metacolus unifasciatus, Rhopalicus quadratus

Pityogenes bistridentatus

89.6

Metacolus unifasciatus

Pityogenes bistridentatus, Pityophthorus pityographus

7.7

Metacolus azureus, Rhopalicus quadratus

Tomicus piniperda, Tomicus minor

14.3

Mechkovtsi

2020

Rhopalicus quadratus

Tomicus piniperda

2.8

Rhopalicus quadratus

Tomicus piniperda, Tomicus minor

2.1

2021

Metacolus unifasciatus

Ips acuminatus

71.4

Venkovets

2021

Heydenia pretiosa, Rhopalicus quadratus

Ips acuminatus

66.7

Dolni Pasarel 1

2021

Heydenia pretiosa, Rhopalicus quadratus, Rhopalicus tutela

Ips acuminatus

66.7

Heydenia pretiosa, Rhopalicus quadratus

Tomicus minor

37.1

Dolni Pasarel 2

2021

Rhopalicus quadratus, Rhopalicus tutela

Ips acuminatus

90.5

Dolni Pasarel 3

2021

Heydenia pretiosa

Tomicus minor

18.8

Discussion

The chalcidoids found in this study are well known as parasitoids of bark beetles: Dinotiscus colon was previously reared from Ips acuminatus, Tomicus minor and T. piniperda; Heydenia pretiosa – from I. acuminatus, I. typographus, T. minor, Orthotomicus erosus (Wollaston, 1857) and Pityokteines vorontzowi (Jakobson, 1895); Metacolus azureus – from I. acuminatus, O. erosus, Pityogenes conjunctus (Reitter, 1887), Pityogenes chalcographus (Linnaeus, 1761), T. minor and T. piniperda (Kenis et al. 2004, Wegensteiner et al. 2015); Metacolus unifasciatus – from I. acuminatus, I. typographus, O. erosus, T. minor and T. piniperda (Kenis et al. 2004, Wegensteiner et al. 2015); Rhopalicus quadratus – from I. acuminatus, Ips amitinus (Eichhoff, 1871), P. chalcographus, Pityokteines curvidens (Germar, 1824), Polygraphus poligraphus (Linnaeus, 1758), T. minor and T. piniperda (Kenis et al. 2004, Wegensteiner et al. 2015); Rhopalicus tutela – from Dendroctonus micans (Kugelann, 1794), I. acuminatus, I. amitinus, Ips duplicatus (Sahlberg, 1836), Ips sexdentatus (Börner, 1776), I. typographus, P. chalcographus, P. curvidens, P. poligraphus, T. minor and T. piniperda (Kenis et al. 2004, Wegensteiner et al. 2015).

Three chalcidoid species (Heydenia pretiosa, Metacolus azureus and Rhopalicus quadratus) were reported as new for the Bulgarian fauna. One of them, H. pretiosa, was recently elevated from Pteromalidae to family rank (Heydeniidae) by Burks et al. (2022).

As concerns the remaining parasitoid species, Dinotiscus colon has been previously recorded from Bulgaria as a parasitoid of Scolytus amygdali Guerin, 1847, Scolytus mali (Bechstein, 1805) and Scolytus rugulosus (Muller, 1818) (Thompson 1954). In addition, another species from the genus, Dinotiscus eupterus Walker, 1836, was established as a parasitoid of Ips typographus (Linnaeus, 1758) in Bulgaria (Georgiev and Stojanova 2006).

Metacolus unifasciatus has been previously recorded from Bulgaria as a parasitoid of Ovalisia (Palmar) festiva (Linnaeus, 1767) (Coleoptera, Buprestidae) (Ruseva et al. 2020).

Rhopalicus tutela was first recorded for the Bulgarian fauna by Vidal (1993) and was reported again later as a parasitoid of I. typographus by Georgiev and Stojanova (2006).

It can be concluded that the species composition and the population dynamics of chalcidoid parasitoids of bark beetles in pine stands in Bulgaria have not been studied sufficiently in the past. In this study, high levels of host mortalities were registered, but more field observations are necessary to evaluate the actual impact of these natural enemies on the pest populations.

Acknowledgements

This work has been carried out in the framework of the National Science Programme "Environmental Protection and Reduction of Risks of Adverse Events and Natural Disasters", approved by the Resolution of the Council of Ministers № 577/17.08.2018 and supported by the Ministry of Education and Science (MES) of Bulgaria (Agreement № Д01-271/09.12.2022).

References

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