Monitoring of Insect-Hosts of Entomopathogenic

Monitoring of Insect-Hosts of Entomopathogenic
Nematodes in Bulgaria
Denis Gradinarov*, Nikola Atanasov**
*Sofia University, Dragan Tzankov 8, 1164 Sofia, Bulgaria;
**Plant Protection Institute, Panajot Volov, 2230 Kostinbrod, Bulgaria
The entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae are intensively investigated because of their potential
as biological control agents, but also because their specific biology. The cases of established naturally infected hosts are relatively rare. The aim of
the following work is to systematize the knowledge of insects – hosts of entomopatogenic nematodes (EPN), discovered in Bulgaria.
The insects from 6 genera and 7 families were found in Bulgaria as natural hosts of entomophatogenic nematodes (Table 1). They belong to the
orders Coleoptera, Hymenoptera and Diptera. Some of them are phytophagous another carnivores and the others are with mixed feeding.
Table 1. Detected natural host insects of the entomopathogenic nematodes in Bulgaria
The
species
S.
intermedium is isolated
from pupae of Cantharidae
in town of Sofia (Fig.1).
Fig.1. Pupa of Cantharis with nematodes
Infected by S. bicornutum larvae or pupae of
Curculionidae, Carabidae (Fig. 4), and Asilidae (Fig.3)
were found in an riverside soil in the Zemen gorge (Fig.
2). This cases of invasion are of special interest. They
shows that EPN parasitized not only phytophagous
insects but also myxophagous and predators.
Fig.2. Zemen Gorge
Nematode
Host insect
Region
Habitat
S. kraussei
Bibio sp.
(Bibionidae)
Vitosha Mts.
beech and pine forest,
subalpine meadows
S. kraussei
Curculionidae g.sp.
Vitosha Mts.
subalpine meadow
S. carpocapsae
Cydia pomonella L.
(Tortricidae)
Kjustendil
apple garden
S. carpocapsae
Limonius sp.
(Elateridae)
Vitosha Mts.
mezophilic meadow
S. carpocapsae
Formica cinerea (Formicidae)
Hadjidimovo
swamp meadow
S. intermedium
Cantharis sp. (Cantharidae)
Sofia
garden
S. bicornutum
Curculionidae g.sp.
Zemen gorge
riverside meadow
S. bicornutum
Harpalus sp. (Carabidae)
Zemen gorge
riverside meadow
S. bicornutum
Asilidae g.sp.
Zemen gorge
riverside meadow
Steinernema sp.
Bibio sp.
(Bibionidae)
Vitosha Mts.
pine forest
Steinernema sp.
Asilidae g.sp.
Osogovska Mts.
subalpine meadow
Steinernema sp. “affine
group”
Bibio sp.
(Bibionidae)
Vitosha Mts.
pine forest
H. bacteriophora
Drasterius bimaculatus Rossi
(Elateridae)
Kostinbrod
strawberry fields
Fig.3. Larva of Asilidae
with nematodes
On Vitosha Mts. (Fig.5) several times we had found infected
by EPN larvae of Bibionidae (Bibio sp.) (Fig.6). Almost in all
cases the invasion density was 1 – 3 nematodes per a
dipterian larva. The EPN appears to be one of the main
factors, which control the density of the bibionid flies in forest
habitats in Bulgaria.
Fig.4. Antenna and urogomphus of Harpalus with nematodes
The species S. carpocapsae was isolated from a larva of Elateridae
in soil from Vitosha Mt. and from female ant (Formicidae) in a
riversides of Mesta. Infected with S. carpocapsae larvae of Cydia
pomonella L. were found also near town of Kjustendil (Vega et al.,
2000). The species H. bacteriophora was isolated from a larva and
a pupa of Drasterius bimaculatus Rossi (Elateridae).
Fig.5. Pine forest on Vithosha Mts.
Fig.6. Infected bibionid larvae
Laboratory tests for parasitized of some economically important insects were performed. We used insects, gathered from an alfalfa
stand in experimental field near Sofia. These are imago of phytophagous Subcoccinella, Phytodecta and the beneficial species
Coccinella septempunctata L. A experimental invasion was with nematode cultures of the species H. bacteriophora and S. feltiae, which
were isolated from Bulgaria.
Even though the dosage of EPN was high, the results proved that these
nematodes have relatively low efficiency against the insects of the genera
Subcoccinella (Fig. 7) and Phytodecta. We determined via dissection that the
mortality rate is Coccinella septempunctata does not account on EPN.
The results of the experiment can be generalized in the following statements:
Fig.7. Infected imago of Subcoccinella
1. The species Subcoccinella and Phytodecta are vulnerable to invasion with the nematode H. bacteriophora;
2. The imago of Subcoccinella sp. is most effectively invaded by the species H. bacteriophora;
3. The species S. feltiae is more pathogenic to Phytodecta then H. bacteriophora;
4. The beneficial species Coccinella septempunctata is not affected from the species H. bacteriophora.

Download Report