Testing of the Egg Parasitoids Trichogramma bourarachae Pintureau and Trichogramma
nerudai Pintureau against some Lepidopterous insect pests in Sudan
Sara A. A. Kehail and Hayder Abdelgader
Agricultural Research Corporation, Crop Protection Research
Centre, P. O. Box 126 Wad Medani, Sudan
Introduction
Trichogramma (Hymenoptera: Trichogrammatidae) are extremely tiny wasps, the female
Trichogramma lay their eggs within a host eggs. Each female parasitizes from 10 to 190
eggs during its life. More than one parasite egg may be inserted into each host egg and this
is based, on the egg size. After hatching, the parasitoid larvae feed on the contents of the
host egg. The wasps pupate within the egg and adults chew an emergence hole to escape.
There are several species and strains of Trichogramma, which vary considerably in their
ability to control different insects and in their adaptation to different environmental
conditions and crops. Trichogramma have been used as inundative biological control
agents against a range of agricultural pests, mainly lepidopterans.
Trichogramma Wasp
A female Trichogramma wasp while
laying her eggs inside a host egg
A Trichogramma wasp while emerging
out of the parasitized egg
Objective
The current study was carried to test the acceptance of two Trichogramma species
(Trichogramma bourarachae Pintureau; and Trichogramma nerudai Pintureau) against
host eggs of different Lepidopterous insect pests in Sudan.
Materials and Methods
Grain moth, Sitotroga cerealella Oliver
Rice moth, Corcyra cephalonica St.
Date moth, Ephestia calidella Guen
Laboratory work was conducted at the Agricultural Research Corporation (ARC),
Wad Medani, Sudan during 2008-09. Trichogramma bouraracha, T. nerudai and
Sitotroga cereallela were brought from AMW-Nützlinge Company (Germany), to
Sudan in 2008 and 2009. Eight species of lepidopterous insect pests were selected
either from storage such as, Sitotroga cerealella, Ephestia calidella and Corcyra
cephalonica or from their host plants such as Helicoverpa armigera, Earias insulana,
Trichoplusia ni, Spodoptera exigua and Sesamia cretica. These hosts were collected
at different stages from the ARC research fields and reared in the laboratory under
room temperature until the adults emerged and laying eggs. The papers containing
eggs were cut to pieces (egg-cards) before offered to different numbers of T.
bouraracha and T. nerudai separately in glass tubes (15 cm long × 3 cm Ø). A small
drop of honey was added to each egg-card to provide a food for Trichogramma
wasps. The parasitized eggs as well as the hatching adults were counted using a
binocular microscope. The experiment was replicated three times (as average), the
unhatch eggs were excluded, average parasitism, emergence rate and female % for
tested Trichogramma / host was determined.
Spiny bollworm, Earias insulana
Boisd
Cabbage looper, Trichoplusia ni Hub.
Leafworm, Spodoptera exigua Hub
Stem borer, Sesamia cretica Led.
Bollworm, Helicoverpa armigera Hub.
Results
All the tested eggs of the pest insects were accepted by the host females of Trichogramma nerudai and T. bourarachae as showed in the results (Table and
fig. 1). The highest average of emergence rates of both Trichogramma species were 2.68 and 2.02 respectively appeared from Sesamia cretica, while the
storage pests (Ephestia calidella and Sitotroga cerealella) showed the lowest appearing for the both Trichogramma species (1.00 - 1.08) in compared to
other tested host. The highest female percent was emerged from Corcyra cephalonica (T. nerudai and T. bourarachae, 82 % and 70 % respectively) and
the lowest percent was emerged from E. calidella for both Trichogramma species (38 % and 21 % respectively). Helicoverpa armigera and Earias
insulana showed similar female percent for both T. nerudai and T. bourarachae (Table and fig. 2).
Table: the emergence rate and the female percentage of different host eggs parasitized by Trichogramma nerudai and T. bouraracha.
cerealella
Hosts
Ephestia
calidella
Number of
parasitized eggs
Number of
Emerged adults
Emergence rate
% Female
T. nerudai
Earias
armigera
insulana
10.67 ± 3.79 30.83 ± 21.39 34.25 ± 12.61 25.57 ± 8.68
30.67 ± 14.19
T. nerudai
47.25± 38.42
T. nerudai
Helicoverpa
Trichoplosia Spodoptera
ni
exigua
Sesamia
cretica
43.0 ± 33.98
T. bourarachae
T. bourarachae
Corcyra
cephalonica
32.67± 14.57
1.07 ± 0.13
T. bourarachae
1.08 ± 0.08
T. nerudai
77 ± 0.05
T. bourarachae
69 ± 0.02
BOU
NER
3.0
9.5 ± 2.89
Emergence rate
Trichogramma
sp.
Sitotroga
16.5 ± 10.85 20.0 ± 14.55
2.0
1.0
0.0
Ses
Hel
Spo
Ear
Tri
Cor
Sit
Eph
Hosts
15.75 ± 7.37
39.6 ± 14.15
32.4 ± 15.27
18.83 ± 7.81
9.75 ± 7.54
6.33 ± 3.79
22.33± 14.94
11.33 ± 3.51
41.83±24.73
62.75± 1.03
51.0±16.11
16.75± 8.85 33.0 ± 28.93
53.0 ± 37.94
Figure 1: the emergence rate of T. nerudai and T. bourarachae
from different host eggs
Trichogramma sp. vrs % Female
15.75 ± 7.37
1.07 ± 0.13
49.6 ± 19.31
1.45 ± 0.26
59.8± 31.50
1.96 ± 0.49
30.83±21.06
2.04 ± 0.49
16 ± 17.36
1.77 ± 0.89
1.00 ± 0.00
1.25 ± 0.15
1.82 ± 0.21
1.57 ± 0.72
1.42 ± 0.40
38 ± 0.38
82 ± 0.09
64 ± 0.13
65 ± 0.11
73 ± 0.09
21 ± 0.43
70 ± 0.16
66 ± 0.13
64± 0.09
60 ± 0.15
9 ± 5.00
1.79 ± 0.59
45 ± 35.44
2.68 ± 0.54
60
2.02 ± 0.42
78 ± 0.14
73 ± 0.11
20
67 ± 0.08
0
SD = Standard deviation
Conclusion and Recommendation
NER
80
1.58 ± 0.52
68 ± 0.21
BOU
100
% Female
Parameter
(Mean ± SD)
Trichogramma sp. vrs Emergence rate
40
Cor
Sit
Spo
Ses
Hel
Hosts
Ear
Tri
Eph
Figure 2: the % female of T. nerudai and T. bourarachae emerging
from different host eggs
All the tested hosts showed the highest emergence rate compared with the storage pest, this difference in the emergence rate might be due to their egg size. More
than 50 % females were emerged from all the tested host eggs except Ephestia calidella for both Trichogramma sp.. T. nerudai was found to be more fecund and
fertile relative to T. bourarachae (high % female). So we recommend to involve the egg parasitoids Trichogramma within the strategy of IPM Program in Sudan.