1. Keiji Takasu Faculty of Agriculture Kyushu University
Reproductive biology of Ooencyrtus nezarae, an egg parasitoid of the kudzu bug Megacopta cribraria in Japan
Keiji Takasu
Faculty of Agriculture
Kyushu University

2. Kudzu was introduced into US 100 yrs. ago

3. The kudzu bug, Megacopta cribraria
M. cribraria is rapidly spreading in the southeastern United States
Significant yield reductions in soybeans

4. Egg parasitoids of Megacopta cribraria in Japan
Paratelenomus saccharalis (Scelionidae)
accidentally introduced into US 2 yrs ago.
Ooencyrtus nezarae (Encyrtidae)

5. Ooencyrtus nezarae Ishii (Encyrtidae)
Polyphagous, more than 10 host species
Soybean and Kudzu
M. cribraria
Riptortus clavatus

6. on Kudzu, Fukuoka, 2010
April　　　May　　　　June　　　　　July　　　　　　　

7. The polyphagous egg parasitoid Ooencyrtus nezarae
Host recognition and acceptance
Host discrimination
Superparasitism

8. Oviposition behavior Drumming Tapping Drilling Host feeding
Ovipositing

9. O. Nezarae accepts plant seeds, glass beads shape and size of which are similar to host eggs
a glass bead
a red clover seed

10. % rejection with examining
Behavioral response by O. nezarae females toward host eggs and plant seeds
Object
No. females examined
% rejection
without examining
% rejection with examining %
acceptance
R. Clavatus eggs
Red clover seeds 32 26
26.9
6.2
15.4
93.8
57.7

11. Behavioral response by O. nezarae toward glass beads
(mm in diameter)
No.
females
examined
% rejection without examining
% rejection with examining
% acceptance
0.6
1.0
1.5
2.0
2.5
3.0 34
100
70.6
50.0
61.8
44.1
17.6
14.7
35.3
11.8
38.2
21.1

12. Host discrimination

13. Host Acceptance of unparasitized and parasitized hosts by
O. nezarae females
The percentage was significantly higher than parasitized eggs
by Fisher’s exact test.

14. A part of O. nezarae eggs deposited into a host egg protrudes from host egg surface
Egg stalks

15. Effect of protruding egg stalk on host discrimination
in O. nezarae
*significantly higher than parasitized eggs with stalks.

16. Host discrimination
External discrimination: Antennal examination of host surface detects the presence of protruding egg stalks
Internal discrimination: Ovipositor insertion into hosts detects Internal changes due to parasitism. Effective one day after parasitism

17. Superparasitism

18. Choice test between unparasitized and parasitized hosts
♀: inexperienced,
oviposited 1 h earlier
oviposited 3 days earlier
An egg mass consisting
5 unparasitized and
5 parasitized hosts

19. * * * Oviposition preference for hosts parasitized 1 h earlier over
unparasitized hosts by O. nezarae * * *

20. Naïve females or females that had oviposited 3 days ago did not
prefer to parasitize hosts parasitized 24 h earlier
(ovipositional holes were sealed by host contents).

21. Time taken for each behavioral event of inexperienced
females
Type of hosts No Mean time (s) taken for
hosts Drum- Drilling Host Ovipo- Total
examined ming feeding siting
Unparasitized a a a a a
Parasitized 1h b b a a b
earlier
Parasitized 24h a a a a a

22. External host recognition and acceptance by
the polyphagous egg parasitoid
Ooencyrtus nezarae
physical cues (shape and size) for external host recognition
protruding egg stalk for host discrimination (quick external discrimination)
Ovipositional hole for superparasitism
(save time and energy)