Biological control of pests by augmentative release of : case study of the millet head miner and the wasps Habrobracon hebetor in West Africa

Malick Ba1, Baoua I., Amadou L., Kabore A., Ndiaye M., Karimoune L., Sarr I., Dabire L.C., Muniappan R.

1ICRISAT-Niger, Email: [email protected] The pest: the millet head miner

• Heliocheilus albipunctella is a univoltine species • Female laid eggs on the spikelet and floral peduncles of newly exerted pearl millet heads • Developing larvae feed on the spike • They chew between the rachis and flowers and cut floral peduncles, The pest: the millet head miner

• As the larvae developed, they lift the destroyed flowers or developing grains, leaving a characteristic spiral pattern on the millet head. • Damage to the crop is due to larvae that feed on the panicle and prevent grain formation. • Typical yield losses range from 40 to 85% • Almost every year, the MHM causes significant damage to pearl millet in the Sahel region Why biological control of the Millet head miner?

• Other control means are either not applicable or inefficient • Effective biocontrol agents are available • The Habrobracon (=Bracon) hebetor Say naturally inflicted significant mortality to MHM. • H. hebetor can be easily mass reared The biocontrol agent: Habrobracon hebetor • It is a minute parasitic wasp of the Braconidae family • H. hebetor is a larval ectoparasitoid of several species of pyralids

• Stored product : Plodia interpunctella, Cadra cautella, Ephestia kuehniella; Corcyra cephalonica; Sitotroga cerealella Olivier, Galleria mellonella.

• Field insect pests: Helicoverpa armigera; Spodoptera species; Earias vittella; vitrata; Diatraea saccharalis; Cydia leucostoma; Pempelia morosalis; Opisina arenosella, Ectomyelois ceratoniae, Palpita unionalis, Heliocheilus albipunctella H. hebetor against MHM : mass rearing of parasitoids

• Colony of H. hebetor are established and maintained in the laboratory on an alternate host, the rice moth Corcyra cephalonica • C. cephalonica is reared on a mixture of millet flour and millet grains and the parasitoids were reared on third and fourth instar C. cephalonica larvae • The subsequent generation of H. hebetor emerged 7–14 days after confinement of female parents with C. cephalonica larvae. H. hebetor against MHM : Releases of parasitoids • The parasitoids are released from small jute bags containing a mixture of millet grains and flour together with 25 larvae of C. cephalonica, and 2 mated H. hebetor females.

• The 2 females then parasitize the 25 C. cephalonica host larvae, and emerging progeny escape through the jute mesh and disperse to parasitize MHM larvae in millet fields. H. hebetor against MHM : Releases of parasitoids

• The jute bags are suspended to the ceiling of traditional straw granaries or directly attached to trees within pearl millet fields.

• A number of 15 parasitoid bags are used for coverage of a 5 km2 area of pearl millet. H. hebetor against MHM : Releases of parasitoids

Daily emergence of parasitoid from jute bags: Initial population

30 Total: 70 parasitoïds 25

20

15

10

No emerging parasitoids No emerging 5

0 6 7 8 9 10 11 12 13 14 Days after bags are placed

Ba et al. (2014): Biocontrol 59, 689-696 H. hebetor against MHM : Releases of parasitoids

Projected numbers of parasitoid produced from Initial population

1600 Burkina Faso Niger 1400

1200

1000

800

600

400 NoH. hebetor females ('000) 200

0 0 14 24 34 No days after parasitoid bags are placed H. hebetor against Millet head miner H. hebetor against MHM : Effectiveness

2007 2008 H. hebetor releases villages Control (no releases) 120

100

80

60

40

% Parasitized head larvae miner % Parasitized 20

0 Burkina Mali Niger Burkina Mali Niger Faso Faso

Ba et al., 2013: Phytoparasitica 41, 569-576 H. hebetor against MHM : Effectiveness

100 ParasitoidH. hebetor bags releases directly villages placed within millet crop A Control (no parasitoid released) 80 A

60

40 head miner larvae miner head

20 B B

0 % parasitized parasitized % 2011 2012 Years

Ba et al., 2014: Biocontrol 59, 689-696 H. hebetor against MHM : Effect of 2 successive releases

Kabore et al., 2017: Biological control 108, 64-69 H. hebetor against MHM: Persistance of parasitoids

1.2 Release Control per 1

0.8

parasitized 0.6 spike

larvae 0.4

0.2 No.MHM 0 2010 2011 2012 2013 2016 Year Kabore et al., 2017: Biological control 108, 64-69 H. hebetor against MHM: Parasitoids dispersal H. hebetor % head miner larvae parasitized by by parasitized larvae miner head %

No days after parasitoid bags are placed Baoua et al., 2017:to be submitted H. hebetor against MHM: Yield gain 30% yield gain

Damaged spike Saved spike Baoua et al 2013: Journal Applied Entomology 138, 281-288 H. hebetor against FAW: Is it feasible?

L. Amadou

L. Amadou

L. Amadou Conclusion

• H. hebetor has a rapid development time • H. hebetor has a high rate of population growth • H. hebetor mass rearing is easy and quit cheap • Effective releases techniques for H. hebetor are available Thank You