Entomopathogenic fungus as a biological control for an important vector of livestock disease: the Culicoides biting midge.
BACKGROUND
The recent outbreak of bluetongue virus in northern Europe has led to an urgent need to identify control measures for the Culicoides (Diptera: Ceratopogonidae) biting midges that transmit it. Following successful use of the entomopathogenic fungus Metarhizium anisopliae against larval stages of biting midge Culicoides nubeculosus Meigen, we investigated the efficacy of this strain and other fungi (Beauveria bassiana, Isaria fumosorosea and Lecanicillium longisporum) as biocontrol agents against adult C. nubeculosus in laboratory and greenhouse studies.


RESULTS
Exposure of midges to 'dry' conidia of all fungal isolates caused significant reductions in survival compared to untreated controls. Metarhizium anisopliae strain V275 was the most virulent, causing a significantly decrease in midge survival compared to all other fungal strains tested. The LT(50) value for strain V275 was 1.42 days compared to 2.21-3.22 days for the other isolates. The virulence of this strain was then further evaluated by exposing C. nubeculosus to varying doses (10(8)-10(11) conidia m(-2)) using different substrates (horse manure, damp peat, leaf litter) as a resting site. All exposed adults were found to be infected with the strain V275 four days after exposure. A further study exposed C. nubeculosus adults to 'dry' conidia and 'wet' conidia (conidia suspended in 0.03% aq. Tween 80) of strain V275 applied to damp peat and leaf litter in cages within a greenhouse. 'Dry' conidia were more effective than 'wet' conidia, causing 100% mortality after 5 days.


CONCLUSIONS
This is the first study to demonstrate that entomopathogenic fungi are potential biocontrol agents against adult Culicoides, through the application of 'dry' conidia on surfaces (e.g., manure, leaf litter, livestock) where the midges tend to rest. Subsequent conidial transmission between males and females may cause an increased level of fungi-induced mortality in midges thus reducing the incidence of disease.
Pure and Applied Ecology, Swansea University, Swansea, United Kingdom. m.a.ansari@swansea.ac.uk
Minshad Ali
MA
Ansari
Edward C
EC
Pope
Simon
S
Carpenter
Ernst-Jan
EJ
Scholte
Tariq M
TM
Butt
D000818:Animals; D001819:Bluetongue / Q000517:prevention & control; D001820:Bluetongue virus; D002519:Ceratopogonidae / Q000382:microbiology* / Q000821:virology; D004199:Disease Vectors; D058751:Livestock; D052981:Metarhizium / Q000472:pathogenicity*; D010572:Pest Control, Biological / Q000379:methods*; D010575:Pesticides; D013172:Spores, Fungal / Q000472:pathogenicity
D010575:Pesticides
Parasit Vectors. 2010 Mar 16;3(1):18
20233423
Malar J. 2009 Dec 23;8:309
20030834
Parasit Vectors. 2010 Sep 15;3:87
20843321
J Invertebr Pathol. 2009 Mar;100(3):160-8
19320043
Annu Rev Entomol. 2000;45:307-40
10761580
Malar J. 2010 Jan 19;9:22
20085659
J Invertebr Pathol. 1988 Jul;52(1):108-18
3418133
Parasitol Res. 2008 Dec;103 Suppl 1:S69-77
19030888
Acta Trop. 2010 Jan;113(1):1-6
19703405
Malar J. 2004 Nov 28;3:45
15566626
Am J Trop Med Hyg. 2009 Jun;80(6):992-7
19478264
Med Vet Entomol. 2008 Sep;22(3):175-87
18816267
Trends Microbiol. 2009 Apr;17(4):172-8
19299131
Vet Parasitol. 2009 Jul 7;163(1-2):110-4
19398160
Science. 2005 Jun 10;308(5728):1641-2
15947190
Bull Entomol Res. 2010 Apr;100(2):175-83
19586576
Malar J. 2003 Sep 15;2:29
14565851