Blowfly infestation of sun-drying fish is a major economic problem in
many developing countries of Asia, Africa and the Pacific. To consider
the ecology of infestation, adult and larval blowfly populations were
monitored between 27 October 1997 and 27 April 1999 at a fish landing
and drying site, approximately 5 km north of Calicut, in Kerala state on
the coast of south-west India.
During the 548-day sampling period, a total of 96 953 adult Diptera was
collected from 16 sticky targets, placed inside and outside eight
fish-storage sheds. Of these, 91 912 (95%) were Chrysomya megacephala,
3719 (4%) were other Calliphoridae and 1322 (1%) were other species,
The population of C. megacephala showed pronounced seasonal fluctuations
in response to climate, particularly relative humidity. Significantly
shorter-frequency fluctuations within fish-processing sheds were also
evident, the periodicity of which corresponded approximately to C.
megacephala generation cycles. Spatial variation in C. megacephala
abundance was evident within the site, higher populations occurring
closest to the beach and numbers declining with distance inland.
The pattern of drying fish infestation by C. megacephala broadly
followed changes in the density of adult flies and the seasonal change
in weather, with peaks during the monsoon and troughs in the dry hot
periods. High relative humidity played a significant but secondary role
in increasing infestation.
Quantification of the relationship between larval infestation and
percentage fish loss suggests that, given the infestation levels
observed, between 10% and 60% post-harvest wet weight losses would be
expected in the monsoon period, depending on the species of fish landed.
The study emphasizes the importance of developing a clear understanding
of the basic ecology and spatial and temporal dynamics of an insect
pest, prior to the design or implementation of any pest management
Wall, R.; Howard, J.J.; Bindu, J. The seasonal abundance of blowflies infesting drying fish in south-west India. Journal of Applied Ecology (2001) 38 (2) 339-348. [DOI: 10.1046/j.1365-2664.2001.00588.x]
The seasonal abundance of blowflies infesting drying fish in south-west India.