Abstract:
Clausena anisata is a medicinal plant used traditionally to treat myiasis and as an insect repellent
by various communities. We have previously demonstrated the effects of C. anisata extracts on
blowfly feeding and development in our laboratory. The impact of C. anisata leaf extracts on
populations of different fly species on farms in Mpumalanga, South Africa was investigated in
this study under field conditions. Flies were exposed to liver baits treated with acetone leaf
extracts of C. anisata (150 mg/mL). Fly numbers and composition on two farms, with and
without C. anisata treated liver, were compared during a period of 12 weeks when fly
populations were expected to be high. Observations were made on fly behaviour and
development, adult sizes and numbers. The flies exposed to liver treated with the leaf extract
of C. anisata had a decreased rate of development, prolonged larval period, smaller body sizes
and more sluggish behaviour compared to those subjected to the control treatment. No
significant differences were, however, found between the numbers and sizes of flies on the
treated and on the control farm, which was most likely due to the limited nature of the baiting
programme we followed. The effects of C. anisata extracts on blowfly behaviour and
development observed in previous laboratory studies were confirmed in this field evaluation.
Although the extracts did not have a significant effect on the overall population size in this
experiment, we believe that the C. anisata leaf extract could be useful in integrated pest
management based on its effect on larval development. In addition, species such as Lucilia
cuprina and Chrysomya marginalis seemed to have been repelled by the C. anisata treated liver;
as a result, further work should explore this aspect and how it can be used for the protection
of animals.
