Conclusions from a dynamic population model for tsetse: response to comments

Abstract

The critique by Hargrove et al. (Popul Ecol, 2011) of our recently published paper on a tsetse population model (Barclay and Vreysen in Popul Ecol 53:89-110, 2011) has made some good points but has also misinterpreted the intent of some of our results as we presented them. Hargrove et al. rightly say that there is a mismatch between the size of the unit cells in the model (1 ha) and the iteration rate of the model (every 5 days), yielding too low a dispersal rate to simulate reality. However, they have misconstrued several of our results that we presented as examples to imply that those results were a necessary condition for control of tsetse, especially using traps and targets.Keywords Glossina Á Insecticidal cattle Á Integrated insect control Á SIT Á Traps Hargrove and his co-workers, Torr and Vale (Hargrove et al. 2011; hereafter called HTV) state that the model published by us (Barclay and Vreysen 2011) (BV) is full of problems so severe that it provides a misleading picture of the various options for tsetse control. While accepting that any model has its limitations, this statement is too broad and general for us to respond to effectively, so we will start out by saying that some of the criticisms are justified, while others are certainly not.The paper had just been published electronically when the senior author (HB) realized, after re-reading the paper by Williams et al. (1992), that the interaction of dispersal and the effectiveness of trapping was not treated properly in our model. This was aided by the unfortunate choice of a dispersal algorithm in which the rate of dispersal from one cell (hectare) to adjacent cells in the model was determined by the attractiveness of the recipient cells, and this was directly proportional to the equilibrium population levels in those cells. This resulted in equal numbers of insects being transferred back and forth between adjacent cells at equilibrium, so the effect on population levels and control efficiency was minimal. This limitation in the model could have been addressed if dispersal were to be based on something other than attractiveness, as the percentage of flies dispersing was limited by the upper limit imposed by highly clumped groups of cells. In addition, our 5-day iteration would also have to be changed to accommodate higher rates of dispersal. We have thus developed another version of the model in which the dispersal is a constant percentage (across all cells, and under user control) of those insects present in each cell and the iteration rate is now daily.Dr. Hargrove has kindly supplied us with mathematical formulations for temperature-dependent pupal developmental rate (and hence duration of the pupal stage), age at first larviposition, and inter-larval period, as well as temperature-independent mating probabilities of newly emerged males and females, all of which fit the published data better than do those originally used by us. The duration of the pupal stage would be important in the timing of This reply refers to the ''notes and comments'' at

The Insect Pest Control Laboratory of the Joint FAO/IAEA Programme: Ten Years (2010–2020) of Research and Development, Achievements and Challenges in Support of the Sterile Insect Technique

“…Spatial models and distribution atlases [ 197 ] were developed to select suitable control tactics for a particular target zone and to predict the outcome of control interventions. These models focused on control tactics for tsetse eradication [ 198 , 199 ], tsetse distribution [ 200 ], habitat suitability [ 201 , 202 ], tsetse dispersal [ 203 , 204 ] and trypanosomosis risk [ 205 ].…”