Table 2.
Standard values of empirical parameters used to model the evolution of Helicoverpa armigera resistance to Bt cotton at three locations in the cotton belt of Cameroon. Sensitivity analyses were performed to evaluate effects of variation in several of these parameters (see Materials and methods)
| Parameter | Definition | Value | References |
|---|---|---|---|
| fnoncot | Proportion of moths originating from non-cotton hosts | Fig. 1 | Present study |
| LS | Survival of larvae to insecticide sprays in non-Bt cotton | 0.20 | Brévault et al. (2009) |
| LB3 ss1* | Survival of ss1 larvae on Cry1Ac cotton in August, September, and October | 0.02, 0.17, 0.37 | Kranthi et al. (2005) |
| c, h | Fitness cost and dominance of cost (Cry1Ac) | 0.34, 0.33 | Bird and Akhurst (2004) |
| Fitness cost and dominance of cost (Cry2Ab) | 0.00, 0.00 | Mahon and Young (2010) | |
| E3 | Number of effective eggs produced by adults surviving on Bt cotton (relative to non-Bt cotton E2) | 0.60 | Mahon and Olsen (2009) |
| p0 | Initial allele frequency (Cry1Ac) | 0.0003 | Mahon et al. (2007b) |
| Initial allele frequency (Cry2Ab) | 0.0033 | Mahon et al. (2007b) | |
| RF, b | Resistance factor and slope (Cry1Ac) | 63, 1.0 | Akhurst et al. (2003) |
| Resistance factor and slope (Cry2Ab) | 6830, 0.76 | Mahon et al. (2007a) | |
| DLC | Dominance of resistance (Cry1Ac) | 0.26 | Akhurst et al. (2003) |
| Dominance of resistance (Cry2Ab) | 0.00 | Mahon et al. (2007a) | |
| MR1† | Proportion of moths migrating from southern regions and colonizing the cotton belt | 0.98 | |
| MR2† | Proportion of moths from the cotton belt contributing to the pool of migrants moving south | 0.20 |
*
Survival on Bt cotton.
†
The West African cotton belt is colonized at the beginning of the growing season (June–July) by moths migrating from the south, and moths from the cotton belt return south at the end of the growing season (October–November).