Optimal Cotton Insecticide Application Termination Timing: A Meta-Analysis

The timing to terminate cotton insecticide applications are disputed among investigators. Nine publically available studies meeting selection criteria were synthesized to identify and develop a comprehensive optimal termination timing principle. The meta-database included 247 trial observations from 53 independent field experiments from the cotton belt between 1993 and 2007. Agronomic optimal timing to terminate insecticide applications when yield reached a plateau was estimated using an original econometric approach. Novel econometric methodology were developed to address multiple time points from multiple means comparison studies. Meta-analysis methodologies along with stochastic plateau theory were used to determine the shape of the functional form of both the optimal agronomic insecticide termination time and corresponding cotton yield potential. The proposed methodology can be extended to other crops and associated limiting factors of production, for further economic analyses. Results provided insights useful to improve production systems by applying inputs only when benefits were expected to be in excess of the respective costs. In addition to estimating the specific number of accumulated heat units needed to reach an overall cotton yield plateau, the developed meta-analysis framework evaluated whether field research results converged to an overall ‘true’ insecticide termination timing thereby addressing the question whether funding sources properly invested resources in later years.