Application of probability distribution to the sampling of cotton bollworms (Lepidoptera : Noctuidae) in Northern Cameroon

The main pests of cotton in Cameroon are the bollworms Helicoverpa armigera, Diparopsis watersi and Earias spp. The implementation of integrated management of these pests requires sampling plans for population monitoring. For practical reasons, these sampling plans have to enable the monitoring of the three bollworm species together rather than each separately. Based on our examination of 2083 samples, 80 or 100 plants each, this study shows that the number of larvae per plant fits a negative binomial distribution (NBD), with a common k value of 5.70, although the numbers of larvae of the three species considered separately fit different NBDs with k values ranging from 1.37 to 3.64. However, we show that possible fluctuations of the distribution resulting from fluctuations in the relative abundance of the three bollworm species would have little or no effect on either the fixed size or sequential sampling plans. We propose the design of a pegboard that allows the extension of sequential sampling in a smallholder context. (Résumé d'auteur