Distribution Pattern and Sequential Sampling Plan for Rice Caseworm Nymphula Depunctalis (Guenee)

Rice caseworm Nymphula depunctalisis (Guenee) is one of the major insect pests that attack rice. Due to its leaf cases, and without taking into account their spatial distribution pattern it is difficult to evolve an IPM strategy against this. Present study is on this and was assessed with field experiments during rainy seasons of 2015, 2016 and 2017. The results obtained with Taylor’s power law (TPL) and Iwao’s mean crowding (IMC) regression show that N. depunctalis followed an aggregation pattern in rice field as revealed by the TPL parameters - Sampling parameter (a) = - 0.023, aggregation parameter (b) = 1.226, R²= 0.851; and IMC parameters- Index of basic contagion (α) = 0.089, and density contagiousness coefficient (β) = 1.204, R²= 0.960). Optimum sample size was estimated with Taylor’s regression coefficients with two precision levels fixed at 0.10 and 0.20, and these revealed that the size increased with TPL parameters with an increased precision level. Sequential sampling decision lines (d = 1n ± 0.38 n) were also determined based on the TPL parameters.