Dispersion of the bagworms Pteroma pendula and Metisa plana in oil palm

An attempt was made to determine optimum sampling unit of between-palm and within-palm distribution of bagworms and their interspecific association distribution in oil palm using aggregation indices or distribution models. The within-frond distribution of bagworms varied significantly within the oil palm crown. Peak bagworm density was recorded between frond numbers 9 and 19. Through polynomial regression, standardised residual and relative net precision analyses, frond number 17 was established as the representative sampling unit for experimental work, and frond numbers 10-19 should be used when a greater precision is required as in life-table construction. A lack of interspecific association suggested these sampling units to be applicable for single and mixed infestations. Evaluation of between-palm dispersion revealed that Taylor’s Power Law gave a more appropriate fit with highly significant r2 values for all categories of assessment. The bagworms were regularly dispersed in oil palm with a general mean-variance relationship of log (s2) = 1.780 + 0.821 log (x¯).