A bioeconomic model for estate rubber is modified to apply to conditions facing Indonesian smallholders in low fertility Imperata areas. The economic component of the model is updated using prices and costs prevailing in South Sumarta in 1995. The modifications to the model are briefly described, then used to analyse the decision of when tapping should commence. It is shown that smallholders who tap prior to recommended minimum tapping girths are acting logically. Early commencement of tapping is consistent with maximising economic returns over the life of the plantation, even though there is a sacrifice in terms of total rubber yield. Bioeconomic modelling is a powerful tool for analysing issues of this type, where the undertaking of long run biophysical experiments is prohibitively expensive.