In accordance with Article 6 of Regulation (EC) No 396/2005, Finland, hereafter referred to as the evaluating Member State (EMS), received an application from BASF SE to modify the temporary maximum residue level (MRL) for the active substance mepiquat in cultivated fungi based on monitoring data. Mepiquat residues in mushrooms do not result from the use of the active substance on mushrooms, but from the uptake of residues via the growth substrate composed of cereal straw that has been treated with mepiquat. Based on a total of 74 samples on oyster mushrooms, three different MRL proposals were derived. A risk management decision is required, considering the acceptable non-compliance rate, in order to decide which temporary MRL is the most appropriate to cover the presence of mepiquat chloride residues in oyster mushrooms. The exposure to residues of mepiquat chloride at the levels observed in the monitoring data on cultivated oyster mushrooms, which were the basis for deriving the MRL proposals, is unlikely to present a risk to consumer health.