askST: What is the cause of these streaks on the leaves of locally farmed baby bok choy?

Reader Joyce Ng wrote in to ask about abnormal patterns found on the leaves of a packet of locally farmed xiao bai cai (baby bok choy): "I would like to find out what is the cause of the problem and if these leaves are still edible?"

Food reporter Kenneth Goh finds out.

After examining the photograph, the Agri-Food & Veterinary Authority (AVA) has concluded that the pale-coloured, squiggly lines on the leaves appear to be leaf mines.


These are caused by leaf miners, which are the larvae of small flying insects such as moths and flies. Leaf miners feed on the leaf tissue as they tunnel through the leaves of the vegetables and make the pale-coloured tracks.

After feeding, leaf miners do not remain on the leaves.

An AVA spokesman says: "Concerned consumers may wish to remove the affected leaves. As a good food safety practice, consumers are always advised to wash their vegetables well before consumption."

According to a guide on good food safety practices on AVA's website (, it advises consumers not to buy fruit and vegetables that are bruised, blemished, shrivelled or mouldy.