Tutin and toxic honey

From the NZ Food Safety Authority website

Managing tutin contamination in honey

Beekeepers and packers of honey for sale or export must comply with a standard under the Food Act to show that their honey does not contain toxic levels of tutin.

Tutin contamination, which causes toxicity in honey, is often found in late-season honey in some parts of New Zealand. It occurs when bees collect honeydew from passion-vine hoppers that have been feeding on tutu (Coriaria arborea), a poisonous New Zealand shrub.
It is a legal requirement that all honey for sale or export must comply with the limits set out in the Code. Beekeepers and packers of honey must ensure that they take appropriate measures to meet these limits, ‘sale’ of honey used in trade as a barter or donation must comply with this standard.

Tutu (Coriaria arborea) is reasonably widespread in Nelson particularly on the the fringe of the bush or any land on that has recently been cleared and left for a few months (eg a slip). In the mid to late summer check up the Brook or the Maitai Valley for evidence of leaf hoppers on the plant.