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BACKGROUND ON TOXIC HONEY

Animal Products Group, Information pamphlet

(Reproduced with permission from M. Reid, AsureQuality Ltd.)

1 April 2008

What is Toxic honey?

Toxic honey is produced as a result of bees feeding on tutu (Coriaria arborea) bushes. Tutu is a widely distributed native species found throughout New Zealand, particularly along stream banks and in regenerating native bush. The poison comes from the native tutu bush but Toxic honey is not produced by bees visiting the flowers of tutu to gather nectar or pollen, but rather when bees gather honeydew produced by the sap sucking vine hopper insect (Scolypopa sp) feeding on tutu plants.

The honeydew (a sweet exudate) produced from the tutu plant contains tutin, a member of the picrotoxin group. The toxin has no effect on bees and honeydew honey is chemically very similar to floral honey and cannot be distinguished by taste, sight or smell from other non-toxic honeys. The toxin cannot be degraded by any heating or processing of honey. The toxins are believed to be very stable, and poisoning cases have resulted from people eating honey that was several years old.

Both comb honey and extracted honey can be poisonous. Comb honey poses a greater risk because it is eaten directly off the comb, increasing the chance of consuming honey with a high concentration of tutin. Extracted honey is often bulked or blended with other honey thereby reducing the concentration of toxin.

While tutin, and its derivative, hyenanchin are extremely toxic to humans, only a few areas in New Zealand regularly produce toxic honey. These areas include the Coromandel Peninsula and Eastern Bay of Plenty (EBOP) and the Marlborough Sounds. To produce toxic honey, all of the following conditions are required:

• concentrations of numerous tutu bushes

• high numbers of vine hoppers

• hot dry weather to allow the honeydew to build up on the tutu (rain can wash it off)

• an absence of more attractive food sources for bees, usually caused by drought

• presence of honey bees (Apis mellifera) being managed for honey production.

A number of people have been killed, incapacitated and hospitalised over the years from eating toxic honey. The last recorded case from commercial honey was in 1974 involving 13 patients. There have been 9 cases since 1974 with the last known poisoning occurring in 1991 in the EBOP area. Two poisonings have been caused by comb honey produced by hobby beekeepers in the Marlborough Sounds in 1982 and 1983 and the highest levels of tutin ever measured in honey were produced in this area.

Managing the Risk

The main risk periods are from late December (EBOP) and mid January to the end of April in the Coromandel and Marlborough Sounds areas.

Beekeepers are required to manage the risk of their honey containing tutin by either:

• removing hives and supers containing honey for human consumption before the risk period, or

• by closely monitoring the tutu, vine hopper and foraging conditions in the areas (3 km radius) around the apiary while honey is being produced.

Poisoning symptoms

Symptoms include vomiting, delirium, giddiness, increased excitability, stupor, coma and violent convulsions. These honey toxins can be lethal, or make a person very sick. It is generally accepted that as little as 1 teaspoon (approximately 10 ml) of toxic honey can have a severe effect on the human nervous system.

Reducing the Risk of Toxic Honey Production

It is in the interests of beekeepers to manage the removal of honey from hives in the risk areas in such a way as to prevent any poisonings of humans with attendant publicity and possible claims for liability.

In all areas where tutu and the vine hopper are abundant, beekeepers should minimise the possibility of toxic honeydew honey being stored in the hive. Bees will forage up to 3-5km from their hives, especially in dry years, and toxic honeydew may be present in an area even if it is not obvious in the immediate vicinity of the apiary.

Tutu plants should be monitored for the presence of vine hoppers. The honeydew can be seen clearly on the leaves and stems of the plants as very small wet sticky droplets. Where vine hopper numbers are high a black sooty mould may be found growing on the honeydew. Check for bees, as well as wasps, gathering honeydew.

All surplus honey should be taken off hives immediately the nectar flow finishes, or sooner if there is any possibility of toxic honeydew being collected. Alternatively, hives can be removed from the toxic honey area. If any honey produced in the risk periods is to be stored and used for bee feed later in the season, frames of suspect honey must be carefully marked so they are not inadvertently extracted. Frames of feed honey should be fed to the bees well before the next honey season so the bees don’t remove any surplus honey and shift it up into the honey supers.

Beekeepers should consider taking most of the honey out of the brood nest as well before the risk period, leaving only 3-4 frames of honey, so that the honey gathered during the risk period is all located in the brood chamber for bee feed. This honey from the brood nest can be stored for feeding back later or used to make nucleus colonies, either to increase hive numbers or to re-queen other hives. Never lift frames of honey from the brood chamber into the honey supers during the risk period.

Do not eat honey taken from feral (wild) hives in the risk areas. It is the beekeeper’s responsibility not to offer toxic honey for sale.

Please be mindful of the potential to produce toxic honey this season.

For further information contact your local AsureQuality Apiculture Officer, 0508 00 11 22.