Karaka Poisoning of Bee Colonies

Karaka , Corynocarpus laevigatus, is a mainly coastal tree native to New Zealand. It is found throughout the North Island and in the South Island as far south as Banks Peninsula. Although it favours coastal areas it is also found inland near old Maori settlements and on river banks. Karaka is a handsome tree with glossy green laurel-like leaves and panicles of greenish flowers in late spring (which are very attractive to bees). The flowers are followed by large berries which ripen to a bright orange colour.

Farmers and horticulturalists are being encouraged to plant karaka as shelterbelts and in native plantings. There is also a project underway researching karaka as a possible new nut crop for NZ. This could be bad news for beekeepers as karaka is extremely toxic to bees.

The symptoms of karaka poisoning are:

• A shower of bees crawling half dead in the grass in front of the hive. Usually young bees.
• The ground in front of the hive littered with dead and dying bees.
• Sometimes dysentery streaks on the front of the hive.
• Queen death, and if supersedure queen this is often poor too.
• If the queen survives brood pattern is spotty.
• In a bad case there will be 50 – 60% bee mortality

Reference books state that karaka can flower any time from August to December. However the flowering in the Coromandel area is usually mid to late October, and November on the NI West Coast. Flowering seems to be just at the onset of manuka flowering. A mild attack of poisoning can cost the beekeeper 1 box of honey. In a serious case of karaka poisoning re-queening will be required and it will be 6 weeks to 2 months before the hive is again capable of honey production.

Karaka poisoning does not happen every year. Anecdotal evidence suggests one in three years. However just one mature karaka can affect an entire yard of bees.