A long warm summer may have been a factor in an explosion of wasps in Central Hawke's Bay, to the extent that a section of the Tukituki riverbank in Waipukurau was closed to the public last week as steps were taken to deal with the pests.

Hawke's Bay Regional Council overseer Joe Genet says the mountain bike track behind Ford Rd was taped off after a resident alerted the council to the large number of wasps along the road and among the trees.

"It's pretty bad - we've already unearthed a couple of big nests in there - along that stretch of the river we guess there could be anything from 10 to 20 nests.

"It's a very unusual year, they are prolific right down the rivers - we have never had this much of a problem with them before.

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Last year my guys sprayed maybe 20 to 30 nests - this year on average we are seeing about five nests a day, and if we start looking for them no doubt we will find more."

Yesterday Mr Genet and his crew moved in with a digger to clear the blackberry and expose the nests so they could be treated with a pesticide dust.

The resident who contacted the regional council said they had not seen wasps to this extent in the 13 years they had lived there.

"This is escalating and if it's not dealt with the problem could be doubled next year."

Hawke's Bay Fly Free pest controller Owen Rees says he gets called out to about 100 or so nest sites each year, but agreed the problem was worse this year.

"All the ripened and rotting fruit that's around this year may be contributing to it, but they are also found in roof and wall cavities, under houses, in the ground and in trees."

Although it was bad this year, he faced one of the worst scenarios he had seen last year,
when he was called to house where wasps had eaten through the ceiling in the middle of the night and fell into a young girl's bedroom.

"It was a like a horror movie."

He's also been to houses where walls were being held up only by the paintwork, with wasps having eaten through the walls and gib.

He says two out of 10 calls he gets are from people who have unsuccessfully tried to treat the problem themselves.

While he uses an industrial product, people can have a go themselves with products that can be purchased from Farmlands.

Last month a swarm of wasps attacked a 60-year-old man in Porangahau after he accidentally chainsawed through a wasp nest.

He went into anaphylactic shock and was airlifted to Hawke's Bay Hospital. He was discharged soon after.