Just some of the hundreds of thousands of bees that have died from suspected poisoning.

Hundreds of thousands of bees are dying in Murchison, near Nelson, and beekeepers are at a loss to save them.

Veteran beekeeper Ricki Leahy said he first noticed dead bees in front of his hives in the Mangles Valley last Friday.

Leahy, who is an ApiNZ board member, produces Tutaki Honey through his business Trees and Bees. He said the 40 hives used for queen rearing around his home had been affected, as well as another 186 hives located half a kilometre down the road.

RICKI LEAHY The Trees and Bees apiary near the Mangles Valley in Murchison where the bees in all 186 hives are dying.

Leahy estimated the number of dead bees to be in the hundreds of thousands.

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"We had a look at them again this morning to see if we could rescue any and it is just hopeless, there are so many dead bees."

RICKI LEAHY Dead bees collected from eight hives at the Trees and Bees apiary in the Mangles Valley in Murchison.

The hives were fine when Leahy checked them on Thursday, but bees had continued to die since Friday.

"What bees are left are looking very unstable on their feet, they have got the jitters and there is actually nothing we can really do to help the situation. There is nothing we can do. "

In his 40 years beekeeping, Leahy said he hadn't experienced a loss of hives on such a scale and that the impact was "absolutely devastating".

RICKI LEAHY One of the hives at the Trees and Bees apiary in the Mangles Valley, Murchison where thousands of bees have died from suspected poisoning.

"We are expecting to have a complete wipeout of all our hives here.

"The heart of our business is being struck with a sword."

Leahy had notified the Ministry for Primary Industries and followed instructions to put some of the affected bees in the freezer so they could be tested. He had also notified the police.

He suspected the bees were dying as a result of ingesting poison, but said they would have to be tested in order to ascertain the cause of death.

Leahy suspected the bees had consumed a sugar-based bait meant to kill wasps (no commercially sold wasp baits kill bees, as outlined in Stuff's wasp wipeout programme).

"We can't prove anything and we can't find any evidence of it but that is what we are assuming. We don't believe there was anything malicious."

The deaths could also be the result of an aerial spray or something used on a neighbouring farm.

"We don't know, we haven't got a clue," Leahy said.

"We would really like to have someone come and verify what is happening."

He said the number of wasps in the Murchison area had increased in the last three weeks and his team had been killing wasp nests and using Vespex, a protein-based bait which was not attractive to bees.

"Anybody who is going to attempt to poison wasps should make sure they don't use bait that attracts bees, they must not use any jams, honey, sugar syrups or anything like that, any bait must be meat-based."

If anyone in the Murchison area thought they might have used something which had resulted in the bee deaths, Leahy would like to hear from them.

"That would make us feel better because we would know we have solved the problem.

"It is a bit of a dilemma if we don't know what the cause is."

Despite their best efforts, Leahy said there was nothing they could do to save the remaining bees, who were continuing to die.

"We have just been tipping dead bees out of the bottom of hives, just piles of dead bees.

"It is just devastating, it is so upsetting for us beekeepers."

Leahy said another beekeeper in the same valley had been affected and faced the loss of up to 80 hives.

He had sent a beekeeper out to apiaries in the surrounding areas to see if other hives had been affected.

Leahy said they had been in the middle of "queen rearing" and had lost up to 400 mated queens, which were ready to put into hives.

The impact of that would have a run-on effect on the quality of hives in the next season.

"It's going to take a lot of labour and work to get them all back up and running."

Until he knew what the cause of death was, it was hard to know what action to take. If the bees had been poisoned, there was no point establishing new hives in the same area as those bees might also die.

"We have to get advice on what to do, we might well have to burn all the frames and everything and start fresh. There is no point us trying to produce queens in a poisoned environment."

The Ministry for Primary Industries and the Environmental Protection Agency have been approached for comment.