The single biggest movement of livestock on the Australian agricultural calendar, the bee muster saw billions of bees from the eastern states freighted to Robinvale for the almond pollinating season. But organisers were concerned to find that one in 10 bees were "weak" from malnutrition, the result of drought conditions that have reached a climax in 2018.

"I'd say 90 percent of them were quite good," said Robinvale beekeeper Trevor Monson, who coordinated the massive migration of bees from Queensland, New South Wales, South Australia and Victoria. "But about 10 per cent did not come out of spring as good as they should have done, and some of those bees have got a bit weak when they've been sent out to work on almond flowers."

Mr Monson said cold weather on the coast and dry conditions nationwide in 2018 combined to provide poor conditions for bees, which are reliable barometers of environmental health. "The ground flora they need hasn't flowered," he said.

"We haven't had rain. We had a heatwave back in January, that sort of burned whatever was around and there's just not the resource for bees. "Even the major trees, you know, if they get dry, then they just don't produce nectar or pollen for the bees, and so we have some supplementary feeds that we can feed them, but they're never perfect."

The conditions, which can make bees seek nutrition by 'stealing' honey from neighbouring hives, have also raised the spectre of the dreaded European and American foulbrood disease strains, the latter which produce spores deadly to bee larvae and can survive in infected hives for up to 70 years.

As plant biosecurity prevention manager Chris Anderson of the NSW Department of Primary Industries explained, it was the perfect storm for the destruction of bee colonies. "What makes it so insidious is beekeepers will often find that their best hives are the ones that get infected, because their bees are very strong, will fly long distances and they're very good at finding food sources," he said.

"When they find another hive that's weak and it's infected with the disease, that hive is a really easy target for them to go and get a quick meal. "They'll go into that weak hive, they'll steal the infected honey out of that hive, and then they'll bring those spores back to the healthy hive and that hive will break down with disease."

Mr Anderson said raising awareness of American Foulbrood was important for the industry. "We encourage beekeepers for AFB Awareness Month (October) to inspect their hives. "It's a disease you really want to try to find early and if found, to deal with it quickly."

Though the DPI and Agriculture Victoria has yet to release details of any biosecurity audits for 2018, the ABC has learned that a regeneration of the foulbrood strains was discovered this year, the disease having been detected in hives originating from a number of different sources.

Plus a worrying number of the 102,000 hives were found to be nearly empty of bees when opened in the north-west. Though Trevor Monson admitted the situation was one that "some people would consider major", he insisted it was no great cause for alarm. "There's always a couple of incidents that happen that are unfortunate," he said.

"The DPI has found a little bit of that [foulbrood] this year. But poor nutrition creates all sorts of problems. "The drought, you know, with lack of nectar, makes bees go back in and consume honey that probably hasn't been consumed for a number of years, and if there was any disease in that honey from years back then it will reinfect the hives again.

"It's a bit like cancer. There are some diseases that lie latent in the hives and just wait for the right conditions that trigger them off." The good news is that the weak bees appeared to recover after a few weeks of feasting on the pollen of the more than 10 million almond trees that grow from the waters of the Murray River. "Almond pollen is very high in protein and is really good for bees," Mr Monson said. "This year, the almond, for some reason unknown to us, yielded a lot more nectar than it normally does.  "So the bees responded very quickly."