I have a question on behalf of someone else on a gardening forum, I hope someone here might be able to shine some light on what is happening. They want to know why the bees keep falling off their currently flowering gums then crawling around on the ground until they get attacked by ants?
Someone suggested the nectar may be fermenting and they might be drunk.
What say you brains trust?
Dropping off flowers in the garden I would suspect poisoning. A chemical spray of some sort. The trees blossom may not be the source of the poisoning but the last place they feed.
My best guess.
Perfectly natural to have dead bees out the front of the hive which is a life cycle thing. The bees get old, die and dumped out of the hive or flown a short distance away
Jaydeb,
Yes ! I would vote for possible insecticide poisoning ā¦ If it seems to be mass dying off and not just a handful or ocassional. The tree near the hive could be just a rest point as the are coming in. See what direction they are mostly leaving for n investigate maybe. You might find the place. Check color of pollen sacs to get a hint what they might be collecting. Not sure if this helps as the damage now is probably after the fact.
Good luck,
Gerald
Iād have to throw my hat in with insecticide poisoning.
If the trees are in their garden Iām sure they would know if they had been sprayed. My money is on nectar toxicity. Here in the UK Tilia (Linden) is well known for narcotising bees which then fall to the ground to sleep it off.
Thanks everyone. Iām trying to figure this out for someone else, theyāre not beekeepers but theyāve noticed it happening in their garden under a flowering eucalyptus. I found this old newspaper article, from California of all places (in 1877 of all times!). Interesting read.
http://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=PRP18770825.2.8.1
Now what is most remarkable about this tree is, as we were informed by Mrs. D., that almost as soon as a bee lights upon one of its flowers it falls to the ground helpless and expires. During the time it was in bloom last spring the ground around it was thickly covered with dead bees, so much so that they could be scraped together by the double handful. There seemed to be an odor about the bloom that was fascinating to the bee, while death lurked within. The scarcity of feed no doubt had much to do with the bees visiting the tree. Humming-birds visited the flowers of the other trees in the yard, but never this one.
Bees do get drunk. When I was a girl we had a santa rosa plum in the yard. It was so prolific it created a thick layer of overripe windfalls on the hot sidewalk next to it. Those sugary sweet plums would ripen and ferment in the hot sun and the bees would drink up the ābee brandyā and then either crash land until they slept it off, or fly in erratic lazy dippy circles and figure eights, like they couldnāt remember the way home.
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Wow, it sounds like that tree produces a toxic nectar. There is probably a species of insect that specializes in pollinating that particular tree. The humming birds probably figured it out to leave that bush alone millions of years ago.
This is possibly an example of what happens when you move species away from their natural environments & mix them up.
Who knows @JeffH the article is anecdotal at best. Itās interesting that so much of California is planted in Australian eucalypts. They were apparently taken over there in the mid 1800ās by Aussies chasing gold in the Californian gold rush and planted in the thousands of acres with encouragement by the government. Bet theyāre sorry now when wildfire season comes alongā¦
Great description @sara - I can imagine drunk bees flying in āerratic lazy dippy circlesā 
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Certain types of eucalypts and other species do affect bees causing them to appear ādrunkā. There has been a really interesting study done by RIRDC. Flowering Ecology of Honey-Producing Flora in South-East Australia. Part 02 (p43) onwards, part of introduction below (itās a really fascinating study!)
ā¦strong evidence of the relationship between honey production, bee
mortality and atmospheric humidity: during the early stages of flowering, this species is one of
Victoriaās main honey producers, yielding up to 3 tins/hive (Table 1.1). The latter stages of flowering,
however, coincide with late autumn/early winter and, therefore, increased atmospheric humidity.
Beekeepers report that the first major autumn rainfall triggers massive bee mortality with several
apiarists reporting losses of up to 90% of hive populations. Common symptoms exhibited by
honeybees prior to death during this period include visible āstreakingā (smears of faecal matter) in and
on hives, dysentery and ādrunkennessā (Section 1.3.4.4). Apiarists often use the term ādrunkā to best
describe the behaviour of bees during this time, whereby bees fall from flowers to the ground, stagger
and move in confused movements and, eventually, die. Generally, bees are not able to return to the
hive and die en masse, often in front of the hive (Figure 2.1).
It is possible that nectar could ferment, as it is a natural sugar solution and is therefore likely to be
colonised by environmental micro-organisms, such as yeasts. In isolation, this would not result in
fermentation, however, as the high sugar concentration would āpreserveā nectar. However, increased
atmospheric humidity could encourage dilution of nectar reserved in the floral cup (atmospheric
moisture - high, nectar moisture - low). In turn, reduced ratios of nectar sugars to water may reduce the
sugarsā ability to inhibit microbial growth (including yeasts) in the nectar. Thus, fermentation could
occur, as ethanol is produced as waste by yeasts during sugar metabolism. Honeybees, when gathering
this nectar, would thus be ingesting nectar laced with alcohol (ethanol) and may exhibit those
symptoms observed by apiarists, the authors and members of the wider community.
I canāt find a page link, its a pdf download but if youād like the whole thing let me know
https://rirdc.infoservices.com.au/downloads/08-098
above might get you there?
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Sorry for the slow response Kirsten. Iāll pass the link on - it is a direct link that downloaded the pdf, maybe it will help them solve their mystery. Thanks.
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No worries, I hadnāt been able to visit the forum for awhile myself, & only saw it a little while ago. We have some Eucalypts on our property & I saw this a couple of times, which prompted the search for info. So fascinating, interesting that doesnāt seem to happen with native bees?