More than 500 million bees have died in Brazil in the last three months.
In the state of Rio Grande do Sul, 400 million dead bees were found - with beekeepers in four states reporting the mass deaths.
Researchers have blamed the use of pesticides - chemical substances which are used to kill pests.
Bees have a really important role in the food chain - with around one-third of the food we eat relying on pollination mainly by bees.
These include fruits and vegetables such as avocados, broccoli and cherries.
What's happened to the Brazilian bees?
The main cause of death for these bees has been the use of pesticides containing products that are banned in Europe, such as neonicotinoids and fipronil.
The EU imposed an almost total ban on neonicotinoids last April because of the serious harm it could cause to bees.
But in the same year Brazil lifted restrictions on pesticides - despite opposition from environmentalists who called it the "poison package".
The use of pesticides in Brazil has increased, according to Greenpeace, with 193 products containing chemicals banned in the EU being registered in Brazil in the last three years.
The country uses pesticides because its economy is so reliant on agriculture.
What's the story globally?
Things aren't looking good for bees around the world.
In the United States, beekeepers lost four in 10 of their honeybee colonies in the past year, making it the worst winter on record.
In Russia 20 regions reported mass bee deaths, with officials also warning it could mean 20% less honey being produced.
At least one million bees died in South Africa in November 2018, with fipronil being blamed.
And countries such as Canada, Mexico, Argentina and Turkey have all also reported mass die-offs of bees in the last 18 months.
How can bees be helped?
The World Wildlife Foundation says unused land that was previously used for development should be managed to better safeguard bee populations.
It adds that with greater urbanisation happening, more urban green spaces should be developed to protect bees.
Your garden can help too as growing plants encourages bees to pollinate - and leaving the grass to grow longer also gives bees more shelter.
For tired bees, wildlife charity Buglife says people should put them onto flowers, where they may be able to find nectar which contains nutrients they need - but sugar water can be more controversial.
You can also create a bee bath - which is filling a small dish with water and stones - that will let bees land on the stone to drink water.
And many environmental groups such as Greenpeace and Friends of the Earth say banning harmful pesticides is vital to stopping bees from dying.