Standing in a small mango packing shed in Western Australia's remote Kimberley, a group of volunteers is hoping to make a big difference — one mango at a time.

For the past seven years, Joan Grosser and her husband Bill, have organised volunteers to come to Kununurra to pick and pack mangoes to raise money for a cause close to their hearts.

"All of those people that you see packing mangoes are doing it for nothing, they're doing it for love," Ms Grosser said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 6 minutes 12 seconds 6 m A Big Country: The mango missionaries Download 2.8 MB

"They get up here from Perth and work in this terrible weather and they don't get paid anything.

"But they do it because they really care."

In 2016 Joan and Bill Grosser sold around 3,700 boxes of mangoes in Perth, raising more than $70,000. ( ABC Rural: Courtney Fowler. )

Ms Grosser said they had a long association with the Kimberley through their missionary work and the idea was born when a farmer donated mangoes for a fundraiser.

"This farmer sent us mangoes for two years to raise money to send to India for the people in palliative care, which was a new thing in India in those days," she said.

"The next year he couldn't do it himself, he was too busy with his other business and I asked what was going to happen to those mangoes and he said they're going to fall on the ground.

"I asked if I brought a team of people up from Perth can we have those mangoes [and] he said yes you can have them all, so that's what we did."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 7 minutes 35 seconds 7 m Joan Grosser talks about raising money for palliative cancer care in India. ( ABC Rural: Courtney Fowler ) Download 3.5 MB

Every year since, they have returned to Kununurra and, with every mango that comes off the tree, vital funds are raised for the Ruma Abedona Hospice, a palliative care centre they sponsor in Kolkata, India.

The facility is the only one of its kind in North East India, which supports approximately 1,500 terminally ill cancer patients and carers a month, who would otherwise be unable to afford care.

"We met a young man in India who lost his wife to cancer and felt he was really called to care for other people in India and help them to understand how to care for people who are dying of cancer," Ms Grosser said.

"I've seen it, I've seen what happens in India and I can't explain the squalor I sit in and see, people who would die in the street of cancer with no painkillers."

Two thirds of the proceeds from each box raises funds for the Ruma Abedona Hospice, a centre that treats terminally ill cancer patients free of charge in Kolkata, India. ( ABC Rural: Courtney Fowler )

Ms Grosser said after a chance meeting 17 years ago with the hospice founder Santanu Charkraborty, she knew they had to help raise funds to keep the centre open.

But what they didn't know was that the humble mango would give them the means to ease the suffering of so many.

"One of the things that we say to the girls helping here, every mango that you put into that box, is worth 50 rupees or one dollar," she said.

"That will buy medication for a patient, so that gives an inspiration to go on helping those people."

In 2016 the Grossers sold around 3,700 boxes of mangoes in Perth, raising more than $70,000.

This year Joan Grosser and her group of 10 volunteers have been invited to pick at several mango orchards around Kununurra, with the local community getting right behind the cause.

"Some of the farmers needed someone to pick and we pay for their mangoes," Ms Grosser said.

"We decide before the season starts how much a box we will pay and they allow us to come in and pick their mangoes for them so they win and we win."

Ms Grosser said it wasn't just local mango farmers who had rolled up their sleeves to help these mango missionaries, adding locals had donated their own time and equipment for the cause.

Volunteer mango pickers Benjamin Chapman and Karl Schroeder can pick up to 50 crates of mangoes a day for the cause. ( ABC Rural: Courtney Fowler )

With a slower start to the mango season in Kununurra this year, the group is expecting yields to be down on 2016 but this has not deterred the group of hardworking volunteers.

Karl Schroder has returned for his fourth year, picking up to 50 crates of mangoes a day under the hot Kimberley sun.

"You can pick a lot of crates, it varies from year to year how much fruit is there," Mr Schroder said.

"Yes, it's hot but at the end of the day it makes your heart feel good and the mind too.

"It's all for a good cause."

The packing shed where Joan Grosser and volunteers from her Christian organisation pack mangoes to be sold in Perth for charity. ( ABC Rural: Courtney Fowler )

And for retiree Malcolm Quinton, standing for eight hours a day in a tin shed packing mangoes, it is about as far away as you can get from his many years working in a city office.

"To come and do something yourself, literally getting your hands dirty makes it more rewarding than just giving a monetary contribution," Mr Quinton said.

"To work with other volunteers, as opposed to getting paid to do something is also very rewarding, not necessarily physically but certainly emotionally and spiritually.

"It's not just packing mangoes but rather it is doing something for the good of other people [and] it gives you a much better appreciation of what the farmers and the people in this area have to go through on an annual basis."

Volunteer Benjamin Chapman picking mangoes in cherry picker at an orchard in Kununurra. ( ABC Rural: Courtney Fowler )

Ms Grosser said the volunteers expected to pick and pack 2,000 boxes of mangoes by next week and orders were already flowing in from mango lovers keen to help a good cause.

"Before we came up we went around the South West and spoke to lots of different groups of people saying why to eat our mangoes," she said.

"Each of those towns now buys a pallet of mangoes, which is 77 boxes.

"They're packed with tender loving care, so we get people who've come to love mangoes who didn't love them before."