In 2014/2015, India exported almost 155,000 tonnes of mango pulp worth 8.4 billion rupees ($126 million) with Yemen, the Netherlands, Saudi Arabia and Kuwait among the top destinations. Some of the world's biggest food and beverage players including PepsiCo, Coca Cola and Unilever buy from the country. But workers' rights campaigners say the industry in Tamil Nadu flourishes on the back of overworked and underpaid seasonal, migrant laborers who comes from the northeastern state of Assam.
A lack of rain, global competition and fluctuating prices are squeezing profit margins of many growers in the region.
"The sector is very labor intensive," Mathew Joji of the non-profit International Justice Mission told the Thomson Reuters Foundation.
"Besides low wages, to ensure there is no manpower lost, there are restrictions on their movements, which is a clear violation of the workers' rights and a method of bondage."
India is home to more than 18 million people living in some form of modern slavery, the greatest number of any country, according to the third Global Slavery Index released on Tuesday by the Australia-based Walk Free Foundation.
On May 10, revenue officials rescued a family of three, including a child tasked with clearing weeds from the fields on a mango farm.
In a complaint filed with the police, Parthiban, one of the victims, said he was working to pay off a 20,000 rupee ($300) loan.
"The owner does not pay us any wages. We borrow from the owner for petty amounts whenever we have to buy groceries and other basic needs," he said in the complaint.
"The owner added these amounts to our advance. The owner says now we have to pay 45,000 rupees ($676) principal amount and an equal amount of interest."
Up to 40,000 people are hired on a temporary basis during mango picking season from February to June when temperatures hover around 40 degrees Celsius (104 degrees Fahrenheit).
Almost all of them are migrants, mainly from the northern Uttar Pradesh, Bihar and Assam states. Hired through contractors, laborers can expect to work up to 15 hours a day for a daily rate of 300 rupees ($5).
Many take advantage of the offer of an advance on their wages and arrive on mango farms already indebted.
