The supervisor took him from Chiquita's Caceles Sarapiqui farm to a clinic in San Jose, the Costa Rican capital two hours away, where doctors stitched together his lacerated arm and put it in plaster. Mr Mendoza, aged 28 and with three children, is worried because once his 19-day annual leave is over he will be docked pay while his injury heals.
"If I speak to you freely, I face persecution," he said. "We are prevented from talking directly to outsiders without permission." And soon after, uniformed security insisted that The Independent left the premises.
From every pounds 1 that a British shopper spends on multinational Central American bananas, 3p goes to the labourer and 40p to the supermarket. In Britain, Chiquita bananas are sold in Tesco, Asda and Safeway.
Everyone on the Chiquita plantation is slick with sweat from the exertion it takes in the tropical heat to plant, prune, weed, spray, or harvest the fruit. Rubber aprons and gloves are needed in the packing plant to keep off the toxic pesticides, preservatives and bleach which sluice off the fruit and into puddles outside, and they chafe badly. Rashes rapidly go septic, and wounds from the sharp knives refuse to heal. Hacking the green bunches apart, sorting and cleaning fruit, spraying it with fungicide, then loading the boxes is relentless toil and a radio crackles out a salsa tune that sets the pace.
After a study by the Health Research Institute at the National University of Costa Rica found that women in the country's packing plants suffered double an abnormal rate of leukaemia and birth defects, protective gear became standard issue. Not everyone wears it, though. Very few bother with cumbersome masks or goggles. Lesions in lungs or eyes can eventually occur after months of exposure. Accidental splashing can be a hazard, and there does not seem to be much clean water on site to douse a chemical burn.
Workers' barracks are adjacent to the fields. When aerial fumigation of bananas is under way, the labourers and their families are told to stay indoors. But they eat the coated herbs from their private gardens, and wash with water that has been sprayed.
Manuel Valdez, who pulls an insecticide-soaked plastic sack over each bunch of bananas, always examines his payslip carefully. Frequently, he claimed, he gets shortchanged and, when he complains, office staff cite computer error. Mr Valdez claimed such mistakes are deliberate - he suspects some people want him to break off his association with independent trade unionists. "This is their way of reminding me not to fight for my rights," he said.
There are tough times ahead for the 52,000 workers in the Costa Rica banana plantations. The current trade dispute between the United States - where Chiquita, Dole, and Del Monte are based - and the European Union over bananas is squeezing growers in Costa Rica, the world's largest producer after Ecuador. "This is a dance of two elephants," observed Victor Herrera, president of Corporacion Bananera Nacional. "And we are like an ant underfoot."
Jose Martinez says that last month he refused to sign a blank paper presented to him by management,and now fears he will lose his job and home. He'd learnt to be wary of paperwork and signatures after his cousin, one of 11,000 banana workers made sterile by prolonged use of toxic Fumazone pest control agent in the 1970s, received a token $200 after a protracted class action suit.
Chiquita said workers on its plantations were free to express themselves and to join independent trade unions. In Costa Rica most workers chose instead to be represented by elected permanent committees on their farms. The allegation that a worker had been asked to sign a blank piece of paper was being investigated.
National insurance, to which all Chiquita workers were entitled, should pay for leave for work-related injuries, the firm said. Workers were paid by cheque and on time, it added.
Medical monitoring was provided for those exposed to agrochemicals. Workers were told when aerial spraying was taking place. In addition, the firm used only products with low toxicity. Water, showers and laundry facilities were provided on all farms, the company said.
A North American epidemiologist who had seen the Costa Rican study on workers' health said it demonstrated cancer among banana workers was reduced among men and similar to the general population among women.
Asda said its buyers and others who had been to oversee banana sites were confident they complied with its code of practice and those applied by the banana industry.
Some names have been altered.
The campaign urges retailers to ensure that sub-contractors' workers do not earn low wages in poor conditions. We ask them to draw up codes of conduct and to have them monitored independently. We also call for:
t Retailers to report yearly on social auditing;
t Country-of-origin labels to be compulsory;
t An "ethical trade kitemark" for pay and conditions.