From horsemeat labeled as beef to tilapia passed off as grouper, fraud has long plagued the food world. Now, taco lovers are crying foul over the discovery that their guacamole might not be what is seems.

First uncovered on social media and reported in Chilango, the magazine that covers Mexico City, some taco stands in Mexico are substituting “calabacitas” – a bright green mexican squash – for pricier avocados in the famous dip. Once boiled and blended up with a holy combination of ingredients – tomatillo, cilantro, garlic and jalapeno – it can be hard to tell the difference.

¿Que edad tenían cuando se enteraron que la salsa de 'aguacate' de los puestos de tacos no tiene aguacate sino calabacita cocida que le da el color y la textura? 🙊 pic.twitter.com/cy7ZhwaZ4x — Karligrafia 💫 (@Karligrafia) July 4, 2019

No one knows how long the guac bait-and-switch has been going on, and it likely isn’t just limited to taquerias in Mexico.

Some side-by-side testers at LA Taco declared the squash sauce just as tasty, with a hint of sweetness. But for other taco lovers, something just isn’t right. The faux-guac doesn’t have the same chunky consistency ideal for dunking chips, even if it does make a convincing stand-in for the drizzly avocado sauce that eaters dab onto juicy meat- or cheese-covered tortillas.

The reason behind the substitution is likely the soaring price of the beloved avocado. “Basically, the prices have gone up significantly over the last year,” says Sylvain Charlebois, director of the Agri-food Analytics Lab at Dalhousie University in Halifax, Canada.

That’s due to a poor crop last year in Mexico that many are still paying for – wholesale prices have doubled and retail prices have tripled, Charlebois says. Rising border trade tensions are also forcing up prices. In addition, the crop in California was low, due to last summer’s devastating heat wave in central and southern California, which slowed down the trees’ blooming. “As the world gets hotter, we’d expect more viruses and problems with the crop,” says Charlebois.

At the same time, the demand for the fruit is going up. From toast to tacos, avocados are everywhere. No diet discriminates against avocados – not vegans, vegetarians, keto diet followers or omnivores, Charlebois points out. “Everyone eats avocados,” he says.

According to the United Nations Food and Agriculture Organisation, the amount of agricultural land dedicated to growing avocado around the world grew from 381,000 hectares in 2006 to 564,000 hectares in 2016.

A large part of that land is in Mexico, the avocado’s ancestral homeland. But there are problems beyond the climate: farmers are turning forests and mountain ranges into avocado plantations.

The good news? When Mexico’s crop begins to hit the US in September, prices will begin to come down. But it remains to be seen whether taquerias that have started using squash as a substitute will return to their old avocado-filled ways. “People always want the real thing,” says Charlebois.

Chef Christy Lujan Kist, who cooks at LA taco spot Cacao Mexicatessen, is sympathetic to businesses using the squash sauce – to her, it’s just another salsa recipe. “We here at Cacao use real avocados in the recipe but when we describe it we do call it an ‘avocado salsa’,” she said.

Keeping and maintaining avocados is not easy either, says Kist. “Their shelf life is ridiculously short and they are very expensive by the case.” She says she can understand why a small business would seek to find a loophole – or a local street taquero would try to avoid spending $2 per avocado when selling tacos for $1.50. “It’s quite smart,” she adds. “I’ve made mock guacamole at home with just onion, garlic and jalapenos on emergency. So I don’t really think it’s a big deal – just another recipe.”