Herrera participated in the isolation and identification of pulque fungi, commonly called “pulqueros”, such as: Saccharomyces cerevisiae, Pichia membranaefaciens, Candida boidini, C. incospicua, and numerous species of the genera Kloeckera, Rhodotorula and Torulopsis.
[4] During the late 1950s he became interested in hallucinogenic mushrooms from several regions of Mexico, specifically Huautla de Jiménez, Oaxaca, in the Mazateca Sierra.
His ecological research in hallucinogenic mushrooms determined the environmental conditions for these organisms to grow: oak and coniferous forests between 1,300 and 2,600 msl.
[4] Further on, he described the hallucinogenic effects of Psilocybe based on personal experience, which were published in the Mexican journal “Neurología”,:[3][4] (Translation to English) “Increased blood pressure and body temperature as well as increased heart rate and pulse, other effects may be present, such as shivers, flushing or paleness, nauseas, tremor and heavy legs; in some cases headache, dizziness, euphoria, and changes in behavior; almost always, occurrence of hallucinations shaped like geometric bright figures of various and changing colors like a kaleidoscope, changes in the understanding with rapid disintegration and confusion of ideas, difficulty to distinguish reality from fiction, loss of space and location, sense of shortening or elongated as well as distorted or disconnected body parts; schizophrenia, namely, split personality, feeling apart from the body and mind.
All of these trigger a state of anguish, unable to distinguish between real and unreal, but generally, a feel that there is direct communication with god or supernatural forces or beings.
With this particular research area, Herrera, instilled interest in the cultivation of Agaricus bisporus and Pleurotus in Mexico;[3] currently is a fruitful and well-remunerated activity.
He carried out research in toxic fungi such as Amanita virosa, A. verna and A. bisporigera, which cause the majority of fatal poisoning in Mexico.
[3] At the end of the 1960s and beginning of the 1970s he became interested in studying the macromycetes from arid ecosystems of Mexico;[3][5] in collaboration with Gastón Guzmán they became pioneers in this research area.
At the same time he characterized the gasteroid fungal diversity of the state of Sonora and studied the ecological distribution and etnomycological importance of the genus Schizophyllum in Mexico.
Additionally he reported new records of several species of Agaricales for the state of Sonora[7] and characterized the diversity of macromycetes of the “Pinacate and great Altar desert reserve”.
[10] In 2011, he published a short communication about the first records of fungi collected in 1793-1794 during the first expedition of Sessé and Mociño to Mexico (called “Nueva España” at the time)(Pérez-Silva et al.. 2011, b).
[4] Another example is the book entitled: “Breve historia de la botánica en México” (Brief history of botany in Mexico”) written in collaboration with M. Ortega, J.L.
[2] He reported for the first time in Mexico, countless fungal species, including: Coprinus plicatilis, Psathyrella pseudocorrugis and P. pseudogracilis.
[2] At the beginning of his scientific career, in the late 1940s, he began the collection of macromycetes at the National herbarium MEXU, which is the largest in Mexico and still remains in operation; at present it carries his name.
[11] Herrera has belonged to the Mexican National Scientists System (SNI) since 1983 and he was named Emeritus Professor by UNAM in 1990.