Three tropical mushroom species were studied to evaluate the possibility of commercial mushroom production on Guam. These were the straw mushroom (Volvariella volvacea), the tropical oyster mushroom (Pleurotus ostreatus sajor-caju), and the medicinal species Ganoderma lucidum, or ling shi. The most reliable species turned out to be the oyster mushroom, but it was also the most labor-intensive. The straw mushroom required less investment; the medicinal mushroom was found to be reliable, but it took the longest time of all 3 species tested (3 months) to harvest. Coffee grounds and newspaper were used as substrates.
Three tropical mushroom species were originally obtained in pure culture from the University of the Philippines, Los Banos. Two of these, Pleurotus ostreatus sajor-caju (tropical oyster mushroom) and Volvariella volvacea (straw mushroom), are edible species. The third, Ganoderma lucidum, is a medicinal mushroom, also known as ling chi.
Pure cultures of these 3 species were maintained at the Plant Pathology Lab throughout the duration of this project. Periodically it was necessary to re-isolate from fresh fruiting bodies.
Various methods were tested to get optimum fruiting body production from all 3 species. The straw mushroom produced fruiting bodies on beds of banana leaves, but the production was not always abundant or reliable. The tropical oyster mushroom produced fruiting bodies abundantly and reliably, but required more attention and more investment in terms of infrastructure and training needed. The medicinal mushroom, Ganoderma, was not as labor-intensive as the oyster mushroom, but took 3 times as long to reach maturity. In all 3 cases, the requirement for organic matter to be used as substrate for the growth of the mushrooms was considered one of the major obstacles in production, because of its scarce availability on Guam.
Some local banana growers have large commercial plantations that could supply the needed dry banana leaves for straw mushroom production, but the one we were able to approach, unfortunately for us, relies on fungicide sprays to control foliar diseases on his banana plantation, and therefore we have not tried his banana leaves for mushroom production.
We relied on shredded newspaper and office paper to mix with spent coffee grounds to produce tropical oyster mushrooms. The substrate was mixed and bagged in autoclavable polypropylene bags fitted with a nylon membrane patch for gas exchange. After sterilization in an autoclave, the bags were inoculated and sealed, and allowed to grow for 1 month until the mycelium fully covered the substrate and mushroom primordia could be seen. They were then opened and placed in a moist chamber for fruiting body production, which normally took place 4-5 days later.
Production of Ganoderma fruiting bodies was similar to the oyster method. The substrate for Ganoderma was bird seed in various formulations, but always containing sorghum. It was also grown in the same bags as the oyster mushroom, but held for as long as 3 months in moist chambers.
Problems encountered in all cases were pests such as rats, cockroaches, gnats and slugs, or fungal and bacterial contaminants. Each of these pest problems was addressed and solutions were found in each case.
During the course of the study, we had 3 different workshops, one at the University of Guam campus, one on the island of Palau, and one on Kosrae. During the time of the project we also had 3 main collaborators to work with. The first one, Mr. Dave Nelson, was producing spawn, which he sold locally and off-island. He traveled with me to the island of Palau to offer a workshop for various groups of interested housewives and to the public in general. After 1 year Mr. Nelson had to leave the island for health reasons. One of the persons who took that workshop contacted me later and has expressed a keen interest in pursuing mushroom production commercially.
After Mr. Nelson left, I got a second collaborator, Mr. Jose Entilla. He had to be trained from scratch, and learned all the techniques on how to maintain pure cultures, how to isolate from field specimens, and how to produce fruiting bodies with all 3 species. He got a third collaborator, Mr. Joe Maria, involved in growing Ganoderma. After 6 months, however, Mr. Maria left island and went to teach English in China. Eventually Mr. Entilla quit.
Periodically we have trained and collaborated with individuals interested in tropical mushroom production. Some of these, notably Mr. & Mrs Francisco of Yigo, Guam, were not only successful in growing straw and oyster mushrooms, but they also donated a home video that they took during the process, and also during the workshop they had attended. At present I am training and helping Mr. Aguilar of Dededo and Mr. Mejos of Yigo, who are interested in the straw mushroom.
The work is done, the deadline for the grant is past, and although no one is producing mushrooms on Guam at this time, the interest is very much alive. It is possible that another collaborator may eventually succeed in this. Mr. Fukuhara, a local entrepreneur, was very interested in getting straw mushroom production established. After talking to me and seeing what I was doing, he claims he was able to get a person under his employ to go to China for training. I don’t know if he has continued with his efforts, as we have lost contact.
As this project was nearing completion, we offered a third workshop on tropical mushroom production, in collaboration with the Secretariat for Pacific Communities (SPC) and the Pacific Islands Forum Secretariat. This one was held in the island of Kosrae, in the Federated States of Micronesia, during the second week of May, 2005.
Kosrae Workshop – There were 15 participants from the various islands in the region, such as Pohnpei, Chuuk, Yap, Palau, The Marshall Islands, Kiribati, and Nauru. We had more people sitting in who were local workers from Kosrae. All together we had 20 people. There was much enthusiasm about mushroom culture. Participants learned about culturing the straw mushroom, Volvariella volvacea. They learned hands-on how to make spawn and how to inoculate mushroom beds made from dried banana leaves. The workshop was sponsored by the Secretariat for Pacific Countries, SPC, and by the Marketing Support Fund of the Forum Secretariat. A manual on the cultivation and production of straw mushroom was prepared for this occasion. Restaurant owners on Kosrae approached me during my stay to inquire about mushroom culture. They showed a great deal of interest.
The pure cultures of the 3 mushroom species will be maintained as long as possible for future use. Funding for more research projects will be sought to try to take mushroom production to fruition eventually.
The best straw mushroom production we got using the banana bed method yielded 5.187 Kg mushrooms per square meter of bed. Not accounting for labor, this gives a small net profit ($8-10 per bed), enough for a hobbyist, but not enough for commercial production. For the latter, the method would have to be refined further.
Major obstacles encountered were:
1. Major storms damaging our facilities
2. Scarcity of suitable organic substrate
3. Working area for mushroom production
4. Temperature and humidity regulation on the mushroom beds.
In spite of doing what we possibly could to avert storm damage, like strapping our
40-ft containers down with steel cable and anchoring them to cement bases, we lost our 2 containers to storms. Later we observed that containers which were clustered side by side fared better during these extremely high winds. In the future we will try to relocate our containers into this configuration. After we lost our containers, which were being used for lab space and growth room space, we moved our operation to a field lab at the Agricultural Experiment Station in Yigo. There we had new problems, as those already using that lab were working in agricultural engineering and had no notion or respect for our need to maintain high standards of cleanliness in order to work with pure cultures.
Substrate availability has always been a problem on Guam because there is no industrial activity providing suitable waste organic matter (except the newspaper), nor any large-scale agricultural operations that may provide the same. Another notable exception is the small-scale manufacture of beer, which provides a certain amount of barley malt. In our trials, none of our fungi liked to grow on this substrate. Our conclusion was that it was perhaps too wet and needed to be amended with something to provide better aeration throughout the substrate. Perhaps in the near future something can be found, either corn straw or this beer waste product, both of which are available to some extent and time, and some solution might be found that would allow us to use this material.
Our research showed that some combinations of substrate are better than others for the production of edible mushrooms. Growth of Volvariella volvacea was best in media containing coffee grounds or coffee chaff (Table 1). We also determined that the paper was suitable as an additive to the substrate in which edible mushrooms could be grown without concern for possible heavy metal contamination from the ink. Both the paper and the mushrooms grown in it were analyzed for heavy metals. All limits were found to be below recommended standards (Table 2).
Oyster mushroom was found to yield best when grown in a combination substrate based on coffee grounds and filter paper. This treatment out-yielded another one in which chemical fertilizer was added; it also had higher biological efficiency (Table 3).
In the course of our investigations, we developed or improved existing methods for organic production of tropical edible or medicinal mushrooms of the 3 species, V. volvacea, P. ostreatus sajor-caju, and G. lucidum. These methods are applicable to a cottage industry for now. With more research in the future, they can be refined to commercial production.
An illustrated instruction manual on the production of straw mushroom was written in simple English language. It was used during the last workshop, held in Kosrae. The document is attached. It is intended for home growers in the Pacific. A similar publication is being prepared for each of the other 2 species, P. ostreatus and G. lucidum. Two additional publications were prepared, one on the general basics of growing mushrooms in the Tropics, and a second one on spawn preparation (see Literature).
Educational & Outreach Activities
Wall, G. C. 2005. Production of Straw mushrooms. AES, CNAS, University of Guam. 8 pp.
Wall, G. C., Barber, L. R., Nelson, D. A. & Imperio, E. N. 2000. Straw and oyster mushroom production. GCE, University of Guam. MR2000-1. 6 pp.
Wall, G. C., Barber, L. R. & Nelson, D. A. 2002. Mushroom spawn and pure culture production. GCE, University of Guam. 5 pp.
This project contained several tables. Please email Western SARE email@example.com to request an electronic copy of this report.