Researchers in Penn State's College of Agricultural Sciences have received a three-year, $950,000 grant from the U.S. Department of Agriculture, National Institute of Food and Agriculture, to develop a suite of organic management options for three of the most challenging mushroom pests.
"Organic mushroom production is particularly susceptible to attack by fungal and bacterial diseases and by fly infestations," said David Beyer, professor of plant pathology and principle investigator on the grant.
"These pests cause reductions in yield, quality and shelf life of the crop and seriously affect the economic viability of organic mushroom production," he said. "Our goal is to develop tools and strategies for adoption by organic growers that address these issues and increase profitability."
According to Beyer, mushroom growers in the United States produced more than 90 million pounds of certified organic mushrooms in 2016, a nearly 50 percent increase over the previous year.
"This rapid growth in demand for organic mushrooms suggests that effective organic-approved production methods will be increasingly sought after," he said.
However, Beyer added, impeding progress in organic mushroom farming is the lack of effective integrated pest management, or IPM, practices against the most important pests of mushrooms — Lecanicillium and Trichoderma fungal diseases, phorid and sciarid flies, and bacterial blotch disease.
Beyer and his colleagues — which include Maria Gorgo-Gourovitch, a Penn State Extension educator in Chester and Berks Counties — will conduct on-farm trials and research into management options for these pests and pathogens with a goal of developing innovative crop production strategies.
Specifically, the team will investigate the role of anaerobic — low oxygen — compost on the growth of the fungus Trichoderma aggresivum.
"Our previous research has found that organic acids are formed under anaerobic conditions and that they stimulate the growth of T. aggressivum," Beyer said. "We will investigate the concentration and timing of T. aggressivum spore infestation and the influence of anaerobic compost conditions on severity and disease development of the fungus. We also will evaluate compost characteristics, such as structure, moisture and nutrition, and their influence on T. aggressivum development.”
The researchers will test the effectiveness of essential oils, along with a naturally occurring bacterium (Streptomyces griseoviridis), in managing T. aggressivum and other fungi.
In addition to fungi, mushrooms are susceptible to two dipteran fly species — the sciarid fungus gnat (Lycoriella mali) and the mushroom phorid (Megaselia halterata).
"Sciarid and mushroom phorid fly larvae not only cause direct damage to the mushroom crop, causing reductions in yield, but also act as vectors of mushroom pathogens, including T. aggressivum and Lecanicillium fungicola, spreading disease throughout the mushroom house," said Beyer. "Mushroom flies are attracted to fungal pathogens, often selecting these areas for egg laying. Furthermore, L. fungicola have sticky spores that attach to adult flies, enabling their spread to uninfected mushrooms."
The researchers will address the lack of effective organic-approved pesticides to deter flies by screening a range of pesticide and biological-control products that are registered for use in other organic crops. Products demonstrating efficacy in the laboratory will be evaluated for efficacy under field conditions.
Finally, the team will investigate control mechanisms for bacterial blotch disease.
"Organic growers frequently cite bacterial blotch of mushrooms as one of the most economically important production problems they face," Beyer said. "This bacterial disease results in a rapid browning or blotching deterioration of healthy mushroom caps."
The researchers will manipulate the microbiome, or collection of interacting microbes, within the mushroom cap with a goal of introducing bacteriophages — viruses of bacteria — that specifically suppress blotch pathogens.
In addition to conducting research, the team is planning several outreach initiatives. For example, the scientists will develop bilingual educational materials and short IPM videos for organic mushroom producers and employees for management of mushroom flies and diseases. They also will create a course-based undergraduate research experience curriculum around organic agriculture for undergraduate students.
Currently, organic standards do not require the raw materials — such as wheat straw and grass hay — that are used for compost to be certified organic. However, there is pressure from the regulatory agencies to require that the raw materials used in compost be grown organically.
"If the raw materials are required to be certified organic, current organic straw and hay production will not be able to meet the needs of the mushroom industry," Beyer said.
The researchers plan to test conventionally produced wheat straw and grass hay to determine if any herbicides or fungicides used in the production of these materials persist in the compost and are subsequently taken up by the mushrooms.
"Our project outcomes will provide organic growers with tools, techniques and strategies to increase production yield and quality and to increase profitability by reducing input and administration costs," Beyer said. "Part of our project also will include evaluating the overall economic benefits, including reduced input and administration costs, of our findings."
In addition, the team will develop an application for mobile devices such as smart phones to assist growers with the certification of crops and tracking of organic mushrooms from harvest to shipping.
"Ultimately, our goal is to help organic mushroom growers obtain increased yields, efficiency, productivity and economic returns," Beyer said.
The idea for the team's proposal came from a strategic planning meeting at which industry leaders and Penn State researchers from many disciplines discussed the needs of the industry and what they could do to answer those needs. More information can be found on the Department of Plant Pathology and Environmental Microbiology website.
Researchers receive $950,000 to develop pest controls for organic mushrooms