Blending Landscape Mulch with Mushroom Compost

A Green Solution to the Artillery Fungus Problem

By Don Davis, Mike Fidanza & Lynda Farrell

   With the increase of both commercial and residential development, beautifully maintained mulch beds are increasingly in demand. Concurrently, the popularity of landscape mulch is rapidly growing and has been an economic boon to the landscape mulch industry. However, the increasing use of landscape mulch has also been associated with an increased incidence of a relatively new plague – the explosive artillery fungus.

THE PROBLEM
   The public has become aware that artillery fungi are the cause of sticky tar-like spots that tenaciously and permanently affix themselves to the sides of buildings, houses, and automobiles. Homeowners whose homes have been bombarded by artillery fungi, and who have contacted their insurance agent, have discovered “artillery fungus” is considered an exclusion (like mold, mildew, and dry rot) by their insurance agent, or in the actual wording of their homeowners’ insurance policy. Their claim denied homeowners at times file costly lawsuits against landscape professionals to obtain compensation. Their reasoning is that, since artillery fungi live in landscape mulch, the landscape professionals must somehow be responsible! Utilizing a decade of research data and expertise as Professor of Plant Pathology at Penn State, Dr. Don Davis has successfully testified on behalf of landscape professionals who have been sued by property owners whose homes have been damagec by artillery fungi living in their landscape mulch.

THE FUNGUS
   Artillery fungi have two entirely different life styles, having developed a very successful “dual ecology” survival strategy. They can survive as white-rotting, wood-decay fungi on dead trees, branches, wood, and bark, and/or they can live on droppings of herbivores such as rabbits and deer. This is important, as it affects how the artillery fungi arrive at a landscaping site, and relates to who is, or is not, responsible for the artillery fungus problem.
   Artillery fungi may already be present at a new job site, due to existing dead trees or old mulch. In such cases, the fungus is acting as a wood decay organism. Rabbit and deer droppings will also cause this fungus to develop. In either case, the existing artillery fungus can immediately infest new, clean applications of landscape mulch.
   In addition, artillery fungus spores may be transported for short distances by the wind or by people from nearby infestations, or even on new plantings that may have spores stuck to their leaves from an infested nursery. Also, sawmill wastes, old wooden pallets, land-clearing material, and other pieces of waste wood are often colonized by artillery fungi as they are lying around. If these infected pieces of wood are shredded and used as landscape mulch, the resultant mulch is infested.
   So, artillery fungus may already be in the mulch when the applicator receives it. All this leads to who (or what) is responsible for a current artillery fungus infestation at a commercial or residential property? As Dr. Davis has testified, it is usually impossible to pin-point the original source of the fungus, even if the history of the mulch is known!

MUSHROOM COMPOST
   Mushroom compost is the leftover growing material (substrate) on which mushrooms, such as the common white button mushroom, are grown throughout the year in Pennsylvania. Since each mushroom crop requires new substrate, the mushroom house is cleaned out after the final harvest of each mushroom crop. Over 700,000 cubic yards of used mushroom compost are produced each year in Pennsylvania alone. Spent compost is not used again to grow mushrooms and must be disposed of. The used compost is pasteurized (by steaming), removing most potential pathogens and weed seeds. If used immediately this clean compost is considered “fresh”; if allowed to weather, or age, it is considered “aged” mushroom compost. One must be aware that aged compost, if stored improperly, may contain weed seeds. Fresh compost, on the other hand, contains few, if any, weed seeds.

PENN STATE RESEARCH
   Penn State researchers wondered if this unwanted byproduct of mushroom production might prove to be an environmentally friendly solution to combating artillery fungi in both residential and commercial applications. Early research at Penn State revealed that aged (1-2 years old) mushroom compost, when blended at 40% or greater ratio (by volume) into landscape mulch, was effective in suppressing artillery fungus sporulation. They also found that mushroom compost appeared to suppress other undesirable fungi, while providing some plant nutrients (1:1:1, N:P:K), increasing moisture holding capacity, and adding organic material to the soil as the compost breaks down.
   The researchers concluded that mushroom compost might be a potentially valuable, “environmentally friendly” and “green” mulch amendment. Since early research had shown that blending aged mushroom compost into landscape mulch resulted in a significant suppression of artillery fungi, the team pondered if fresh mushroom compost in the blends would work as well. It takes time and money to age mushroom compost, so it seemed logical to evaluate the ability of fresh mushroom compost (right out of the mushroom house) to fight artillery fungi, thereby producing an economically viable, green alternative for mushroom growers, landscapers, and homeowners in the fight against artillery fungi.
   To study this, research plots were established at the Penn State Berks Campus (Reading, PA) using fresh mushroom compost. The most recent data (collected November 2007 and May 2008) are preliminary, but are very promising. The data continues to show that landscape mulch blended with ≥40% fresh mushroom compost is also effective, as was previously shown with aged compost, in suppressing artillery fungi. The authors of this article are currently conducting a project geared to bring together landscape personnel, mulch producers/applicators, and mushroom industry partners to participate in needs assessment and marketing research for a blended compost/mulch product. The goal is to create a plan to facilitate the use of fresh mushroom compost blended into landscape mulch at a 40% ratio, and to identify and address perceived obstacles to use of the blended product.

ON-SITE BLENDING PROJECT
   Needs assessment data indicates that mulch producers perceive unknown factors that concern them regarding mushroom compost. To identify the factors, and to alleviate concerns, the authors of this article produced a “Mushroom compost & artillery fungus fact sheet” that can be found on the web at www.mushroomcompost.org.   Since the ability to view a commercial site was a common denominator among concerns, partners sought to complete an on-site blending prototype in 2008, using the recommended ratio of 40% mushroom compost blended into common landscape mulch. Laurel Valley Soils, Georgi Mushrooms, and Hy-Tech Mushroom Compost offered to partner by donating and delivering fresh mushroom compost for the project. Pretty Dirty Ladies, Inc owner Gloria Day, who has “worked under an organic philosophy from day one”, had a customer site in West Chester, PA, that had been bombarded by the artillery fungus. Gloria was anxious to try the compost:mulch blend in what she termed, “a trend-setting application”. Gordon Eadie Associates Landscape and Design offered to partner in the project by supplying a blending pad, landscape mulch, and by physically mixing the blend.
   Finally, in June of this year, the product of months of research and partnering was realized. Laurel Valley Soils donated and delivered fresh mushroom compost to a blending pad at Gordon Eadie Associates. The mushroom compost was blended into landscape mulch at a ratio of 40% mushroom compost to 60% landscape mulch. Our first commercial on-site blending of mushroom compost and landscape mulch had been completed.
   The compost/mulch blend was then transported and applied at a residential site in West Chester, PA which was previously contaminated by artilarry fungus. Gordon Eadie Associates, Pretty Dirty Ladies, Inc., the mushroom compost suppliers of Southeastern Pennsylvania and the authors of this article will continue to monitor this first on-site application of mushroom compost and landscape.

SUMMARY
   Having completed our first commercial blending of mushroom compost with landscape mulch, our research team facilitated what many landscape professional have been looking for: a successful mushroom compost/mulch blend that can be applied in a commercial or residental setting. We also identified and supplied answers to hesitations about blending mushroom compost into landscape mulch.
   In this green market of environmental and cost-conscious consumers, blending fresh mushroom compost with landscape mulch offers many valuable benefits. This economic and green solution to pesky artillery fungi simultaneously adds plant nutrients to landscaped beds, reducing the need to fertilize, and increases the health of the soil and landscape plants.

For additional information on artillery fungi, visit Dr. Davis’ Web page at http://www.personal.psu.edu/faculty/d/d/ddd2