The recent shortage of straw and hay in parts of North America and Europe has sparked a flurry of questions regarding what can be used as a substitute for compost ingredients. We thought a quick review of materials listed by Dr. Lee Schisler at the North America Mushroom Conference in the 80s and other materials that may be available around North America and elsewhere would be of some interest. There may be materials that we are not discussing that could be used as compost ingredients, but most likely in areas where better materials are not readily available.

Bulk Ingredients
Straw, whether it be straight wheat straw or bedded horse-manure straw, is the most common bulk ingredient used around the world. Other varieties like barley and rye can be used, although composting practices will need to be modified for these types of straw. The nitrogen, cellulose, hemicellulose, and lignin content of these straws may vary based on the variety, but differences are probably more related to where and how it is grown. Rice straw, although used in SE Asia, is generally not a desirable material as it is physically short, tough, and hard to break down. Oat straw is also a poor material; as it composts, it quickly becomes flat and soft, contributing to anaerobic conditions. Sorghum and sugar cane fodder can be used, but the stalks should be physically crushed before starting the composting process.

Corn fodder is starting to be used; our research has suggested 25% might be the most one could add to a straw-hay formula without negatively influencing yields. Its structure may also limit its use in systems that do not physically chop the fodder. In Pennsylvania and parts of Canada, mulch hay is a common bulk ingredient, timothy and orchard grasses being the most common varieties. Alfalfa can be used, but it is higher in N and physically can be more challenging to compost. Generally, in hay-based formulas, other bulk ingredients are used to provide additional carbohydrates to the formula. These bulk ingredients include corn cobs (ground or pelletized), cottonseed hulls (as is or pelletized). Less common are items such as hardwood bark or chips; deciduous leaves are used seasonally at one progressive farm, but the collection and storage of this material are challenging. Potato peel and slicer waste has been reported to be an option, but it is probably not commonly used because of problems associated with handling and storage of these high-moisture materials.

Other bulk ingredients that have been tried include peanut and rice hulls, but they are very high in lignin and hard to break down in the short composting times found at most commercial farms. Softwood barks have compounds (phenolic?) toxic to Phase 2 microbes and mushroom mycelium. Kenaf core, a by-product of the fiber collection process, and recycled paper wastes are possible ingredients, but at low amounts, say no more than 5-10% of the total volume. Additional research should be conducted, as paper waste is much different today than when this work was first reported in the 1970s. At this time, we consider spent mushroom compost as a filler material with no useable nutrients or used as an avenue to dispose of small quantities; however, research is being done to determine if larger quantities can be used as a bulk ingredient or as a supplement. Mushroom stumps are often disposed of in compost, but add little to the value of the compost.

Supplements
The “inorganic” sources of nitrogen, those with no carbohydrates, are historically used in synthetic formulas only and at no more than 25 lbs. per dry ton of other ingredients. The most common and only one still readily available is urea, often used with straight wheat straw formulas as a starter ingredient to “soften” the straw early in the pre-conditioning process. Calcium Cyanamid has been reported to be a substitute but must be pH adjusted and is not a commonly available ingredient, and hence not widely used. These inorganic supplements need to be added early in the composting process and are not readily available to the Phase II microbes.

More “organic” supplements, ones with carbohydrates readily available, are valuable but more expensive and therefore generally used later in the composting process to ensure there is a balanced formula. These ingredients include more common materials such as brewer’s and or distiller’s grain, cocoa bean hulls (contain an oil that microbes like), cottonseed meal, bedded poultry manure, ground soybean, rapeseed screenings, and sugar cane bagasse. Poultry manure for broilers is most common, but layer poultry manure, dried and processed, may also be used. The nitrogen content of poultry manure may vary depending on the source, number of flocks bedded on it, and other factors, so it is suggested to analyze the N content on a regular basis. Liquid poultry manure is used in some tunnel facilities that are designed to handle it. Rapeseed oil meal (expeller or solvent) or screenings are more likely to be available in the northern states and in Canada.

Other not so common supplements would be brewers dried yeast, buckwheat millings, castor bean meal, corn gluten feed (include bran), corn gluten meal, feather meal, fish solubles, linseed oil meal (Flax seed), malt sprouts, peanut oil meal, safflower oil meal (expeller or solvent), sesame oil meal (expeller or solvent), single cell protein, soybean screenings, soybean oil meal (expeller or solvent), cocoa hulls, sugar beet pulp (source of carbon), sunflower oil meal (expeller or solvent), wheat bran, wheat germ meal, and wheat mill run. Feather meal is high in N, so it is important to have a good distribution in the mixing. Fish solubles are high in moisture and difficult to handle.

Other feedlot manures can be used if generously bedded on straw with an effective pre-conditioning period, although I know of a small hobbyist grower who was composting straight cow manure (no straw) and successfully growing mushrooms. Blood meal has nitrogen, but in a form that has very little available to the microbes in Phase II. Apple pumice and paunch are too acidic and easily go anaerobic; therefore, they would not be adding desirable characteristics to the formula.

As you can see, there is a wide variety of raw materials available, and it is up to each of you to decide what works. What works in one part of the world, or at one farm, might not necessarily work in a different system. Material availability and economics will also play an important role in deciding what raw materials work for you.

LaFrance virus disease

Of all the diseases confronting mushroom growers, none have been the subject of more confusion than viral diseases. Viral diseases can be confused with the effect of poor cultural practices or the bacterial disease mummy. Since no known commercial mushroom strain is resistant to viruses, growers must incorporate preventive measures into the IPM plan and rigorously carry out control measures.

The virus lives in mushroom spores and mycelium (spawn). Infected spores spread the disease to other new crops. Infected mycelium (spawn) may survive in the bed boards or quickly spread in bulk phase III facilities. Spores survive many years and can be released during farm renovations.

Symptoms (Figure 1-4):

• Portabellas don’t size up; lower yield, Fig 1.
• Bare areas with few pins and mushrooms, Fig 2.
• Premature opening of the veil (small caps)
• Mild yield loss

Severe infection:

• “Drumstick” (small caps, long stems) Fig 3.
• Weak growth in the casing that often disappears over time
• Die-back of mycelium in the compost, Fig 4.
• Stems discolor quickly when cut
• Significant yield loss

Control:

• Exclude, eradicate, or reduce inoculum.
• Mushroom spores at spawning
• Mushrooms should be harvested before they mature and the caps open, releasing spores.
• Infected mycelium at spawning or casing
• Isolate the crop.
• Regularly scheduled replacement of filters/filtration
• Air movement—high positive pressure in spawning and casing areas
• Practice postharvest steaming to eliminate pathogens and mushroom mycelium/spores between crops.
• Virus-infected mycelium in the wooden tray/bed boards
• Virus-infected mushrooms and spores left on the bed

figure 1

figure 2

figure 3

figure 4

Bacterial diseases

1)  Bacterial Blotch

Signs and Symptoms:

• Superficial discoloration which leads to lower quality in the marketplace
• First pale yellow, then darkens to golden yellow to brown color.
• Bacterial pathogen: Pseudomonas tolaasii, recently other species have been found to cause similar symptoms

2)  Mummy Disease

Signs and Symptoms:

• Stunted growth, swollen base
• Sometimes mushrooms develop curved stipe with translucent, longitudinal streaks on the side
• Tissue appearance: spongy, dry and leathery
• First break can be harvested; second break mushroom does not grow in the affected area
• Scientific name: Pseudomonas species

By David M. Beyer, Penn State University

We are observing that the amount of mycelium in the casing soil often leaves much to be desired. Ideally, thick mycelium strands should grow from the bottom to the top of the casing soil, while leaving enough casing soil not yet overgrown with mycelium. This remaining casing soil serves as a water buffer for the compost and mushrooms.

It's crucial to remember that this water buffer also determines how long and how much you can evaporate in the growing room before the casing soil dries out. If the casing soil dries out, you will need to water, even if it's not ideal for the mushroom quality. Therefore, it is important to pay close attention to the mycelium growth in the casing soil.

If there is structurally too much mycelium in the casing soil, a few adjustments can improve the situation. One option is to start ventilating earlier, although this means the mycelium may not reach the surface as much as usual. You can also adjust the watering schedule.

Once the mycelium starts growing from the top layer of compost and the casing material, it is essential to keep the casing soil well-moisturized. Each watering essentially stops the mycelium; weak mycelium struggles with this and can barely continue developing, whereas strong mycelium has fewer issues and continues to grow. In this way, you encourage more strong mycelium and reduce the amount of mycelium in the casing soil.

Our mushroom strains tend to form pins quite spontaneously, so many growers are ventilating extremely slowly. While this isn't necessarily a problem, it's important to realize that as long as the compost temperature is above 23°C, the mycelium will keep growing in the casing soil. Therefore, you should start ventilating earlier or increase circulation to bring the compost temperature below 23°C quickly. Once the compost temperature reaches 23°C, you can reduce circulation and control the number of pins by adjusting the air temperature.

I believe that with this method, you can control the amount of mycelium to some extent without leading to too many pins or a lack of distribution in the first flush. You might also consider using slightly heavier casing soil.

Slightly drier casing soil offers more certainty in terms of mycelium growth. Also, pay attention to covering. Avoid running the pinning axis and leveler too quickly to prevent structural damage. The mixing of the casing should be adequate, but more speed is unnecessary for the pinning axis.

Written by: Jeroen van Lier | Total Mushroom Service

One of the most effective ways to avoid diseases in the mushroom industry is a cook-out at the end (or beginning) of each cycle.

To reduce the chance that some spores of diseases or insects will survive in the growing rooms after the last day of harvest, it is vital to thoroughly cook out the growing rooms. To ensure that all diseases and pests are killed, it is necessary to heat the entire growing area to 70 ° C for 8 to 12 hours using steam. The entire growing area means that the compost also reaches this temperature for 8-12 hours. Why do I say 8 to 12 hours? In highly effective farms the whole room will be on the same temperature (compost, floors, corners) and 8 hours will be enough, in other farms where you are less effective, meaning the entire room will not be at the same temperature, it would be better to extend the cook-out time to 12 hours.

Often, for reasons of cost or time savings, it is decided to shorten the time or keep the temperature lower, which has the risk that virus can survive. However, to be on the safe side, 70 °C for 8-12 hours is the benchmark, especially if there are diseases or pests on your farm. Some farms decide to cook-out on lower temperatures, especially phase 3 compost farms, to just eliminate the spores for bubbles and cobweb and those are eliminated on lower temperatures. With the high energy prices, a very understandable approach. If there is no virus or Trichoderma on the farm it is probably enough to cook-out on only 60 °C.

After the cook-out, the new growing cycle begins, so it is important that from this moment on no traces of mushrooms, germs or insects end up in the growing area. This is often neglected during emptying, which means that the usefulness of the (expensive!!!) cook-out has been for nothing.
Be aware of that, you invest a lot in cook-out.

Some farms in several countries have not the possibility to cook-out because they have no boiler present on the farm. That means your hygiene has to be excellent, but some farms manage that well. I know farms where they have no boiler and keep the infection very well under control. On the other hand, there are farms that don’t trust their first cook-out and decide to cook the rooms out after emptying and cleaning again before they fill the new compost. Empty rooms are easier and more efficient to cook out.

Of course, you need time in your cycle as well to cook-out. Including the warmup and cooldown period you will need around 24 hours to finish a full cycle. Warming up and especially cooling down needs to be done with a slope up and down in temperature to avoid negative affects to your building.

There are different cooking methods used worldwide. Choose what works best for your farm. If you're building a new farm, consider adding a boiler. Regular cookouts can help prevent problems and keep infections low. This is an effective way to maintain cleanliness and bio security on your farm.

Erik de Groot
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