Maximizing Log Based Shiitake Mushroom Production by Determining Optimal Fruiting Conditions

Maximizing Log Based Shiitake Mushroom Production by Determining Optimal Fruiting Conditions

Summary

Nicholas Laskovski, owner/founder of Dana Forest Farm and Bridgett Jamison, Graduate Student at UVM have collaborated to perform on farm research at Dana Forest Farm in Waitsfield, VT.

The research goal will seek to provide optimal fruiting times and conditions for the production of log-based shiitake mushroom cultivation.

In the first year (2011), our research tested several methods for determining mycelial colonization and moisture levels within inoculated shiitake logs (aka bolts). We performed preliminary trials on the effectiveness of using a hammer corer to estimate log moisture content (LMC) (measured as a percentage). The results revealed were that LMC was highly variable when using a hammer corer, both between different logs and also within the same log when measuring cores along the length of the log. We experimented with the use of an industrial strength moisture meter which measures LMC within wood samples at a depth of 5cm. In many trails LMC exceeded the capacity of the moisture meter and gave us a poor sampling data set. We lastly experimented with the cookie method to measure LMC. This is a method which relates LMC in the log to a slice or “cookie” of that same log. By understanding the fresh weight and dry weight of the “cookie” and fresh weight of the bolt, a ratio can be used to determine the dry weight of the bolt, ultimately allowing us to determine the LMC of the bolt. Using this information, we have redesigned our experiment and sampled our bolts twice with the cookie method, albeit more difficult and time consuming in determining LMC, but overall a larger data set was able to be acquired.

Ultimately, our goal is to determine conditions which will allow for increasing shiitake yields. By increasing yield, our research will allow current log based shiitake farmers to save time and money while increasing farm revenue. New or upcoming shiitake farmers could justify adding or increasing log-based shiitake cultivation to their current farm or forests, ultimately diversifying operations, creating a more sustainable economic future for farmers of the Northeast.

Objectives/Performance Targets

In the spring of 2011, I felled thirty sugar maple trees. Trees were cut into three-foot length generating 500 three-foot long logs with a diameter between 4 and 6 inches. The bolts were inoculated on either 4/17/11 or 5/1/11 following standard procedures. 100 logs were randomly selected for the experiment. Each log was labeled using a durable metal tag. Initial log weight, diameter, and length were recorded.
We accomplished our performance target in regard to bolt inoculation and selection with one exception. After reviewing other log based shiitake production experiments and the experimental objectives, we decided to include 100 logs, rather than 160 logs in the experiments. Treatments will remain identical however, the number of replications per treatment were reduced from 15 to 10. We decided this was appropriate given that the standard deviation between shiitake mushroom production per log is fairly low.

Our experiment was designed to track the rate of mycelium growth within log by monitoring the weight loss of the log over time. This requires having an estimate of the log’s moisture content during each sampling event. There are many ways of measuring moisture content in a log. The tradition method involves removing a round slice from the log (cookie) and measuring the moisture of the slice by weighing, drying, and reweighing. However, this process is fairly destructive and time consuming.

There are many other ways of measuring moisture that are less time consuming and destructive. One ways we had proposed in our experimental design involving using a unique type of hand drill called an increment corer. We planned on removing a 6-10 cm core from each log; we would then measure the percent moisture within the core by weighing, drying and reweighing the core. We would then use this value for percent moisture to estimate the percent moisture within the entire log. Another idea recommended to us was using a hammer corer to more rapidly remove a smaller core from the uppermost 3 cm. Lastly, we had the option of using a unique electronic moisture meter designed for measuring moisture of timber to a depth of 5 cm.
In the spring of 2011, we tested the three techniques mentioned above against each other. The results of our trials are provided in Figure 1. Our trials showed that log moisture was too variable to be assessed used either an electronic probe or through small subsamples (cores). As a confirmation, we conducted another trial comparing the measure of percent moisture using a hammer corer against the standard cookie method. See figure 2. Although, there is a definitive relationship, we realized that the variability was too large to make the hammer corer a viable alternative to the cookie method. After seeing results of this trial, we agreed to use the traditional cookie method to measure log moisture.

Our next question was (1) how large a cookie would be needed and (2) from how deep within the log will we need to cut to get accurate consistent results. To answer these questions, we conducted another trial. This time we cut two cookies from one side of log (each approximately 4 cm thick) and measured the moisture in each of the cookie. The results indicated that there was no difference in the moisture content between a cookie taken on the inside and outside of a log. Therefore, we decided to collect cookies from the outside each bolt during each sampling event. This reduces the overall destructiveness of our sampling.

Our experimental design specified that we would measure mycelium colonization every six weeks after inoculation. During each sampling event, we would measure the density, weight, moisture, and pH of the each log.

We accomplished this performance objective. On September 25th, 2011 weights of the logs were measured using a portable digital scale. Percent moisture was estimated by measuring the percent weight loss from a 4 centimeter wide cookie after 24 oven drying. This revised methodology was adopted following the trials described in Subsection Two: Use of an Increment Borer to Determine Log Moisture Content.

Density was determined as the weight of the oven dry core divided by the volume. Percent change in log dry weight was determined for each log as a estimate of mycelium colonization.

• Scatterplot matrix of the correlation between measures of percent moisture within a bolt obtained using three different mythologies: The electronic probe was a ____ probe. The estimates of moisture for increment corer and hammer corer were obtained by dividing the difference between the fresh weight and dry weight of the cores by the dry weight. The results indicate that there is not relationship between the measures of percent moisture within a bolt obtained using these three techniques; therefore neither method would be able to assess the true moisture of the log.
• Correlation between the measures of percent moisture obtain by drying and reweighing a sub-sample of the log and a large cookie of the log. The results indicate a clear relationship but too much variability between the measures.

Accomplishments/Milestones

• Accomplishments:
  – Felled 100 Sugar Maple Bolts in Preparation for shiitake spawn inoculation
  — Dates 2/27/11, 3/5/11, 4/911
  – Inoculated 100 Sugar Maple Bolts to initiate experiment
  — Dates 4/17/11, 5/1/11
  – First Sampling Date
  –Dates 5/8/11
  – Second Sampling Date
  — Dates 6/12/11, 6/19/11
  Re-Sampling Date
  — Dates 9/25/11

  Milestones:
  – Future Sampling
  — Dates 5/19/12 (Suggesting before first initialized shocking)
  – Shocking/Shiitake Cultivation
  –Dates Initialized after first sampling
  – Develop Air Temp/Water Temp matrix which will help us determine the ‘optimal’ delta variations when force fruiting shiitake.

Impacts and Contributions/Outcomes

This first year produced some interesting results. Most notably, we discovered a relationship between the prevalence of the fungus Trichoderma (Trichoderma longibrachiatum) on the rate of shiitake mycelium colonization (Figure 1). Logs infected with some degree of Trichoderma lost significantly less weight over the five month long spawn run (on a dry weight basis) indicating significantly less respiration by shiitake mycelium. Many growers this year expressed concern that their own logs had been colonized trichoderma however expectations in the field did not know how this fungus affected shiitake mycelium. Our results show definitely that trichoderma does negatively affect shiitake.

In addition, our mini trials of different methods of measuring log moisture were informative. We were able to show that the moisture of shiitake logs exceeds the capacity of moisture meters available on the market today. We also showed that other methods of collecting small sub-samples (using either a hammer corer or increment corer). Lastly our results confirmed that log moisture content increases the rate of mycelium colonization (Figure 2) and the smaller logs are colonized faster than larger logs (Figure 3).

• Impact of Trichoderma (Trichoderma longibrachiatum) on mycelium growth, five months after bolt inoculation. The prevalence of trichoderma on the ends of the bolts was compared to the percent weight loss experience by bolts after five months (on a dry-weight basis) using a Tukey-Kramer analysis. At the 0.05 significance level, the weight loss from loss without trichoderma was significantly greater than the weight loss from logs with trichoderma. Error bars are constructed using one standard deviation from the mean.
• Correlation between bolt diameters and the percent weight loss from bolts after five months of spawn run length. The bivariate normal ellipse (P=0.90) is indicated in green highlighting 90% of the data. This figure shows a clear negative relationship between (p<0.001) the diameter and the log and the rate of mycelium colonization.
• Correlation between bolt moisture content and the percent weight loss from bolts after five months of spawn run length. The bivariate normal ellipse (P=0.90) is indicated in green highlighting 90% of the data. This figure shows a clear positive relationship between (p<0.001) the moisture content of the log and the log and the rate of mycelium colonization.

Collaborators: