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A Report on recent work on mushrooms in Belgium 1995-1999
Peter Flegg
(B. Desrumaux, P. Sedeyn, A. Overstijns, H. Desmedt, A. Werbrouk and P.
Lannoy, Provinciaal Onderzoek - en Voorlichtingscentrum voor Land-en Tuinbouw,
Proefcentrum voor Champignonteelt, Province West Vlaanderen, 336 pages with
French and English summaries)
White button mushroom
Amounts of water applied from casing to ruffling.
Applying 10, 20, 30 and 40 litres of water per square metre to mushroom
beds from casing until the casing layer was ruffled (about 1 week) had no
significant effect on crop yields. Measurements of the water content of the
compost showed that the upper layer of the compost loses water and the bottom
layer becomes wetter. The higher levels of watering hardly affected the water
contents of the upper and middle layers of compost but the bottom layer became
increasingly wetter with the heavier waterings. It is concluded that much of
excess water applied drained through to the bottom layer. Even though the
bottom compost layer reached a water content of 80% yields of mushrooms were
not affected. Adding a water-absorbent polymer to the upper layer (5 cm) of
compost did not affect yield. The water content of the casing layer was hardly
affected by the amount of water applied.
Pesticide phytotoxicity
Three pesticides, diflubenzuron, teflubenzuron and a commercial nematode
preparation continaing S. feltiae, which are used to control sciarids,
were tested for their effects on mushroom cropping. Although the yield of
mushrooms following treatment with diflubenzuron was 1.07 kg/m2
lower than from the untreated beds (35.3kg/m2) none of the pesticide
treatments significantly reduced yields nor was the average weight per mushroom
affected. The conclusion is that all three pesticides can be used watered onto
the casing without any adverse effects on cropping.
Cac-ing materials
Over three experiments the use of sterile cac-ing spawn and fully spawn run
compost were compared for their effects on the mushroom crop. Neither crop
weight nor average mushroom weight were affected by the type of cac-ing
material used, but mycelial growth into the casing was slower and less dense
when cac-ing spawn was used. As a result, greater care in watering was needed
on the beds receiving that treatment. The use of fully spawn run compost
resulted in the first and second flushes starting two days earlier than with
cac-ing spawn, but the difference had disappeared by the start of the third
flush.
Spawn running temperature
Compost from the same source was kept in two separate tunnels during spawn
running. One was maintained between 25-27°C and the other between 30-32°C.
After spawn run was completed, half of each tunnel was suppplemented with a
standard material at 1kg/m2. Yields after three flushes from each of
a series of 4 experiments, showed no statistical differences although the
'high' temperature spawn run treatement resulted in a crop of 27.74 kg/m2,
5.4% lower thatn from the 'normal' spawn run termperature treatment. There was,
however, a noticeable crop loss from the high temperature treatment in two of
the experiments and in one experiment supplementation increased the crop loss.
As a result, it is considered advisable to avoid high temperatures (above
30°C) during spawn run.
Supplements
Four commercial supplements were compared over a series of 4 experiemtns
using the application rate of 1 kg/m2. None of the four supplements
Champfood, Champlus-For, Millichamp 3000 and Substradd Forte caused any
problems with over-heating and no significant differences between them in
resulting crop yields were found. They all yielded between about 4-5 kg/m2
more than the untreated control.
Supplement dose rate
A combination of four rates of filling spawn run compost and three
supplement dose rates was used in a series of 5 experiments. The crop yields
from filling compost at 85, 90 and 95 kg/m2 were significantly
different, a higher fill rate resulted in a better yield. Differences in yield
resulting from adding supplement at 1.4 and 1.8 kg/m2 were not
statistically significant between each other but both were significantly
greater than from the lower supplement dose rate of 1kg/m2. It is
pointed out that increasing both the fill rate and the supplement dose rate can
have a beneficial effect on crop yields but a supplement dose rate above 1.4
kg/m2 does not increase yield further. A warning of possible crop
loss when increasing supplement dose with poor quality compost is given.
Dry bubble resistance to Sporgon
Twenty-four samples of Verticillium fungicola collected by the
Belgian Mushroom Research Institute Consultancy Service were tested for
resistance to Sporgon. After five replications of the tests it is concluded
that a total resistance does not exist, but the sensitivity to Sporgon of the
isolates derived from the farm samples varied considerably.
Use of a bacterial formulation against sciarids
A formulation of Bacillus thuringiensis has been tested for its
efficacy against sciarids and compared with diflubenzuron. No adverse effects
on yields of mushrooms were found and mishapen mushrooms were not a problem.
Whereas the B. thuringiensis product reduced artificial infestation by
56% when applied at spawning and 66% when applied at casing, the diflubenzuron
product resulted in reductions of 89% and 98% respectively.
Phytotoxicity of Sporgon when used with cac-ing
In crops grown with the use of cac-ing and the ruffling technique, doses of
Sporgon at 1, 2, 3 and 4g/m2 reduced the four-flush yield of
mushrooms. The crop loss was greater with increasing dose rate and losses were
incurred over all four flushes. The main reason for loss of crop is given as
the high concentrations of Sporgon in the upper layer of the casing layer. Not
even the highest dose rate of Sporgon produced detectable residues in first
flush mushrooms.
Variation of mushroom colour with flush number
The effect of flush number on the colour of mushrooms was evaluated over 7
experiments. Only closed mushrooms free from casing material and bacterial
blotch were examined. A distinct difference in colour between mushrooms of the
first and second flushes and the third and fourth flushes was found. The later
flushes had a lower lightness and a higher yellow/blue colour, that is, they
were slightly darker. Little difference between the first and second flush
could be found.
Effects of calcium chloride solutions used for watering on crop quality
Several series of experients on various factors relating to watering the
beds with calcium chloride solutions have been carried out. An early series
showed no adverse effects on yield of watering with 0.1, 0.2, 0.3 and 0.4%
solutions and no benefits to crop quality either. Whether the hardness or
softness of the water affected the outcome was also tested. The degree of
hardness of the water had no major effects when no calcium chloride was
present, but the use of water of medium hardness resulted in slighter better
quality mushrooms (colour) after several days storage than did the use of hard
water. This effect, though, was noticeable only in the later flushes. The
possibility that degree of water hardness could affect the effect of calcuim
chloride was further tested by including soft water (rain water) irrigation in
some experiments, but it was concluded that the positive effects on crop
quality of irrigation with calcium chloride solutions must be due to other
factors than water type. Under Belgian/Dutch conditions the use of calcium
chloride seemed to have no value. Following a further lengthy series of tests,
it was concluded that the use of calcium chloride could have a positive effect
but mainly on mushrooms after a lengthy (6 days) period of storage. Small crop
losses and increased dry matter content of the mushrooms were thought to be
related to the increase in casing layer salinity caused by using calcium
chloride.
Minerals, microelements and supplements
Earlier tests showed that little or no further benefit in yield was gained
by increasing the supplement dose rate from 1.4 to 1.8 kg/m2. A
series of 5 trials was conducted to find out if adding a mixture of minerals
and microelements had any effect. A commercial product, Micromax, was used.
Although the addition of both supplements and the mineral mix separately
resulted in increased yields, there was no interaction. Adding the
mineral/microelement mix at a higher dose rate did not give a further
significant increase in yield and the effects on crop yield of the mix are
reported to be irregular. Adding the mineral mix did not improve the
performance of the higher level (1.8 kg/m2) of supplements. Further
trials with Micromax alone confirmed its beneficial effects on yield but the
results were irregular. The possibility that this relates to variations in the
composition of the poultry manure used to prepare the substrate has yet to be
confirmed. Chemical anlayses indicated that it may not always be true to think
that poultry manure always contains enough minerals and microelements to
guarantee maximum yields.
The oyster mushroom
Adding corn steep liquor to the substrate
Adding 0.5% corn steep liquor to the wet substrate confirmed the
results of previous tests, giving an increase in yield of 4.85 kg of mushrooms
per 100kg of pasteurised substrate. There were no differences between two
products, which were tested. The 27% yield increase is described as
economically important and consequent increases (1-2°C) in substrate
temperature resulting from adding the liquor are regarded as irrelevant.
However, a further series of tests comparing corn steep liquor and a dried
variant showed that only the dried variant gave a significant yield increase
thus contradicting previous results obtained with corn steep liquor. There was
also considerable variation in the results, more experiments showing no effects
than those which showed benefit. Given this inconsistency in the results the
report states that further experiments are needed, but points out that so far
no adverse results have been obtained.
Plastic bag perforations
In a series of 4 experiments the effects of the number of holes and
area of production surface were examined. In vertical plastic substrate bags,
perforations on both sides instead of only on one gave a higher yield per
weight of substrate which was statistically significant, but there was no
difference between having 168 holes instead of 84. It is concluded that the
distribution of holes is more important than their number. Testing the effects
of the hole diameter, numbers of holes and the total fruiting surface area
showed that yield was improved by increasing hole diameter and by an increase
in the number of holes when the fruiting area was kept the same.
First report of a disease
In 1999 the Belgian Mushroom Research Centre observed outbreaks of a
disease caused by Stemonitis herbatica. The disease is a myxomycete (a
slime mould) and affected substrate and fruit bodies. This is believed to be
the first report of such an infection. Spread of the disease in healthy crops
is thought improbable.
For copies of the full report or for further information please contact:-
Proefcentrum voor Champignonteelt
Iepersweg 87
B8800 Rumbeke,
Belgium
Phone: 00 32 51 261 430
Fax: 00 32 51 240 020
Email: bernard.desrumaux@west-vlaanderen.be
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