Mold on Wood: Mold, Mildew and Decay

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Mold on Wood Mold, Mildew and Decay
Carol Clausen June 7-8, 2007

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Outline

• Introduction/Problem
• Differentiating fungi
• Phytosanitation issues
• Fungal inhibition strategies
• Designing mold inhibitors
• Summary

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Fungal growth requirements

• Water (gt20 MC)
• Food source
• 10-35oC (50-95oF)

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Differentiating fungi on wood

• Mold
• Brown-rot
• White-rot
• Soft-rot

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Brown-rot decay

• Extensively removes cellulose
• Preferentially attacks soft woods
• Dark brown crumbly, cubical cracks across grain,
  shrinks

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White-rot decay

• Selectively removes cellulose and lignin
• Preferentially attack hard woods
• Bleached appearance, retains outward dimensions

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Mold

• No significant damage to wood/Surface only
• Requires free water
• Easy to remove, equally easy to return

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Problem

• Aesthetics
• Strength loss
• Short service life

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Phytosanitation issues

• Invasive species
• Trade disruptions
• Market loss
• High risk pathways
• Logs
• Green lumber
• Wood packaging

• ISPM-15 Standard
• 56oC, 30 min
• Fumigation
• Alternative treatments
• Ozone
• Chemical impregnation
• Borates
• Oxine copper

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Fungal inhibition strategies

• Keep it dry!!!!!
• Low cost treatments
• Ease of use and handling
• Advantages
• Prevent re-infestation
• Increase service life
• Disadvantages
• Cost
• Toxicity

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Designing fungal inhibitors

• Multi-component synergistic approach vs. fumigant
• Low solubility
• Odorless
• Nonvolatile
• Low mammalian toxicity
• Easy to handle
• Environmentally friendly
• Low cost

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Potential compounds
Wood preservatives
Food preservatives
Pharmaceuticals
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Potential compounds
Wood preservatives
Food preservatives
Pharmaceuticals
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Potential compounds
Wood preservatives
Food preservatives
Pharmaceuticals
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Screening method

• ASTM D4445-91
• Test fungi
• Aspergillus niger
• Penicillium
• chrysogenum
• Trichoderma viride
• Inoculum 3 x 107 spores
• 05 rating system

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Food Preservatives

• Food preservatives
• Sodium benzoate
• Sodium acetate
• Calcium propionate
• Potassium sorbate
• Sodium formate
• Sodium nitrite

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Results
Food preservatives
Sodium acetate
MFC K sorbate 4.0 Na benzoate 5.0
Aspergillus
Penicillium
Trichoderma
Pros Low toxicity, odorless, nonvolatile Cons Hi
gh solubility, short-term protection
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Wood Preservatives

• Existing Experimental
• IPBC (control)
• Cu
• DOT
• CuBor
• BOR A
• NHA

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Results
Wood preservatives
MFC Cu 5.0 Bor-A-Plus 7.6 IPBC 0.1
Aspergillus
Penicillium
Trichoderma
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Pros Borate is insecticidal and a fire
retardant Cons Metals may be restricted
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Azoles

• Thiabendazole
• Triazole
• Sodium triazole
• Voriconazole
• Itraconazole
• Clotrimazole
• Difluconazole

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Results
Azoles

• MFC
• Thiabendazole 0.02
• Voriconazole 0.04

Pros Specific fungal toxicity, low solubility,
efficacious at low concentration Cons ???
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Plant Extractives

• Thujaplicin
• Pine resin
• Soybean ester
• Essential oils
• Ajowan
• Dill weed
• Geranium
• Lemongrass
• Thyme
• Tea Tree
• Rosemary

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Results
Plant extracts
MFC Thujaplicin 0.78
Thujaplicin
Aspergillus
Pros Low solubility, pleasant odor,
medicinal Cons Availability, cost?
100 soybean ester
Trichoderma
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Assessing MFC90

• Bracket a dilution series
• SAS statistical analysis
• At least 90 probability of a 0 rating(i.e.
  clean specimen)

Results Bor A 7.6 Thiabendazole 0.02 Voriconaz
ole 0.04 Thujaplicin 0.78
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Summary

• 12/28 compounds inhibited test fungi
• Azoles showed lowest MFC (0.02)
• Thujaplicin MFC0.78
• Boron-based compounds are advantageous for
  secondary characteristics
• Food preservatives were as effective as Cu and
  Bor-A
• Some compounds augmented mold growth

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Experimental Methods

• Vapor exposure
• Modified ASTM 4445
• Constant vapor source
• 24-hr exposure
• 5 replicates
• 3 test fungi
• 20-wk incubation
• MFC

• Dip treatment
• ASTM 4445
• 15-second dip
• 5 replicates
• 3 individual test fungi
• Aspergillus
• Trichoderma
• Penicillium
• 20 wk incubation
• Retention

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Dip treatment results

• Average retention 0.04g/cm3
• Time to failure (wks)

Ajowan 4 Dill weed 10 Geranium
gt20 Lemongrass 4 Rosemary 4 Tea Tree
6 Thyme gt20
Egyptian geranium
Thyme
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Vapor Exposure

• 24-hr exposure
• 0.6 mg/cm3

No long term effect
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Vapor Exposure Results

• Constant exposure
• Time to failure (wks)

Ajowan 4 Dill weed gt20 Geranium
10 Lemongrass 10 Rosemary 12 Tea Tree
4 Thyme 6
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Essential oil conclusions

• Geranium and thyme oils were effective as dip
  treatments gt20 weeks
• Retention level 0.04 g/cm3
• Dill weed and rosemary oils were effective
  fumigants
• Application level 0.22 g/m3
• Cost 18/pound

• Volatilized dill weed oil acts as a fumigant

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Multicomponent system design

• BorA
• 5 boric acid
• 25 propionic acid
• 55 DMCA
• 15 propylene glycol

• Supplemental components
• 0.1 voriconazole
• 0.1 thiabendazole
• 0.5 thujaplicin

Bor A with one supplemental componentDurazol
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Objectives

• Evaluate multi-component biocide systems for
  long-term mold inhibition
• -on unseasoned southern pine, Douglas- fir and
  aspen
• -compare unseasoned and K-D southern pine
• Compare efficacy of different supplements in the
  multi-component system

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Retention
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Resistance relative to retention-thiabendazole
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Conclusions

• Durazol system supplemented with thiabendazole
  provided protection against mold fungi for 12
  weeks on aspen and Douglas-fir
• Treatments were least effective on pine despite
  4-fold increase in chemical retention
• Application method immersion
• Retention rate on unseasoned0.5-0.8 kg/m3
• Cost0.05/m3

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Effectiveness against decay fungi

• AWPA E10-01 soil block test
• Test fungi
• Gloeophyllum trabeum
• Postia placenta
• Coriolus versicolor
• Assess specimens for mass loss

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Decay results
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No choice termite test
Control 38 Durazol 4
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Field tests
Ground proximity test
Above-ground deck test
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Summary
Development of multicomponent biocides and
natural fumigants

• .strategies to provide long-term protection of
  wood-based materials from mold, decay and insect
  damage

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Thank you!

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