This study evaluated the ability of chlorothalonil (CTL) to allow for reductions in creosote retentions for wood preservative treatments. Southern pine wood was treated with varying retentions of creosote alone and creosote combined with CTL. Samples were exposed to field tests and evaluated annually for decay and termite damage. The results showed that even at reduced creosote retentions below AWPA minimum levels, the addition of CTL improved performance. For retentions at or above AWPA minimum levels, significant improvements were only seen with the highest levels of added CTL. Therefore, the study concluded that CTL allows creosote retentions to be reduced while maintaining or improving durability performance against decay

1. Session 28: It’s not Just Rot: Towards Holistic Evaluation of Wood
Product Durability
Ground Contact Performance of
Creosote Amended with Chlorothalonil:
Can we Reduce Retentions?
H. M. Barnes, M. G. Sanders, G. B. Lindsey, and
T. L. Amburgey
Forest Products Laboratory

2. Background
 Creosote supply
 Reduction of impact (92-192 kg/m3)
 BMPs
 Chlorothalonil highly effective
 Ag crops, paints, mold & sapstain
 Broad spectrum, low mammalian toxicity
 Combined with insecticides,
antioxidants
 Removed from AWPA BoS,
2004, lack of use

3. Objectives
This study asks:
To what extent can creosote
retentions be reduced by the
addition of chlorothalonil?

4. Materials & Methods
Wood
 All sap southern pine
 19 x 19 x 1120 mm (r x t x l)
 Cut into matched halves
Preservatives
 P2 Creosote
 Chlorothalonil
 Both met AWPA 2003 specs

5. Sample Treatment
 Treated full cell at room
temperature
 91 kPa vacuum for 30 min
 Introduction of preservative
under vacuum
 Pressure increased to 1034
kPa in 5 minutes
 Held for 60 min
 Vent to atmospheric, drain,
remove samples, wipe & weigh
 102 mm retain cut from end

6. Sample Exposure
& Evaluation
 Matched samples placed in
Dorman (AWPA Hazard
Dorman = silty clay loam Zone 4) & Saucier (AWPA
Hazard Zone 5) test plots
at depth of 230 mm
 Rows 0.75 m apart
Saucier = loamy sand

7.  Evaluated annually for decay
and termite attack

8. AWPA (2003) visual grading scale for
rating decay and termite attack
Decay Rating Termites
Sound; suspicion of decay 10 Sound; 1-2 small nibbles
permitted permitted
Trace decay to 3% of cross 9 Slight feeding to 3% of cross
section section
Decay from 3-10% of cross 8 Attack from 3-10% of cross
section section
Decay from 10-30% of cross 7 Attack from 10-30% of cross
section section
Decay from 30-50% of cross 6 Attack from 30-50% of cross
section section
Decay from 50-75% of cross 4 Attack from 50-75% of cross
section section
Failure (>75% of cross section) 0 Failure (>75% of cross section)

9. Data Evaluation
 Approach 1:Dose response curves
CTL after 6 years of exposure

10. •Approach 2: Depreciation curves

11.  Curves were fitted
 Time to score of 70 (t70) was
calculated for comparison purposes

12. • Fitted curves constructed to give a
dose-response curve over time

13. Organism Response
 Decay was more severe than termite
attack in both test plots
 Decay was generally greater at the
Dorman site than Saucier
 Termite attack was generally greater at
the Saucier site compared to Dorman

14. Test Plot Response

15. Impact of CTL addition

16. What does the study show?
 At P2 retentions lower than the AWPA
minimum (<92 kg/m3), the addition of
CTL improves the performance even for
the lowest CTL addition rates
 For P2 retentions >92 kg/m3, significant
improvement is seen only for the
highest CTL addition rate

17. So, can we reduce creosote
loadings and get equivalent or
better performance by adding
CTL?
 YES,
. . . . . but,
Will we?

18. Future research papers will
report on
 Different species including:
 Red oak (Quercus rubra)
 Sweetgum (Liquidambar styraciflua)

19. Thank you----Any questions?????