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

Session 28: It’s not Just Rot: Towards Holistic Evaluation of Wood Product Durability

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

Objectives

This study asks:

To what extent can creosote retentions be reduced by the

addition of chlorothalonil?

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

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

Sample Exposure & Evaluation

Matched samples placed in Dorman (AWPA Hazard Zone 4) & Saucier (AWPA Hazard Zone 5) test plots at depth of 230 mm

Rows 0.75 m apart

Saucier = loamy sand

Dorman = silty clay loam

Evaluated annually for decay and termite attack

Decay Rating Termites

Sound; suspicion of decay permitted

10 Sound; 1-2 small nibbles permitted

Trace decay to 3% of cross section

9 Slight feeding to 3% of cross section

Decay from 3-10% of cross section

8 Attack from 3-10% of cross section

Decay from 10-30% of cross section

7 Attack from 10-30% of cross section

Decay from 30-50% of cross section

6 Attack from 30-50% of cross section

Decay from 50-75% of cross section

4 Attack from 50-75% of cross section

Failure (>75% of cross section) 0 Failure (>75% of cross section)

AWPA (2003) visual grading scale for rating decay and termite attack

Data EvaluationApproach 1:Dose response curves

CTL after 6 years of exposure

•Approach 2: Depreciation curves

Curves were fitted

Time to score of 70 (t70) was calculated for comparison purposes

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

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

Test Plot Response

Impact of CTL addition

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

So, can we reduce creosote loadings and get equivalent or better performance by adding

CTL?

YES,

. . . . . but,

Will we?

Future research papers will report on

Different species including: Red oak (Quercus rubra)

Sweetgum (Liquidambar styraciflua)

Thank you----Any questions?????