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Washboard effect: A surface deformation of spruce resulting from vacuum-pressure impregnation with water-borne preservatives
1987 - IRG/WP 3450
The washboard effect has been observed in sawn spruce after both commercial and laboratory based preservative treatments and is of increasing economic importance. The effect is defined as a specific phenomenon at the wood surface. It is distinct from internal collapse in the wood, but it may occur in association with internal collapse damage. Experimental investigations on the causes of washboarding and preliminary results indicate that a combination of several factors induce the effect. At treating pressures below about 10 bar washboarding appears to develop with post treatment drying of the wood whereas with higher pressures it will occur during the impregnation cycle. Further research has been started to develop measures to minimise the problem.
H Willeitner, R J Murphy

Step-wise pressure process for reducing surface roughness in Japanese cedar timber
2003 - IRG/WP 03-40256
Sixteen dried sawn-timber (10.5 x 10.5 x 360 cm) were cut into half. The half of them was treated by step-wise pressure process with 2.5 MPa maximum, and the other half was treated by conventional pressure process with 2.5 MPa maximum. Average DDAC preservative absorption was 461 kg/m3 in the former and 525 kg/m3 in the later. Surface roughness was expressed as the profile element height of collapse on the surface of treated timber. The maximum profile element height was 1.10 mm in the former and 3.10 mm in the later. The average value height ranged between 0.35 mm and 0.58 mm in the specimens by conventional process, and 0.19-0.24 mm in those by step-wise process. Step-wise pressure treatment reduced the surface roughness but also reduced preservative absorption.
K Yamamoto, M Nozoki

The potential of high pressure pulsation processes to treat white spruce lumber with water-borne preservatives
1988 - IRG/WP 3471
Laboratory work using end sealed 4x8x46 cm³ white spruce samples has been done to explore the suitability of three variants of a 2.1 MPa pulsation process for the impregnation of white spruce with CCA. The results showed that the process improved significantly the penetration of the preservatives and reduced significantly cell collapse, when compared with the results of treatment using a 2.1 MPa empty cell process. The comparison of the three variants indicate that the process has potential for further improvements.
J P Hösli, J N R Ruddick

Observations on colony collapse in Reticulitermes flavipes (Kollar) in laboratory and field settings in Wisconsin
2010 - IRG/WP 10-10709
Parallel strategies were designed to eliminate Reticulitermes flavipes (Kollar) from a field site in Endeavor, Wisconsin and a simulated field test setup of approximately 20,000 workers in the laboratory. Indoor and outdoor colonies of R. flavipes were baited with commercial cellulose monitoring stations and rolled cardboard stations. If the commercial cellulose baits were attacked, they were replaced with termidicidal baits containing 0.25% diflubenzuron (a chitin synthase inhibitor). In active cardboard stations, termites were dusted with N’N-naphthaloylhydroxylamine (NHA) and released back into the colony. Overtime, diflubenzuron gradually suppressed worker activity and termite numbers both in the laboratory and the field. However, sharp reductions (>90%) in foraging workers were observed in both field and laboratory colonies with the addition of dusting with NHA. Termidicidal baits containing 0.5% hexaflumeron were secondarily evaluated in the field as a comparison to diflubenzuron. Observations indicated five notable characteristics or criteria of a colony on the verge collapse in one or both venues: i) increasing soldier to worker ratios >20% in the lab, ii) decreasing overall counts of workers collected, iii) increasing numbers of secondary reproductives captured in hexaflumeron bait cartridges outdoors, iv) increasing susceptibility to mites, and v) higher microbial load including bacteria, fungi and slime molds within the colony. Shortly after these events occur—foraging workers disappeared from both commercial and cardboard stations and the colony was essentially eliminated. Although laboratory results do not exactly mirror field results, observations regarding colony decline in both venues are significant when attempting termite control. We conclude that combinations of termite toxicants are more effective than either one alone, and that the above observations may be used as an indicator of sucessful termite treatment.
F Green III, R A Arango, G R Esenther