Solid Wood Packing Material as a Pathway for Nonindigenous Species

 Eric Allen

In the past decade, solid wood packing material (SWPM) has become recognized as a major pathway for the introduction of woodborne nonindigenous species. Infested SWPM has been implicated as the source for several recently discovered exotic pests, notably the pine shoot beetle (Tomicus piniperda) in eastern North America, the Asian longhorned beetle (Anoplophora glabripennis) in New York and Chicago, and the pine wood nematode (Bursaphelenchus xylophilus) in Portugal. With the increased movement of trade goods around the world in recent years, the problems associated with SWPM have become a global issue that will require global-scale solutions. This paper will describe the nature of SWPM, why it poses a risk, the magnitude of the risk, and what steps might be taken to reduce the risk.

What is solid wood packing material?
The USDA APHIS defines solid wood packing material as “wood packing materials other than loose wood packing materials used or for use with cargo to prevent damage, including, but not limited to, dunnage, crating, pallets, packing blocks, drums, cases and skids” (USDA, 1998 http://www.aphis.usda.gov/oa/alb/interimalb.html) (Fig. 1). Manufactured wood products, such as plywood, particle board, or oriented strand board, are not considered a risk.

Figure 1. Solid wood packing: pallets and crates

Why is solid wood packing material a problem?
The properties of the wood commonly used as packing material contribute to the hazard. SWPM is typically made from rough-sawn, low-quality wood or by-products of milling that are not acceptable as higher lumber grades. The wood may include bark or wane from the outside of the stem, insect grub holes, and fungal decay or stain. Such low-value wood is generally green, untreated by heat or chemicals, and may remain a favorable substrate for living organisms, particularly insects and fungi. In addition to problems related to these physical characteristics, SWPM pose other concerns. Except for the direct trade of packing materials, they are not a commodity and are difficult to monitor during quarantine inspection procedures. Even when high-risk packing is identified in a shipment, the inspection process is complicated by limited access to visible surfaces (most surfaces are not facing the inspector or the cargo is buried deep in a container) and the cryptic nature of many wood-inhabiting organisms (little or no sign of their presence is evident at the surface). Latent fungal infections or insect larvae (e.g. the wood-wasp Sirex) are virtually impossible to detect through inspection of outer wood surfaces. Packing materials may also be repaired, reused, and moved from country to country before they are disposed of. This furthers the likelihood of unintentional movement of infested wood or wood that is reinfested in transit. Disposal methods may also add risk. In Canada, wooden cable spools carrying cable for forestry use have been left in forest settings-potentially moving wood-inhabiting pests directly to the forest (Fig. 2).

Figure 2. Infested wire rope cable spools

What is the magnitude of the SWPM problem?
Although quarantine interception records have provided an indication of the kinds of pests moving with solid wood packing materials, only recently have studies quantified the risk associated with known volumes of packing wood. A 1997 Canadian Forest Service audit of 50 Chinese wire rope spools revealed that 24% of the spools examined still contained live wood borers, while a total of 31% of the spools had some evidence of past wood borer activity. Six species of longhorned wood borers (Cerambycidae), including Monochamus alternatus, Hesperophanes (=Trichoferus) campestris, Ceresium flavipes, Psacothea hilaris, Megopis sinica, and Rhagium inquisitor and one species of Anobiidae, Ptilineurus sp., were reared from these spools. There was often no visible external evidence of the presence of live wood borers in these spools: only 63% exhibited external signs of wood borer activity, while all were found to have some evidence of past insect activity when disassembled (Allen et al., 1997 http://www.pfc.cfs.nrcan.gc.ca/health/exotics.htm).

In a subsequent study in July 1998, live beetles were found associated with shipments of granite from Norway. Green spruce bolts had been used to brace large granite blocks inside shipping containers (Figs. 3 and 4). More than 2,500 adult insects representing more than 40 species of bark beetles, wood borers, and their associated parasitoids, predators, and scavengers, such as well as bluestain fungi and nematodes were recovered from 29 log bolts (Table 1). At least three species of Scolytidae of quarantine significance, Pityogenes chalcographus, Polygraphus poligraphus and Ips typographus, were recovered from these bolts.

Figure 3. Unloading imported granite blocks. Figure 4. Green Norway spruce bolt bracing granite blocks.

Table 1. Bark and wood-boring beetles and wasps reared from intercepted spruce bolts from Norway used as dunnage.

Family and Species

No. of Individuals

Scolytidae

Pityophthorus micrographus

942

Pityogenes chalcographus

284

Polygraphus poligraphus

207

Ips typographus

27

Crypturgus hispidulus

16

Pityophthorus pityographus

1

Cerambycidae

Tetropium fuscum

44

Callidium coriaceum

3

Molorchus minor

1

Pogonocherus fasciculatus

1

Semanotus undatus

1

Anobiidae

Anobium sp.

10

Ernobius explanatus

4

Curculionidae

Rhyncholus sp.

1

Melandryidae

Serropalpus barbatus

7

Siricidae

Sirex juvencus

21

What steps might be taken to reduce the risk?
With the heightened awareness of SWPM as a significant pathway for invasive species, a global effort has been initiated to develop international standards for the treatment and regulation of SWPM. Although such an initiative will result in added costs to shipping and packing industries, it is clear that the phytosanitary benefits of such a program be worthwhile. This type of approach, in conjunction with enhanced surveillance, using improved detection tools and inspection methods will greatly reduce the negative impacts of nonindigenous species.

Further Reading
Allen, E.A., Humble, L. M., Dawson, J. L. M., and Bell, J.D. 1997. Exotic interceptions from wooden dunnage and packing material. North American Plant Protection Organization Bull. No. 15, Abstracts of the 21st annual meeting and colloquium on quarantine security. Seattle, WA Oct 20-24, 1997. http://www.pfc.cfs.nrcan.gc.ca/health/exotics.htm (accessed Jan 12, 2001)

USDA 1998. Solid wood packing material from China; Interim Rule 7 CFR Parts 319 and 354 http://www.aphis.usda.gov/oa/alb/interimalb.html (accessed Jan 12, 2001)

USDA 2000. Draft pest risk assessment for importation of solid wood packing materials into the United States. Primary contact: J. Pasek, USDA APHIS Raleigh NC.