Hazards Associated with Different Forest Pest Pathways and Their Economic Impacts-Other Forest Products

Mike D. Ormsby

The category “other forest products” potentially has a very broad scope. For this paper, however, I have restricted the discussion to two main types of forest products:

Household items manufactured from wood or wood-related products,

Nonmanufactured forest products such as cones or Christmas trees.

Potential Hazards
The potential pest hazards associated with manufactured wood are, in most cases, restricted to pests able to infest dry woods, usually after the product has been manufactured. A notable exception to this is the Bostrychids, which attack seasoning timber while it still has a high moisture content. The larvae working in the wood continue to grow and feed as the wood dries out and may be found still active in the seasoned product. Bostrychids lack the enzyme cellulase. Consequently, they have to make use of starch and sugars in the wood and, therefore, are unable to infest seasoned timber directly.

The main pests likely to be a hazard on manufactured wood products are wood borers, although some termite species can be found in small wood pieces.

The following are examples of the types of pests intercepted by the New Zealand Ministry of Agriculture and Forestry (NZ MAF) on imported wood products over the last 50 years:

The European house longhorn, Hylotrupes bajulus, is believed to be native to the Atlas Mountains of northern Africa. It has, however, spread through Europe and northern Asia and has been established in North America, South Africa, tropical Asia, and possibly Australia. This longhorn is a serious pest of untreated coniferous house timbers in Europe. The larval stages may take from 3 to 6 years to develop. During this long feeding period, larvae seldom break the wood surface, making early detection of the pest difficult.

Stromatium barbatum has economic importance in the tropics and prefers seasoned timbers. It is known to attack furniture, wooden structures, rafters, door and window frames, shelves, and museum wood specimens, etc. In woodland areas, it oviposits only on dry wood, such as the crowns of dead trees.

The bamboo tiger longicorn, Chlorophorus annularis, is particularly prevalent in oriental bamboos, but is also found in the sapwood of teak, Shorea, and some other woods. Larvae feed in seasoned wood, but under dry conditions, development may be retarded with the beetles finally emerging from manufactured articles. One particular specimen was returned to a shop by a customer together with a rolling pin, the pin having been in a warehouse for about a year.

The West Indian drywood termite, Cryptotermes brevis, is thought to have originated in the Caribbean. It is a true drywood termite and is considered to be one of the most destructive termites in the world. Because of its ability to thrive in very dry timber (including small items of furniture), it has been more widely and frequently introduced to new countries then any other species of termite. The colonies are small, and several can be found in one piece of heartwood and sapwood. Any damage is often not detected until the timber collapses.

Figure 1. Borer damage on an imported cricket bat.

The potential pest hazard associated with nonmanufactured forest products such as cones or Christmas trees, includes all forest pest types. These products, therefore, should be considered a much greater risk when traded internationally.

As seed from cones, and some types of woven baskets (e.g., willow), can often be propagated, this type of forest product is equivalent to other propagative materials, unless steps have been taken to ensure their viability has been destroyed.

Potential for damage by the pests associated with each pathway
While a pest may successfully infest a wood product before the product is exported, for the pest to cause any economic or environmental damage (other than that caused to the product itself) the pest must successfully find a way to establish and (in most cases) spread in the new environment. For wood borers in household items the likelihood of the infesting pest avoiding detection on entry into a region and escaping and infesting surrounding timbers may seem reasonably high. A number of simple steps can be taken to dramatically reduce the overall likelihood of establishment of this type of pest imported on these products.

Inspection at the border
Where possible forest products should be inspected for evidence of infestation by wood-boring pests. Manufacturers of wood products such as furniture are unlikely to use hole-ridden materials when producing their products. Therefore, any fresh holes would suggest the products have become infested. Arrangements can also be made with the exporting countries to ensure measures have been taken to reduce the likelihood of infestation after manufacture.

Treatment of forest products
A number of treatments are available for manufactured wood products and are covered in other workshop papers.

Education of importers and the public
Raising the awareness of importers and the general public to the risks associated with the pests on imported wood products can aid in the early reporting of any infestations that have appeared within a region or country. For many of the wood borers likely to be associated with these products, eradication relies on early detection.

Even without any phytosanitary measures in place, successful establishment and spread of these pests depends on the availability of suitable environments. A good example of pests found in one region that are unable to establish in another is Sinoxylon conigerum and the very similar S. anale. These species are widespread throughout the tropics and are serious pests of milling, plywood, and other timber-using industries in hot countries. While these species have been intercepted on more than 600 occasions in New Zealand on imported wood products, these tropical insects are unlikely to establish in New Zealand's colder climate.

Nonmanufactured products, such as cones or Christmas trees, have a far greater potential to act as vectors (carriers) of a much wider variety of forest pests. As many of the pests are not visible to the naked eye (e.g., fungi, nematodes), visual inspection of the products cannot be considered a reliable method of determining where a product is infested or infected. For the movement of the products from a region containing forest pests that are not found in the importing country (assuming the importing country has a suitable environment for the establishment of the pests), treatment may be the only way of adequately reducing the pest risks.

Acknowledgements:

Information about the intercepted pests was provided by staff of Forest Research, Private Bag 3020, Rotorua, New Zealand, www.forestresearch.co.nz

Thanks to Ken Glassey, program coordinator, MAF Biosecurity Authority, for his comments.