Such diseases might not even come from within New Zealand; one potential threat that could cause havoc if it reached New Zealand is pine wilt disease, caused by the pinewood nematode, Bursaphelenchus xylophilus[5]. This nematode works mutually with the pine sawyer beetle, Monochamus alternatus [8]. The cycle of the disiease begins when the adult beetles transmit the nematode to healthy trees as they feed on the bark. Two to three weeks later, the tree ceases production of a substance called oleoresin as the nematode grows and multiplies within the tree [5]. Eventually, the tree wilts and dies within a year; before that happens, however, female sawyer beetles lay their eggs within the weakened tree. They cannot oviposit on healthy trees, as the oleorosin the nematode affects acts as a physical barrier to egg-laying.
This disease was introduced to Japan in the early 1900s and now affects almost half the country, killing trees within a year. [5] As one of New Zealand's main timber supplies is the Monterey Pine, Pinus Radiata [6], this disease could cripple the industry if protection is not put in place.
Spread of pine wit disease in Japan over several decades[5]; if this disease reached NZ there would be serious consequences
Disease
Author: Isaac Middlemiss
One of the vulnerabilities of the timber industry is the susceptibility of trees to parasites, fungi and disease. After all, there can be no timber industry without timber. As well as the local threats that New Zealand faces to trees, such as kauri dieback, there are a plethora of diseases overseas in countries like America and Japan that could wreak havoc if they reached our shores. Take, for example, pine wilt disease, which has affected almost half of Japan in less than a century [5]. But what makes these diseases so lethal?
First, let us take kauri dieback, which since its identification around 1940 has killed thousands of our native kauri [7] and been responsible for closure of many popular walkways around areas of New Zealand. The disease is caused by an agent called Phytophthora taxon Agathis (PTA) [1], which infects the nutrient-carrying tissue and causes foliage yellowing and loss, dead branches and death of the tree [2]. There is no known cure [3], and a miniscule amount of PTA spores are enough to infect an area of trees. This is why many tracks and walkways around New Zealand require trampers to scrub all loose soil from their boots and spray them with disinfectant.
This disease is lethal and has been in New Zealand for close to 40 years [1], yet was only identified in 2008. It is not too hard to imagine, then, that there are many other potential or even existing threats to NZ trees and timber. In a worst-case scenario, such a disease could completely wipe out New Zealand's timber supply, crippling our economy. .
The threat of tree disease is real and dangerous; these two diseases and many others like them can spread like wildfire, leaving useless, dead trees in their wake. If we fail to take action against the future dangers, we may find one of our largest industries on the brink of extinction.