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Pesky Pines

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Since being introduced from North America, Pine trees have changed the face of the Australian landscape. While Pine plantations have certainly boosted our economy, there are untold costs for councils and land care groups left with the task of removing renegade pine trees from protected bushland reserves.

Pine trees are classified as environmental weeds or significant environmental weeds across the country due to their ability to spread, affecting the biodiversity of sensitive areas.

The history of Pines in Australia Pinus radiata (Radiata Pine) was grown in the Sydney Botanic Gardens as early as 1857. It is thought these trees were brought here by miners coming from the Californian gold rushes to the Australian goldfields. They grow naturally on a narrow stretch of coast in southern California and on two small islands off Mexico.

A similar widespread species is Pinus elliottii (Slash Pine); it grows in areas from South Carolina to Florida and west to Louisiana.

Both species, along with other introduced Pines, have become naturalised in Australia, particular near forestry plantations.

The Negatives

Pines have winged seeds which has aided their dispersal into bushland where they compete with native species. Growing up to 50 metres tall, they block out sunlight and smother the earth with fungi resulting from fallen leaf, branches and cones. Viable seeds may remain in the cones for several years and are often shed abundantly after fire, which kills the parent tree.

In practical terms it may never be possible to eliminate this dispersal while the seed source remains. Genetic modification to produce sterile Pines which put more energy into wood production than reproduction appears to be the only solution to invading Pines; however this scientific achievement is a long way off.

Arborist Ken Folkes has been around Pines most of his life and is of the opinion that if the natural environment is intact, Pine wildling invasion is very minimal due to the allopathic effects of the native biosphere.

“Like all flora and fauna, including humans, we are all opportunistic and will invade a given area at the first chance,” said Ken.

“I’ve worked in a Pine plantation and also in bush regeneration removing Pine wildlings, and am aware of the allopathic effect on other plant species and other environmental nasties they cause. However, Pines are an important commercial timber and are here to stay, although plantation management practices are much more sustainable and environmentally friendly than years gone.

The Positives

According to latest updates in Australian plantation statistics 2018, the total area of softwood plantations is approximately 1,036,900 hectares. Most of the timber harvested is used for structural timber for houses. The industry produces enough timber each year to build around 14 percent of houses built in Australia each year.

“Arborist Ken Folkes has been around Pines most of his life and is of the opinion that if the natural environment is intact, Pine wildling invasion is very minimal.”

The Forestry Corporation of New South Wales manages state forests on behalf of the NSW Government. It has over 230,000 hectares of Pine plantations, consisting of about 90 percent Radiata. The bulk of the resource underpinning today’s industry was established from the late 1950s to mid 1970s. The first commercial Radiata pine plantation in NSW was established at Tuncurry on the mid-north coast in 1914.

In 1920, Pinus elliottii was introduced into Queensland, and in 1970 it was crossed with Caribbean Pine to form the hybrid Southern Pine. The hybrid combines the best attributes of both species to yield higher proportions of structural timber grade than Radiata. It is grown by HQ Plantations in coastal regions from northern New South Wales to Rockhampton.

Pests and Diseases of Pines

Pinus species are restricted strongly to the latitude where they occur naturally. Southern Pines originate from latitudes equivalent to that of Queensland, and Radiata from latitudes the same as southern New South Wales. If grown in Queensland, Radiata is highly susceptible to attack from Diplodia and does not perform well.

There are a number of potential pests of Southern and Radiata Pines that are not known to exist in Australia yet but are incorporated into Australian biosecurity programs.

Sirex wasp is a potential pest, which currently only extends from the southern states (in Radiata) to just over the Queensland border; it is not yet established in the main Southern Pine estate in Queensland.

When plantations become stressed from drought or fire they become susceptible to attack from other pests such as the Five-spined bark beetle (Ips grandicollis) and Californian Pine aphid (Essigella californica).

The recent Giant Pine Scale incursion into certain urban areas in Victoria and South Australia is another potential pest that could impact Southern Pines if it spreads north. Fortunately, this pest is yet to be detected in any commercial Pine plantations in Australia.

Pest and Disease Workshop

Janet McDonald has been working with the Forest Health Surveillance (FHS) team since 1998 conducting pest and disease surveys in forestry plantations throughout Queensland. On March 6, 2019 Janet will conduct a Pest and Disease Workshop at QAA Headquarters in Redland City to help arborists to recognise and identify problems in all kinds of trees. (Visit qaa.net.au to register.)

How to Identify Pines

Radiata Pine (Pinus radiata) has relatively large asymmetrical cones (7-17 cm long) that are borne on short curved stalks. Its leaves are relatively short (8-15 cm long) and usually borne in groups of three (rarely in twos). Radiata bark is dark brown in colour with deep ridges.

Slash Pine (Pinus elliottii) has relatively large symmetrical cones (7-20 cm long) that are borne on short stalks. Its leaves are relatively long (15-30 cm long) and borne in groups of two or three (usually in twos). The bark is grey to rusty brown and sheds in flat discs, and the cones of Slash pines have small prickles on the tips of their woody scales

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