The ancient pines in the nationally acclaimed landscaped garden -- the North Tomb Park -- in Shenyang, capital of northeast China?s Liaoning Province, have been plagued by both plant diseases and insect pests. Already 1,500 are dead and visitors to the park say how sad they are to see the losses. Those most closely involved are now appealing for help.
Shenyang North Tomb which is also called Qing Zhaoling originally served as the burial place of Huang Taiji (1592-1643) who founded the Qing Dynasty (1644-1911). It has been opened up to the public as a park in more recent times and is famous throughout the country for its pines.
Some 5,000 pines were transplanted from Qianshan Mountain in southern Liaoning back in 1643. Some 2,300 of these have survived to the present day.
These ancient trees have stood as guardians to the imperial mausoleum for over 300 years. They constitute a key feature of the Zhaoling landscape and take their place amongst the historical relics of the site.
According to Liu Yanfen, horticulture engineer at the North Tomb Park, the pines have been plagued from the 1970s onwards by insect pests such as pine beetles and longicorn beetles. At present some 70 pines are dying each year, and this number is thought likely to soar.
The ancient pines in the park belong to the Chinese pine category (Pinus tabulaeformis). For them a life span of 200 to 500 years is normal. So the pines in the park should be considered as ?elderly? pines. Weakened by age, they present an easy target for the pests. First to launch their attacks are the pine snout moths and red pine spiders. Their actions inhibit new growth. Then came the pine beetles, longicorns and other pests also seeking the opportunity to infest the pines.
No ordinary pests these are for they live on the underside of the bark. They damage the cambium layer -- the vital highway of living cells that lies between the bark and the sapwood. The effect is just like slowly cutting off a person?s blood supply. Out of reach under the protection of the bark they are not easily tackled.
But the horticulturists of Shenyang North Tomb Park are fighting back. They have brought an impressive range of weapons into their war on the pests. Their campaign has involved ?bait branches? to lure the pests off the pines, parasitic wasps, digging ditches, sinking wells, improving air flow, fumigation and the speedy removal of all infected materials. This is not to mention the insecticide that has been sprayed, injected and even buried around the roots. But all this is barely holding back the tide of the invasion being mounted by these pests.
Engineer Liu Yanfen sees this plague on the pines as a multifaceted problem. The very age of the pines means that they are no longer growing vigorously and so are prone to die back. Then there is the air pollution and deteriorating environment associated with the park?s downtown location. And there are limitations on the resources available to be deployed in this battle.
According to Liu, the revenue budget to cover the application of fertiliser, irrigation, weed control and pesticide alone runs at some 400,000 to 500,000 yuan (US$48,000-60,000) a year. The equipment currently available for applying pesticides is not able to spray to the required range. Funds are not available to procure the equipment and laboratory facilities necessary for rigorous scientific research. The horticultural technicians have plotted the location of each of the pines. They have kept individual records with special attention paid to those trees which are most affected. However all this has been based on an intuitive approach.
Liu Yanfen is worried about these old pines. She says that the only thing they can do meantime is to use tree surgery techniques to maintain the trees in a good balanced shape and to continue with their pest control measures.
Liu hopes that experts in the field both at home and abroad might turn their attention to this challenging problem and help save these historic pines. She asks that anyone with expertise in the area or who can offer help with equipment or who would be interested in conducting scientific research should contact the North Tomb Park in Shenyang.
(china.org.cn by Zhang Tingting, August 20, 2002)
