The oldest record on the occurrence of pine wilt disease in Japan is at Nagasaki in Kyushu island in 1905. The first outbreak in Honshu island was at Aioi in 1914.
Both Nagasaki and Aioi are old sea ports, and the disease spread from the wood preserving areas. This fact suggests that pine wilt disease is imported disease.
During the 1930s the disease was not so serious, but became serious after 1946, probably because of the abandonment of control effort during World War II. After World War II, the pine mortality declined. This seems to be due to the extensive effort to eradicate this disease by felling and burning of dead trees, which was suggested by General Head Quarter of Occupied Japan.
In the 1970s, this disease became again serious, and the loss of pine woods exceeded 2 million cubic meters in 1979.
In 1977, Japanese government issued the Special Law to control this devastating disease as a national project by aerial spray of insecticides to eradicate vector beetles, Monochamus alternatus, of pine wood nematode. As the result, the disease declined in some extent but the annual loss of pine wood has still exceeded 1 million cubic meters.
There are several reasons for the recent seriousness of pine mortality: the drought and hot summer condition diminish the resistance of pine tree to this disease. The most important factor seems to be the energy revolution. That is, motorization of traffics forced to change the energy source from coal to petroleum. At the time when coal is the main energy source, pine wood is the most valuable mine pillar, but nowadays, many coal mines have been closed. As the result, the economic value of pine tree declined, and the infected pine trees in the forests had been left untreated. Thus the vector beetles increased and transmitted pathogenic nematode from dead trees to Healthy trees. The construction of highway also accelerate the disease outbreak because of the change of the water condition (drought) of the forest area.
The pine wood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, causes the serious pine wilt disease. This nematode was discovered at Nanjing city in 1982, and now occurs in 5 provinces. However the diseased area is still very limited. This paper reviews the pine wood nematode situation in China, focusing attention on the history, distribution and hosts, vector insects, current research program, and control.
The potential risks to the European Union (EU) from Bursaphelenchus xylophilus have been evaluated using Pest Risk Analysis (PRA)guidelines being developed by FAO and EPPO. The PRA showed: following detailed evaluation of published and unpublished information, that there is a significant risk to the EU, especially to the forests in the warmer south of the region. The greatest risks come from importation of both B. xylophilus and its vectors in the genus Monochamus, but it also recognised that nematodes in wood could come into contact with suitable breeding sites. Measures to prevent importation could include effective forest selection of healthy trees, heat treatment or chemical treatment. These require evaluation before use.
The potential for establishment of the pinewood nematode Bursaphelenchus xylophilus in countries of the former USSR and their possible threat to conifers in these areas are discussed. B. mucronatus is wide-spread, however B. xylophilus has not been found in the former USSR territories. Conditions exist which are suitable for the colonisation by B. xylophilus, and the resultant occurrence of pine wilt disease, in both the European and Asian parts of the former USSR: vectors (Monochamus), susceptible plants, and favorable climatic factors. Based on an analysis of the potential distribution of B. xylophilus it it may be concluded that a threat exists to conifer forests in several areas and territories of the former USSR. This threat is mainly from B. xylophilus, which has the potential to develop as a major factor to the detriment of Russian forestry due to both disease establishment and problems presented with international export of timber product.
From 1986 to 1994 investigation was carried out, and now the distribution of pine wilt diseased (Bursaphelenchus xylophilus(Steiner & Buhrer) in Anhui China was made. At most of the countries and cities of Anhui, example for Muanshan, Wuhu, Chuxian, Huoxian, Mingguang, and Ningguo, we found the disease only taking place on the Pinus massoniana and P. thunbergii, but little on P. taeda and the cross-breed of the P. thunbergii x P. massoniana. The present measures are plant quarantine, chemical control, clear away the dead trees, biological control.
Bursaphelenchus xylophilus Steiner & Buhrer was found from five dead black pines (Pinus thunbergii) at the area of Zhongshan Mausoleum Nanjing in Autumn 1982 first. The nematode was spread to many places around the city of Nanjing within a few years. According to many reports at present, most of the nematodes were only found in local areas of coastal cities of China. The origin of B. xylophilus in China was inferred from other countries by transport in the past ten years and more, although the nematode was carried by long horned beetle as a vector.
About 1 million pines have been killed since the pine wood nematode disease had occurred in 1991, a lot of money and materials have been spent to prevent the spread of the disease in recent years, and it only distribute in limited areas of Xiangshan and Zhoushan by now. The disease may by prevalent in other places, especially east coast areas, because the host plants widely arrange in our province, the main species are: Pinus massoniana and P. thunbergii, they are all highly sensitive to pine wood nematode (Bursaphelenchus xylophilus). The natural vector, Monochamus alternatus is distributed where the pine planted. We do not know whether there is any other natural vectors in our province yet. The climate here is suitable for both pathogen and vector. The pine wood is mainly used as packaging materials for industry products in east coast where the industry is more developing than that of inland, it is so cheap that any other timber can not instead of it, maybe it is the most important pathway for far dissemination of the disease.
Several measurements have been taken to control the disease, they are: clearing away the forest stand, burning branches and roots, fumigating wilted wood and spraying chemical insecticide. It is most effective measurement that all of forest stand infected with the disease should be cleared away.
This paper deal with the studies and analysis on the pathogenicity, resistant evaluation of the pine species (included provenance of Pinus massoniana) and suitability and epidemy of pine wood nematode (PWN),suitability of vector of Monochamus alternatus and their control treatment. The research results showed that: 1. Three species of pine, six provenances and 3-15 year-old natural stand of Masson pine resistance to PWN. 2. In the natural stand, the more number of PWN inoculated in the tree, the faster of the disease developed. Pine wilt occurrence peak has been correlated with drought-stressed tree and mean air temperatures above 25¡æ in August and the dead woods have not attacked by larva of beetles, Cerambycid, during Oct.-Dec. annually. 3. The first year's high temperature result in the early emergence of the beetle adults and the more rainfall limited the beetle adults' flying and their spread, the more concentration of their occurrence in the next year. 4. The spread of the pine wood nematode has the form of point emergence immigrated from far distance, and the fact that the man's spread along the railroad and main highway, then it become wide spread to the whole forest. 5. We especially stressed that select the high resistant species and provenances of pine, plant the mixed forest, cut clearly everyone of the PWN of dead tree and fume them with fumigant, and intensify the job of quarantine, It is the basic treatment of control of widespread of PWN.
The death of a large number of red pine (Pinus densiflora) and black pine (P. thunbergii) occurred in Yuntai Mountain of Lian Yun Gang. In 1984 over 300 Mu pine trees died in Jinping Hill of Yuntai Mountain. From the Autumn of 1994 to the Spring of 1995, only in back Yuntai Mountain, the area of dead pine trees added up to 40,000 Mu. The geographic position of Lian Yun Gang is so close as that of Japan, which is epidemic region of wilting disease of pine trees caused by the pine wood nematode, Bursaphelenchus xylophilus. And they have the same pine species. Moreover, from Japan tens of thousands of containers and hundreds of ships come to Lian Yun Gang annually with many pine dunnage materials. Therefore, we have in several decades conducted serial monitoring of nematode in Yuntai Mountain, especially in back Yuntai Mountain nearby the Lian Yun Gang port. During monitoring no wood nematode was found to line in the wood of dead pine trees, except large quantities of pine sawyer (Monochamus alternatus), the vector of wood nematode, B. mucronatus, a species very similar to B. xylophilus and the other species of Aphelenchoides. The death reason of a number of pine trees is that Dendrolimus spectabilis eats a lot of leaves to make the trees grow weakly and then many species insects of bark and wood borers attack and kill the trees. About 80% of dead pine trees were infested by the nematodes, with the maximum density of the nematode in fresh wood being 10,850 per gram. The result shows that the nematode has weak ability to infest black pine and red pine.
Identification and classification of geographical isolates of Bursaphelenchus was carried out using a repeated DNA sequence isolated from Bursaphelenchus xylophilus. Genotype profiles were monitored over two years and were found to be consistently reliable for identifying the isolates used. PCR amplification was also reliably applied using primers derived from within the repeated sequence probe.
Several isolates of Bursaphelenchus xylophilus and B. mucronatus were collected from Asia, North America and Europe. Using virgin females and young males, reciprocal crosses were made. In general, intraspecific hybridization was successful regardless of combinations. On the other hand, number of progenies from interspecific hybridization was small, suggesting that reproductive isolation may exist between B. xylophilus and B. mucronatus. But, degree of reproductive isolation is variable according to combinations. It is interesting to note that F1 progeny from hybridization including such as French or Finland isolates is fertile.
The genetic analysis was conducted by crossing experiments to use 5 strains of B. xylophilus from China, Japan, Canada and 5 strains of B. mucronatus from China, Japan, France. The results indicated that the two species of China might cross successfully, but the number of hybrids were limited and hardly fertile, so the two species were different in heredity. There was not different in the strains of conspecies of China. When the two species of China cross with strains of Japan, France and Canada separately, there was evident difference in interspecific crossing and some difference in intraspecific crossing.
The F1 generation females of interspecific hybridization had mucronate tails similar to B. mucronatus in reciprocal crossing. F1 hybrid females by back crossing with their parent males were more difficult to produce progenies. The rate of deformations in hybrid adults ranged 10-60 %. Major deformations were no spicules in males and crooking of bodies in females and larvae. On the shape of male spicule, the interspecific strains was not distinct greatly between B. xylophilus and B. mucronatus, and the intraspecific strains were not same evidently in B. xylophilus or B. mucronatus. So the shape of male spicule was not fit for one of taxonomic characteristics.
The researches on differentiation of pathogenicity of pine wood nematode, Bursaphelenchus xylophilus for the reason of Pinus massoniana naturally infected by pine wood nematode in Jiangsu since 1986 were carried out. The result was arrived at that the JRPma-86 is more pathogenicity than NJPth-84, using the indexes such as the days of the first death branch after inoculation, wilt percent, Pf/Pi after the 4-5 years pine seedlings planted of P. massoniana, P. thunbergii, P. taeda, P. elliottii and the masson pines in the forest inoculated by NJPth-84 and JRPma-86. Some pinewood nematodes which are living more than one year were found in the health 10 years masson pines inoculated by pinewood nematodes.
It has been proved that cellulase has important effect on the aetiology of the pine wood disease. A new biochemical method, i.e. the diffusion assay cellulase that is a special material of the pine wood nematode, Bursaphelenchus xylophilus has been reported. This method has simple, quick and sensitive properties. The reaction was taken place on thin layer agar plate using RnoCH2COONa as substrate and stopped by adding acetic acid after staining with Congo red. By using this method we found that both extract and secretion of B. xylophilus has positive reaction, whereas both extract and secretion of B. mucronatus which is very similar with B. xylophilus in morphological and biological characteristics except aetiology, were negative. It is thus important by using this method to diagnose and quarantine for the pine wood disease as well as to distinguish these two similar nematode.
Some isolations and culture experiments were conducted to learn the role of fungi associated with pine wood nematode, Bursaphelenchus xylophilus parasitizing Pinus massoniana in Shenzhen, China. The following fungi were isolated from Pinus of associated beetles: Pestalotiopsis, Fusarium, Ceratocystis, Colletotrichum, Alternaria ,Sordaria, Chaetomium, Nigrospora, Phomopsis, Curvularia, Monochaetia, Trichoderma, Rhizopus, Penicillium, Aspergillus and more than ten other genera of unidentified fungi. The nematode multiplied on colonies of Colletotrichum, Pestalotiopsis, Monochaetia, Alternaria, Ceratocyctis, Phomopsis, Sordaria, Fusarium, Nigrospora and two unidentified fungus genera grown on PDA plate medium. It could also multiply on wood discs with fungi, but not on wood discs sterilized with hot steam.
A plantation of Masson pine provenances and other pine species was planted in 1984 near Nanjing. 135 13-yr old trees of 39 Masson pine provenance and 6 other pine species from the plantation were inoculated through a stem cut with 5,000 Bursaphelenchus xylophilus per tree originally collected from several dead trees of Masson pine in July 1995 near Nanjing city. The resistance and process of susceptibility in different provenances and species to the nematodes varied greatly. Four Masson pine provenances from Guangdon Luyang & Xinyi, Guangxi Gongcheng, Hubei Yuanan are more resistant than other provenances but less than P. elliottii, P. taeda, P. echinata and P. rigida. The pattern of variation in Masson pine resistance to B. xylophilus contained a latitudinal gradient through the natural range with a South to North trend.
Fusarium sp. is the most favorable fungus for multiplying Bursaphelenchus xylophilus increased 467 times after ten days' culture on the colony of Fusarium sp.. The pathogenesis of B. xylophilus did not change after culturing on Fusarium sp..
Abnormal metabolites toxic to pine seedling were extracted from leaves of pine trees (Japanese red pine) naturally infected by pine wood nematodes and identified as benzoic acid and catechol. From wood of infected pine, benzoic acid, 8-hydroxycarvotanacetone, and dihydroconiferyl alcohol were isolated and identified. These compounds were not found in healthy pine trees. Among these compounds, benzoic acid and 8-hydroxycarvotanacetone caused very similar symptoms on pine seedlings as caused by inoculation with the pathogenic nematode. All four compounds accumulated to the toxic level in 15-to 25-year-old natural pine stands 50 days after inoculation with pine wood nematodes.
All four compounds stimulated multiplication of pathogenic nematode at low concentrations. 8-hydroxycarvotanacetone and dihydroconiferyl alcohol inhibited the multiplication of nematodes at concentrations higher than 30 ppm and 100 ppm, respectively. Bolla and others in US identified 10-hydroxyverbenone, in addition to 8-hydroxycarvatanacetone as toxic metabolites from nematode-infected European red pines.
Pine wood nematodes cause abnormal cavitation in Pinus thunbergii tracheids, and the xylem-sap ascent is blocked at cavitated area. Infected trees wilt for water deficit. Such cavitation events were not visible from outside of trunks, but can be detected by acoustic emission (AE) technique. Prior to the inoculation of pine wood nematode, the author attached AE sensors (140kHz) onto the base of pine trunk. In healthy pines, AE associated with active transpiration was detected 2 to 6 times/min. during sunshiny period. After 1 or 2 weeks after the nematode inoculation of August 4, AE signal abruptly began to continue through nights. The AE frequency increased to the order of 100 times/min. from 8 to 14 o'clock. Tracheid cavitation should have developed drastically and widely in the trunks during the period of highly frequent AE detection. After the high AE period, which was different in individual trees from 1 to 4 weeks, AE suddenly decreased, and disease symptom such as leaf-color fading or yellowing became visible.
The development process of pine wilt disease was studied ecophysiologically in relation to pathogenicity of pine wood nematode (PWN). In virulent PWN inoculated-pines, the predawn xylem pressure potential of needles abruptly decreased resulting from xylem embolism when the colour of needles changed to brown and the water conducting function of xylem was lost completely. In avirulent PWN inoculated-pines, needle colour and xylem pressure potential did not change, and hydraulic conductance of xylem lost partially. In virulent PWN inoculated-pines, cavitation events detected by acoustic emission technique occurred before abrupt decrease in xylem pressure potential. The count of events after infection with PWN was more than that before infection at an given xylem pressure potential.
To clarify the effect of co-occurring tree species on the susceptibility of Pinus densiflora to pine wilt disease, field-grown P. densiflora seedlings were inoculated with the Bursaphelenchus xylophilus in early July 1991. Sixteen weeks after inoculation, 48,33,14 and 18% of pine seedlings were diseased when they grew with Alnus sieboldiana, with Sarothamus scoparius, with the naturally associated species of P. densiflora, and in a pure stand of P. densiflora, respectively. When associated with A. sieboldiana or S. scoparius, pine seedlings quickly had visual discoloration of foliage. Consequently, the susceptibility of P. densiflora seedlings to pine wilt disease appeared to be enhanced by some tree species co-occurring with the seedlings.
The pine wilt disease which is caused by the pine wood nematode, Bursaphelenchus xylophilus, is one of the most serious disease of pine forests in Japan and other countries. Developments of the pine wilt disease have been discussed in relation to the nematode population growth within pine trees by many workers, But there are controversies as to relationship between the nematode population and disease developments.
Populations of only virgin females were made by picking up forth stage juveniles molting to adult female. Each of four 2-year-old seedlings of Japanese black pine, P. thunbergii, were inoculated with virgin females (1,000 or 3000) and the symptom developments were observed. Seedlings inoculated with ordinary population of 500 nematodes served as control. Exudation of oleoresin in seedlings inoculated with virgin females were once reduced, but the symptom did not develop, and non of pines died at all. Two months after inoculation, oleoresin exudation of the seedlings recovered to healthy level. On the other hand, all seedlings inoculated with ordinary population were killed within two months. Through this experiments, the author came to a conclusion that population growth of nematodes within pine seedlings is necessary for disease developments and death of pines.
Many years survey and study show the phenomenon of wilt pine is very common in Summer in Ningbo, China. Hot and dry Summer is the most facts to increase in the numbers of wilt pines. M. alternatus is the only beetles associated with mortality of pines. There are many nematodes species in the xylem of pine. Nematodes species carried by M. alternatus is similar with those in the xylem. Based on observation of the species of nematodes and beetles, and their combination, there are at least four distinct patterns of wilt pine occurring in Ningbo:TYPE I, M. alternatus ¡Á B. xylophilus, accounting for 17.35 percent; TYPE II, M. alternatus ¡Á B. mucronatus, 75.37 percent; TYPE III, M. alternatus ¡Á other nematodes, 5.36 percent; TYPE IV, M. alternatus ¡Á no nematodes, 1.92 percent.
The sap flow of pine seedlings was traced by acid fuchsin. Cross-sections of the stem developed unstained white patches around resin canals as early as 10 days after inoculation with Bursaphelenchus xylophilus on Pinus massoniana. This caused by abnormal leads and the diffusion of oleoresin from resin canals into adjacent tracheids, which in turn block sap flow. As the disease advances, the white patches become more distinct and widen. The stem and root both developed distinct white patches 40 days after inoculation. At this stage, the plant inoculated with the nematodes observed no different from the health one. The method described here can be used as a early diagnostic tool for the pine wilt disease caused by Bursaphelenchus xylophilus.
The pine wood nematode (PWN), Bursaphelenchus xylophilus (Steiner &Buhrer) Nickle, causal agent of pine wilt disease (PWD), is native to North America (N.A.). The North American pines appear resistant to PWD; however, some introduced pines, such as Scots pine (Pinus sylvestris L.), are susceptible when growing on dry, warm sites in N.A. During 1987,110 Scots pine trees (20 years old) growing in a plantation in northern Vermont USA, were inoculated with approximately 30,000 nematodes in each of 2 drill holes in the main stem. To determine how long the PWN would survive in inoculated pines, the study trees were observed and sampled for the PWN each year through 1994. Trees will be sampled again during 1995. The PWN can persist in living, healthy-appearing Scots pines 7 or more years after inoculation; however, only about 20 percent of the inoculated trees were found to be infested. Of the trees containing the PWN, 68 percent were living at the time of the first positive extraction and 50 percent of the living trees had healthy-appearing crowns with crown ratios ranging from 30-50 percent. Most nematodes were extracted from samples taken near the point of inoculation. In trees harvested in 1994, almost all nematodes were recovered from the sap wood, a few were recovered from bark samples, and none were recovered from the heartwood. Apparently, the PWN can survive in low numbers in asymptomatic trees for many years without causing PWD. Thus, harvesting of only healthy-appearing trees may not be an adequate measure to prevent movement of the PWN in wood products.
Even after enormous control efforts have been made to suppress the epidemic development, the pine wilt disease has still been spreading and causing serious loss of pine forests in Japan. For instance, we find newly-killed pine trees in the forests where thorough eradication of infested trees were carried out in the previous year. The results of some surveys suggest the important role of the trees which were infected in the previous year and keep healthy-looking in spreading the disease. Here, I call the phenomenon 'latent infection', and will explain the mechanism how such asymptomatically-infected trees play a role in spreading the epidemics referring some interesting results of surveys.
Considerable effort has been expended to survey and eradicate new populations of the pine wilt disease (PWD) along its expanding front in Japan. Though these efforts have failed to stop the spread of PWD, they have slowed spread in Japan, these barrier zones have historically moved as population boundaries have expanded. National and some prefecture governments are planning to adopt a new control strategy to remove pine trees from a fixed barrier zone. Buffer zones will be made on both sides of this barrier zone, intensive survey and eradication of new pest population will take place in buffer zones.
The merit of this strategy is as follows:
1. Barrier zone without host trees will decrease the invasion of PWD into buffer zone.
2. Fixed boundaries make the survey and eradication easy. The width of the barrier zone will be determined from estimates of costs and benefits. The dispersal capabilities of Monochamus alternatus Hope suggest that the barrier zone should be wider than 2 km.
The dispersal stage of Bursaphelenchus xylophilus (Steiner and Buhrer)Nickle, the JIV juvenile, is vectored by cerambycid beetles in the genus Monochamus. This non-feeding stage is filled with lipids for survival during its residence within the respiratory system of beetle vectors. The mediation of JIV entrance into and exit from beetle vectors is poorly understood. A lipid-dependent differential attraction to plant-and beetle-associated chemical compounds was noted. JIV dispersal juveniles with high lipid contents were attracted to a beetle-associated hydrocarbon, while those with low lipid contents were attracted to pine volatiles and fatty acids. The lipid content of recently exited JIV dispersal juveniles was significantly lower than that of JIVs remaining within the beetle. We hypothesize that JIV dispersal juvenile response to exogenous chemical cues is mediated by endogenous lipid storage levels and that this interaction properly synchronizes nematode entrance into and exit from its beetle vector.
To confirm averting of larval diapause after overwintering and manifest the effects of fresh inner bark on it, the 1st to 4th (final) instar larvae of the Japanese pine sawyer, Monochamus alternatus, were collected from dead pine trees in December 1989 and placed in Pinus densiflora bolts of 3 different conditions, i.e. fresh bolts, fresh and old bolts immersed in hot water of 60-70¡æ for about 12 hours. After larval inoculation, the bolts were put into outdoor cages and daily monitored for beetle emergence between May 1 and August 31. Prediapause, 3rd and 4th instar larvae averted diapause and pupated after overwintering when the food condition was poor such as inner bark of old pine bolts. But, they molted into further larval instar and entered diapause after they resumed feeding on suitable food in Spring. Diapause larvae of 4th instar pupated without resuming feeding in Spring. The 3rd instar larvae had entered diapause before winter as well as the 4th instar if the larval instar determination by head capsule width was correct. A hypothesis is presented on the regulation mechanism of life cycle by inducing and averting larval diapause.
Beauveria bassiana was found to be the most promising agent for the control of Monochamus alternatus in a survey of its pathogens. Attempts to utilize an isolate of B. bassiana in ordinary spraying onto beetle-infested pine tree trunks have shown only moderate mortalities of the larvae although this isolate was highly virulent in laboratory tests. Some novel methods of application of this fungus to improve contact between the fungus and the larvae under the bark were investigated. Methods involving implantation of the wheat bran pellets on which B. bassiana was cultured into the infested trees, and placing non-woven fabric strips having B. bassiana conidia onto the infested trees, have produced high mortality of the larvae. The difficulties and importances for the control pine wood nematode (PWN) and its control strategy.
This article carried out the study of the law of occurrence and damage of PWN (Bursaphelenchus xylophilus) and its vector insect pine sawyer (Monochamus alternatus). We selected the most suitable time and pesticide for control and its control treatment methods for usage about 3 years. It can significantly reduce the population of vector and the number of dead trees damaged by PWN. The most difficult points for the control disease of PWN are clear cutting of dead trees infected by PWN and bore by larva of pine beetle inside, their treatment, and forbid them transport out of the area of plague. However, if the management is not suitable the disease will be wide spread quickly. According to the different area and the situation of plague of disease PWN, we established the specialized staff for the PWN management. It is most important point for the control PWN that every dead tree must fumed with fumigant thoroughly. The scenarios above will probably prevent the pine wilt disease from spreading and reduce its damage.
From 1982 to 1995, the number of died pine trees, which were caused by the pine wilt disease, rose from 260 to 375,000 per year, reaching over 1,400 times more than they were in the beginning. During the past 13 years, the total number of died pine trees was 2,310,000 and the volume of which was 16,000 cubic meter. The recent survey shows that the disease has distributed to the cities of Nanjing, Zhenjiang & Wuxi, and the total area of infected pine forest is 9,000 ha. The main experiments are as follow: 1. The combination of pine wilt disease control technology with administration management is effective; The governments are in charge of organizing the people to cut and treat (with fumigant or fire) the infected pine trees in time. 2. Forest quarantine is a very important measure to obstruct the spread of the disease. 3. Pesticides (MPP Emulsion, MPP oil, fenitrothion etc.) are necessary to control the density of Monochamus alternatus. 4. The rate of infected pine trees is related to the conditions of weather and forestry management. Some suggestions are given as follow: 1. To reinforce the administrative measures of the governments in various levels. 2. To be strict with forest plant quarantine; Considering of the present economical situation of forestry farms, we should take some measures to deal with the problems of how to treat the infected pine trees. 3. To do more research work on the disease, and to put there search results into practice. 4. To publicise the disease's seriousness to pine forest extensively. 5. To invest more money and adopt the way of prevention project to control the spread of the pine wilt disease. A preliminary study on aerial spraying pesticide to control Monochamus alternatus
After cut down the dead pine trees damaged by pine wood nematode (PWN) Bursaphelenchus xylophilus and fumed with fumigant, we carried out aerial spray pesticide at adult stage of pine sawyer. According to the characteristics of adult stage occurred during rainy season, the protection control of the time spraying twice of pesticide (the early stage and emerge 50% adults stage) changed to the time of first and second peak of the emergence in the last ten days of May and the second ten days of June. The test result showed that it can significantly reduce the population of the pine sawyer and the number of dead pine trees damaged by PWN.
Fumigation with methyl bromide (CH3 Br) is a major method to treat the wood infested by the pine wood nematode (PWN) (Bursaphelenchus xylophilus) at present. The important factors, such as temperature, dosage, duration of fumigation, the wood size, moisture of the wood, size of the wood stack, and the position of the wood in stack ,were analyzed respectively. The effect of fumigation was retarded by low temperature and improved by the increase of dosage. The duration of 72h fumigation was proper. The worse result was obtained while the wood moisture was higher. The fumigation effect of the stack in bottom was the best. The sizes between 50 to 70 m3 was suitable for fumigation. The important factors affecting the results were temperature, dosage and duration of fumigation. The good results were achieved by increasing dosage and shortening duration of fumigation or prolonging the duration of fumigation and reducing dosage. The mortalities of PWN and Monochamus alternatus were 100% under CT value of 5,000-6,000 at 4-10¡æ.
The last ten days of June, 1994, 23 test points were set up, at 7 released regions in Shenzhen Forest Farm etc., and total 500,000 heads of a kind of parasitic wasp (S. guani)were released in forest to control a pine sawyer (Monochamus alternatus Hope), the vector of pinewood nematode. The parasitic rate was 12.1-65.4% in the first generation of the wasp in forest, averaged 35.2%, the controlled area was over 18 hm2 . Due to the development and expanding of wasps in forest, by the last ten days of October to ten first the days of November, the controlled area reached up to 162.5 hm2 . After controlled by the wasp in the pine forest, the withered rate of pine trees by pine wood nematode disease was about 2-5%, while the withered rate in the empty regions was about 10-20£¥. The control effect in forest was about 70-90%. Therefore releasing wasps in forest is a kind of economical and effective control methods to control the pine wood nematode disease.
As a present of Nagoya government to Nanjing, the giant sightseeing-wheel like windmill was packed in 69 wooden cases, and transported to Nanjing Xinshenwei Port from Japan by M.V. "Big Eight" and arrived at Dec.19, 1992. A lot of pine sticks and trunks used in fixing the case was found in the ship's hold. The wood borer's galleries (include longhorn beetle) and the evident dark-blue veins symptom remind us of pine wood nematode immediately. The samples were taken back to the laboratory for separation and examination of the nematode. In result, the third stage larva of pine wood nematode (Bursaphelenchus xylophilus)was found. We cultivated it to adult with fungi (Botrytis cinerea)under laboratory condition for further identification. As a result of pine wood nematode was issued by Prof. Chen Hurui, Nanjing Agricultural University.
The seedlings and mature trees of five conifer were inoculated with PWN, Bursaphelenchus xylophilus, in the nethouse and forest. Both seedlings and mature trees of deodar cedar (Cedrus deodara Loud) were found highly resistant to PWN, the result was well coincidence for our investigations that none of deodar cedar trees being wide spread planted in Jiangsu Province was dead due to PWN. Pine wilt disease incidence of four-year old loblolly pine seedlings (Pinus taeda L.) was 40-80%, which shows that the seedlings of loblolly pine are middle to highly susceptible to PWN. Only one of 93 mature loblolly pine trees inoculated PWN was dead, which demonstrated that it is highly resistant to PWN. To slash pine (Pinus elliotii Engelm.) the disease incidence in seedlings inoculated PWN in nethouse (21.4-66.7%) was apparently higher than that in forest (0-14.3%). Slash pines, either four-year old or 13-year old, were generally more susceptible to isolate 3 than isolate 1 of PWN. Our experimental results suggest the seedlings of four-year old Huangshan Mountain pine (Pinus taiwanensis Hayata) is highly susceptible to PWN. Most of Huangshan Mountain pines grown at 700-800 metres above sea level, we conclude that pine wilt disease may not be able threat Huangshan Mountain pines. The seedlings of northern pitch pine (Pinus rigida Mill.) show middle susceptible to PWN. It is clear that different pathotypes of PWN occurred in China.
Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle and its insect vector, Monochamus carolinensis are symbionts developing within a rapidly degrading pine log. We investigated the influence of physical and biological factors on the development of pinewood nematode dispersal juvenile stages. Third-stage dispersal juvenile(JIII)density was related to within-wood moisture content and time but the influence of time was eliminated in further experiments. Thus, the switch from reproductive juvenile stages to the JIII stage appeared to be related to the moisture content of the wood or other factor related to moisture content. Production of fourth-stage dispersal juveniles (JIV) occurred, almost exclusively, in the presence of M. carolinensis late pupae or callow adults. M. carolinensis larvae, early pupae or sclerotized adults failed to induce production of JIII's. The switch from JIII to JIII appeared to be related to the molting process in beetles from the pupal to the callow adult stage.
Pine Wilt disease caused by pine wood nematode, Bursaphelenchus xylophilus, is a serious disease of pines. Since 1982 the disease was discovered in Nanjing, Jiangsu, this nematode has distributed in 5 provinces in China. Masson pine, Pinus massoniana Lamb. is the most important forest tree species and planted widest in China, especially in South China. About the resistance of this pine to pine wood nematode there are different results. So, repeated studies are needed. The studies show that the masson pine in different age is variable in resistance to the nematode, the 1 year pine is not resistant to it but the 2-10 year pine is. The masson pine diseased by B. xylophilus in field is that the pine is so the best favorite for beetle maturation feeding that the high inoculum potential from the insect may overcome the resistance of the pine species. And other factors infected masson pine in field is discussed in the paper.
From the time of the ancient Chinese civilisations through the early European traders to modern times there have been enormous amounts and a great diversity of goods and quality of product has improved significantly over this period . The volume and intensity of trade in wood and forest products has increased steadily throughout this trading period until now when the availability of this slowly renewable resource is becoming limiting . despite the endeavours of governments and industry in many countries the econopolitical agendas of these relatively ephemeral organizations , and the conflicting circumstances of the times , are not necessarily leading to an optimum solution of sustained forest productivity in harmony with a maximized value of traded wood products . This paper will consider the effects of climate and trading pattern on the biology of the participating organisms associated with pine wilt disease and its ultimate effect on crop production.
Of the large number of commercial species of wood traded relatively few are Pinus spp. that are susceptible in the field to Bursaphelenchus xylophilus. B. xylophilus and B, mucronatus have been convincingly demonstrated by molecular means to be separate species, but the European populations of B. mucronatus are not easily separated by DNA examination from the Japanese populations despite some clear biological differences . B. xylophilus reproduces rapidly and , under optimum conditions , soon produces very large populations in the wood of healthy, susceptible pine trees and in their fungus infected, rotting trunks and branches , These nematodes appear to have a phoretic relationship with a range of Monochamus species that occur in many countries , including those of Europe . Asia and North America.
The rare of population build-up of the pinewood nematode and of B. mucronatus , the success of Monochamus spp. in vectoring these nematodes and the response of the tree host is significantly influences by climate , especially temperature, and by biospheric factors , The direct and indirect ecosystem feedback to these climatic and biospheric factors undoubtedly influences the occurrence of pine wilt disease , and especially the survival of individual nematodes and populations of nematodes and their vectors and the physiological response of the infected tree , Ultimately , the availability of high quality wood and wood products for the international market is determined by its quality and availability at source.
Heavy mortalities of pines in Japan have been occurring for several decades. Since the detection of causal agent in 1970 by Tokushige and Kiyohara, the pine wood nematode, Bursaphelenchus xylophilus(Nematode; Aphelenchoidae). and its vector , the Japanese pine sawyer, Monochamus alternatus (Coleoptera; Cerambycidae). various new as well as traditional control measures have been developed and improved. The traditional cut-and-burn, or cut-and spray methods have been widely applies, of which effectiveness for prevention of pine mortality in and around the infested stands is not always certain. ON the other hand a new prevention method, preventive spray of chemicals aiming to stop adult sawyers' feeding on the bark of young twigs has been developed successfully. Also injection of nematicide into pine tree trunk has been well developed . Besides these technologies, strategy and tactics have been considered important and improved. We Japanese scientists consider it our duty as well privilege to offer our facts internationally about successful and unsuccessful experiences in managing pine mortalities for years.
1. Dr. Kazuyoshi Futai Laboratory of Applied Botany, Faculty of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606, Japan
2. Dr. Katsumi Togashi Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739, Japan
3. Dr. Naoto Kamata Tohoku Research Center,Forestry and Forest Products Research Institute, Nabeyashiki 72, Shimo-kuriyagawa Morioka, Iwate 020-01, Japan
4. Dr. Katsunori Matori Kyushu Research Center, Forestry and Forest Products Research Institute, Ministry of Agriculture, Forestry and Fisheries Kurokami 4- 11-16, Kumamoto 860, Japan
5. Dr. Mitsuaki Shimazu Forestry & Forest Products Research Institute., P.O.Box 16 Tsukuba Norin Kenkyu Danchi-nai, Ibaraki 305, Japan
6. Dr. Tomoya Kiyohara Forestry & Forest Products Research Institute., P.O.Box 16 Tsukuba Norin Kenkyu Danchi-nai, Ibaraki 305, Japan
7. Dr. Keiko Kuroda Kansai Research Center Forestry & Forest Products Research Institute, Momoyama, Fushimi, Kyoto 612, Japan
8. Dr. Takefumi Ikeda Kansai Research Center Forestry & Forest Products Research Institute, Momoyama, Fushimi, Kyoto 612, Japan
9. Dr. Akiomi Yamane College of Agriculture and Veterinary Medicine, Nihon University, Kameino 1866 Fujisawa City 252, Japan
10. Dr. Oku Hachiro 2-1-95 Ejiri-asahigaoka Seto-cho, Okayama 709-08, Japan
11. Dr. Yamazaki Saburo Ningxia Forest Protect Research Center, South Street of Shenli, Yinchuan, Ningxia Hui Autonomic Region, Yinchuan 750004
12. Dr. Marc Linit Department of Entomology, University of Missouri, Columbia, Missouri 65211, USA
13. Dr. Dale Roger Bergdahl Department of Forestry, University of Vermont, Burlinyton, Vermont 05405-0088, USA
14. Dr. Hugh Francis Evans Forestry Commmission Research Station, Alice Holt Lodge, Wrecclesham, Farnham Surrey, GU 10 4LH, UK
15. Dr. John M. Webster Department of Biological Sciences, Simon Fraser,University, Burnaby, B.C. Canada V5A 1S6
16. Dr. Matthew Anthony Harmey National University of Ireland, Department Botany, University College Dublin, Dublin 4,Ireland
17. Oleg A. Kulinich Institute of Parasitology, Russian Academy of Sciences, Leninsky Prospect 33, Moscow 117071,Russia
18. Cai Simin Shenzhen Animal and Plant Quarantine Bureau, 40 Heping Road, Shenzhen, Guangdong, China 518010
19. Cao Yue Department of Forestry, Nanjing University of Forestry, Nanjing Jiangsu, China 210037
20. Chou Hong Animal and Plant Quarantine Bureau of Liangyungang City, Liangyungang City, Jiangsu, China 222042
21. Cui Xiangfu Forest Plant Quarantine Station of Xianju County, Xianju County Zhejiang, China 317300
22. Du Shengming Dexing Forestry Bureau, Dexing City, Jiangxi, China 334200
23. Fang Guangming Dexing Forestry Bureau, Dexing City, Jiangxi, China 334200
24. Feng Jihua Forest Protection Station of Beijing, Beijing, China 100029
25. Gao Chongsheng Tianjin Animal and Plant Quarantine Station, Tianjin, China 300457
26. Ge jianjun Institue of Plant Quarantine, Ministry of Agriculture, Bldgs 241, Huixin Li, Beijing, China 100029
27. Ge Minghong Forestry Research Institute of Jiangsu Province , Nanjing, Jiangsu, China 211153
28. Gu Rongbang Forest Protection Station of Linhai City , Linhai City , Zhejiang China 317000
29. He Zhihua Forestry Research Institute of Zhejiang Province, Hangzhou, Zhejiang, China 310023
30. Hu Jiaqi Forest Protection Station of Linhai City, Linhai City, Zhejiang China 317000
31. Jiang Liya Anhui Forest Biological Control Center, Hefei 230031
32. Lai Yanxue Ningbo Forest Plant Quarantine Station, Ningbo, Zhejiang, China ` 315000
33. Li Guilin College of Forestry, Shandong Agricultural University, Taian, Shandong, China 271028
34. Li Xiaoping International Department, Chinese Society of Forestry, Beijing, China 100091
35. Li Yaping Forestry College, Jiangxi University of Agriculture, Nanchang, Jiangxi, China 330045
36. Liang Forest Protection Station of Taizhou City, Linhai City, Zhejiang, China 317000
37. Lin Maosong Department of Plant Protection, Nanjing Agricultural University, Nanjing 210095
38. Liu Guangxiang Forestry Bureau of Longyan District, Longyan, Fujian, China 364000
39. Liu Wei Forest Protection Research Institute, The Chinese Academy of Forestry, Beijing, China 100091
40. Liu Yining Ningxia Forest Protect Research Center, South Street of Shenli, Yinchuan, Ningxia, China 750004
41. Ma Yigui Tianjin Animal and Plant Quarantine Station, Tianjin, China 300457
42. Ren Guolan College of Forestry, Henan Agricultural University, Zhengzhou, Henan, China
43. Ruan Xiangsheng Animal and Plant Quarantine Bureau of Fuzhou City, Fuzhou, Fujian, China 350013
44. Shen Jie Forest Plant Quarantine Station of Zhejiang,Hangzhou,Zhejiang, China 310004
45. Shen Ruixiang Department of Forest Protection, Beijing University of Forestry Beijing, China 100083
46. Shen Yingjie Forest Protection Station of Pengze County, Pengze County, Jiangxi, China 332700
47. Shi Dongping Forestry College, Jiangxi University of Agriculture, Nanchang, Jiangxi, China 330045
48. Song Yushuang The General Station of Forest Pest Management, Ministry of Forestry, Shenyang, Liaoning, China 110034
49 Sun Tong Shenyang Forest Protection and Quarantine Station, Shenyang, Liaoning, China
50. Sun Yongchun The Sun Yat-sen Mausaleum Landscaps Forest of Management Bureau of Nanjing, Nanjing, Jiangsu, China 210014
51. Wang Qiming Forestry Research Institute of Jiangsu Province, Nanjing, Jiangsu, China 211153
52. Tong zhaoji Xijiang Forestry Bureau of Guangdong Province , Xijiang, Guangdong, China
53. Wang Yuyan The General Station of Forest Pest Management, Ministry of Forestry, Shenyang, Liaoning, China 110034
54. Wei Chujiang Forest Protection Station of Fujian Province, Fuzhou, Fujian, China 350003
55. Wu Hongyuan Forest Protection Station of Qinghai Province, Xining, Qinghai, China 810007
56. Wu Huiping Department of Plant Protection, Anhui Agricultural University, Hefei, Anhui, China 230036
57. Wu Shufang Zhumadian Forestry Bureau, Zhumadian City , Hinan , China 463000
58. Xu Fuyuan Forestry Research Institute of Jiangsu Province, Nanjing Jiangsu, China 211153
59. Xu Keqin Forest Protection Station of Jiangsu Province
60. Xu Meiqing Research Institute of Forestry, The Chinese Academy of Forestry Beijing, China 100091
61. Xu Peifang Nanjing Animal and Plant Quarantine Bureau, Nanjing, Jiangsu, China 210009
62. Xu Wenli Forestry Bureau, Department of Agroforestry of Jiangsu Province, Nanjing, Jiangsu, China 210008
63. Xu Zhihua Forest Protection Station of Hebei Province, Shijiazhuang, Hebei, China 050081
64. Yan Donghui Forest Protection Research Institute, The Chinese Academy of Forestry, Beijing, China 100091
65. Yang Baojun Research Institute of Forest Protection, The Chinese Academy of of Forestry, Beijing, China 100091
66. Yang Rongzheng Department of Plant Protection, Anhui AgriculturalUniversity,Hefei 230036
67. Yang Weidong Shenzhen Animal and Plant Quarantine Bureau, Shenzhen, Guangdong, China 518010
68. Yin Donghui Forest Protection Research Institute, The Chinese Academy of Forestry, Beijing, China 100091
69. Zhang Aili Shenyang Forest Protection and Quarantine Station, Shenyang, Liaoning, China
70. Zhang Lianqin Guangdong Forestry Research Institute, Guangzhou, Guangdong, China 510520
71. Zhang Xuefan Forest Protection Station of Huangshan City, Huangshan City, Anhui, China 245000
72. Zhao Xiaoming Ningxia Forest Protect Research Center, South Street of Shenli, Yinchuan, Ningxia, China 750004
73. Zhao Zhengdong Research Institute of Chemical Processing and Utilization of Forest Products , CAF, Long Pan Road, Nanjing 210037
74. Zhou Guoliang Shanghai Animal and Plant Quarantine Service, Shanghai, China 200032
75. Zhou Xihua Forest Protection Station of Hebei Province, Shijiazhuang,Hebei China 050081