Host-tree conditions affecting the oviposition activities of the woodwasp,Sirex nitobei Matsumura (hymenoptera: Siricidae)

Experiments were conducted to elucidate how the oviposition activities ofSirex nitobei Matsumura could be affected by different conditions of the host trees, using logs from felled healthy trees and the dead and living trees ofPinus densiflora Sieb. et Zucc. According to days elapsed after tree-felling, the proportions of oviposition defined as the proportion of eggs laid to the potential fecundity of a female during her lifetime, could be divided arbitrarily into three groups. The proportions of oviposition on the logs within 0–3 days after felling,i.e fresh logs, varied greatly from log to log, and about half of female adults showed proportions of oviposition under 50% (mean ±SD: 39±32%). However, all the females that oviposited on the logs 4–24 days after felling,i.e. intermediate logs, invariably showed proportions of oviposition over 50% (88±1.5%). On the other hand, proportions of oviposition in most of the females that oviposited on the logs over 25 days after felling,i.e. old logs, were less than 50% (26±17%). The proportions of oviposition were significantly different between intermediate logs and old logs. The mean proportion of oviposition on living trees and that for dead trees were 45 and 58%, respectively. Thus,S. nitobei in the field would exhibit its preference for weakened trees ofP. densiflora as oviposition sites, as it did for the logs 4–24 days after felling in this study.     

Survival ofPinus densiflora andP. thunbergii forests in Ibaraki Prefecture severely damaged byBursaphelenchus xylophilus

The total area ofPinus densiflora andP. thunbergii forests in Ibaraki Prefecture in 1978 was 65,200 ha, which decreased to 30,300 ha by 1985 mainly due to pine wilt mortality caused byBursaphelenchus xylophilus. This damage has also continued thereafter. To estimate the survivability of pine trees in Ibaraki Prefecture, pine tree mortality has been studied in eight experimental forests for over 20 years, and ground surveys throughout the Prefecture were also conducted in 1995. Survival in the experimental forests corresponded well to the results of ground surveys. Pine forests remained as pure stands if control measures were undertaken or if they were located in cool areas. In warm areas where no control was undertaken, most of the pine forests disappeared and only a few pine trees remained in mixed forests, while on dry soils no mature or old pine trees survived. Since surviving pine forests are often cut for wood utilization,P. densiflora andP. thunbergii may decrease in area to become rare species in the future unless controls are applied and/or reforestation with resistant pines is carried out. A part of this paper was orally presented at the 108th Annual Meeting of the Japanese Forestry Society (1997).     

Oviposition and larval performance of Monochamus alternatus (Coleoptera: Cerambycidae) on the Japanese cedar Cryptomeria japonica

To determine whether Monochamus alternatus can use the Japanese cedar (Cryptomeria japonica) as a host tree, experiments were conducted in a laboratory using three insect populations of different localities. Adult females chose Pinus densiflora bolts as oviposition substrate when supplied with cedar and pine bolts simultaneously, whereas some females from one locality oviposited on cedar bolts when supplied with them exclusively. Seventy-three percent of 40 eggs hatched in cedar bolts. When the first instar larvae were inoculated on cedar bolts, the development was stunted greatly and all died during the larval stage. Two of 20 larvae that were inoculated on cedar bolts at the third instar entered the diapause and one larva developed into an adult female, which produced viable eggs but was much smaller than those obtained from pine bolts. The results did not exclude the possibility that M. alternatus can use recently killed C. japonica trees as a host.     

Different development of pine wilt disease in artificially infectedPinus thunbergii seedlings potted together with different tree species

To evaluate the effect of adjacent tree species on the susceptibility of Japanese black pine (Pinus thunbergii) to pine wilt disease, an inoculation experiment was conducted usingP. thunbergii seedlings potted with seedlings of six tree species,i. e. Alnus sieboldiana, Eurya japonica, Lespedeza bicolor formacutifolia, Pinus thumbergii, Robinia pseudo-acacia andSarothamus scoparius. About ten months after planting, they were inoculated with the pinewood nematode (Bursaphelenchus xylophilus) in early July 1992. After that, the proportion of pine seedlings with completely discolored foliage increased more quickly when the seedlings were potted withR. pseudo-acacia, S. scoparius orA. sieboldiana than when potted withP. thunbergii, L. bicolor orE. japonica. At the end of the study period, 17 weeks after inoculation, it reached 90.6%, 90.0%, 87.5%, 72.7%, 63.3%, and 59.4% when the pine seedlings were potted withR. pseudo-acacia, S. scoparius, A. sieboldiana, P. thunbergii, L. bicolor andE. japonica, respectively. This indicated that the susceptibility ofP. thunbergii seedlings to pine wilt disease was influence by the species of adjacent trees.     

Recessive inheritance of morphological characteristics of utsukushimatsu,<Emphasis Type="Italic">Pinus densiflora</Emphasis> f.<Emphasis Type="Italic">umbraculifera</Emphasis>

Pinus densiflora f.umbraculifera, commonly known as utsukushimatsu, is a distinctively shaped form of Japanese red pine whose growth is restricted to a forest stand in Shiga Prefecture, Japan. The inheritance mode of morphological characteristics of utsukushimatsu was studied to preserve the genetic resource of this pine. As previously reported, F₁ trees grown from open-pollinated seeds harvested from trees inhabiting the native stand showed two phenotypes: one resembling utsukushimatsu, which produces multiple trunks, and the other resembling normalP. densiflora, which produces one or a few trunks. In the present study, controlled pollination was carried out using F₁ and normalP. densiflora trees. Segregation ratios of the two phenotypes observed in the F₂ population showed that the morphological characteristics of utsukushimatsu are inherited recessively. This suggests that the mutation of one gene or a few closely linked genes controls the morphological characteristics of utsukushimatsu. Since multiple trunk formation of utsukushimatsu might be related to a loss of lateral bud inhibition, it follows that a simple gene mutation breaks apical dominance inP. densiflora.     

寄生小蜂对小青×黑杨树皮及杨圆蚧挥发油的行为反应

Four-armed airflow olfactometer was used to determining the foraging behavior ofPteroptrix longgiclava (Girault) (Hymenoptera: Aphelinidae) andEncarsia gigas (Tshumakova) (Hymenoptera: Aphelinidae) to the essential oils which emitted from the healthy bark ofPopulus pseudo-simonii×P. nigra, the infested bark injured byQuadraspidiotus gigas (Thiem & Gerneck), the body and scale of fixed 1st-instar-nymph ofQ. gigas. The results from these experiments showed that the volatile oils produced from the injured bark and from the scale of fixed 1st-instar-nymph had a higher attractive ability to female adults of the two species of wasps. The essential oil produced from the scale of the pest at dosages of 3–7 μL and the essential oil emitted by injured bark at dosages of 5–9 μL had a stronger alluring effect on the host searching behavior ofPteroptrix longgiclava. The essential oil from the body of fixed 1st-instar-nymph ofQ. gigas also had certain effect on the host locating effort ofPteroptrix longgiclava andEncarsia gigas. Those two wasps did not shown any reaction to the essential oil produced by the healthy bark of poplar. Foundation item: This paper was supported by National Natural Science Foundation of China (39970620) and the “TRAPOYT” Biography: CHI De-fu (1962-), male, Ph.D., Professor in Northeast Forestry University, Harbin 150040, P.R. China Responsible editor: Chai Ruihai     

Response of Japanese red pine to inoculation with a blue stain fungus,Ceratocystis piceae

To confirm the pathogenicity of a blue stain fungus,Ceratocystis piceae (Münch) Bakshi to the Japanese red pine (Pinus densiflora Sieb. et Zucc.), the responses of healthy young pine trees and stressed trees which were girdled by the half-circumferential girdling technique were investigated by the fungal inoculation test. Although neither of the pine trees inoculated withC. piceae in the non-girdled treatment nor the controls died, mortality of the trees girdled and inoculated withC. piceae was 28.6%. In the pine trees inoculated withC. piceae, the mean area of the necrotic lesion of the sapwood was significantly larger than that of the controls, and the mean of the water pressure potential of the xylem decreased, regardless of the girdling treatment. TheC. piceae was reisolated from the wood pieces near the inoculation points on the inoculated trees, but not from the controls. These results suggest that under strongly stressed conditions, the Japanese red pine trees might have been killed by heavy infestations ofC. piceae carried by bark beetles. A part of this paper was presented at the 103rd Annual Meeting of the Japanese Forestry Society (1992).     

Host selection of small cedar longicorn beetle, <Emphasis Type="Italic">Callidiellum rufipenne</Emphasis> (Coleoptera:Cerambycidae), on Japanese cedar, <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>, in terms of bark water content of host trees

We caught the adults of a secondary wood-boring insect, Callidiellum rufipenne (Motschulsky), on Japanese cedar, Cryptomeria japonica D. Don., trees and logs with manipulated bark water contents to clarify the mechanism of host selection by C. rufipenne. More C. rufipenne were trapped when the bark water content range was ca. 120–200%. Fewer C. rufipenne were trapped at higher and lower bark water contents. These findings indicate that C. rufipenne adults do not simply select weakened or dying trees. Bark water content is one of important factors for C. rufipenne choosing their host for oviposition.     

The external morphological characterization ofTricholoma matsutake infection of hostPinus densiflora lateral roots

The external morphology ofTricholoma matsutake/Pinus densiflora mycorrhizal lateral roots, collected from a Shiro in Tottori Prefecture, western Japan, was described in detail. Four distinct stages within a progressive developmental continum were recognized and color illustrations of each stage were presented. This research was supported by a grant from the Bio-oriented Technology Research Advancement Institution (BRAIN).     

Reutilization of culture wastes ofPleurotus ostreatus andPhollota nameko for cultivation ofLyophyllum decastes

Possible reutilization of fresh and aged culture wastes of mushrooms for cultivatingLyophyllum decastes was investigated, although bark compost has commonly been used as a substrate for cultivating this fungus. The culture wastes studied were obtained after harvestingPleurotus ostreatus andPholiota nameko mushrooms. Mycelia ofL. decastes grew in the media containing both the fresh culture waste ofP. nameko and bark compost. However, it did not grow in the medium containing only the fresh culture waste ofP. nameko or in any media containing the fresh culture waste ofP. ostreatus. The mycelial growth inhibition in the fresh culture wastes ofP. ostreatus might be caused by the water-soluble inhibitors present. Mycelia ofL. decastes grew in all the media with aged culture wastes of bothP. ostreatus andP. nameko, which had been left outdoors for 6 months, regardless of whether bark compost was mixed. Fruit bodies were produced on all the tested media with aged culture wastes of both mushrooms, which had been left outdoors for a year. The aged culture waste ofP. nameko gave greater yields than the bark compost. This investigation shows that the aged culture wastes ofP. ostreatus andP. nameko could be reutilized for producingL. decastes mushrooms.This study was presented in part at the 47th annual meeting of Japan Wood Research Society, Kochi, April 1997     

黑松和马尾松苗受松材线虫侵染后部分化学物质的响应

为研究松材线虫侵染对寄主植物生理生化物质代谢的影响,以黑松和马尾松4 5年生苗为实验材料,测定了接种松材线虫对2种寄主植物的营养物质和次生代谢物质含量的变化及其规律。结果显示:接种松材线虫初期,黑松和马尾松的总糖含量均较高,随接种时间的延长,总糖含量呈不断下降趋势;黑松的可溶性糖含量一直降低并明显低于对照,马尾松的可溶性糖含量在侵染前期与对照相比变化不明显,而15 d后快速降低;黑松和马尾松的可溶性蛋白含量侵染前期均低于对照,后升高,再降低;黑松的单宁含量明显高于对照,马尾松的单宁含量接种第1天略低于对照,第3天后开始升高;黑松和马尾松的总酚含量均在侵染前期高于对照,而后降低。这些物质的变化趋势显示松材线虫侵染不同寄主植物的生理反应。     

Detectionin situ of endophyte withinTricholoma matsutake/Pinus densiflora mycorrhizal roots

Tricholoma matsutake/Pinus densiflora mycorrhizas andP. densiflora roots were collected from beneath matureT. matsutake fruit-bodies in a Shiro in central Japan and investigated for evidence of endophytic infection.Tricholoma matsutake infection was determined microscopically on cleared, bleached and stained mycorrhizas by the presence of both a thin, discontinuous mantle and highly branched, sparingly septate Hartig net mycelium within the root cortex. Endophytic infection of Matsutake mycorrhizas was characterized by intracortical sclerotia, simple septate mycelium within the cortex and vascular cylinder and intracellular spore masses within the root cortex. This research was supported by a grant from the Bio-oriented Technology Research Advancement Institution (BRAIN).     

Seasonal variations in the incidence of pine wilt and infestation by its vector, Monochamus alternatus, near the northern limit of the disease in Japan

During the last few decades, pine wilt disease has spread to cool-climate regions in Japan and, more recently, the potential risk of it spreading into the European midwest has also become a concern. In a coastal pine stand (84.7?ha) in Akita, near the northern limit of pine wilt disease in Japan, we investigated seasonal variations in the incidence of damage caused by the disease to trees and oviposition by the disease’s insect vector, Monochamus alternatus, during a two-year period. Foliage discoloration occurred throughout each year, and its seasonal variation showed a bimodal pattern in Pinus thunbergii (a higher peak in May–June and a smaller peak in October) and a clear peak in June in P. densiflora, which differed from the patterns in seasonal variation seen for warm-climate regions. Oviposition scars by M. alternatus were found in 40–45% of the trees damaged each year. The percentage of trees that had oviposition scars was higher in P. thunbergii than in P. densiflora. This appeared to reflect the difference in seasonal discoloration pattern between the two species. Analysis of the oviposition risk showed that trees that exhibited discoloration starting between July and October had a significantly higher risk or significantly higher oviposition scar densities, particularly for those that became discolored between August and September (2.5–14.6-fold higher risk than during other months). Oviposition scar densities per damaged tree were similar within the period of higher oviposition risk. Considering both oviposition risks and scar densities, we concluded that trees with discoloration that become apparent between July and October are important targets for preventing the spread of pine wilt disease in Akita.     

Inhibiting factors of symptom development in several Japanese red pine (<Emphasis Type="Italic">Pinus densiflora</Emphasis>) families selected as resistant to pine wilt

Pinus densiflora and P. thunbergii, native to Japan, are highly susceptible to pine wilt disease caused by infection with a pine wood nematode (Bursaphelenchus xylophilus). Trees of these susceptible species have occasionally been found surviving in forests that are extensively damaged by this disease. Seedlings from a part of surviving trees that were selected as resistant families indicate lower mortality rates after the infection. The factors that prevent the symptoms from developing in resistant families of a susceptible species, P. densiflora, as based on the analysis of the pathogens behavior in the tree tissue and the anatomy of the resistant families, are presented in this paper. Nematode populations remained lower in the stems of seedlings from resistant families of P. densiflora than in the stems of non-resistant families. Areas dysfunctional in water transport developed in the stems of resistant families, but did not reach a size large enough to seriously block the ascent of sap. These results suggest that there are systems within the seedlings that prevent nematode migration and reproduction. The 2-year-old seedlings from resistant families of P. densiflora, however, did not suppress the pathogen activity. Numerous branches are a visible characteristic in the seedlings of some resistant families. The arrangement of the resin canals, the only channels in the tree to the pathogen migration, was disoriented at the joints between the branches and the main stem. Such a structure may be effective as a barrier to nematode dispersal.     

Susceptibility of adult trees of the endangered species Pinus armandii var. amamiana to pine wilt disease in the field

Adult trees of Pinus armandii var. amamiana (PAAm) and P. thunbergii grown in the field were inoculated with 100000 or 1000 of the nematode Bursaphelenchus xylophilus to evaluate their susceptibility to pine wilt disease. PAAm trees inoculated with 100000 nematodes started to show disease symptoms 2 weeks after inoculation, and all died within 29 weeks. Although the PAAm trees inoculated with 1000 nematodes tended to show delayed disease symptoms compared with those inoculated with 100000 nematodes, all of them died within 33 weeks after inoculation. All P. thunbergii trees inoculated with 1000 nematodes had died 6 weeks after inoculation. In the nematode-inoculated PAAm trees, death of branches distal to the nematode inoculation site was the first visible symptom, followed by the systemic discoloration of needles, whereas the whole tree wilted simultaneously in P. thunbergii trees. In nematode-inoculated PAAm trees, the period from inoculation to death was longer than that in P. thunbergii. These results suggest that adult PAAm trees are susceptible to pine wilt disease, but are less vulnerable than P. thunbergii.     

Influence of host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on some of the biological and ecological characteristics of the entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae)

The entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae) is an effective predator of some whitefly species. However, information on the influence of the preys host plant species on its biological and ecological characteristics is still lacking in the literature. Therefore, the current study focuses on the possible influence of three greenhouse and two field host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on the number of eggs laid by S. parcesetosum. In addition, because of the economic importance and widespread planting of cucumber in greenhouses and cotton in the field, these plants were selected for further investigation into the development, mortality, longevity and reproduction of S. parcesetosum at a high temperature in the laboratory. Results showed that S. parcesetosum was able to lay eggs on all five host plant species of B. tabaci, whether greenhouse or field plants. However, among the three greenhouse plant species studied, S. parcesetosum females laid the highest number of eggs on cucumber followed by tomato and then sweet pepper. Of the two field plant species, significantly higher numbers of eggs were laid on tobacco than on cotton. S. parcesetosum could develop either on cucumber or on cotton as preferable host plant species for B. tabaci. There were significant differences in mean developmental duration of larval instars of the same sex between both host plant species; the duration was significantly shorter on cucumber than on cotton. There were no significant differences for mean total developmental duration from egg to adult emergence between both host plant species within the same sex; females showed a mean of 15.9 days and males of 15.1 days on cucumber, while on cotton the means were 17.2 days for females and 16.2 days for males. Total mortality percentage of S. parcesetosum during development from egg to adult stage was lower on cucumber than on cotton, 20.6 and 23.8%, respectively. Longevity of S. parcesetosum varied according to host plant species and sex with a mean of 63.4 days for females and 50.3 days for males on cucumber, and 92.4 days for females and 52.5 days for males on cotton. On cucumber, mean period of oviposition of S. parcesetosum was significantly longer than on cotton. Mean total fecundity was significantly higher on cucumber than on cotton, with means of 97.7 and 31.0 eggs/female, respectively.     

Relationships between mass mortality of two oak species (Quercus mongolica Turcz. var.grosseserrata Rehd. et Wils. andQ. serrata Thunb.) and infestation by and reproduction ofPlatypus quercivorus (Murayama) (coleoptera: Platypodidae)

This study investigated the number of adults ofPlatypus quercivorus (Murayama) captured on host oak (Quercus spp.) trees, the attack density (the number of entry holes per 100 cm²), and the number of emerging adults to clarify the relationships between the beetle’s colonization on trees in oak stands and tree mortality. The initial attack ofP. quercivorus, which was the most intense attack, was observed on most living trees simultaneously. Although some attacked trees died within the year of the attack or in the next year, a high density of attack did not usually cause the death of host trees. Surviving trees suffered low levels of consecutive attack after the initial attack. BecauseP. quercivorus successfully produced broods only in the dead trees, the population of the insect seems to be maintained only in stands where oak mortality occurs. However, the adults that landed on most of the surviving trees appeared unable to reproduce probably due to degradation of host quality. Thus, oak mortality probably ceases within 3 or 4 years after the start of infestation in a stand, with subsequent reductions in population density of the borer.     

Lateral female strobili production in a Japanese red pine (Pinus densiflora Sieb. et Zucc.) clone by exogenous cytokinin application

Application ofN ⁶-benzylaminopurine (BAP) and gibberellin (GA₃) to a grafted Japanese red pine (Pinus densiflora Sieb. et Zucc.) clone promoted flowering. BAP (250 mg/l) was sprayed five times to the top of branches in July or September 1992. GA₃ (100 or 500 mg/l) was applied five times to the whole plants by spray treatment during the above period, or GA₃ solution of the same concentration was injected once into a small incision made in the main stem of clone trees at the beginning of July or the middle of September 1992. In May 1993, no apical female strobili were observed at the top of the new shoots in any treatment. However, lateral female and bisexual strobili were produced in the lower part of new shoots by BAP application in September, regardless of GA₃ application. BAP applied in September without GA₃ application was sufficient to produce lateral female and bisexual strobili. In such treatment, production of female and bisexual strobili was 47 and 25, and they occurred in 16 out of 68 new shoots, 11 out of 15 treated branches and 5 out of 5 treated trees. The average number of female and bisexual strobili per new shoot was 1.06. BAP treatment either in July or in September significantly decreased (p<0.05) the production of male strobili. These results indicate that BAP application induces the development of lateral female strobili in Japanese red pine when applied during the period of floral differentiation. A part of this paper was presented at the 105th annual meeting of the Japanese Forestry Society.     

Susceptibility of eliteAcacia mearnsii families to Ceratocystis wilt in south Africa

Ceratocystis albofundus is a recently described pathogen infectingAcacia mearnsii in South Africa, and it causes a disease known as Ceratocystis wilt. Symptoms of the disease include die-back, gummosis and wilting of infected trees. In order to select trees tolerant to this fungus, susceptibility tests were conducted on trees representing fourteen families ofA. mearnsii. A virulent isolate ofC. albofundus was selected and inoculated into the stems of twelve-month-old plants in a plantation. Lesion lengths, in the bark, and disease development were assessed after 6 weeks. All fourteen families ofA. mearnsii were susceptible to infection byC. albofundus. Considerable variation was, however, noticed between individual trees within the same family and the incorporation of disease tolerant trees into breeding programmes is proposed.     

Population dynamics of <Emphasis Type="Italic">Monochamus galloprovincialis</Emphasis> Olivier (Coleoptera: Cerambycidae) in two pine species under laboratory conditions

The study of the life history dynamics of the pine sawyer beetle Monochamus galloprovincialis (Olivier) is important because the beetles vector the pinewood nematode. The objectives of this study were to investigate differences in beetle life history parameters between the two common host tree species in Turkey, Pinus sylvestris and Pinus nigra. Relationships between the number of oviposition sites, holding time (time between log cut and oviposition), log moisture content, log volume and area, and adult survivorship were evaluated. No significant differences were found between the two tree species except adult density per m². The holding time did not influence the number of oviposition sites, larval entry holes or adults for P. sylvestris. There was a negative correlation between the holding time and the number of oviposition sites for P. nigra. The number of adults emerged per log was correlated with the number of larval entry holes only for P. sylvestris. Only 12 and 15% of the initial cohort completed development and emerged as adults for P. sylvestris and P. nigra, respectively. Both tree species are equally suitable hosts for M. galloprovincialis development. We conclude that the high within-log mortality of beetles is a combination of resource quality and quantity factors and intraspecific competition and cannibalism during larval development.