Aggregation ofPlatypus quercivorus (Murayama) (Coleoptera: Platypodidae) on oak logs bored by males of the species

To provide evidence for the aggregation ofPlatypus quercivorus (Murayama) (Coleoptera: Platypodidae) in association with the mass mortality of oak trees in Japan, we compared the number of beetles attracted to oak logs bored by males with the number of beetles attracted to logs that had not been bored. Large numbers of males and females were attracted to the bored logs, and the total numbers increased as the number of entry holes in the logs increased. This result shows that both male and female beetles aggregate on logs bored by the males. We collected a large number of beetles attracted to living trees bored by the beetles, and the total number of beetles collected increased as the number of entry holes/m² on the tree trunk increased. Beetles also aggregated on living trees bored by the males.     

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.     

Interactions between<Emphasis Type="Italic"> Orthotomicus erosus</Emphasis> (Woll.) (Col., Scolytidae) and the Argentine ant<Emphasis Type="Italic"> Linepithema humile</Emphasis> (Mayr) (Hym., Formicidae)

Interactions occurring between Orthotomicus erosus, an economically important pine bark beetle in Portugal, and the aggressive Argentine ant Linepithema humile were investigated. Tri-trophic experimental enclosures consisting of Pinus pinaster logs, O. erosus adults and L. humile workers were set up in the field and in the laboratory. Interactions between ants and scolytids were observed and quantified in terms of the bark beetles success in colonizing the logs. The presence of L. humile did not influence the ability of O. erosus to colonize the logs, apparently due to the difficulties met by the ants in handling the bark beetles and to their inability to injure them. Thus, although abundant in many pine stands in Portugal and in spite of its aggressiveness, L. humile does not seem to affect populations of O. erosus.     

Inducing infection of oak logs by a pathogenic fungus carried byPlatypus quercivorus (Murayama) (Coleoptera: Platypodidae)

This study examined the frequency of infection by an unidentified pathogenic fungus of oak logs bored into by males alone or by both males and females ofPlatypus quercivorus (Murayama) in the field. The fungus, which is associated with mass mortality of oak trees in Japan, was not isolated from logs bored into by males alone, which bored only short entrance galleries. However, it was isolated from logs bored into by both males and females, which together bored longer galleries and reproduced successfully. This suggests that it is difficult for the fungus to colonize logs bored into by males alone. The fungus was not isolated from a log in which the beetles failed to reproduce, and in which the galleries were significantly shorter than in logs where reproduction succeeded, but it was unclear whether the shortness of the galleries prevented colonization of the log by the fungus. The study also revealed that some gallery-initiating males survived for at least 2 months in the absence of females, and that females elongated entrance galleries that had been bored by the gallery-initiating males.     

Types of frass produced by the ambrosia beetle <Emphasis Type="Italic">Platypus quercivorus</Emphasis> during gallery construction,and host suitability of five tree species for the beetle

We studied the biology of the ambrosia beetle Platypus quercivorus in the logs of five tree species to determine: (1) the relationship between the amount of frass produced by beetles and tunnel length, (2) the relationship between frass shape and the morphological characteristics of P. quercivorus mouthparts, and (3) the suitability of five tree species for P. quercivorus reproduction. Five logs each from healthy Quercus crispula, Q. serrata, Castanea crenata, Sorbus japonica, and Cryptomeria japonica trees were used in this experiment. The results showed that there was a linear relationship between the amount of frass and tunnel length. Whenever powdery frass was produced, larvae were found in the gallery in the log, while fibrous frass was present only in galleries that contained just adults. The mouthparts of adults were completely sclerotized, which likely accounts for the fibrous frass production. Host preference of P. quercivorus was examined at two stages using five tree species. The first stage is digging initiation, which concerns male preference for digging a tunnel. More holes were made by males on S. japonica and Q. serrata logs, while fewer holes were made on C. japonica logs. The second stage is characterized by female orientation, mating, and progeny development. Platypus quercivorus could complete its lifecycle only in the two Quercus spp.     

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.     

A low <Emphasis Type="Italic">Platypus quercivorus</Emphasis> hole density does not necessarily indicate a small flying population

The ambrosia beetle Platypus quercivorus causes mass mortality of Fagaceae trees in Japan, and tree species differ in their susceptibility to P. quercivorus. We hypothesized that interspecific differences in susceptibility are caused by differences in beetle infestation patterns, that is, how many beetles fly to a tree and how many of those arriving bore holes. To examine how tree susceptibility is related to these parameters, two tree species with different degrees of susceptibility were studied (highly susceptible Quercus crispula and less susceptible Q. salicina). Specifically, we measured the number of male beetles per unit area that flew to the host trees (NFM) and the density of holes bored by male beetles (DH). From these two values, we calculated the proportion of male beetles flying to a host tree that bored holes (PBM). These parameters were compared for the two Quercus species. Although the two species did not differ in NFM in 2003, PBM was markedly lower for Q. salicina than for Q. crispula and DH was significantly lower for Q. salicina than for Q. crispula. Thus, the lower susceptibility of Q. salicina is partly explained by its low PBM.     

Effects of mating on the termination of aggregation by the oak borer,Platypus quercivorus (Murayama) (Curculionidae: Platypodinae) during host colonization

We conducted a field experiment to determine whether logs bored by male Platypus quercivorus beetle were less attractive to conspecifics after beetles had mated. Bored (with male beetles) and unbored logs were placed in a beetle-infested forest and enclosed within a cage. For half of the bored logs, female beetles were released to mate with the male beetles. Log attractiveness was determined by assessing the number of beetles captured on adhesive paper placed on each cage enclosing the log. On the logs on which female beetles were released, the number of beetles captured decreased distinctly after release, and did not differ from the number captured on the unbored logs. In contrast, the number of beetles captured on logs with only unpaired males was higher than the number captured on the unbored logs. This result confirms that the attractiveness of logs bored by male P. quercivorus beetles declines after mating occurs. To our knowledge, this is the first evidence for the relaxation of aggregation pheromone following mating for beetles in the subfamily Platypodinae.     

Blue stain fungi associated withTomicus piniperda (Coleoptera: Scolytidae) on Japanese red pine

A number of various species of blue-stain fungi were isolated fromTomicus piniperda adults at various stages of development, as well as from the galleries, pupal chambers and sapwood underneath galleries on Japanese red pine. This study was an attempt to identify the species, composition of blue-stain fungi associated withT. piniperda, the frequency of occurrence of the fungi, and their role in the sapwood-staining of Japanese red pine in Tsukuba City, central Japan. Among the seven species of blue-stain fungi isolated, an undescribed species ofOphiostoma together withO. minus were the dominant species and closely associated withT. piniperda. These two species occurred on newly emerging adults more frequently than the overwintered adults.Hormonema dematioides was also associated with the beetle, however, its frequency of occurrence from the emerged new adults was very low. Although the two other species,O. ips andGraphium sp. were also isolated from emerged beetles, the frequency of these fungi from gallery systems suggested that they were accidentally carried byT. piniperda. Leptographium wingfieldii, known to be associated with the beetle in Europe, was also isolated at a very low frequency and the fungus seemed not to be closely associated with the beetle.Ophiostoma sp. andO. minus appear to be the most important causes of blue-stain of Japanese red pine sapwood after infestation byT. piniperda.     

Field trap test for bioassay of synthetic (1<Emphasis Type="Italic">S</Emphasis>,4<Emphasis Type="Italic">R</Emphasis>)-4-isopropyl-1-methyl-2-cyclohexen-1-ol as an aggregation pheromone of <Emphasis Type="Italic">Platypus quercivorus</Emphasis> (Coleoptera: Platipodidae)

An ambrosia beetle, Platypus quercivorus, is a vector of Japanese oak wilt, which causes massive mortality of oak trees in Japan. Previous studies have identified (1S,4R)-4-isopropyl-1-methyl-2-cyclohexen-1-ol ((−)-IMCH) as the major component of the aggregation pheromone of P. quercivorus. We tested the ability of synthetic (−)-IMCH to attract P. quercivorus adults. The synthetic compound attracted 14.4 times as many P. quercivorus, of both sexes, as control traps. Control and (−)-IMCH-baited traps both captured 3.32 times as many males as females, probably because of the nature of Lindgren funnel traps and of male-biased emergence sex ratio early in the season of adult flights. (−)-IMCH was proved to be a major component of the aggregation pheromone of P. quercivorus.     

Harmfulness of eriophyid mites (Eriophyoidea,Acari) causing galls on trees and shrubs in the Czech Republic

Fifteen eriophyid mite species are the most abundant species in the Czech Republic from which four, viz.Eriophyes fraxinivorus onFraxinus excelsior, E. platanoideus onAcer platanoides, Phytoptus pyri onPyrus communis andStenacis triradiatus on various species ofSalix injure their host plants and are evaluated as pests. The weight of the leaves attacked by eriophyid mites increase with increasing number of galls pro leaf but the surface of attacked leaves decrease with increasing attack. Harmfulness of eriophyid mites manifests by reducing of assimilation processes, retardation of growth, precocious drying and fall-off of attacked leaves. Heavily attacked young shrubs and trees may dry and decease.With one figure and 2 tables     

Factors influencing the parasitism of codling moth eggs by Trichogramma cacoeciae March. and T. principium Sug. et Sor. (Hymen. Trichogrammatidae)

Non-choice laboratory experiments were conducted to evaluate the influence of host acceptance, previous rearing host, host age and the contact time between parasitoids and host on the efficacy of Trichogramma cacoeciae Marchal and T. principum Sug. et Sor. against the codling moth Cydia pomonella. The tendency of T. cacoeciae and T. principum females to attack the codling moth was similar to E. kuehniella, and it was not affected by the previous rearing host. T. cacoeciae showed a greater preference for codling moth eggs than T. principum. A high mean number of emerged F₁ progeny was observed when both parasitoids were sequentially reared on codling moths. Codling moth acceptance, the number of parasitized eggs and the number of emerged progeny were higher when younger codling moth eggs were offered. The tendency of female parasitoids to oviposit remained unchanged when the contact time with the host was prolonged. When the contact time was increased, the number of parasitized eggs and emerged offspring was higher. The results showed that the codling moth fertility (egg hatch) was reduced when younger eggs were offered and when the contact time with the parasitoids was increased. T. cacoeciae was more efficient in reducing codling moth fertility. The current study provided essential information necessary to increase the efficiency of T. cacoeciae and T. principum against the codling moth.     

Untersuchungen über die Eiparasiten (Hym.: Chalcidoidea) der rotgelben Kiefern-BuschhornblattwespeNeodiprion sertifer Geoff. (Hym.: Diprionidae)

IV. Summary 1. Four or five species of egg parasites ofNeodiprion sertifer have been found in central Europe.2.Dipriocampe diprioni is a primary parasite which overwinters as a first instar larva within the host's egg, The larvae complete feeding in early spring and enter an obligatory diapause which lasts until July–August. Under the influence of the parasite, the egg shell of the host turns brownish. The adults emerge from mid-August onward. The univoltine parasite is thus well synchronized with its major host,N. sertifer.3. A second species, or form, ofDipriocampe has been found, the taxonomic status of which is still unresolved. It is here referred to asDipriocampe sp. forma ignorata. Although not yet separable fromD. diprioni morphologically, its biology is quite different. The larvae mature before the winter and the adults emerge in April–May of the following year, being dependent on alternate hosts. This form is exceedingly rare in lowland areas but possibly common at high altitudes. It remains to be seen whether it is a separate species or a polymorphic, non-diapausing form ofD. diprioni. Host eggs attacked byDipriocampe sp.forma ignorata turn blackish.4. Two species ofAchrysocharella have been found,A. ruforum andA. ovulorum. In lowland areas,Achrysocharella spp. attack the eggs ofN. sertifer in a hyperparasitic capacity, developing at the expense of the larvae and pupae ofDipriocampe spp. or of larvae and pupae of their own kind. There are two or three such hyperparasitic generations during the summer, the last entering hibernation before the new eggs ofN. sertifer make their appearance, thus failing to attack them in a primary capacity.In mountainous areas, where the eggs ofN. sertifer appear earlier,Achrysocharella spp. pass the first generation as primary parasites in the sawfly eggs, and the second (summer) generation as hyperparasites of larvae and pupae ofDipriocampe spp. or of larvae and pupae of their own kind.5.Tetrastichus oophagus has been associated with the eggs ofN. sertifer in a few cases only, but has been more common as a parasite of the eggs ofDiprion pini.6. The importance of the egg parasites ofN. sertifer has to date been underestimated. Egg parasitism is apparently density-dependent and can reach high values during, and immediately after, the break-down of the sawfly populations.     

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.     

Discrimination among host tree species by the ambrosia beetle Platypus quercivorus

The ambrosia beetle Platypus quercivorus is a vector for the fungus that causes Japanese oak wilt, and susceptibility to infestation by P. quercivorus varies by tree species. We postulated that P. quercivorus discriminates among host tree species differing in susceptibility to attack. To test this postulate, we counted the number of flying male beetles (NFM), the number of holes bored by male beetles (NH), and the number of flying female beetles (NFF) per unit area of bark surface in three fagaceous tree species: Quercus crispula (with high susceptibility to infestation) and Q. serrata and Castanea crenata (both with low susceptibility). NFM and NH were used to calculate the proportion of male beetles that bored holes out of those that flew to the tree (PBM). We used generalized additive models to predict NFM, NFF, and PBM. The locations of trees, expressed as x and y coordinates, numbers of weeks after the first male beetle’s flying (WEEK), diameters of trees 130 cm above ground (DBH), and tree species (SP) were incorporated into the models as candidate explanatory variables. The best-fit models for NFM and NFF included WEEK and DBH and the effect of location; SP was not included in the models. For PBM, the best-fit model included WEEK, DBH, and SP. The results indicate that male P. quercivorus prefer Q. crispula to Q. serrata and C. crenata and that selection is made before boring holes on trees, but that P. quercivorus do not discriminate among host species when they fly to trees.     

Die blaue HolzwespeSirex cyaneus F. (Hym., Siricidae) und der TannendüsterkäferSerropalpus barbatus Schall. (Coleoptera,Serropalpidae) als technische Holzschädlinge an Tannen in Südtirol

In the summer of 1983 dead firs were found near Kaltern, South Tyrol, Italy attacked heavily bySirex cyaneus (60%) andSerropalpus barbatus (40%). The slipping holes of both species were identical. The numerous relation between females and males ofS. cynaea was 1∶10. About 26% of this species were parasitized byIbalia leucospoides Hoch. (Cynip., Ibaliidae).Sirex cyaneus andSerropalpus barbatus must be considered as important wood destroyers of silver firs.     

Attacks of bark‐ and wood‐boring coleoptera on snow‐broken conifers over a two‐year period

The attacks of bark‐ and wood‐boring Coleoptera on broken conifer stems after severe snow‐breakage in early 1988 were studied in autumn 1988 and 1989. The study included twelve stands in the county of Värmland in central Sweden differing in age and edaphic conditions. The tops on the ground as well as the remaining rooted stem stumps of 94 Picea abies and 61 Pinus sylvestris were inspected. The presence of living branches on the stumps strongly influenced the incidence of insect attack. All stumps without branches were attacked during the two‐year period, whereas only a few spruce stumps with more than ten branches and no pine stumps with more than five branches were attacked. On spruce stumps, the most frequently encountered Coleoptera were all scolytids, i.e. the species Pityogenes chalcographus, Hylurgops palliatus, and the genera Polygraphus, Dryocoetes, and Trypodendron. On pine stumps, Tomicus piniperda was the most common species. Most of the spruce tops and virtually all pine tops were attacked during the two‐year period, and most of these attacks occurred during the first summer. P. chalcographus, Dryocoetes, and weevils of the genus Pissodes were the most frequent Coleoptera on spruce tops. On pine tops, the dominant insects belonged to the genera Pissodes and Pityogenes.     

Comparative study on drought resistance ofLarix olgensis Henry andPinus sylvestris var.mongolica (I)

Water potential (ϕ w) and net photosynthetic rate (Pn) ofLarix olgensis andPinus. sylvestris var.mongolica decreased with the decrease of soil water content. ϕ w and Pn ofL. olgensis changed hardly during the first 9 days after stopping watering, then decreased sharply at the 10th day Pn ofP. sylvestris varmongolica decreased slightly during the first 8 days, then decreased sharply at the 9th day. Their respiration rate, chlorophyll content and their a/b ratio changed hardly. The following 3 conclusions were obtained and discussed exhaustively. (1) ϕ w can be used to direct watering as a sensitive index of judging whetherL. olgensis andP. sylvestris var.mongolica lacking water. (2) The decrease of Pn ofL. olgensis andP. sylvestris var.mongolica when drought had nothing to do with chlorophyll. (3)P. sylvestris var.mongolica had morphological drought resistance, while Lolgensis had physiological drought resistance, and their drought resistance was discussed comparatively first time.     

Relative dominance of the mold fungus,<Emphasis Type="Italic">Raffaelea</Emphasis> sp., in the mycangium and proventriculus in relation to adult stages of the oak platypodid beetle,<Emphasis Type="Italic">Platypus quercivorus</Emphasis> (Coleoptera; Platypodidae)

Microorganisms associated with the oak platypodid beetle,Platypus quercivorus (Murayama), were isolated from the mycangium of adult females, from the proventriculus of adults of both sexes, and from galleries in the period before dispersal. Fungi isolated from female mycangia were separated into three groups:Raffaelea sp., yeasts (mainlyCandida spp.), and other species.Raffaelea sp. was isolated predominantly from the teneral stage to the dispersal stage, but was not isolated from the mycangia of mother beetles in new galleries. Yeasts were isolated in every beetle stage tested and their isolation rate was over 80% from the teneral stage to the dispersal stage. All three fungal groups were found in the female proventriculus.Raffaelea sp. was isolated only in the dispersal stage at a rate of 40%, whereas the isolation rate of yeasts gradually increased beginning in the mature stage and reached 100% in the rearing stage. In contrast, in the male proventriculus, onlyRaffaelea sp. and yeasts were isolated in the dispersal and rearing stages. The isolation rate in the rearing stage ofRaffaelea sp. was less than 20%, but that of yeasts was 100%, although these rates were almost the same in the dispersal stage.Raffaelea sp. and yeasts were also isolated from cradles containing eclosing pupae. These results suggest thatP. quercivorus acquiresRaffaelea sp. and yeasts in their mycangia from the cradles immediately after eclosion, and maintain them to the dispersal stage. Then, they transmit these fungi from old to new galleries by way of mycangia, and possibly the digestive system.     

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