Induced defenses of loblolly pine, Pinus taeda: potential impact on Dendroctonus frontalis within-tree mortality

Loblolly pine (Pinus taeda L.) produces an induced defensive hypersensitive response in inner bark colonized by the southern pine beetle, Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), and its associated fungi. Adult beetles forced to colonize the induced response tissue in a laboratory study constructed galleries that were the same length as adults boring in normal phloem. However, each female laid fewer eggs in the induced tissue. Larval and pupal mortality were also higher in this tissue when compared to surrounding phloem. Beetles colonizing trees in response to pheromone baits constructed less gallery and laid fewer eggs in induced tissue than in surrounding normal phloem. These results suggest that the lesions produced by the induced defense system in conifers may not only contain the growth of fungi inoculated into trees during the attack phase of beetle colonization, but may also affect survival of bark beetle progeny.

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Résumé Une réaction hypersensible de défense a été induite dans les couches profondes de l'écorce de P. taeda colonisée par D. frontalis et le champignon qui lui est associé. Au laboratoire, des adultes, contraints de coloniser les tissus où une réaction hypersensible e été induite, ont foré des galeries de même longueur que celles creusées dans du phloème sain. Cependant les femelles ont pondu moins d'oeufs dans les tissus induits; les mortalités larvaires et nymphales étaient aussi plus fortes dans ce tissu que dans le phloème voisin. Les scolytes, ayant colonisé les arbres après attraction par des pièges à phéromones, forent moins de galeries et pondent moins d'oeufs dans le tissu induit que dans le phloème sain voisin. Ces résultats suggèrent que les lésions, provoquées par le système de défense induit des conifères, peuvent non seulement limiter la croissance du champignon inoculé dans l'arbre au cours de la colonisation des scolytes, mais aussi affecter la survie des descendants dans l'écorce.

     

Laboratory study of conspecific avoidance by host-colonizingDendroctonus frontalis Zimm. (Coleoptera: Scolytidae)

Bark/phloem disk sandwiches (100 cm²) were colonized with one to six mating pairs of the southern pine beetle, Dendroctonus frontalis Zimm., to observe gallery construction and evaluate if avoidance behavior occurs between beetles. Frequencies of turn aways, touches, and crosses (three characteristics used to describe conspecific interaction) all increased significantly with beetle density. A threshold of three mating pairs within the 100- cm² phloem area was the density at which avoidance behavior became evident. At a threshold of five mating pairs the number of gallery crossings was significantly greater than at lower densities. Single and paired female beetles introduced into artificial galleries crossed empty neighboring galleries significantly more often than when neighboring galleries were occupied with other D. frontalis. The data suggest that D. frontalis females can regulate gallery spacing within the host through their ability to detect nearby beetles and their galleries. Possible spacing mechanisms are discussed.     

Dendroctonus frontalis Infection by the DD-136 Strain of Neoaplectana carpocapsae and its Bacterial Complex

The DD-136 strain of Neoaplectana carpocapsae Weiser (Steinernematidae) after spray application to pine bark in 0.1% Formalin plus wetting agent entered pine bark beetle tunnels and killed 44% of the brood and adults of Dendroctonus frontalis Zimmermann at 18 and 26 C, 60% relative hummidity and at ambient temperatures and humidities.     

Transmission of the Pinewood Nematode, Bursaphelenchus xylophilus,to Slash Pine Trees and Log Bolts by a Cerambycid Beetle,Monochamus titillator, in Florida

Field-collected adults of the southern pine sawyer, Monochamus titillator (F.) (Coleoptera: Cerambycidae), naturally infested with fourth-stage juveniles (dauerlarvae) of the pinewood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer, 1934) Nickle, 1970, were maturation fed on excised shoots of typical slash pine, Pinus elliottii Engelm. var elliottii, for 21 days. During August 1981, a male and female adult beetle were held in a sleeve cage placed on the terminal of a side branch of each of seven replicate, healthy 10-year-old slash pine trees. All seven branch terminals showed evidence of beetle feeding on the bark after 1 week, and pinewood nematodes were present in wood samples taken near these feeding sites. Four of the seven trees showed wilt symptoms in 4-6 weeks and died about 9 weeks after beetle feeding. Pinewood nematodes were recovered from the roots and trunks of the dead trees. Each of seven replicate slash pine log bolts was enclosed in a jar with a pair of the same beetles used in the sleeve cages. After 1 week, wood underlying beetle oviposition sites in the bark of all replicate log bolts was infested with the pinewood nematode.     

Fungi associated with the southern pine beetle: avoidance of induced defense response in loblolly pine

Summary Loblolly pines (Pinus taeda) are rapidly killed by colonizing southern pine beetle (Dendroctonus frontalis). The female beetles carry two species of fungi (Ceratocystis minor var. barrasii and an unnamed basidiomycete) within a mycangium. The insects are also frequently associated with a blue-staining form of C. minor. These fungi are inoculated into the tree during colonization. The tree has an induced defensive response that involves resin soaking and necrosis of affected tissue isolating the invading organlsms. The blue-staining fungus stimulates formation of this response in the tree, but the two mycangial fungi do not. These results suggest that the beetles are closely associated with two highly pathogenic fungi that do not stimulate one of the critical components of tree defense.     

基于实验种群两性生命表的伊氏叶螨在番茄和龙葵上的适应性评价

【目的】伊氏叶螨是一种世界性入侵害螨,在我国的潜在危害目前尚不明确。本研究旨在明确其在我国对2种常见茄科寄主植物番茄和龙葵的适应性,为伊氏叶螨的科学防治提供理论依据。【方法】在温度(25±2)℃、相对湿度(70±5)%、光暗比L∶D=16 h∶8 h的实验室条件下,应用两性生命表方法测定伊氏叶螨在番茄和龙葵上的相关生物学参数,评估其对番茄和龙葵的适应性。【结果】取食番茄的伊氏叶螨的成螨前期为14.41 d,显著长于取食龙葵的12.08 d (p<0.05);取食番茄和龙葵时成螨均可存活20 d以上,雌成螨产卵前期分别为1.51和1.43 d。取食番茄的伊氏叶螨种群的内禀增长率、周限增长率、净增殖率、平均世代周期分别为0.17 d^-1、1.18 d^-1、37.17和21.85 d;而取食龙葵的则分别为0.19 d^-1、1.21 d^-1、34.55和18.63 d。【结论】伊氏叶螨在番茄和龙葵上均能完成完整的生活史,且对龙葵的适应度高于番茄。因此推测龙葵可能比番茄更适合作为伊氏叶螨入侵后的寄主植物。     

Arthropods and nematodes co-occurring with the eastern larch beetle,Dendroctonus simplex [Col.: Scolytidae], in Newfoundland

Fifty-four species of insects, 5 of spiders, 5 of mites, 1 harvestman and 1 nematode co-occurred with the eastern larch beetle,Dendroctonus simplex LeConte, on tamarack,Larix laricina (Du Roi) K. Koch, at 2 localities in Newfoundland. The most abundant predators were the flyMedetera gaspensis Bickel and the beetleRhizophagus dimidiatus Mannerheim and the most abundant parasitoids were the HymenopteraSpathius canadensis Ashmead,Rhopalicus tutela (Walker) andRoptrocerus xylophagorum (Ratzburg).D. simplex is recorded as a new host for 9 predator and 3 parasitoid species.      

The use of life tables to assess varietal resistance of cotton to spider mites

Life tables of Tetranychus urticae Koch were used to assess resistance to spider mites in five varieties of cotton in the southern San Joaquin Valley of California. Experiments were conducted during midseason and again in mid- to late season. The most resistant variety was Pima S-5 and the most susceptible was Acala SJ-2. Resistance of S-5 was expressed primarily as lower mite survivorship and fecundity. Developmental rates were similar on all 5 varieties. Although differences in the net reproductive rate (R_o) were large, there were only slight differences in the intrinsic rate of increase (r). Comparisons of the data in the first and second experiment, showed that resistance to spider mites increased as the plants matured. It is hypothesized that increased resistance associated with plant maturation results from a decrease in available nutrients in the leaves of older plants.

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Résumé Les tables de vie de T. urticae Koch ont servi à la mise en évidence de la résistance de cinq variétés de coton dans la partie méridionale de la vallée de San Joaquin en Californie. Les expériences ont eu lieu à la mi-saison et à nouveau de la mi à la fin saison. La variété la plus résistante a été Pima S-5 et la plus sensible Acala SJ-2. La résistance de S-5 s'est traduite d'abord par une diminution de la survie et de la fécondité des acariens. Les taux de développement ont été les mêmes sur les cinq variétés. Bien que les différences entre les taux de reproduction nets (R_o) aient été importants, il n'y a eu que de légères différences entre les taux intrinsèques d'accroissement (r). La comparaison des résultats des lère et 2ème expériences a montré que la résistance aux acariens a augmenté quand les plantes ont mûri. L'hypothèse est émise d'un accroissement de la résistance lié à la maturation par suite d'une diminution de la quantité de'éléments nutritifs dans les feuilles des plantes âgées.

     

Parasitoids of Monochamus galloprovincialis (Coleoptera,Cerambycidae), vector of the pine wood nematode,with identification key for the Palaearctic region

The parasitoid complex associated with Monochamus galloprovincialis (Olivier), vector of the pine wood nematode, is discussed. Four species of the family Braconidae and one Ichneumonidae were found associated with Monochamus galloprovincialis in Portugal, namely Atanycolus denigrator (Linnaeus), Atanycolus ivanowi (Kokujev), Cyanopterus flavator (Fabricius), Doryctes striatellus (Nees) (Braconidae), and Xorides depressus (Holmgren) (Ichneumonidae). Atanycolus ivanowi, Atanycolus denigrator, Doryctes striatellus and Xorides depressus are new species for Portugal fauna, and Monochamus galloprovincialis is recorded as a new host of Xorides depressus. A key for determination of the ichneumonoid parasitoids of the pine sawyer is provided for the Palaearctic fauna.     

Nemtaode-Vector Relationships in the Pine Wilt Disease System

Pinewood nematode, Bursaphelenchus xylophilus, is the causal agent of pine wilt disease in North America and Japan. Dispersal stage dauer larvae are transported to new host trees on the body surface and within the tracheal system of several beetle species. Worldwide, 21 species of Cerambycidae, 1 genus of Buprestidae, and 2 species of Curculionidae are known to carry pinewood nematode dauer larvae upon emerging from nematode-infested trees. Five species of cerambycids in the genus Monochamus are known to transmit dauer larvae to new host trees, four North American species and one Japanese species. Primary transmission to healthy trees occurs through beetle feeding wounds on young branches. Secondary transmission to stressed trees or recently cut logs occurs through Monochamus oviposition sites.     

Effect of density on age-specific mortality in Drosophila: a density supplementation experiment

Age-specific mortality rates were studied at two adult density levels in four inbred lines of Drosophila melanogaster. In experimental populations, adult densities were maintained at constant levels throughout the experiment by replacing dead flies with live, marked mutants. In control populations, densities declined naturally as the cohorts aged. For all experimental populations the best mortality model is the two-stage Gompertz model, with slower mortality acceleration at older ages. Flies in the experimental populations generally lived longer than flies in control populations, regardless of sex, genotype, or initial density level. The data demonstrate that deceleration of age-specific mortality rates at older ages is not caused by declining cohort densities. Mortality deceleration is a real phenomenon that raises serious questions about the evolution of senescence.     

Artificial diet and rearing methods for Thanasimus dubius (Coleoptera: Cleridae), a predator of bark beetles (Coleoptera: Scolytidae)

Clerid beetles are common natural enemies of bark beetles, and could potentially be used as biological control agents if they could be reared in sufficient numbers. We developed an artificial diet devoid of insect components for rearing Thanasimus dubius (Fabricius), a clerid that attacks several economically important bark beetles in eastern North America. We reared larvae of this predator using the artificial diet, and then used either natural or factitious prey to feed the adults so produced. Two different methods of presenting the diet were also examined. We then compared the performance of T. dubius reared on the artificial diet with newly-emerged wild individuals collected from the field. Our results suggest that adult predators reared on the diet are near in quality to wild ones, and high R₀ values can be obtained. No difference in prey preference was found between wild and diet-reared individuals after five generations in the laboratory. Sufficient numbers of predators could be generated using these techniques to permit limited field trials of augmentative biological control.     

The red turpentine beetle, <Emphasis Type="Italic">Dendroctonus valens</Emphasis> LeConte (Scolytidae): an exotic invasive pest of pine in China

An exotic invasive pest of pines, the red turpentine beetle, Dendroctonus valens LeConte (Scolytidae) (RTB), was first detected in Shanxi Province, northern China, in 1998 and started causing widespread tree mortality there in 1999. This outbreak continues and has spread to three adjacent provinces, causing unprecedented tree mortality. Although it is considered a minor pest of pines in North America, RTB has proven to be an aggressive and destructive pest of Pinus tabuliformis, China’s most widely planted pine species. The bionomics and occurrence, distribution, response to host volatiles, and host preference of this pine beetle in China are compared with what is known of the beetle in its native range in North America. Factors likely contributing to D. valens success in China and control of the beetle outbreak are discussed. (−)-β-pinene was shown to be the most attractive host volatile for D. valens from the Sierra Nevada of California, whereas 3-(+)-carene is the most attractive host volatile for beetles in China. Monocultures of Pinus tabuliformis, several consecutive years of drought conditions and warm winters have apparently factored D. valens invasion and establishment in China.     

大型海藻龙须菜抽提液对褶皱臂尾轮虫生命表参数的影响

大型海藻富含多种活性物质,具有抗衰老等生物活性;轮虫是良好的潜在抗衰老研究模式生物。本研究以褶皱臂尾轮虫(Brachionus plicatilis)作为实验对象,研究了不同浓度的大型海藻龙须菜抽提液(0,250,500,750,1000 mg/L)和不同浓度的食物(蛋白核小球藻和普通小球藻)对褶皱臂尾轮虫生命表参数的影响。结果表明:与对照组相比,食物浓度为1.0×10~6个/mL蛋白核小球藻时,不同浓度龙须菜抽提液对轮虫产卵数、平均寿命、净生长率以及世代时间有显著促进效应(P0.05);轮虫平均产卵数及寿命在龙须菜抽提液浓度750 mg/L处达到最高,分别为16只和13.9d(P0.05)。食物浓度为2.0×10~6个/mL普通小球藻时,轮虫平均产卵数和寿命在抽提液浓度为500 mg/L处达到最高,分别为16只和13.6d(P0.05),轮虫平均寿命和净生长率均有显著提高(P0.05)。相同龙须菜抽提液浓度下,食物浓度为1.0×10~6个/mL蛋白核小球藻下轮虫的净生长率、世代时间均显著高于食物浓度为2.0×10~6个/mL蛋白核小球藻培养的轮虫(P0.05);食物浓度为2.0×10~6个/mL时,普通小球藻培养轮虫的净生长率和世代时间均显著高于蛋白核小球藻实验组(P0.05)。交互作用分析显示,龙须菜抽提液与小球藻的交互作用对褶皱臂尾轮虫的内禀增长率有显著影响(P0.05)。研究结果表明,大型海藻龙须菜抽提液对褶皱臂尾轮虫的生长与生殖有促进作用,延长轮虫寿命。     

盐酸四环素浓度和食物密度对萼花臂尾轮虫生活史特征的综合影响

近年来,抗生素的环境污染问题已引起人们的广泛关注,其在环境中的残留可对水生态系统的结构和功能产生重要影响。迄今,盐酸四环素浓度和食物密度对轮虫生活史特征的影响研究尚未见报道。以萼花臂尾轮虫(Brachionus calyciflorus)为受试动物,研究了在不同斜生栅藻(Scenedesmus obliquus)密度下,不同浓度的盐酸四环素(Tetracycline hydrochloride)对萼花臂尾轮虫生活史特征的影响。结果表明,食物密度和盐酸四环素浓度对轮虫的生命期望、净生殖率、世代时间、内禀增长率、平均寿命和后代混交率,以及食物密度和盐酸四环素浓度间交互作用对除了内禀增长率外的其他5个统计学参数均具有显著影响。在各食物密度下,轮虫的特定年龄繁殖率高峰值随着盐酸四环素浓度的增加呈现先增加后降低的趋势;盐酸四环素对轮虫生长和繁殖参数的影响呈现"低促高抑"的特点。3个食物密度下,高浓度的盐酸四环素显著提高了萼花臂尾轮虫的后代混交率,且在1.0×10~6个/mL藻密度下毒物浓度与轮虫后代混交率间具有显著的剂量-效应关系。食物密度的高低显著影响盐酸四环素对萼花臂尾轮虫的毒性效应。     

西花蓟马在6种蔬菜寄主上的实验种群生命表

自西花蓟马Frankliniella occidentalis传入我国后,该虫对蔬菜寄主的危害趋于严重,组建了25℃条件下,西花蓟马在黄瓜、甘蓝、莴苣、茄子、芹菜和大蒜叶片的实验种群生命表,以研究西花蓟马的危害差异性,为西花蓟马的防治提供基础数据。结果表明西花蓟马的生长发育、繁殖和生命表参数等在不同寄主之间有明显差异。西花蓟马在黄瓜上发育最快,其未成熟期为11.43 d,同时在黄瓜上最先开始产卵,产卵前期为1.22 d,在芹菜上发育最慢,为16.11 d。其每雌每天在甘蓝上和莴苣上产卵量最大,分别为2.88粒和2.48粒,在大蒜上最小,为0.77粒;每雌每天产雌率、子代雌性比在甘蓝和莴苣上都大于其他寄主。雌虫寿命在甘蓝上最长(29.06 d)、雄虫寿命在莴苣上最长(13.22 d)。西花蓟马在黄瓜、莴苣、茄子、甘蓝、芹菜和大蒜上的内禀增长力rm值分别为0.1318、0.1228、0.1154、0.1197、0.0860和0.0791;净增殖率R0分别为19.1248、30.8523、17.9322、34.5322、8.9491和8.3536。种群趋势预测指数(I)在甘蓝(34.17)、莴苣(30.09)上明显高于其它寄主,在芹菜(8.00)和大蒜(8.22)上最低。     

Take-off capacity as a criterion for quality control in mass-produced predators,Rhizophagus grandis (Col.: Rhizophagidae) for the biocontrol of bark beetles,Dendroctonus micans (Col.: Scolytidae)

Time spent by adult beetles in cold storage at 3–7°C accounted for 81% of the loss of take-off capacity inRhizophagus grandis Gyllenhal in windtunnel experiments. At the age of three weeks, the insects were at their highest take-off capacity at about 80%. This was followed by a steady decrease, 7% of the insects failing to take-off each month. Changes in the fat reserves during cold storage could explain at least partly this reduction of flight capacity although there was no significant difference in fresh weight between insects that were able/unable to take-off. Sex had a significant influence on take-off rates, with an 8.7% higher take-off rate in females. Take-off capacity was further reduced when the insects were mass-produced in cultures using parent beetles submitted to a blend of synthetic oviposition stimulants instead of live prey larvae. Response to synthetic attractants by those insects which took-off, however, was not influenced by cold storage or by the use of synthetic stimulants in the culture medium.

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Résumé Le temps passé en conservation à basse température (3–7°C) depuis la métamorphose est intervenu pour 81% dans la perte de la capacité d'envol chez le coléoptère prédateurRhizophagus grandis Gyll. lors d'expériences en tunnel de vol. A l'age de trois semaines, les insectes sont à leur plus haut niveau d'envol (envol d'environ 80% des insectes). Par la suite, il y a un déclin constant de la capacité d'envol, à raison de 7% des insectes chaque mois. Des changements dans les réserves lipidiques peuvent partiellement expliquer cette réduction, bien qu'il n'y ait pas eu de différence entre le poids frais d'insectes capables de s'envoler et celui d'individus qui en étaient incapables. Le sexe a une influence sur le taux d'envol, avec un taux d'envol significativement plus élevé de 8.7% chez les femelles. La capacité d'envol est encore réduite chez des insectes qui ont été produits dans des élevages de masse où les parents étaient soumis à un mélange de stimuli de ponte de synthèse au lieu d'être mis en présence de larves deD. micans vivantes. Chez les insectes qui prennent leur vol, cependant, la réponse aux attractifs de synthèse est indépendante de l'age ainsi que des conditions d'élevage.

     

Biology and life tables for the predaceous earwig,Doru taeniatum [Derm.: Forficulidae]

The biology of the earwig,Doru taeniatum (Dohrn), a reported predator ofSpodoptera frugiperda (J. E. Smith), was studied in the laboratory.D. taeniatum under laboratory conditions was easily reared, mated readily and females tended eggs and first instar nymphs.D. taeniatum developed through 4 nymphal instars and reached imago in approximately 30 days. It is an omnivore in the laboratory and capable of developing and reproduction on plant pollen alone, and on Lepidoptera eggs (Sitotroga carealella) (Olivier) alone. Immatures developed most rapidly and females were most fecund when fed either a combination ofS. cereallea eggs and pollen, orS. cerealella eggs alone. Approved as TA 20744 by Director, Texas Agricultural Experiment Station.