Entomopathogenic nematodes to control black vine weevil (Coleoptera: Curculionidae) on strawberry.

We investigated the potential of heterorhabditid nematodes to control larvae of the black vine weevil, Otiorhynchus sulcatus (F.), in 2 field experiments in commercial strawberry plantings. In both experiments, nematodes were applied directly onto the straw mulch, or onto the soil after temporary removal of the mulch. Heterorhabditis marelatus Lui & Berry (Rhabditida: Heterorhabditidae) reduced numbers of weevil larvae and the percentage of plants infested in both experiments, irrespective of straw removal. In the 1st field experiment, a sponge-packed H. marelatus formulation produced lower numbers of O. sulcatus larvae per strawberry plant (mean O. sulcatus larvae per plant = 0.7) and proportion of infested plants (42%) compared with a vermiculite formulation (mean O. sulcatus larvae per plant = 1.8, proportion infested plants 67%) and an untreated control (mean O. sulcatus larvae per plant = 1.9, proportion infested plants 75%). In the first 2 wk after application, more H. marelatus were found in soil samples collected from plots treated with sponge-packed nematodes, than from plots treated with vermiculite-formulated nematodes. In the 2nd field experiment, sponge-packed formulations of H. bacteriophora Poinar (Rhabditida: Heterorhabditidae) and H. marelatus were tested. H. marelatus caused a reduction in both numbers of weevil larvae (mean O. sulcatus larvae per plant = 0.1) and proportion of infested plants (9%) but H. bacteriophora did not (mean O. sulcatus larvae per plant = 0.45, proportion infested plants 34%). More H. bacteriophora were recovered from soil samples than H. marelatus during the first 7 d of this experiment. However, laboratory studies revealed no difference in the persistence of these 2 nematodes in sand.     

Laboratory Trials of the Efficacy of the Crown Weevil Mortadelo horridus (Coleoptera: Curculionoidae) for the Biological Control of Slender Thistles Carduus pycnocephalus and C. tenuiflorus in Southwestern Australia

The hypothesis that larval crown weevil (Mortadelo horridus Alonso-Zarazaga and Sanchez-Ruiz) can suppress vegetative growth, seed set and viability in the winter annual slender thistles (Carduus pycnocephalus L. and C. tenuiflorus Curt.) was tested in laboratory gardens. Different densities (eight and 16) of M. horridus larvae and eggs were inoculated onto slender thistle rosettes between one and four times. Controls received no eggs or larvae. Larval feeding destroyed the apical meristems of treated plants, producing multi-crowned rosettes and significant declines in leaf area in both species, irrespective of the number of larvae. Treated thistles bolted at the same time and had a 4-fold increase in stem number compared to controls. The stems of control plants were up to one-third taller and thicker than attacked plants. Relative to controls, the leaves of treated plants had significantly fewer spines, decreased leaf area and decreased leaf perimeter, with less deeply lobed leaf margins. The total number of capitula produced by control and experimental groups was not significantly different, but consideration of fertile capitula only revealed a reduction in fertile capitula production following weevil attack. This was most marked in C. pycnocephalus. Control plants also produced significantly wider capitula. No control plants died, compared to 17 and 26% of the attacked plants of C. pycnocephalus and C. tenuiflorus, respectively. Implications for biocontrol of slender thistles are discussed.     

Suppression of Anthonomus eugenii (Coleoptera: Curculionidae) pepper fruit infestation with releases of Catolaccus hunteri (Hymenoptera: Pteromalidae)

The pepper weevil, Anthonomus eugenii Cano, is an important pest of Capsicum spp. pepper in Florida, Puerto Rico, and Central America. Catolaccus hunteri Crawford is the most abundant parasitoid attacking pepper weevil larvae in Florida. Weekly releases of C. hunteri at a rate of 1600 adults per 0.2-ha plot in organically-grown bell pepper, C. annuum L., beginning at first bloom resulted in fewer weevil infested fruit compared to 0.2-ha plots where no parasitoids were released. Weekly releases of C. hunteri adults on nightshade, Solanum americanum Mill, during the fall/winter off-season followed by weekly releases of the same parasitoid in adjacent bell pepper during the spring in-season resulted in fewer infested pepper fruit compared to off-season nightshade and in-season pepper where no parasitoids were released. The results of these experiments demonstrate the potential of augmentative releases of C. hunteri for suppressing infestations of pepper fruit by pepper weevil larvae.     

Use of ablated stalks to assess field rates of parasitism of Diatraea saccharalis (Lepidoptera: Crambidae) by Cotesia flavipes (Hymenoptera: Braconidae)

We evaluated a technique that used ablated sections of corn stalks infested with larvae of Diatraea saccharalis F. to assess parasitism by Cotesia flavipes (Cameron) in a corn field. Stalkborer larvae were retrieved successfully from the artificially infested, ablated stalks for at least 96 h after deployment in the field. Levels of parasitism in ablated stalks attached to corn plants were comparable to levels of parasitism measured using whole plants that were artificially infested. Olfactometer comparisons showed preference by female C. flavipes for both whole plants and ablated stalks containing larval D. saccharalis, over uninfested stalks and plants. This technique provides a means to estimate parasitism of stalkborer larvae by C. flavipes without destructive sampling of agronomic plants.     

Intraguild predation and interference by the mealybug predator Cryptolaemus montrouzieri on the parasitoid Leptomastix dactylopii

The compatibility of the encyrtid parasitoid Leptomastix dactylopii with the coccinellid beetle Cryptolaemus montrouzieri against the citrus mealybug, Planococcus citri, is determined by the extent of intraguild predation and interference by the predator. We tested the preference of the adults and fourth-instar larvae of C. montrouzieri for healthy mealybugs and parasitized mealybugs harboring 1-, 4-, 7- and 14-day-old parasitoid larvae. The experiments were conducted in no-choice (only unparasitized mealybugs or parasitized mealybugs of one parasitoid age were offered at one time) and choice (unparasitized and parasitized mealybugs of a specific age were offered simultaneously) tests. Both the adults and larvae of C. montrouzieri fed on unparasitized and parasitized mealybugs but strongly discriminated against the hardened mummies (14 days old). We also investigated the influence of the presence of C. montrouzieri to the foraging effectiveness of L. dactylopii. The level of parasitism by L. dactylopii was reduced from about 13 to 6% when the number of the C. montrouzieri was increased from zero to four. We recommended that the releases of C. montrouzieri should be conducted 14 days after the releases of L. dactylopii to reduce intraguild predation on the parasitized mealybugs and to avoid interference with the foraging parasitoids.     

Studies on the immune response of sheep to Chabertia ovina (Fabricius, 1788)

The immunological basis of host resistance to C. ovina was established by the demonstration of a marked anamnestic response by 6 sheep to a second infection of C. ovina after previous sensitization. Reaginic antibody was detected in the circulation of 20 sheep tested during both primary and secondary infection. It was first detected 5 weeks after infection with 2000 larvae, 8 weeks after infection with 1000 larvae and 12 weeks after infection with 400 larvae. In contrast, precipitating antibody was detected in only 10 per cent of sheep tested, while in vivo and in vitro tests for delayed hypersensitivity were negative. Studies on the effect of antilymphocytic serum on immunity to C. ovina suggested that the development of resistance to C. ovina requires the participation of the thymus-derived lymphocyte.     

Preliminary host specificity testing of Endophyllum osteospermi (Uredinales, Pucciniaceae), a biological control agent against Chrysanthemoides monilifera ssp. monilifera

Chrysanthemoides monilifera ssp. monilifera, indigenous to the Western Cape Province of South Africa, is a serious invader of native vegetation in south-eastern Australia. The rust fungus Endophyllum osteospermi causes witches' brooms on C. monilifera ssp. monilifera in South Africa, and is associated with a reduction in growth and seed production of its host under natural conditions, as well as mortality of severely infected bushes. This rust fungus is considered to be a potential biological control agent for use against C. monilifera ssp. monilifera in Australia. Endophyllum osteospermi has a long latent period, typically between 6 and 24 months between infection and the initiation of witches' brooms. This long latent period makes the logistics of doing traditional host specificity testing, in which all test plant species are inoculated and observed for symptom development, unfeasible for this rust fungus. Germination of aecidioid teliospores and penetration by basidiospores were observed on the surface of excised leaves of 32 test plant species at 4 days after inoculation, and compared to that on C. monilifera ssp. monilifera. Germinating aecidioid teliospores aborted on 14 test plant species, whilst no penetration was attempted on a further 12 test plant species. Penetration only occurred on nine of the 32 test plant species, in addition to C. monilifera ssp. monilifera. Inoculating whole plants of nine selected test plant species confirmed the above results. Therefore, only the test plant species in which penetration occurred, or at least was attempted, need to undergo comprehensive host specificity testing. Pending these results, E. osteospermi may be suitable for release in Australia for the biological control of C. monilifera ssp. monilifera.     

Attack, escape and predation rates of larvae of two aphidophagous ladybirds during conspecific and heterospecific interactions

The attack, escape and predation rates for larvae of aphidophagous ladybird Propylea dissecta (Mulsant) and Coccinella transversalis Fabricius were quantified as a potential mechanism leading to the differences in the incidence of cannibalism and intraguild predation. These rates were compared at four larval instars within and between the species. The attack rates of larvae of C. transversalis were significantly higher than those of P. dissecta towards conspecific and heterospecific victims. For both species, third instars exhibited maximum tendency to attack. Escape rates in C. transversalis were higher than P. dissecta. In P. dissecta, the second instars made a greater number of escapes than other conspecific instars after being attacked by same stage cannibal or heterospecific predator. In P. dissecta, first instars suffered maximum mortality due to cannibalism and intraguild predation by conspecifics and heterospecifics of the same and older developmental stage. No larvae of C. transversalis were eaten by P. dissecta of the same stage. These results suggest that the larvae of P. dissecta were more often potential cannibals than intraguild predators, while the reverse was the case in C. transversalis. Based on this finding, it could be predicted that in patchy prey habitats, high rates of larval cannibalism in P. dissecta would occur with a high risk of cannibalism of first instars. Larvae of C. transversalis would respond as intraguild predators, while those of P. dissecta as intraguild prey. The greater size and walking activity of C. transversalis could be possible reason for this tendency.     

内生真菌感染对宿主羽茅及邻生植物抗病性的影响

Epichloë内生真菌能够影响宿主植物的抗病性, 但目前关于内生真菌感染对宿主邻生植物抗病性影响的研究很少。该研究首先调查了内蒙古呼伦贝尔天然草地中植物病害发生情况, 发现在常见牧草中禾本科植物病害最为严重, 其中感染内生真菌的羽茅(Achnatherum sibiricum)的总病情指数最低。进一步比较了与羽茅邻生及非邻生植物的病害差异, 结果显示羽茅显著降低了邻生羊草(Leymus chinensis)、狼针草(Stipa baicalensis)和冰草(Agropyron cristatum)的褐斑病病情指数。为探究羽茅对邻生植物病害的影响是否与其内生真菌有关, 分别从内生真菌发酵液、离体叶片和植株层面进行了室内验证试验。结果表明: 羽茅的2种内生真菌Epichloë gansuensis和Epichloë sibiricum发酵液显著抑制了新月弯孢(Curvularia lunata)、根腐离蠕孢(Bipolaris sorokiniana)、核盘菌(Sclerotinia sclerotioru)和三叶草核盘菌(Sclerotinia trifoliorum)的生长; 对于离体叶片, E. gansuensis和E. sibiricum显著减小了宿主叶片受4种病原真菌侵染后的病斑长度。在新月弯孢和根腐离蠕孢的植株接种条件下, 内生真菌显著降低了宿主羽茅及邻生植物羊草的病害程度。该研究首次发现并验证了羽茅内生真菌对邻生禾草抵御褐斑病有一定的增益作用。     

少花蒺藜草入侵对沙质草地氮库的影响

以我国北方大面积发生的入侵植物少花蒺藜草为对象,研究了其对科尔沁沙质草地土壤氮库和地上植物氮库的影响,并在室内条件下,以自然生境中少花蒺藜草伴生牧草披碱草和扁穗冰草为对照,利用¹⁵N同位素技术分析了少花蒺藜草的生物固氮能力.结果表明:与对照裸地和本地植物鹅观草样地相比,少花蒺藜草入侵地土壤总氮库分别显著增加47.5%和20.8%,土壤铵态氮库分别显著降低25.6%和25.2%.与鹅观草相比,少花蒺藜草地上部分植物氮库显著降低18.7%.少花蒺藜草的¹⁵N原子丰度、¹⁵N原子百分超、¹⁵N原子加权百分超均显著低于披碱草和扁穗冰草.少花蒺藜草和披碱草的氮肥利用率分别为48.5%和47.0%,差异不显著.与披碱草相比,少花蒺藜草生物固氮率为60.2%Ndfa.少花蒺藜草对氮素高效利用的特征,揭示了其适应沙质草地生态系统并蔓延的一种生态适应机制.     

西藏马鹿与同域野生有蹄类、家畜草青期食性比较

西藏马鹿为我国特有种,曾一度被认定为野外灭绝。在其生境中有多种食性相近的野生有蹄类及家畜同域分布,探究青藏高原特殊环境下西藏马鹿与这些有蹄类的食物资源种间竞争与共存关系十分必要。2013年和2014年8—9月,采用粪便显微分析法确定了桑日县西藏马鹿自然保护区西藏马鹿、白唇鹿、藏原羚、牦牛、山羊草青期食物组成,并比较分析了西藏马鹿与同域野生有蹄类、家畜之间的食物重叠和分化状况。结果表明: 西藏马鹿与其他有蹄类具有相似的可食植物种类组成,但所占食谱比例不同。西藏马鹿主要可食植物多为其他有蹄类次要可食植物,其中弱小火绒草为西藏马鹿(在动物食谱中的百分比为11.2%)与牦牛(10.2%)共同的主要食物,西藏柳为西藏马鹿(9.6%)和白唇鹿(11.4%)共同的主要食物。从科级水平来看,豆科植物为西藏马鹿(21.4%)与藏原羚(42.5%)的共同主要可食植物,莎草科植物为白唇鹿(49.2%)、牦牛(33.4%)、山羊(50.3%)的共同主要可食植物。菊科植物作为西藏马鹿(29.6%)的主要可食植物,也是白唇鹿(7.6%)、藏原羚(11.6%)、牦牛(17.3%)和山羊(14.1%)的次要可食植物。禾本科植物作为西藏马鹿(7.1%)次要可食植物,较其他4种有蹄类(白唇鹿13.6%、藏原羚12.3%、牦牛11.5%、山羊16.0%)所占比例低。西藏马鹿与其他有蹄类食物重叠度均高于0.5,与牦牛的重叠度最高(0.65)。西藏马鹿食物多样性指数(1.32)、均匀度指数(0.37)和生态位宽度指数(15.79)均较高。与2007—2008年相比,西藏马鹿食物组成变化较大,豆科植物比例增大,莎草科植物比例降低,食物质量总体有所提高。西藏马鹿与家畜之间存在较高的食物资源竞争,这将进一步影响西藏马鹿的分布范围和生存空间。     

Influence of Insect Larvae and Plant Roots on the Host-finding Behaviour of Heterorhabditis megidis

We studied the host-finding and dispersion behaviour of Heterorhabditis megidis (strain NLHE 87.3) in the presence of Galleria mellonella or Otiorhynchus sulcatus larvae and strawberry roots. In large Petri dishes (19 cm diameter) filled with moist sand (8% w/w), and incubated at 15°C over 24 h, infective juveniles (IJs) responded positively to the presence of G. mellonella , to roots of a single strawberry plant and to O. sulcatus larvae in direct contact with roots of a single strawberry plant. A neutral or negative response was observed when IJs were presented with only O. sulcatus larvae or a combination of several strawberry plants with O. sulcatus larvae, either in contact or not in contact with the roots. IJs responded strongly to the combination of plant roots and feeding larvae indicating that the tritrophic interaction formed by IJs - O. sulcatus larvae - strawberry plants may be an infochemical-mediated interaction.     

4种不同生活型湿地植物对富营养化水体的净化效果

选择4种湿地植物菖蒲、香蒲、浮萍和金鱼藻,研究单一及组合湿地植物对高浓度污水(污水处理厂进水)、低浓度污水(污水处理厂出水)中营养物质的去除效果.结果表明: 水体中总氮(TN)、总磷(TP)、化学需氧量(COD)浓度呈现试验前期快速下降,后期缓慢下降的趋势,表明湿地植物能有效净化污水中的TN、TP、COD,但不同湿地植物及湿地植物组合的净化效果存在差异.多种湿地植物组合比单种湿地植物对TN的净化作用强,其中香蒲＋浮萍＋金鱼藻对TN的净化效果最佳;高浓度污水中,单种挺水植物对TP的净化效果较好,低浓度污水中,则是多种湿地植物组合对TP的去除率较高;高浓度污水中,湿地植物对COD的去除率为85.1%～96.0%,其中菖蒲、香蒲去除效果最佳,低浓度污水中,湿地植物对COD去除率为76.9%～94.8%,以菖蒲＋浮萍＋金鱼藻去除效果最好.总体看来,湿地植物对高浓度污水中TN、TP、COD的净化效果好于低浓度污水,两种水体的pH都得到改善.     

The influence of ants and water availability on oviposition behaviour and survivorship of a facultatively ant-tended herbivore

1. The lycaenid butterfly Hemiargus isola associates facultatively with the ant species Formica perpilosa in arid areas of south-western North America. Ants solicit liquid food rewards from butterfly larvae as larvae feed on the host plant, Acacia constricta . Previous studies have shown that tending by F. perpilosa enhances larval growth and pupal survivorship.
2. The effects of ants and plant water content on oviposition behaviour and survivorship to the last larval instar were tested by excluding ants and supplementing water to host plants in a two-way factorial experiment.
3. Butterflies, which lay eggs singly on host plant inflorescences, laid significantly higher egg numbers and densities (eggs/inflorescence) on plants with ants than on plants without ants. This is the first report of a facultative, generalized ant-associate using ants as oviposition cues. Water supplements increased the number, but not the density, of eggs laid on plants. Therefore, it appears that egg-laying butterflies responded to number of inflorescences, rather than plant tissue water per se .
4. Plants with ants had significantly greater numbers of inflorescences during the experiment than plants without ants. Water supplements increased number of inflorescences slightly, but not significantly.
5. Ants increased larval survivorship. Twice as many fourth-instar larvae survived per egg laid on plants with ants than on plants without ants. Ants did not reduce the number of predators present on acacias, but may have reduced predator effectiveness. Ants also did not reduce the numbers of potential H. isola competitors present.
6. Water supplementation affected neither the survivorship of H. isola larvae, nor the intensity of ant tending. Water supplementation did not affect the abundance of predators on plants, but did increase the abundance of several herbivorous insect taxa.     

不同季节杉木幼苗叶片养分和代谢组分对增温和减少降水的响应

研究冬季和夏季亚热带杉木幼苗在增温5 ℃和减少50%自然降水处理下叶片养分和代谢组分的变化.结果表明: 由于不同季节温度和水分差异,杉木叶片的养分和生理代谢组分在不同季节有不同的表现.冬季杉木叶片碳、氮、磷和钾含量显著高于夏季.夏季减少降水、增温处理对杉木叶片各类抗氧化酶活性均无显著影响,冬季减少降水处理分别显著降低超氧化物歧化酶活性20.7%和过氧化物酶活性17.8%.冬季增温后杉木叶片非酶促的抗坏血酸含量显著增加132.5%.冬季增温+减少降水处理降低杉木碳含量,促进渗透物质脯氨酸和氮含量的累积.夏季增温+减少降水处理显著提高杉木叶片碳含量3.3%.无论是冬季还是夏季,增温+减少降水处理对杉木叶片抗氧化系统无显著影响.植物对夏季增温的适应机制与冬季增温不同,杉木叶片的养分变化对同时增温+减少降水更加敏感.为了更好地管理种植林,以提高植物的生产力,在未来气候变化下,应提高植物对养分供需和对季节响应的关注.     

武夷山中亚热带常绿阔叶林样地的群落特征

武夷山保存了典型的中亚热带原生性森林生态系统。由于以往研究的空间和时间尺度较小, 方法规范性不强, 该地区尚缺少大型的、规范的综合性观测和研究平台。本文依托环境保护部南京环境科学研究所等单位按照CTFS调查技术规范建立的武夷山中亚热带常绿阔叶林9.6 ha动态监测样地开展植物群落调查, 从物种组成、区系特征、径级结构和空间分布格局等方面分析了其群落特征。结果表明: 样地内有维管植物68科135属232种, 其中乔木层内胸径≥ 1 cm的植物有44科86属171种。热带性质的科和属分别占总科数和总属数的68.58%和58.83%, 热带特征明显。珍稀濒危物种较多, 有4种国家II级重点保护野生植物、2种《中国生物多样性红色名录——高等植物卷》中的“近危”物种、1种《濒危野生动植物种国际贸易公约》(CITES)附录II物种以及72种中国特有物种, 具有较高的保护和研究价值。稀有种29种, 占总树种数的16.96%。重要值最大的科是壳斗科和山茶科, 二者的重要值之和大于40%。米槠(Castanopsis carlesii)、毛锥(C. fordii)、甜槠(C. eyrei)和少叶黄杞(Engelhardtia fenzlii)的重要值较大, 但没有明显的优势种。小径木较多, 所有个体的平均胸径为5.10 cm, 整体径级分布呈倒J形。乔木层可分为两个亚层, 米槠、毛锥、甜槠等在第I亚层中占优势。米槠和毛锥呈均匀分布, 甜槠、少叶黄杞、赤楠(Syzygium buxifolium)和木荷(Schima superba)呈聚集分布。     

Feeding behavior of bollworm and tobacco budworm (Lepidoptera: Noctuidae) larvae in mixed stands of nontransgenic and transgenic cotton expressing an insecticidal protein

Feeding behavior of third-instar bollworm, Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.), was observed in pure and mixed stands of nontransgenic and transgenic cotton (BTK), Gossypium hirsutum L., expressing an insecticidal protein CryIA(c) from a bacterium, Bacillus thuringiensis Berliner subsp. kurstaki. Five plant stands composed of BTK and non-BTK plants were evaluated; two pure stands and three mixed stands. Percentage ratios of BTK to non-BTK plants in the stands were 100:0, 75:25, 50:50, 25:75 and 0:100, respectively. In all stands with BTK plants, fewer bollworm and tobacco budworm larvae were found on BTK plants than non-BTK plants 24 h after infestation with third instars. At 48 h, significantly fewer tobacco budworm larvae, but not fewer bollworm larvae, were found on BTK plants. However, the number of larvae of either insect did not increase on non-BTK plants compared with the initial infestation density of three larvae per plant. The number of obacco budworm injured flower buds, and capsules was lower in all plant stands containing BTK plants compared with the pure stand of non-BTK at 48 h after infestation. Higher numbers of larvae on non-BTK plants were possibly the result of larval intoxication, reduced feeding, and increased plant abandonment and death on BTK plants rather than a classical feeding preference. Unexpectedly, the number of flower buds and capsules injured by bollworm and tobacco budworm when averaged per plant for all plants in a stand, differed little among the 75:25, 50:50 and 25:75 plant mixtures. These data suggest that larvae of both species frequently moved among plants, feeding indiscriminately on BTK and non-BTK plants.     

Infectivity and ecology of Pseudomonas spp. from natural epizootics in the rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) in India

In 2001, populations of the leaf folder (LF) (Cnaphalocrocis medinalis Guenee) reached 19-30 larvae/hill in Rabi rice (variety Lalat) fields at Choudwar, Baranga, Alani and Tangi, Orissa, India infesting 61-98% of the plants. Three bacteria viz. Pseudomonas aeruginosa (Pa1 and Pa2) and P. fluorescens (Pf) infected 62-98% of the larvae in different fields. No correlation was found among populations of the Pseudomonas spp. on the rice phyllosphere and larvae harboring the bacteria at different fields. The median lethal concentrations (LC₅₀s; ×10³ bacteria/mL) of Pa1, Pa2 and Pf were 4-4.2, 4.8-4.9 and 5.7-5.9, respectively, for the leaf piece assay and 4.8-4.9, 5-5.1 and 6.3-6.7, respectively, for the potted plant assay against second to fifth instar larvae. The median lethal times (LT₅₀s) were 2.1-2.4, 3.2-3.5 and 5.3-6 days for the leaf piece assay, and 4-4.7, 4.7-4.9 and 6.1-6.8 days for the potted plant assay with Pa1, Pa2 and Pf, respectively. The Pa1 and Pa2 were compatible, exhibited synergistic effect and co-inoculation reduced the LC₅₀ and LT₅₀ as compared to inoculation with individual organisms. The Pf had no synergism with Pa1 or Pa2, and therefore, the lethal values for Pf alone or with the other bacteria were similar. Fulfillment of Koch's postulates confirmed that Pa1, Pa2 and Pf were pathogens of C. medinalis.     

晋西北丘陵风沙区不同林龄人工柠条生长与繁殖动态特征

晋西北丘陵风沙区生态环境脆弱,是我国风沙活动危害最为严重的地区之一.本文以晋西北典型丘陵风沙区0(撂荒地)、6、12、18、40和50年生人工柠条为研究对象,分析了不同林龄柠条的土壤含水量、地上和地下生物量、个体形态特征、生长繁殖及光合生理特征,研究0～50年长时间序列人工柠条的生长和繁殖动态特征.结果 表明:人工柠条...     

七星瓢虫成虫对枸杞木虱的捕食作用

为了测定七星瓢虫成虫对枸杞木虱4种虫态的捕食作用,分别在室内测定七星瓢虫的捕食功能反应、种内干扰、自身密度干扰、捕食偏好性以及在田间七星瓢虫对枸杞木虱的捕食效果.结果表明: 七星瓢虫对枸杞木虱的捕食功能反应符合Holling Ⅱ型方程,其中对卵的最大捕食量为112.6粒,对1～2龄若虫、3～5龄若虫、成虫的最大捕食量分别为536、415和113.9头;田间罩笼试验结果证明,七星瓢虫成虫在其生长周期30 d内能使枸杞木虱总虫口密度下降80.1%;七星瓢虫对1～2龄枸杞木虱若虫的搜寻效率参数a=0.9451,处理时间参数T_h=0.001865,整体优于卵、3～5龄若虫与成虫,且在每皿100头的猎物密度下七星瓢虫的最大捕食率能达80.2%,益害比参考值为1∶100.七星瓢虫对枸杞木虱的捕食作用受自身密度的影响显著大于种内干扰.在混合猎物密度为每皿100头下,七星瓢虫更偏好木虱成虫,在密度为每皿300头下,七星瓢虫更偏向于木虱若虫.表明七星瓢虫是很有控制潜力的捕食性天敌,人工释放七星瓢虫成虫可有效取食枸杞木虱初孵若虫,降低木虱为害.