温度对抗性二点叶螨种群生命力和繁殖力影响的研究

将二点叶螨的三种性种群所产生的卵分别置于１６℃、２１℃、２６℃、３１℃、３６℃的条件下系统饲养。结果表明：温度对抗性二点叶螨的发育有明显的刺激效应,刺激效应从大到小依次为：产卵前期、卵期、幼螨期、成螨期、若螨期、产卵期,２６℃时刺激效应最低。与敏感种群相比,不同温度下的各抗性种群发育历期缩短率分别为：甲氰菊酯种群为２０．２８％、氧化乐果种群为２３．２１％、螨嗪菊酯种群为３５．６５％,各抗生种群在２６℃时的产卵期最长,产卵量最高。各抗性种群在不同温度条件下的产卵量和产卵期均低于敏感种群,表现出明显的生殖不利性。     

国槐截形叶螨的生物学特性及防治

北京地区国槐普遍受截形叶螨（ＴｅｔｒａｎｙｃｈｕｓｔｒｕｎｃａｔｕｓＥｈａｒａ）危害，从５月下旬至１１月上旬均有发生，危害盛期在７—８月份，有螨叶率市区达７０％，近郊区可达９０％以上。根据有效积温及气象资料推算，截形叶螨在北京地区每年发生１５—１７代。在２８℃、ＲＨ６７℃条件下，室内饲养，发育一代平均６．７天，在２７℃、Ｒｈ７２％条件下，雄成螨平均寿命７．５天，雌成螨１０．７天。截形叶螨以成螨越冬，其场所主要在树干及粗枝树皮裂缝内，极少部分在小校、树冠下草地及根际土壤中。早春用生物制剂—２．５％日光霉素１０００倍，１０％增效浏阳霉素２０００倍７３％克螨特乳油２０００倍及洗衣粉４００倍，碳酸氢铵颗粒剂１００倍防治，均能取得很好的效果。     

风雷激防治山楂叶药效试验

在苹果树山楂叶螨发生盛期喷布三种浓度的风雷激均收到了较好的防治效果，药后１５天的防效分别为９３．９％，９１．８％和８８．２％，防效级显著地高于三氯杀螨醇，且对果树安全。     

月斑鼓额食蚜蝇有效积温的研究

月斑鼓额食蚜蝇（ＳｃａｅｖａｓｅｌｅｎｉｔｉｃａＭｅｉｇｅｎ）是落叶松球蚜（ＡｄｅｌｇｅｓｌａｒｉｃｉｓＶａｌｌｏｔ）的重要天敌。１９９３年对其卵、幼虫、蛹的发育起点温度和有效积温分别进行研究。结果表明，卵发育起点温度和积温分别为６．０４±１．６１℃和４０．５５±２．６２日度，１～２龄幼虫期分别为４．９１±４．８４℃和６８．０２±３５日度，３龄幼虫分别为９．５６±０．７４℃和３６．８１±９．７２日度，蛹期分别为８．０６±２．３５℃和４０．５１±２６．０８日度。     

枣树红蜘蛛在自然变温下有效积温的研究

该文对枣粮间作地中枣树红蜘蛛──截形叶螨的卵、幼螨、前若螨、后若螨４个虫期在自然变温下的有效积温进行了研究，结果表明，卵的发育起点温度１４．８±１．５６℃，有效积温为３９．３５６３日度；幼螨发育起点温度为１１．５±２．７３℃，有效积温为２７．８４日度；前若螨发育起点温度为１１．０±２．０８９℃，有效积温为４２．１３４７日度；后若螨发育起点温度为１２．８±１．８７℃，有效积温为３７．１日度；世代发育起点温度为１１．２±１．８３６℃，有效积温为１１６．２４４６日度。年发生１３代。     

枣粮间作地枣树红蜘蛛种群数量动态规律研究

枣树红蜘蛛的优势种是截形叶螨，在不同类型的枣粮间作地中，种群数量动态规律基本相同，一年中都有两个高峰。在５月底前呈缓慢增长，６月上中旬枣、麦、玉米间作型和枣、棉间作型增长较快，达到一个小高峰，而枣、麦、大豆间作型仍增长缓慢。以后种群数量均维持平衡并有所减少。到７月初都先后迅速增值，７月中旬达到高峰，７月底数量急剧下降。８月中下旬数量又有回升，达到第二高峰，８月底种群数量又很快下降。调查中发现，枣树上的红蜘蛛数量动态与地面杂草、强度降雨、中耕锄草及天敌有关。     

几种杀螨剂对山楂及苹果叶螨的防治试验

我区果园每年均遭受不同程度螨类害虫的危害.危害后的果树,叶片退色变黄,并有早期落叶现象.发生种类,多以山楂叶螨为主.少数果园以苹果叶螨为主.无论那种为主,均伴有少量苜蓿苔螨.     

太行山浅山沟地山楂—小麦间作小气候研究

在辉县市北部太行山浅山区，有许多不规则的果、农间作园，其中以山楂－小麦间作园较为普遍，于春末、夏初，干旱、高温、多风灾害严重期，对山楂－小麦间作园和山楂不同行距密度与小麦地同步进行小气候测定，结果表明：气温和土温、温度日较差、风速均随山楂种植密度、单位面积覆盖度增大而减少，空气湿度也随树体加密而增大。山楂行距６ｍ、８ｍ、１０ｍ、对照日内最高气温分别是２８．７、２９．０、３１．１和３２．９℃，０ｃｍ地温日较差分别是８、１１、１７和２１℃，１６０ｃｍ高处上平均风速分别是０．７、０．９、１０．５和１１．７ｍ／ｓ．空气相对湿度，山楂－小麦间作园分别增加（与对照相比）７．６％、４．７％和２．２％。     

昆明地区华山松球蚜发生规律研究

１９８９年３月－１９９２年８月在嵩明县大哨及白邑两乡的５－７年生华山松幼林内设立标准地１０块,结合室内饲养,观察华山松球好的发生规律及各环境因子对其种群消长的影响。结果是：华山松球蚜在昆明地区１年发生８代;２月上旬当日均温达到８℃左右时越冬雌成虫开始产卵繁殖;１１月,当日均温降至５℃以下时雌应停止产卵;雌成虫分别于３月中旬、５月下旬、１０月中旬出现３次产卵高峰;降雨强度、天敌是影响林间球蚜种群的重要因子,其次是华山松的营养状况、温度。其化学防治时间以 ４月中旬－ ５月上旬以及 １０－ １１月最好, ５－ ６月以天敌控制。     

山楂扦播苗白绢病的研究

山楂白绢病是山楂扦插苗上常见的病害。病原菌为齐整小核菌（ＳｃｌｅｒｏｔｉｕｍｒｏｌｆｓｉｉＳａｃｃ．）。菌丝生长及菌核萌发的最适温度为２５～３０℃；在ｐＨ值２～１３范围内，菌丝均能扩展并形成菌核；河北地区该病从６月底开始发生，一直持续到９月上旬，其中７月上旬至８月中下旬为发病高峰期，高温高湿有利于病害发生。药剂试验表明：５０％退菌特、５０％克腐特、３６％甲醛、７０％代森锰锌对菌核萌发有明显抑制作用。木霉菌株Ｔ－８８能有效地抑制病菌的菌丝生长和菌核的形成，也能抑制菌核的萌发。     

Improving the evaluation of multiple-dowel-type connection strength

Our study focuses on predicting the ultimate short-term load carrying capacity of timber-to-timber connections with dowel-type fasteners. The wide range of possible configurations in practice makes the resolution of these values by tests unrealistic. Moreover, different current regulations do not consider some specific failure mechanisms. In many countries, the reduction of resistance involved by this phenomenon is taken into account by considering an effective number of dowels (n_ef) smaller than the actual number of dowels (n) in the connection. However, these different regulations disagree on the values of n_ef and on other points (spacing, partial coefficient of security, formulas). These discrepancies in design rules invite the fundamental research on this topic and, therefore, new methods are sought in order to estimate the load carrying capacities of the connections. In the light of these, our approach consists of predicting the load carrying capacity with the neural network numerical tool. The results obtained by this analysis tool are satisfactory, although the model remains complex. Subsequently, we focus on the simplification of this numerical model with classical regression techniques in order to implement it in a design code.     

<Emphasis Type="Italic">Ophiostoma</Emphasis> species associated with bark beetles infesting three <Emphasis Type="Italic">Abies</Emphasis> species in Nikko,Japan

Ophiostoma species were isolated from bark beetles and Abies mariesii, A. veitchii and A. homolepis attacked by the beetles in Nikko, Tochigi, central Honshu, Japan. One to two Ophiostoma species were frequently isolated from each species of bark beetle. Ophiostoma subalpinum was the most common associate of Cryphalus montanus. Ophiostoma sp. B as well as O. subalpinum was a common fungus associated with Polygraphus proximus. Ophiostoma europhioides was isolated from Dryocoetes hectographus and D. autographus as one of the common associates. Ophiostoma sp. J and Ophiostoma sp. S were frequently isolated from D. autographus and D. striatus, respectively. These fungi seem to have specific relationships with particular bark beetles. Ophiostoma sp. B, Ophiostoma sp. J and Ophiostoma sp. S have unique morphological characteristics and appear to be new species. Five trees of A. veitchii, approximately 43 years old, were inoculated with five Ophiostoma species to assess the relative virulence of the fungi. Ophiostoma subalpinum, Ophiostoma sp. B, and O. europhioides had relatively higher virulence than the other species studied.     

Parasitic Ichneumonoidea on the horse chestnut leaf miner, Cameraria ohridella (Lepidoptera: Gracillariidae) in Slovakia

Parasitic Hymenoptera from the suprafamily Ichneumonoidea attacking the horse chestnut leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) were studied in southwest Slovakia during 2000 and 2001. The search for such species resulted in the determination of eight ichneumonid species, Gelis agilis (Fabricius), Itoplectis alternans (Gravenhorst), I. clavicornis (Thompson), I. maculator (Fabricius), Scambus annulatus (Kiss), S. brevicornis (Gravenhorst), Zatypota percontatoria (Müller), Adelognathus sp. and a braconid Colastes braconius Haliday. The most abundant species was S. annulatus. All these species recorded are polyphagous and often facultative hyperparasitoids, except C. braconius, which departs from this norm in not being hyperparasitic. The presence of more diversified native parasitoids and hyperparasitoids from the Ichneumonoidea predicate a slow successive adaptation of the parasitoid fauna to the invasive host, Cameraria ohridella.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Insecticidal activity of certain medicinal plants

The methanol extracts of eight species of medicinal plants were tested for insecticidal activity in third instar larvae of Egyptian cottonworm (Spodoptera littoralis). All extracts showed a certain degree of larval toxicity. The extracts of Ocimum basilicum, Origanum majorana and Salvia officinalis appeared to be highly toxic. The extracts significantly affected the growth indexes [relative growth rate (RGR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD)].     

A new norlignan from Taxodium ascendens

A new norlignan, (2R,3R,4S,5S)-2,4-bis(4-hydroxyphenyl)-3,5-dihydroxy-tetrahydropyran (1), together with 9 known compounds were isolated from the branches and leaves of Taxodium ascendens. Their structures were mainly determined on the basis of MS, IR, 1D and 2D NMR spectral evidences. Methanol extract showed inhibitory activity on carbonic anhydrase II with an IC₅₀ value of 4.27 µg/ml, acetone extract and methanol extract inhibited activity of cathepsin B with IC₅₀ values of 2.12 and 3.71 µg/ml, respectively.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Pinus contorta growth in northern Sweden as affected by soil scarification

The aim of this study was to quantify the effects of different soil scarification methods on tree growth. Soil scarification influenced stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in a 17-year-old field trial in boreal Sweden. Soil scarification (disc trenching, mounding and ploughing) resulted in an average stem volume yield of 3.1 and 34.2 m³ ha^–1 on the poor and intermediate sites, respectively, while corresponding values for no soil scarification were 0.9 and 16.7 m³ ha^–1. In comparison to no scarification, ploughing increased volume yields by 500% on the poor site and by 200% on the intermediate sites. The ranking according to stem volume yield was ploughing > disc trenching = mounding no soil scarification. Averaged over the two sites, the mean annual increment of stem biomass was 219% and 145% higher (in d.w., 0.26 kg and 0.34 kg per sample tree) after ploughing compared with no soil scarification, for the average and dominant sample trees, respectively. Although not significant, the increased growth rate after soil scarification decreased the average stem basic wood density of the sample trees with 1.6% and 5.3%, at the poor and intermediate sites, respectively. In conclusion, soil scarification significantly increased the 17-year stem volume yield compared with no scarification. The results also indicate that the difference in stem biomass yield between ploughing and the other methods, especially no soil scarification, will increase even more in the near future.     

The potential use of different predatory bug species in the biological control of<Emphasis Type="Italic"> Frankliniella occidentalis</Emphasis> (Pergande) (Thysanoptera: Thripidae)

In the present study, the suitability of different predatory bug species, such as Dicyphus tamaninii Wagner, Macrolophus pygmaeus (Rambur), Orius albidipennis Reuter, Orius majusculus Reuter and Orius sauteri Poppius, for the biological control of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), were investigated. Development of the predatory bug species, their reproduction as well as their daily and total prey consumption over a 18-day period with F. occidentalis larvae or various stages of Tetranychus urticae Koch (Acari: Tetranychidae) individuals as prey species were studied during the experiments in the laboratory. In further experiments, the efficiency of D. tamaninii, M. pygmaeus, O. albidipennis and O. majusculus in controlling F. occidentalis under glasshouse conditions was investigated. Results showed that all the predators could develop under the experimental conditions with either F. occidentalis larvae or different stages of T. urticae as prey. When F. occidentalis larvae were offered as prey, the shortest duration of development was observed for O. albidipennis with a mean of 17.7 days, while D. tamaninii took the longest to develop with a mean of 36.3 days. With different stages of T. urticae as prey, the duration of development ranged from 19.3 days in O. albidipennis to 42.9 days in M. pygmaeus. Mean daily fecundity ranged from 0.8 eggs/female for O. majusculus to 2.2 eggs/female for O. sauteri with F. occidentalis larvae as prey and from 0.6, O. majusculus, to 2.3 eggs/female/day, O. sauteri, when different stages of T. urticae were offered as prey. Over the 18-day reproduction period, O. sauteri was the most fecund predatory species, laying a mean total of 31.6 and 31.3 eggs/female with F. occidentalis and T. urticae as prey, respectively. Daily consumption from F. occidentalis larvae ranged between 5.5 individuals consumed per day by O. majusculus and 29.1, by O. sauteri. When different stages of T. urticae were offered as prey, maximal consumption was observed in D. tamaninii with a mean of 29.0 individuals/day, while O. albidipennis consumed the least with an average of 8.1 preys/day. Over the 18-day prey consumption period, D. tamaninii consumed the highest mean number of 422.8 F. occidentalis larvae, while O. majusculus only consumed 98.8 larvae. Also, D. tamaninii had the maximum consumption of different stages of T. urticae with a mean of 522.4, while M. pygmaeus and O. albidipennis consumed the least, with an average of 146.1 and 146.0, respectively. The predatory bugs D. tamaninii, M. pygmaeus, O. albidipennis and O. majusculus significantly reduced the density of F. occidentalis on hybrids of Euphorbia milii, Serissa foetida and Saintpaulia ionantha in the glasshouse, which confirms their efficiency against this pest on different hosts under controlled climatic conditions.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.