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.     

Responses of the stem borer larval endoparasitoid Cotesia flavipes (Hymenoptera: Braconidae) to plant derived synomones: Laboratory and field cage experiments

Laboratory and field cage experiments investigated the response of females of the stem borer larval endoparasitoid Cotesia flavipes to two synthetic synomone components, the terpenoid (E)-β-farnesene and the green leaf volatile, (Z)-3-hexenyl acetate, both compounds identified previously in headspace volatiles of maize plants damaged by stem borer (Chilo partellus). In dose response tests performed in a Y-tube olfactometer, parasitoids were significantly more attracted to the arms bearing 10 or 15 µg of (Z)-3-hexenyl acetate and (E)-β-farnesene than to the control arm. (E)-β-Farnesene was as attractive as the essential oil from the plant Hemizygia petiolata (Lamiaceae) rich in the same compound (80% relative amount). The plant essential oil elicited responses from females of the parasitoid comparable to those elicited by two positive controls, stem borer larval frass and adult parasitoid diet (20% honey solution), tested in the laboratory assays. In field cage trapping experiments, captures in traps baited with the terpenoid, the plant essential oil, (Z)-3-hexenyl acetate and the control of 20% honey solution, were not significantly different relative to captures in unbaited traps. Addition of the green leaf volatile (Z)-3-hexenyl acetate to the plant essential oil to yield a 1:1 two-component blend captured significantly more female parasitoids than traps baited with either of the two components alone. The results show that blends of green leaf volatiles and sesquiterpenoids may have potential in monitoring C. flavipes populations in the field.     

Reproductive compatibility of several East and West African Cotesia sesamiae (Hymenoptera: Braconidae) populations and their crosses and backcrosses using Sesamia calamistis (Lepidoptera: Noctuidae) as the host

The relative importance of the braconid Cotesia sesamiae, a gregarious larval parasitoid of lepidopteran stemborers, varies greatly with region in Africa; while the most common parasitoid of noctuid stemborers in eastern Africa, it is rare in western Africa. Thus, several strains of C. sesamiae from Kenya are envisaged for introduction into western Africa. The present study investigates the reproductive compatibility between four populations of C. sesamiae from West Africa and Kenya with the noctuid Sesamia calamistis as the host using reciprocal crosses as well as backcrosses of hybrid females with males of the parental populations. Searching time of the male for the female and mating period varied significantly with couple and ranged between 0.78-1.9 min and 3.4-12.8 s, respectively. Crosses that involved females from inland Kenya (KI) did not yield any female offspring. However, backcrosses of hybrid female bearing a KI male genome with a KI male yielded both female and male offspring. Thus, there was a partial reproductive incompatibility between KI and West African populations which suggested that the latter were infected with Wolbachia sp. However, this should not affect the efficacy of a population introduced from East into West Africa, as there is a high degree of sib-mating in this gregarious parasitoid species. It was concluded that the regional differences in the relative importance of C. sesamiae was due to differences in the insect and plant host range of the different populations.     

The influence of humidity on emergence in Dacnusa sibirica Telenga (Hymenoptera: Braconidae)

The effects of four humidities (33, 55, 76 and 93% relative humidity) and four ages (0–1, 2–3, 4–5, 6–7 days) of parasitized Chromatomyia syngenesiae puparia on adult emergence in the leafminer parasitoid Dacnusa sibirica were examined in the laboratory. Parasitized puparia harvested at 0–1 days were susceptible to low humidities resulting in a significantly reduced parasitoid emergence. Aging of the puparia appeared to protect the developing parasitoid from low humidities. Increasing humidity produced a corresponding increase in the longevity of the adult parasitoid.     

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.     

Susceptibility of Eldana saccharina (Lepidoptera: Pyralidae), Busseola fusca and Sesamia calamistis (Lepidoptera: Noctuidae) to Bacillus thuringiensis Cry toxins and potential side effects on the larval parasitoid Cotesia sesamiae (Hymenoptera: Braconidae)

Laboratory trials were conducted to determine the efficacy of four Bacillus thuringiensis (Bt) Cry toxins at five different concentrations (0.016, 0.08, 0.4, 2, 10 μg/mL) for controlling three lepidopteran stem-borer species (i.e., the pyralid Eldana saccharina and the noctuids Busseola fusca and Sesamia calamistis) as well as to evaluate their indirect effect on the braconid larval parasitoid Cotesia sesamiae. In addition, larvae from the treatments above, after having been parasitized, were either fed a contaminated (group 1) or a toxin-free (group 2) diet and compared with a control (i.e., parasitized larvae which have never fed on Bt-toxin). All Bt Cry toxins induced larval feeding inhibition. Compared with the control, significant mortality resulted at all concentrations and for all species of Lepidoptera. Cry1Ab was the most toxic with 10 days post treatment mortalities ranging from 81% in B. fusca and S. calamistis to 100% in E. saccharina. In contrast, Cry1Ac had comparatively low toxicity particularly for B. fusca and S. calamistis (e.g., respectively, 54 and 74% mortality at 10 days at the highest concentration). In the toxin-treated group 1, percentages of C. sesamiae cocoon-producing moth larvae were higher compared to group 2 and the control, whereas clutch size was higher than in group 2 but similar to the control. In both groups, 0.016, 0.08 μg/mL CrylAc yielded lower female-biased sex ratios than the control. It was suggested that paralyses of the moth larvae caused by the toxin may have facilitated parasitization leading to higher parasitism and clutch size.     

Effect of relative humidity of hot air on the heat resistance of Bacillus cereus spores

The heat resistance to hot air of spores of Bacillus cereus (ATCC 14579) attached to carriers of stainless steel or silicone rubber was investigated in a range from 1% to 100% relative humidity (RH). Apart from an initial stage, linear survivor curves were obtained for all relative humidities. Neither the attachment itself nor the material of the carrier had an influence on the resistance. A distinct maximum of heat resistance was found at 40% RH. At 122°C the rate constants at 40% RH were five orders of magnitude smaller than at 100% RH and two orders of magnitude smaller than at 1% RH. At relative humidities of more than 40% the rate constants were strongly temperature dependent, whereas at lower relative humidities they were less temperature dependent. No significant influence of the relative humidity on the Arrhenius activation energy was found within each humidity range. The mean values were 295 kJ mol^-1 for relative humidities of 60% to 100% RH and 165 kJ mol^-1 for 1% to 20% RH. The occurrence of a maximum is ascribed to the existence of two inactivation mechanisms, the first is retarded and the second is accelerated by a reduction of relative humidity. It is assumed that the first mechanism is a protein denaturation. The second mechanism may be an oxidative process.     

Influences of the complex of environmental temperature, relative humidity and air velocity on the body temperature of restrained mice (author's transl)]

Effects of the complexes of environmental factors, such as ambient-temperature, relative humidity and air velocity, on the body temperature were investigated in restrained mice. Observations were carried out before and after 60 min-exposure to various triple combinations among environmental temperatures of 15, 25 and 35 degreesC, relative humidities of 40, 65 and 90%, and air velocities of 0.2, 1.0 and 2.0 m/sec. The analysis of variance about the differences of body temperature revealed significant effects of the environmental temperature and the air velocity levels, while no significant effects were recognized of the relative humidity. Effects of the double factors, either the environmental temperature plus the relative humidity or the environmental temperature plus the air velocity, were significant at 5 or 1% level respectively. However, effects of the double factors the relative humidity plus the air velosity, as well as the triple factors were not significant. Under the environments consisted of triple factors, the environmental temperature of 20 and 25 degreesC, the relative humidities of 40 and 70% and the air velocities of 0.1 and 0.5 m/sec, significant effects at 1% level were recognized only in the environmental temperature levels. In the relative humidty or the air velocity levels, and the double or triple factor levels, no significant effects were recognized. From the results obtained, the effective temperature (Te) was indicated by the formula, Te=t+100x-v square root 38-t, in which were given the environmental temperature in t degrees C, the absolute humidity in x kg/kg and the air velocity in v m/sec.     

The effects of temperature and humidity on the nocturnal activity of different shell colour morphs of the land snail Arianta arbustorum

The noctural activities of the phenotypic shell colour morphy and age classes (adults and juveniles) of Arianta arbustorum were recorded 1 day week^-1 for 4 weeks in several laboratory microclimatic conditions. Six constant temperatures between 3 and 18C and four levels of relative humidities between 34 and 98% were maintained. A light regime of 16 h light: 8 h dark was used. There are highly significant differences in activity at different levels of adaptation temperature and relative humidity. The interaction between these factors is significant. There are no significant differences in nocturnal activity between the two phenotypic shell colours nor between the two age classes, but the interaction between morph and relative humidity is significant. The interaction between age classes and relative humidity is also significant. Yellows are more active than browns at high humidities, but less active at low. They are therefore likely to be behaviourally more responsive than browns in an environment of fluctuating humidities. This result is discussed in relation to the maintenance of the polymorphism.     

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.     

温度对取食玉米籽粒桃蛀螟生长发育、存活和生殖的影响

为了明确不同温度对取食玉米籽粒桃蛀螟生长发育、存活和生殖的影响,本研究依据年龄-龄期两性生命表理论计算了在21、24、27和30 ℃下取食玉米籽粒的桃蛀螟种群的生命表参数,并基于这些参数预测了未来80 d的种群动态。结果表明: 在21、24、27和30 ℃下桃蛀螟均能完成1个世代,随着温度升高,各阶段的发育历期缩短,且温度间差异显著。24 ℃下的平均单雌产卵量最高(116.7粒),成虫前期存活率最高(84.7%),雌虫占比最高(0.46),均显著高于其他温度。24、27、30 ℃下种群的内禀增长率分别为0.1059、0.1101、0.1045 d^-1,周限增长率分别为1.1117、1.1164、1.1102 d^-1,处理间差异不显著,但均显著高于21 ℃处理。21、24、27和30 ℃下的净增殖率(R₀)分别为17.3、53.7、36.9、19.8个后代个体,其中24 ℃时的R₀最高且显著高于其他温度处理。表明桃蛀螟种群在24～27 ℃下的存活率高、繁殖力大、雌性占比较高,是其生长发育、生存和繁殖的适合温度。     

基于生态位模型预测野生油茶的潜在分布

油茶(Camellia oleifera)是我国第一大木本油料作物, 野生油茶是油茶育种的宝贵遗传资源。本研究从中国数字植物标本馆(CVH, http://www.cvh.org.cn/)获得可靠的野生油茶分布点数据, 结合气象和土壤数据, 分别应用最大熵(MaxEnt)模型和规则集遗传算法(GARP)模型构建了野生油茶的生态位模型, 预测了野生油茶的潜在分布区, 并分析了影响野生油茶分布的主要环境变量。根据生态位模型预测的分布概率值, 对野生油茶的潜在分布区划分适生等级, 并与主要油茶产地的实际分布数据进行比较, 以验证适生等级划分的可靠性。结果表明, 两种模型的预测结果均能较好地反映油茶的分布情况。GARP模型预测的潜在分布区更广, 而MaxEnt模型的预测结果更精确。两种模型的预测结果均显示, 野生油茶的潜在分布区大部分位于中国, 但在中南半岛也有部分分布。MaxEnt模型预测的野生油茶在中国的潜在分布区与我国亚热带常绿阔叶林的分布区基本吻合, 高适生区主要可以分为3大区域: (1)东北-西南走向的武夷山脉及附近的群山区域; (2)东西走向的南岭山脉及附近的群山区域; (3)东北-西南走向的武陵山脉及附近的群山区域。MaxEnt模型分析显示, 影响野生油茶分布的主要环境变量是昼夜温差月均值、最干季降水量与最暖季降水量。油茶生长面积较大的地区绝大部分都位于MaxEnt模型预测的中、高适生区, 说明适生等级的划分较可靠。实地考察显示, 生态位模型的预测结果对于寻找野生油茶资源具有较高的参考价值。此外, 本研究也充分显示, 利用中国数字植物标本馆的植物分布数据, 结合相应的环境数据构建生态位模型, 有助于了解作物野生近缘种的地理分布。     

外来入侵菊方翅网蝽生物学特性及实验种群生命表

为了解近年来入侵我国的菊方翅网蝽的生物学特性,并为该昆虫种群在我国未来发展的趋势及防治提供科学依据,我们在温度(25±2) ℃、湿度(80±5)%、光周期L∶D=14∶10的实验室条件下,饲养、观察并记录了其各龄幼虫的形态特征,测定了该虫生长发育历期、存活率和产卵量等,构建了实验种群繁殖特征生命表,并计算了种群动态的相关参数.结果表明: 菊方翅网蝽的卵期为(14.58±1.17) d,若虫期为(14.88±1.45) d,成虫寿命为(59.88±5.85) d,单雌产卵量为(87.2±17.8)粒.该实验种群的内禀增长率(r_m)为0.05,周限增长率(λ)为1.06,世代平均历期(T)为46.11 d,净繁殖率(R₀)为11.88,种群加倍时间(t)为12.91 d;此外,在种群的稳定年龄组配中,若虫期占59.3%,成虫期占40.7%.预计菊方翅网蝽有可能会在中国进一步扩散并造成潜在的危害.     

Effects of relative humidity on enzyme activity immobilized in sol–gel-derived silica nanocomposites

Enzyme immobilization has attracted great interest in biotechnology processes. Herein we report the immobilization of urease from Canavalia ensiformis (jack bean) in sol–gel-derived silica nanocomposites. Urease activity, differential scanning calorimetry (DSC), nitrogen and water adsorption isotherms were used to characterize the effect of storage at various relative humidities on enzyme activity immobilized in sol–gel-derived silica nanocomposites. In this study, the nanocomposites consist of tetraethoxysilane, as inorganic silicate precursor, in combination with glycerol or trehalose as organic additives. Entrapped urease was more stable for all the formulations aged with a relative humidity of 80%. However, significant differences (p < 0.05) in enzyme activity recovered at this relative humidity were observed between samples with different formulations, reflecting the effect of additives during the immobilization process. The applications of biocompatible sol–gel-derived matrices can be further extended and utilized in the development of biosensors with immobilized biomolecules that can be used for long time periods by taking into account different factors, among which the storage relative humidity has permitted to greatly improve the stability of the immobilized urease.     

Multitrophic influences on egg distribution in a specialized leaf beetle at multiple spatial scales

Egg distribution in herbivorous beetles can be affected by bottom-up (host plant), and by top-down factors (parasitoids and predators), as well as by other habitat parameters. The importance of bottom-up and top-down effects may change with spatial scale.

In this study, we investigated the influence of host plant factors and habitat structure on egg distribution in the leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae), a monophagous herbivore on Salvia pratensis L. (Lamiales: Lamiaceae), on four spatial scales: individual host plant, microhabitat, macrohabitat, and landscape. At the individual host plant scale we studied the correlation between egg clutch incidence and plant size and quality. On all other scales we analyzed the relationship between the egg clutch incidence of C. canaliculata and host plant percentage cover, host plant density, and the surrounding vegetation structure. Vegetation structure was examined as herbivores might escape egg parasitism by depositing their eggs on sites with vegetation factors unfavorable for host searching parasitoids.

The probability that egg clutches of C. canaliculata were present increased with an increasing size, percentage cover, and density of the host plant on three of the four spatial scales: individual host plant, microhabitat, and macrohabitat. There was no correlation between vegetation structure and egg clutch occurrence or parasitism on any spatial scale. A high percentage of egg clutches (38–56%) was parasitized by Foersterella reptans Nees (Hymenoptera: Tetracampidae), the only egg parasitoid, but there was no relationship between egg parasitism and the spatial distribution of egg clutches of C. canaliculata on any of the spatial scales investigated. However, we also discuss results from a further study, which revealed top-down effects on the larval stage.     

Interaction between algae and seed germination in tropical dune slack species: a facilitation process

The importance of algae dune slack stabilisation has been extensively analysed, but little has been done regarding their potentially favourable role in germination and establishment of phanerogams. Dune slack is a seasonal freshwater habitat that depends on water table level fluctuation. Our hypothesis is that in these highly unpredictable systems, algae maintain a certain degree of humidity in the soil and, thus, permit phanerogam germination and establishment. The objective of this study was to compare the germination of four species characteristic of tropical dune systems: Cyperus articulatus L., Fimbristylis cymosa R. Br., Fuirena simplex Vahl and Rhynchospora colorata (L.) Pfeiffer, in different substrates and degrees of humidity. For germination trials, seeds of the four species were placed each on three substrates: in sand (control), filamentous algae on sand and cotton on sand. Two irrigation protocols were followed: continual watering (wet treatment) and weekly watering (dry treatment). Each week during a 21-week period, the number of germinated seeds from each species was recorded. The highest percentage of germination for the four species was observed during wet treatment. C. articulatus had the highest germination rate of the four species in algae (70%), and cotton (51%) on sand. Highest germination for F. simplex, F. cymosa and R. colorata took place in algae, although the percentages were very low. Differences in germination between the three substrates for these species were statistically significant (P<0.05). During dry treatment, C. articulatus was the only species that exhibited a significant germination, principally in algae and cotton. The results suggest that algae maintain substrate humidity and favour germination of the four species. This could be important in sand dune slacks where marked fluctuations in temperature and humidity occur.     

嗜卷书虱实验种群生命表的研究

在不同温度和湿度条件下对嗜卷书虱进行饲养,分别组建春实验种群特定年龄和特定时间生命表,并应用Morris模式及SWeibull频数分布以探讨温、湿度与嗜卷书虱种群数量变动的关系。结果表明,温、湿度对存活率的作用是影响该实验种群趋势指数（I）值最重要的因子,在适宜温、湿度条件下,种群存活曲线属DeeveyⅠ型,而在不太适宜条件下则属DeeveyⅢ型,理论上30.63℃时周限增长率（λ）最大,达1.0628倍／天,该虫发育和繁殖的最适温区为28-30℃,最适相对湿度在80％左右。     

Influence of shell colour on the mortality rate of the land snail Arianta arbustorum under different microclimatic regimes

The mortality of phenotypic shell colour morphs and age classes of the snail Arianta arbustorum in several microclimatic conditions was recorded. An analysis of variance was performed on five factors: adaptation temperature, relative humidity, shell colour, age class and test temperature. There were no significant differences in the mortality between different adaptation temperatures or relative humidities, but the interaction of these two factors was highly significant. There were significant differences in mortality rate between test temperature and age class. The mortality of the brown morph was higher than the yellow one at all adaptation temperatures (overall, P < 0.05). There were no significant differences between the mortality rates of the two morphs at different relative humidities. The mortality of the brown morph was higher than that of the yellow at six out of seven test temperatures. Juvenile snails survived significantly better than adults at all test temperatures.     

Morphology and germination characteristics of the cysts of Chattonella ovata (Raphidophyceae), a novel red tide flagellate in the Seto Inland Sea, Japan

To elucidate the mechanism of bloom outbreaks of Chattonella ovata (Raphidophyceae), we investigated the cysts of C. ovata and succeeded in finding them from the bottom sediments of Hiroshima Bay. The morphology of the cysts was mostly hemispherical in shape, with a diameter of ca. 30 μm and height of ca. 20 μm. The cysts were usually adhering to solid materials, such as diatom frustules, yellow-greenish in color and had several dark brown grains. The cyst wall was smooth and had no ornamentation. Because the morphological characteristic of the cysts was in general agreement with those of Chattonella antiqua and Chattonella marina, it was difficult to differentiate the cysts of these three species. Germination of the cysts of C. ovata was observed at temperatures from 17.5 to 30 °C, but not at 15 °C or below. The number of the germinated cysts increased with increasing temperature and the optimum temperature for germination was 30 °C. Although cysts of C. antiqua and C. marina germinated at temperatures from 15 to 30 °C, optimum temperature of germination was 22.5 °C. The lower limit and optimum temperatures for germination of C. ovata cysts was higher than for C. antiqua and C. marina. The role of cysts in the population dynamics of C. ovata is discussed.     

白音华矿区草地群落主要物种组成及空间分布

以内蒙古白音华矿区周边草地为对象,研究了矿区草地植物群落的主要物种组成及其空间分布特征。结果表明: 草地群落共出现55种植物,优势种为大针茅、黄囊苔草和糙隐子草,常见种有羊草、冰草和知母等,该6个物种的累计相对重要值为79.6%,其密度分别为 26.6、204.7、105.4、107.1、68.2和55.1株·m^-2。对6个主要物种的种群密度通过半方差函数进行模型拟合, 其种群分布分别符合指数模型、指数模型、指数模型、球状模型、线性模型和高斯模型;对其空间分布格局进行分析,各种群的结构比分别为59.2%、97.2%、89.1%、94.5%、62.6%和72.1%,表明黄囊苔草、糙隐子草和羊草种群的空间自相关性程度均较高, 主要受结构性因素影响, 而大针茅、冰草和知母种群主要受随机性因素影响。对分形维数进行分析发现, 大针茅、黄囊苔草、糙隐子草和冰草种群分布格局较简单,空间依赖性较强,而羊草和知母种群分布格局较复杂,空间依赖性较弱,结合2D及3D图看, 大针茅和知母呈现出梯度扩散,而黄囊苔草、糙隐子草、羊草和冰草则主要呈现斑块化分布,表明矿区草地群落主要物种的空间分布与开矿无显著关联性。