Overwintering and population dynamics of Bemisia tabaci biotype B in greenhouse during the spring in northern China

Since the sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B invaded southern China in the mid-1990s, it had spread to most other regions of the country, and become an important pest in agricultural and horticultural production. Investigations on overwintering of B. tabaci biotype B and its spring reproduction in northern China were conducted to determine the main factors that might contribute to an understanding of the population dynamics of this pest for developing improved pest control strategies. A cold hardiness test showed that when exposed for 10 h at −10 °C, mortalities of eggs, nymphs, and adults reached to 86.6%, 88.4%, and 100%, respectively, suggesting that it is probably impossible for feral populations of B. tabaci to survive in the winter under natural environmental conditions in northern China. A survey on vegetables, ornamental plants and weeds in greenhouses at Hebei Province and Beijing in northern China revealed at least 14 species of plants on which B. tabaci fed during the winter and spring. Lycopersicon esculentum Mill, Brassica alboglabra Bailey, Ficus carica L., Euphorbia pulcerrima Wild, and Hemelia patens Haence were the main host plants. Further research on the population dynamics of B. tabaci on three major greenhouse hosts; tomato, cucumber, and melon, indicated that densities remained at a low level during the winter, but increased steadily from February to March until migration into field crops in April. It is concluded that the control of the insect in greenhouse in winter and spring can play an important role for seasonal management of this pest in northern China.     

Seasonal abundance of the mirids, Lygus lucorum and Adelphocoris spp. (Hemiptera: Miridae) on Bt cotton in northern China

Lygus lucorum Meyer-Dür, Adelphocoris fasciaticollis Reuter and Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) are important secondary insect pests in cotton fields in northern China. The seasonal dynamics of their mixed populations on a transgenic variety expressing the insecticidal Bt protein Cry1A, and a cotton line expressing proteins of Cry1A and CpTI (cowpea trypsin inhibitor gene) were compared to seasonal dynamics on similar but non-transgenic varieties from 1998 to 2001. No significant differences were detected between population densities of these bugs on unsprayed normal cotton and unsprayed transgenic cotton. However, mirid damage on unsprayed transgenic cotton was significantly higher due to a reduced number of insecticide sprays against Helicoverpa armigera compared with the number of sprays in the normal cotton. This suggests that the mirids have become key insect pests in transgenic cotton fields, and that their damage to cotton could increase further with the expansion of the area planted to transgenic cotton if no additional control measures are adopted.     

Incidence and population fluctuation of Diuraphis noxia in Hungary

A yellow water pan trap was used to collect Diuraphis noxia (Mordvilko) in Central Hungary in 1989. In 1990 a Rothamsted-type suction trap collected 31 individuals. A D. noxia infestation was found in an autumn-sown wheat field in October 1990. The D. noxia population that overwintered was holocyclic. The life-span of fundatrices was 43.2 days at 18–22°C. The number of nymphs produced per fundatrix was 46.6. Average progeny numbers of first-generation apterae and alatae were 29.4 and 21.4, respectively. Second-generation apterae produced an average of 48.8 nymphs; 35.9% of nymphs were alatiform. The D. noxia population reached its peak on 3 July in the field, at which time the mean number of individuals per wheat plant was 3953.6. By 20 July, the wheat plants had matured and the D. noxia colonies had disappeared from the wheat.     

Bayesian salamanders: analysing the demography of an underground population of the European plethodontid Speleomantes strinatii with state-space modelling

Background  

It has been suggested that Plethodontid salamanders are excellent candidates for indicating ecosystem health. However, detailed, long-term data sets of their populations are rare, limiting our understanding of the demographic processes underlying their population fluctuations. Here we present a demographic analysis based on a 1996 - 2008 data set on an underground population of Speleomantes strinatii (Aellen) in NW Italy. We utilised a Bayesian state-space approach allowing us to parameterise a stage-structured Lefkovitch model. We used all the available population data from annual temporary removal experiments to provide us with the baseline data on the numbers of juveniles, subadults and adult males and females present at any given time.     

Effects of formamidines on the population growth of Tetranychus urticae Koch

The formamidines chlordimeform, amitraz, and N²-(4-n-butylphenyl-N′,N′-dimethylformamidine (BDMF) caused a reduction in survival and fecundity which significantly decreased the intrinsic rate of increase of population growth of the two-spotted spider mite, Tetranychus urticae Koch. Amitraz was the most potent inhibitor of population growth; chlordimeform was intermediate, and BDMF was least potent. Effects of amitraz on population growth were attributable mainly to its lethal action on the various life stages, whereas BDMF inhibited fecundity. The activity of chlordimeform was attributed to its lethality to life stages as well as to its inhibition of fecundity.     

Effectiveness of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. for control of the stem borer Chilo partellus (Swinhoe) in maize in Kenya

The fungus Beauveria bassiana (Bals.) Vuill. and insecticide trichlorfon were compared for the control of stem borer, Chilo partellus (Swinhoe) in field experiments at different times of infestation. Egg masses of C. partellus at the blackhead stage were pinned to the undersurface of the maize leaves. Two fungal formulations, conidial aqueous suspensions and a granular formulation, were applied. Compared with the untreated checks, the numbers of surviving C. partellus larvae were significantly reduced in treatments where B. bassiana was applied at a concentration of 10¹³ conidia ha⁻¹ as granules and as two aqueous spray formulations. No significant difference in numbers of stem borer larvae was found between trichlorfon and the untreated check. Fungus granules persisted longer in the field than did one spray of the fungus inoculum at the same concentration, or trichlorfon. A major increase in grain yield was obtained with two fungal sprays and with fungus granules both applied at a concentration of 10¹³ conidia ha⁻¹. A granular formulation of B. bassiana should be considered for the control of the stem borer C. partellus.     

Screening of Natural Plant Volatiles to Control the Potato ( Solanum tuberosum ) Pathogens Helminthosporium solani , Fusarium solani , Phoma foveata and Rhizoctonia solani

The potential utility of natural volatiles in various essential oils (EOs) from plants as fumigants to control potato tuber (Solanum tuberosum L.) pathogens was assessed. The antifungal effects of the volatiles at various concentrations were studied at 10 °C both in vitro using conidial suspensions of Helminthosporium solani, Fusarium solani var. coeruleum and Phoma foveata plated on agar, and in vivo by inoculating potato tubers. The effects of the volatiles on the mycelial growth of Rhizoctonia solani were also studied, but only in vitro. Vapours of many of the EOs tested exhibited some fungicidal activity but volatiles of garlic, Allium sativum, were, with few exceptions, most effective on all four pathogens in all experiments. An exposure time of at least 2 weeks was usually required for good control of disease development in vivo. Vapours of A. sativum never stimulated conidial germination, as was observed with some other oils, or damaged tubers, but those of Armoracia rusticana caused tuber collapse. Volatiles from thyme (Thymus vulgaris) EO showed antifungal activity in vitro on all four pathogens, but did not control F. solani, P. foveata or H. solani in vivo. In contrast, sage (Salvia officinalis) EO was ineffective against P. foveata and H. solani in the in vitro system, but controlled disease development in vivo at similar doses. The sometimes conflicting results obtained in the two test systems show that screening in vitro only is insufficient for evaluation of potent antifungal substances to be used in practice.     

抗啶虫脒椰心叶甲种群对椰甲截脉姬小峰和椰心叶甲啮小蜂抗药性选育的影响

筛选椰心叶甲对啶虫脒的抗药性,并以筛选后的椰心叶甲作为椰甲截脉姬小峰和椰心叶甲啮小蜂的寄主,观察这两种寄生蜂后代种群的抗性水平变化情况.结果表明,经筛选后,椰心叶甲的抗性水平增长了1.33倍,椰甲截脉姬小峰和椰心叶甲啮小蜂的抗性倍数分别增长了2.3倍和2.73倍,且椰心叶甲及其寄生蜂的后代种群抗性个体频率均显著高于初始种群.表明可利用椰心叶甲的抗药性来促进椰甲截脉姬小峰和椰心叶甲啮小蜂的抗性选育.     

Effect of pre-emergence herbicide mixtures on cowpea (Vigna unguiculata (L.) Walp) at Samaru, in northern Nigeria

Field experiments were conducted in the wet seasons of 2005 and 2006 to evaluate the effect of pre-emergence application of herbicides on cowpea. A mixture of metolachlor and prometryn at 1.25+0.08 kg a.i./ha was consistent in better growth and seed yield. However, application of mixtures of metolachlor and terbutryn at 0.99+0.50 kg a.i./ha and ametryn and terbutryn at 1.60+1.00 kg a.i./ha gave lower vigour score of the crop, higher crop injury, smaller canopy spread and lower seed yield. It can be concluded that the metolachlor and prometryn mixture gave good selective weed control and can be used instead of hand weeding in cowpea in northern Nigeria.     

The use of micro-beam X-ray diffraction for the characterization of starch crystal structure in rice mutant kernels of waxy, amylose extender, and sugary1

Micro-beam X-ray diffraction analyses were carried out on slices from wild-type rice and mutants. The method permitted the crystalline structure to be analyzed with less destruction of cells and fewer artificial effects that occur during the purification of starch from tissue and provided information concerning the localization and crystalline structure of starches distributed in the endosperm. The starch on kernel slices from the wild-type and waxy mutant, carrying a defect for the Granule-bound starch synthase I (GBSSI) gene, displayed an A-type of diffraction pattern; no difference in the crystalline patterns between starches located in the inner and outer region in a kernel were observed. A double mutant of the waxy and amylose extender (ae) mutant carrying a defect for the Starch branching enzyme IIb gene accumulated amylose-free B-type starches. The kernel slice from the double mutant of waxy and sugary1, mutated on the Isoamylase I locus, displayed an A-type diffraction pattern in the outer region and was amorphous in the inner region. A chain-length distribution analysis of polyglucans in kernels from wild-type and mutants showed that ae amylopectin had more long chains and less short chains than the wild-type and waxy amylopectin. On the other hand, the water-soluble polysaccharide in the inner region of the sugary1 endosperm had more short chains than the amylopectin in the outer region counterparts. These results indicate that branch chain length in amylopectin is crucial in determining the formation of A- and B-type starches.     

Effect of tillage intensity on population densities of Heterodera glycines in intensive soybean production systems

The effects of tillage on Heterodera glycines, the most important yield-reducing pathogen of soybean in the U.S., were examined in a long-term tillage and crop sequence study initiated in 1975 on a mollisol at Purdue University. Population densities of H. glycines were monitored under corn–soybean rotation and soybean monoculture in 2003 and 2004. Tillage treatments included: (A) fall moldboard plow + spring secondary tillage; (B) fall chisel plow + spring secondary tillage; (C) ridge tillage; and (D) no-tillage. In both years in the rotational plots, final population densities of H. glycines were proportional to tillage intensity. Under both soybean and corn rotation crops, highest population densities were observed with plowing + secondary tillage and lowest population densities were detected under no-tillage. In 2004, population densities in monoculture soybean soil declined with depth intervals in layers of 0–10, 10–20, and 20–30-cm depth under no-till, but not in plowed plots. Multiple regression analysis determined that the stratification of nematode population densities was strongly correlated to penetrometer resistance and potassium concentration of the soil. Tillage seemed to affect population densities of H. glycines by modification of the soil physical parameters in corn–soybean rotation plots. Reducing tillage intensity was beneficial in reducing population densities of H. glycines in rotational soils. Thus, the choice of tillage system can reduce the risk for damage by this widely distributed pathogen.     

Controlled-release insecticide granules, compared with other soil insecticides, for use against the termite, Macrotermes natalensis Haviland, in the establishment of Eucalyptus plantations

Following the banning of DDT and dieldrin, and pending the withdrawal of other organochlorine insecticides in many countries, there is a need to find alternative treatments against termites for the establishment of Eucalyptus forestry plantations. Controlled-release granules (CRG) of carbosulfan, carbofuran and phorate were nearly as effective as chlordane emulsifiable concentrate (0·6 g a.i./tree) in reducing attack on Eucalyptus grandis W. Hill ex Maiden by Macrotermes natalensis Haviland. The optimum application rate of CRG formulations was 1·0 g a.i./tree mixed with the surrounding soil at planting out. Changes in granule size and release rate had no discernable effect on the efficacy of the granules, nor was there any advantage in incorporating part of the dose in the seedling planting medium. Chlorpyrifos CRG was significantly less effective in protecting the trees. There was evidence that under dry soil conditions phorate CRG was ineffective. Of 11 other non-controlled-release insecticides tested, alphamethrin suspension concentrate at 0·1 g a.i./tree was the only non-organochlorine material as effective as the CRG formulations.     

Comparative efficiency of chemical compounds for in vitro and in vivo activity against Clavibacter michiganensis subsp. michiganensis, the causal agent of tomato bacterial canker

Bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis produces considerable economic losses in many countries because effective control measures are lacking. The extent to which bactericides control this disease effectively is low and has not yet been well documented for Southern European conditions. In this study the bactericidal effect of several products on this pathogen was assessed in vitro and in vivo in tomato plants under greenhouse conditions. Seven antibacterial substances (bronopol, copper sulphate, kasugamycin, oxolinic acid, oxytetracycline, streptomycin and 8-hydroxy-quinoline), three commercial formulates (Antibak RZ, an oligoelements mixture containing copper plus zinc; Orthopol, a potassium soap; and Param, a resistance inductor) and combinations thereof were tested. In vitro assessment showed that minimal inhibitory concentration (MIC) of antibacterial substances was between 4–8 μg ml⁻¹, except for copper sulphate with a MIC value of 150 μg ml⁻¹ and kasugamycin, which was not active at 500 μg ml⁻¹. MIC values of commercial formulates ranged between 5 and 40 μl ml⁻¹. Furthermore, combinations of 8-hydroxy-quinoline+copper sulphate, 8-hydroxy-quinoline+Antibak RZ, streptomycin+Antibak RZ and streptomycin+Orthopol showed a synergistic effect at sub-inhibitory concentrations. Treatments containing copper sulphate greatly reduced disease symptoms on plants sprayed with the bacteria, whereas streptomycin was less effective. In two independent trials, the percentage of leaves showing symptoms was significantly lower (2.4% and 11.9%) after treatment with copper sulphate combined with 8-hydroxy-quinoline at half-dose, than in inoculated controls (75.1% and 59.6%). These results were better than copper sulphate alone. However, plants inoculated by pricking rapidly developed systemic infection, which no product managed to control significantly, although several treatments did reduce symptoms. We conclude that copper sulphate combined with 8-hydroxy-quinoline may be useful in controlling external symptoms of this disease in greenhouses, and is environmentally friendly, reducing the amount of copper applied to crops.     

人工改造基因Cry1Abm的合成、原核表达及其抗虫鉴定

根据植物密码子的偏好性及使用频率,对苏云金芽孢杆菌Cry1Ab野生型基因的编码区序列进行优化和改造,改造后的Cry1Abm基因序列与原始序列同源性为66.2%,G+C含量由37.3%提高到62.7%。人工合成Cry1Abm基因,并将人工合成的改造后的Cry1Abm基因构建到原核表达载体pET28b中,构建原核表达载体pETAbm。将原核表达载体转入大肠杆菌BL21（DE3）中进行诱导表达,用诱导表达的蛋白进行饲虫（玉米螟）实验。结果表明,该蛋白对幼虫具有很强毒性,幼虫的死亡率高达86.63%,同时,存活幼虫的生长发育也受到明显抑制。该基因可以作为杀虫工程及培育转基因抗虫作物的候选基因。     

Natural enemies of the bagworm, Metisa plana Walker (Lepidoptera: Psychidae) and their impact on host population regulation

The bagworm, Metisa plana (Lepidoptera: Psychidae) is an important pest of oil palm, capable of being present as outbreak, which could cause a crop loss of up to 44%. Circumstantial evidence has long indicated that natural enemies play an important role in the population regulation of this pest. However, direct field data on the enemies themselves has been lacking.

A field study on a population of M. plana was made at PORIM Kluang, Johor, Malaysia from September 1988 to December 1992. The population of bagworm was initially high (late 1988, up to 38 larvae/frond, and in early 1990, up to 30 larvae/frond) but remained extremely low in the subsequent period (< 10 larvae/frond).

The population of M. plana was affected by both primary and secondary parasitoids and predators. Among the primary parasitoids, Dolichogenidea metesae was the most pronounced larval parasitoid of M. plana. This parasitoid was commonly attacked by hyperparasitoids, particularly Pediobius anomalus and Pediobius imbreus. A hypothetical life table constructed from the mortality figures of the declining part of the population during late 1988 confirmed that the natural enemies played a key role in suppressing the bagworm population.

The present study confirmed that overlapping generations were vital for the persistence of parasitoids of M. plana. The paper also suggested a possible need of alternative hosts. An active predator, Callimerus arcufer was also commonly encountered.     

Aromatic plants as a source of important phytochemicals: Vitamins, sugars and fatty acids in Cistus ladanifer, Cupressus lusitanica and Eucalyptus gunnii leaves

The phytochemical composition of three aromatic plants (Cistus ladanifer L., Cupressus lusitanica Mill. and Eucalyptus gunnii Hook. f) was evaluated, in order to valorize them as sources of nutraceuticals. Samples were analysed for ascorbic acid by spectrophotometric assay, tocopherols by high performance liquid chromatography (HPLC) coupled to a fluorescence detector, sugars by HPLC coupled to a refraction index detector (RID), and fatty acids by gas-chromatography (GC) coupled to a flame ionization detector (FID). The analysed plants contain very useful compounds such as vitamins (ascorbic acid and tocopherols), reducing sugars (glucose and fructose) and polyunsaturated fatty acids (linoleic, α-linoleic and eicosadienoic acids). Their vitamins and sugars could be useful in diseases related to oxidative stress, in dermatological applications or in cosmetics. The polyunsaturated fatty acids, including omega-3 and omega-6 families, detected in the plants constitute another important class of phytochemicals due to their generalized beneficial health effects.     

立枯丝核菌RsCAT基因的克隆及在菌核形成中的表达分析

在玉米纹枯病菌Rhizoctonia solani AG-1-IA中克隆CAT基因,利用生物信息学软件推测其理化性质、结构域、二级结构并构建该蛋白的三维模型,分析过氧化氢酶(CAT)在立枯丝核菌菌核形成中的作用。系统进化树分析表明,该蛋白与Laccaria bicolor同源性最高。利用real-time qPCR分析RsCAT在正常情况下和H_2O_2胁迫条件下的表达差异,结果表明,RsCAT在菌核形成过程中表达量持续升高,在第6天时表达量最高然后开始下降。在H_2O_2胁迫条件下,处理组CAT基因的表达量、菌丝生长速率均高于对照组,表明H_2O_2在菌核形成过程中作为一种信号分子促进了CAT基因的表达。初步判断RsCAT参与了玉米纹枯病菌菌核的形成,并且起到清除H_2O_2等自由基的作用。     

Survival of submerged larvae of cranberry girdler, Chrysoteuchia topiaria, in the laboratory

Flooding for several days in late summer or early fall is reported to control larvae of the cranberry girdler, Chrysoteuchia topiaria (Zeller) (Lepidoptera: Pyralidae), which feed on roots of cranberry, Vaccinium macrocarpon Aiton (Ericales: Ericaceae). During flooding, larvae float to the surface or remain submerged. Floating larvae are vulnerable to bird predation, but the fate of submerged larvae has not been studied. The factorially designed laboratory experiments reported here examined survival of submerged cranberry girdler larvae at water temperatures of 10, 15 or 20 °C, and flood durations of 24, 48 or 72 h. These conditions are characteristic of floods applied to western Canadian cranberry farms. In the first year of the study, more submerged larvae survived at 10 °C than at 15 or 20 °C, and more survived 24-h submersion than 48- or 72-h submersion; there was no difference between survival at 15 and 20 °C or 48- and 72-h submersion. In the second year of the study, when there were no 10 °C treatments, more submerged larvae survived at 15 than at 20 °C, and more survived 24-h submersion than 72-h submersion; survival after 48 h was not significantly different from survival after 24 or 72 h. In both years, there was no interaction effect of water temperature and duration of submersion: survival of submerged larvae decreased with longer flood durations and higher temperatures. Dissolved oxygen concentrations before submersion ranged from 5.8±0.1 to 6.3±0.2 ppm in the first year, and 5.5±0.1 to 5.7±0.1 ppm in the second. After submersion, dissolved oxygen concentrations in cups with larvae were approximately 0.5 ppm lower than in cups without larvae, suggesting that larvae continued to respire and use oxygen for some time after submersion. Results of the experiments are used to improve guidelines for flooding to control cranberry girdler larvae.     

小麦ArfGAP基因的克隆、半定量RT-PCR分析及原核表达

为明确小麦ArfGAP基因在非生物胁迫中所行使的功能,采用电子克隆技术分离普通小麦ArfGAP基因后对其在不同非生物胁迫下的表达特性进行了分析,并在大肠杆菌中表达了该基因。结果表明,从扬麦18号中克隆得到的TaArfGAP基因ORF全长为2 121bp。生物信息学分析表明,TaArfGAP蛋白氨基端方向存在一个典型的ArfGAP蛋白结构域,在亲缘关系上与山羊草、乌拉尔图小麦和短柄草较近,而与甘蓝等作物关系较远。半定量RT-PCR分析表明,TaArfGAP基因在干旱、PEG和NaCl胁迫下显著上调表达,但在高温条件下则显著下调表达。SDS-PAGE检测结果表明,IPTG终浓度为0.8~1.0mmol·L-1、诱导温度为24℃及诱导时间为10h时,在分子量大小为81kD左右可以得到较大的可溶性表达蛋白量,且与预期结果一致,说明TaArfGAP基因在原核表达体系中成功表达。