Abundance of Sitona lineatus L. (Col., Curculionidae) in peas (Pisum sativum L.): Effects on yield parameters and nitrogen balance

In a four-year study, we investigated the relationship between the damage to root nodules of organically produced pea (Pisum sativum L.) by the larvae of the pea leaf weevil (Sitona lineatus L.) and the abundance of adult weevils. In addition to studying natural infestations, we established artificial infestations within cages to assess the impact of different weevil densities on yield parameters and determinants of the nitrogen balance. Densities of 0.2 adult S. lineatus per plant (20 individuals per m²) reduced the number of seeds and pods per plant by 18% and 15%, respectively; seeds per pod and thousand-seed weight remained unaffected. A three-fold or five-fold increase in weevil abundance (13–40 or 20 to 100 individuals per m²) did not result in an additional reduction in yield. Moreover, the higher weevil abundance did not adversely affect the N-harvest index or soil nitrogen content. We suspect that the impact of adult S. lineatus on yield and nitrogen parameters is limited by the density-dependent mortality of the larvae. Survival of larvae in turn depends on the nodulation of the plants, which is largely regulated by the supply of water. The assumption that organic cropping systems are at specific risk from the pea leaf weevil was confirmed by increasing population densities during the study period. However, yield losses were independent of adult attack within a wide range of weevil abundance, which indicates the complexity of assessing larval damage based on adult infestation level. An enhanced intraspecific competition among larvae may account for the absence of linear relationships, considering that especially young instars failed to establish in root nodules at higher densities. We found that adult densities of 0.2 individuals per plant and subsequent larval densities of 7 individuals per plant resulted in destruction of 37% of the root nodules on primary roots, which was much below destruction values reported in other studies. In conclusion, we recommend an early monitoring of weevils and early initiation of control strategies because yield losses were caused by even low weevil densities. Finally, the tolerance of P. sativum to S. lineatus was influenced by the yield level, i.e., tolerance to S. lineatus decreased as yield increased.     

尼加拉瓜Chacocente野生动物保护区三种干旱落叶阔叶树种的天然更新动态(英文)

在尼加拉瓜Chacocente野生动物保护区对极又平荚木,毛风铃木和Lonchocarpus minimiflorus(Donn.Sm.)树种的天然更新进行了调查,并分析了更新异质性与地形坡度和入射光的关系。从2001到2003连续3年记录了高度10m以下和直径10cm以下的苗木和幼树。结果表明,3个树种的天然更新的个体数量的密度明显不同,并随时间存在差异。与极叉平荚木相比,L.minimiflorus和毛风铃木天然更新密度较大,只有毛风铃木种群密度方面的净变化是正相关。在树冠部分曝光的条件下,在缓坡和陡坡上更新较好,形成了分布聚集分布,尤其是L.minimiflorus和毛风铃木。仅靠天然更新不足以维持这些树种理想的立木数量,应当采取直接的恢复措施以促进天然更新过程。参47表3图3。     

Evaluation of the biocontrol potential of various Metarhizium isolates against green peach aphid Myzus persicae (Homoptera: Aphididae)

BACKGROUND: Twenty‐three isolates of Metarhizium anisopliae (Metschnikof) Sorokin and M. acridum (Driver & Milner) JF Bischoff, Rehner & Humber from non‐aphid host insects around the globe were evaluated for their aphid biocontrol potential, which is not well known. RESULTS: The apterous adults of green peach aphid Myzus persicae (Sulzer) were exposed to the fungal sprays of 11.5, 99 and 1179 conidia mm^?2 and blank control in three leaf‐dish bioassays. All the tested isolates except one were proven to be infective to the aphid species at 21 ± 1 °C and 14:10 h light:dark photoperiod, causing corrected mortalities of 10.1–95.3% at the high spore concentration. The data from ten isolates causing > 50% mortality at the high concentration were found to fit a time–concentration–mortality model well, yielding parameters for the estimates of their LC₅₀ and LT₅₀ that vary with post‐spray time and spore concentration respectively. Four isolates of M. anisopliae (ARSEF 759, 4132, 2080 and 576) had LC₅₀ values of 44–80 conidia mm^?2 on day 8 and LT₅₀ values of 4.9–6.8 days at 100 conidia mm^?2, with 91–98% of the killed aphids being well mycotised after death. CONCLUSION: The Metarhizium infectivity to M. persicae differs greatly among the tested isolates. The four mentioned isolates with desired virulence and sporulation potential are excellent candidates for microbial control of aphids. Copyright © 2010 Society of Chemical Industry     

热带次生林2种不同捕食策略地表蜘蛛的种内、种间竞争强度及土壤N的调节作用

为了进一步了解热带森林生态系统中不同捕食策略蜘蛛的种内、种间关系以及环境资源对其的调节作用。本研究采用室内微生态系统,对蜘蛛个体密度和弹尾目数量变化对不同捕食策略蜘蛛功能群种内、种间竞争关系的影响进行了研究。研究发现：在猎物弹尾目数量丰富的微生态系统中,蜘蛛个体数增加可导致主动捕食策略的游走型狼蛛死亡率显著升高,被动捕食策略的结网等待型地蛛生物量生长呈现明显的负增长,非同种蜘蛛组合的混合功能群中蜘蛛群落生物量的损失量显著增大。在弹尾目数量较少的微生态系统中,蜘蛛个体数增加使游走型蜘蛛的死亡率显著升高,生物量的损失量显著增大,但对结网型蜘蛛的死亡率和生物量生长没有显著影响,非同种蜘蛛组合的混合功能群中蜘蛛的死亡率显著增高、生物量则出现正增长状况。由此表明,游走型蜘蛛的种内竞争方式主要体现在个体死亡率,结网等待型蜘蛛则更多表现在生物量的损失上,不同种蜘蛛种间竞争受食物资源的影响,蜘蛛死亡主要以游走型蜘蛛为主。     

Are standing dead trees (snags) suitable as climate proxies? A case study from the central Scandinavian Mountains

Standing dead trees (snags) play important roles in forest ecology by storing carbon as well as providing habitats for many species. Moreover, snags preserved for hundreds of years can provide useful data to extend tree-ring chronologies used for climatological and ecological studies beyond the lifespans of living trees. Here we examined the growth patterns of Scots pine snags from the central Scandinavian Mountains, in relation to still living trees. Using changes point analyses, we showed that a majority (74%) of the snags displayed significant negative growth changes prior (on average 17 years) to death. Change points around the same years were also seen in living trees, but they recovered their growth. The average growth reduction of snags showing negative growth changes before death was 46%. In most cases the final growth change points coincided with very cold summers, or to a lesser degree to period of cool summers. It was suggested that pines ending up as snags were less resilient than the trees which continued living, and thus not able to recover after cold summer events. Since the snag growth reductions prior to death were partly unrelated to climate, care should be taken when using such data in dendroclimatological studies.     

Toxicity of selected biorational insecticides to Pulvinaria aurantii Cockerell and its predator,Cryptolaemus montrouzieri Mulsant in citrus field

The citrus cottony scale, Pulvinaria aurantii Cockerell, is the most important pest of citrus orchards in northern Iran in recent years. Owing to the harmful impacts of chemical insecticides, the use of biorational pesticides seems a safe and convenient way to control this pest. The present investigation was set up to study contact toxicity of various biorational and chemical compounds on the first, second instar nymph and overwintering adult of the citrus cottony scale, P. aurantii, and its predator, Cryptolaemus montrouzieri Mulsant under field conditions. The results indicated that the highest percentage of mortality of first instar nymph of the citrus cottony scale was observed in the Dayabon treatment of 9 and 10?ml/L, 100.0%?±?0.0% and the lowest percentage was observed in Palizin treatment of 1.5?ml/L, 34.7%?±?2.9%. In the second instar nymph, the highest mortality was seen in the Dursban treatment of 2?ml/L, 94.7%?±?2.4% and the lowest mortality in the Palizin treatment of 1.5?ml/L, 30.0%?±?2.3%. Also, for overwintering adults Dayabon 10?ml/L caused the highest mortality, 96.0%?±?4.0% during 24?h. In the case of ladybird insects, the highest and lowest percentage of mortality was observed in the Dursban treatment of 2?ml/L, 76.7%?±?8.8%, Dayabon 5?ml/L, and Palizin 2?ml/L, 3.3%?±?3.3%, respectively. The highest and lowest mortality rate of larvae of ladybird was estimated in the Dursban treatment of 2?ml/L, 83.3%?±?3.3% and Dayabon 5?ml/L, 3.3%?±?3.3%, respectively. Also, for overwintering predator adults Palizin 1.5?ml/L had the lowest mortality, 3.3%?±?3.3% during 24?h and this rate remain unchanged after 96?h after treatment. According to the results obtained, treatments with Dayabon 9 and 10?ml/L, can be a viable alternative to other high-risk chemical pesticides in addition to effectively controlling citrus cottony scale without having any adverse impacts on predator ladybird.     

Confirmation of bioactivities of active ingredients of nemarioc-AL and nemafric-BL phytonematicides

Nemarioc-AL and Nemafric-BL phytonematicides consistently reduced populations of plant-parasitic nematodes. The contribution of juvenile hatch inhibition to the overall reduction of the nematode numbers by the two phytonematicides, with cucurbitacin A and B as active ingredients, respectively, remains undocumented. The objectives of this study were to examine (i) the response of Meloidogyne incognita second-stage juveniles (J2) hatch to increasing concentration of cucurbitacins A and B, (ii) the potential saturation of J2 hatch when exposed to cucurbitacins for extended incubation periods, (iii) the minimum inhibition concentration for J2 hatch and (iv) the reversibility of J2 hatch inhibition.. Eggs of M. incognita were exposed to a series of purified cucurbitacin A and B concentrations over five incubation periods of 24, 48, 72?h and extended incubation periods of 7 and 10 days. Methanol-dissolved cucurbitacin A and B were each diluted and pipetted into well-plates making 11 concentrations, ranging from 0.0 to 2.5 µg.ml^?1 water solvent. Juvenile counts were made after 24, 48 and 72?h, with those for saturation assessed at 7 and 10 days. Thereafter, treatments were diluted five times, incubated again for 5 days and counted to establish reversibility of J2 hatch inhibition. In all incubation periods, treatment effects were highly significant (P?≤?0.01), with J2 hatch and cucurbitacin concentrations exhibiting quadratic relations. Minimum inhibition concentrations of the two cucurbitacins were between 1.13 and 1.40?µg.ml^?1. Treatment effects for reversibility to J2 hatch inhibition were not significant (P?>?0.05). In conclusion, J2 hatch inhibition could be one of the waysthrough which the two phytonematicides reduced population densities of Meloidogyne species.     

适合机械化收获的甘薯品种筛选及育种研究

甘薯机械化收获程度过低是阻碍中国甘薯产业健康发展的瓶颈,而农机农艺不配套则是导致无法很好地进行机械化收获的主要因素之一.笔者主要通过对5个薯形大小不同的甘薯品种进行机械化收获试验,分析了甘薯的薯形和大小对甘薯机械化收获的影响.结果表明:‘徐紫薯5号’的机械化收获破损率最小,因此该品种更适合田间机械化收获.同时,在调查参试品种的薯形、破损率和明薯率后,发现甘薯的薯形与其破损率具有极显著线性关系,扁率越大其破损率越大,反之则破损率越小,但对薯块明薯率没有显著影响.因此,在甘薯品种选育过程中,在考虑农艺性状的同时应当选择薯形扁率较小的品系.     

新疆褐牛与荷斯坦牛犊牛死亡率的影响因素分析

犊牛的健康状况关系到整个牛群的质量,降低犊牛的死亡率对提高牧场的效益具有十分重要的意义。为了掌握犊牛死亡率及影响犊牛死亡的因素,试验采取实地调查与资料分析相结合的方法,对新疆褐牛犊牛及荷斯坦牛犊牛死亡率进行了分析,通过Excel对某牛场近16年的7 157条产犊记录进行初步统计,根据新疆的气候特点划分季节,3~5月为春季,6~8月为夏季,9~11月为秋季,12~次年2月为冬季;品种为新疆褐牛犊牛和荷斯坦牛犊牛,年份从1999年到2014年分为16个水平,出生犊牛性别划分为公、母2个水平。利用SAS 8.1软件分析不同年份、品种、出生季节、犊牛性别及不同月龄等因素对新疆褐牛与荷斯坦牛犊牛死亡率的影响,结果表明,品种、年份、产犊季节和犊牛性别对新疆褐牛及荷斯坦牛犊牛死亡率有不同程度的影响,新疆褐牛的犊牛死亡率显著高于荷斯坦牛（P＜0.05）,1月龄时,新疆褐牛的犊牛死亡率显著高于荷斯坦牛（P＜0.05）;2006、2009、2010年的犊牛死亡率显著高于其他年份（P＜0.05）,在2011~2014年,犊牛的死亡率相对较少;冬季的死亡率显著高于夏季（P＜0.05）。降低犊牛的死亡率是牛群繁育过程中一个不可忽略的问题。犊牛的死亡率受到遗传和环境因素的共同影响,只有将各种环境因素给予合理控制,才能提高犊牛的健康水平。     

Early autumn soil disturbance decreases persistence of volunteer summer‐annual oilseed rape (Brassica napus)

Volunteer summer‐annual oilseed rape (sOSR; Brassica napus) is an ongoing concern in Canadian crop production. Large harvest seed losses and secondary dormancy in this species generate a persistent volunteer seedbank. Yield loss in subsequent crops, potential sOSR oil profile contamination and herbicide‐resistance trait introgression create a need for effective sOSR seedbank management. This field study evaluated the effects of timing and type of implement of post‐harvest soil disturbance and seeding a winter cereal on volunteer sOSR population persistence and demographic life‐stage transition rates at five locations in Manitoba, Canada. Following sOSR harvest and supplemental seed rain, seedbank densities ranged from 6770 to 15360 and 50 to 2610 seeds m^?2 among sites in autumn and spring respectively. In contrast to European research on winter‐annual oilseed rape, early autumn soil disturbance, shortly after sOSR harvest, was the best strategy to decrease volunteer sOSR persistence (3% population persistence from autumn to spring, compared with 6% in zero tillage). Substantial autumn seedling recruitment (38% of the autumn seedbank) and subsequent winterkill contributed to lower population persistence. Soil disturbance in spring stimulated spring seedling recruitment compared with other disturbance timings (11% and 3% of the spring seedbank, respectively). The implement used for soil disturbance and seeding winter wheat (Triticum aestivum) had minimal effect on population persistence. This research showed that timing of post‐harvest soil disturbance should be utilised as an effective tactic to decrease population persistence of volunteer sOSR via stimulation of autumn seedling recruitment and concomitant winterkill.