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1.
The aphid-pathogenic fungus Erynia neoaphidis, as dried fungus-infected aphids, was applied to caged plots of winter wheat infested with cereal aphids at two sites, one in Hertfordshire and the other in Hampshire, in 1983. In each trial, the fungus became established in the aphid populations in the treated plots even though conditions were drier than average and therefore sub-optimal for fungus spread. Treatment applied in the third week of June increased the proportion of infected aphids more than that applied two weeks later at one site, and the early application was the only treatment to have an obvious effect at the other. In spite of the observed effect of treatments on the proportion of infected aphids, the fungus failed to reduce the numbers of aphids relative to those in untreated plots, chiefly because in these plots many aphids were killed by fungi of the same species as that introduced and other related species from natural sources. Artificial introduction of E. neoaphidis acts too slowly and unpredictably to be likely to form a practical alternative to conventional insecticides for cereal aphid control.  相似文献   
2.
《Current biology : CB》2020,30(10):1801-1808.e5
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3.
1. The invasive ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is implicated in declines of native ladybirds with intraguild predation identified as an underlying mechanism, however, less studied are the effects on non‐coccinellid predators. Intraguild predation between Anthocoris nemoralis Fabricius (Heteroptera: Anthocoridae) and H. axyridis and the relative effects of inter‐ and intraspecific competition on predators on potted Tilia cordata Mill. was investigated, at two aphid densities. 2. Intraguild predation was unidirectional in favour of H. axyridis in Petri dishes although a low level of ladybird egg predation by A. nemoralis occurred. However, on trees intraguild predation was rare. 3. A positive effect of aphid density on H. axyridis weight gain, and increased survival when reared with A. nemoralis on potted trees indicated stronger effects of intraspecific competition on H. axyridis. Consistent suppression of aphids by ladybirds revealed their superior competition for aphids. 4. Anthocoris nemoralis weight gain was reduced when reared with H. axyridis on potted trees, indicating a potential for a sublethal effect through interspecific competition. Survivorship of A. nemoralis did not differ between con‐ and heterospecific treatments, but high aphid density enhanced A. nemoralis survival. Overall, high mortality among nymphs across treatments suggested effects related to both inter‐ and intraspecific competition for resources. 5. Results provide evidence of a sublethal effect by invasive H. axyridis through resource competition, suggesting that where these predators co‐occur, competitive interactions for shared prey are more likely to affect A. nemoralis populations than intraguild predation by H. axyridis.  相似文献   
4.
5.
The effectiveness of natural enemies to control pests can be enhanced through habitat manipulation. However, due to the differences in their ecology, generalist and specialist species may respond differently to the same manipulation. Moreover, interactions among natural enemies (i.e. cannibalism, intraguild predation, hyperparasitism) may complicate the assumption that a higher density of natural enemies would increase the level of biological control. We investigated the natural enemy guild composition and the predation rate along flower vs. grass margins at the edge of winter wheat (Triticum aestivum) fields in Denmark. Natural enemies were sampled by pitfall trapping and by suction sampling; predation intensity was measured using two different sentinel prey methods: artificial caterpillars made of plasticine, and sentinel aphid colonies. Specialist and generalist species responded differently to the two margin types: specialists (mostly parasitic wasps) were attracted by the flower margins, while generalists (ground beetles, rove beetles and spiders) were more active in grass margins. The number of artificial caterpillars attacked was significantly greater in grass margins (mean = 48.9%, SD = 24.3) than in flower margins (mean = 30.7%, SD = 17.4). We found a significant positive relationship between the number of artificial caterpillars attacked by chewing insects, and activity density for large (≥15 mm) ground beetles. Predation of sentinel aphids in wheat fields did not vary significantly in relation to margin type. Our results suggest that flowering margins may be beneficial for canopy‐active specialist natural enemies, but grassy margins are more useful for ground‐active generalist predators.  相似文献   
6.
  1. Field margin vegetation provides resources for natural enemies of crop herbivores. Thus, the design of plant mixtures improving resource provisioning is being discussed increasingly with respect to improving herbivore control.
  2. We set up a field experiment to assess the effect of (i) a wildflower strip optimized for nectar provisioning; (ii) a grass strip and (iii) spontaneous vegetation on herbivore regulation in oilseed rape and wheat. We also analyzed the attractiveness of plant species to natural enemies.
  3. The cover of flowering entomophilous plant species as a proxy of floral resource provisioning was twice as high in wildflower strips compared with the other strip treatments. Natural enemy densities were higher within and close to wildflower strips in the field. A corresponding effect on aphid predation and aphid infestation was observed. Significant negative correlations between natural enemy abundance in the margin and aphid infestation in the fields supported a causal relationship. The sown wildflower strip species were more attractive to natural enemies than spontaneous vegetation.
  4. The results of the present study demonstrate that improved nectar provisioning increased the predation and parasitism of crop herbivores. Further research on the spatio‐temporal dynamics of interactions is needed to determine why not all crop herbivores respond to an increase of natural enemies in field margins.
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7.
By means of a simulation model we are showing that the rates of migration can be related to avoidance of competition between relatives, especially in clonal organisms. This could result in a strong selective pressure for migration, even at a high cost. In addition, if the habitat is fragmented, migration can strongly affect local dynamics and result in a dramatic decrease of the densities in some places. In parthenogenetically reproducing organisms like aphids, the level of relatedness in local populations is expected to be very high and therefore they can serve as a good model group for testing these hypotheses. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
8.
利用生态位理论,对新疆塔城、伊犁两地区麦田的麦双尾蚜Diuraphis noxia (Mordvilko)、麦二叉蚜Shizaphis graminum (Rondani)、麦长管蚜Sitobion avenae (F.)和禾谷缢管蚜Rhopalosiphum padi (L.)等4种麦蚜生态位宽度和重叠度进行了估测和分析。在塔城麦田麦双尾蚜时间生态位宽度最大,麦双尾蚜和麦二叉蚜时间生态位重叠最大,竞争激烈。伊犁麦田禾谷缢管蚜时间生态位宽度最大,麦二叉蚜在空间生态位和时 空二维生态位上均占有明显的优势,麦长管蚜和麦双尾蚜的时间生态位重叠最大,麦长管蚜和麦二叉蚜在空间生态位和时 空生态位重叠最大。  相似文献   
9.
Aphid species within the genus Tuberculatus Mordvilko (Hemiptera: Aphididae) exhibit a variety of interactions with ants, ranging from close associations to non‐attendance. A previous study indicated that despite wing possession, ant‐attended Tuberculatus species exhibited low dispersal rates compared with non‐attended species. This study examined if presence or absence of mutualistic interactions and habitat continuity of host plants affected intraspecific genetic diversity and genetic differentiation in mitochondrial DNA cytochrome oxidase I (COI) sequences. Sympatric ant‐attended Tuberculatus quercicola (Matsumura) (Hemiptera: Aphididae) and non‐attended Tuberculatus paiki Hille Ris Lambers (Hemiptera: Aphididae) were collected from the daimyo oak Quercus dentata Thunberg (Fagales: Fagaceae) in Japan and examined for haplotype variability. Seventeen haplotypes were identified in 568 T. quercicola individuals representing 23 populations and seven haplotypes in 425 T. paiki representing 19 populations. Haplotype diversity, which indicates the mean number of differences between all pairs of haplotypes in the sample, and nucleotide diversity were higher in T. quercicola than T. paiki. Analysis of molecular variance (AMOVA) showed higher genetic differentiation among populations within groups of T. quercicola (39.8%) than T. paiki (22.6%). The effects of attendant ant species on genetic differentiation in T. quercicola were not distinguishable from geographic factors. Despite low dispersal rates, host plant habitat continuity might facilitate widespread dispersal of a T. quercicola haplotype in Hokkaido. These results suggested that following T. quercicola colonization, gene flow among populations was limited, resulting in genetic drift within populations. However, frequent T. paiki dispersal is clearly evident by low genetic differentiation among populations within groups, resulting in lower haplotype diversity.  相似文献   
10.
油菜田害虫调查及蚜虫防治药剂筛选   总被引:1,自引:0,他引:1  
田间调查试验表明,合肥市油菜田害虫的发生种类有15种,主要害虫为蚜虫类、油菜潜叶蝇Phytomyza horticola、小菜蛾Plutella maculipennis和菜青虫Pieris rapae。其中,以蚜虫类危害最重,全生育期在冬、春季各有一个峰值。油菜苗期以萝卜蚜、小菜蛾危害较重,后期以桃蚜Myzus persicae、油菜潜叶蝇危害较重。蚜虫防治药剂筛选试验表明,70%吡虫啉水分散粒剂防治蚜虫药效高,持效期长,且对油菜安全,10%烯啶虫胺可溶液剂和25%吡蚜酮可湿性粉剂防效也较好,可作为70%吡虫啉水分散粒剂的轮换药剂。  相似文献   
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