Test Bench for the Mechanical Distribution of Predators to Control Insect Pests

In agriculture, chemical insecticides are widely used to protect crops from insect pests. Over a period of years, some insects such as Colorado potato beetle （CPB） succeed in developing resistance to most of the registered chemical insecticides. Consequently, heavy applications of chemical insecticides to control this pest become ineffective on a long-term basis and can lead to serious health and environmental problems. The use of natural enemies to control CPB is an interesting alternative to chemical means However, hand release of predators is not feasible on a large scale in the field. The main objective of this research study was to design and build a test bench to investigate the technical feasibility of mechanically releasing predators. The test bench consisted of a vertical chain conveyor mounted on two vertical shafts driven by an electric motor. Since the predators are small and fragile, they were placed in a specially designed container to preserve their physical integrity. Trials using this test bench showed that a carrier material was required, because most of the predators remained inside the container. The success of this mass predator release system will be highly valuable for the biological control of insect pests in many crops.

The Predatory Function of Three Spiders to Two Insect Pests in Rice Within a Multi-species Co-existence System

The prey-seeking behavior of three spiders (X1-Pirata subpiraticus, X2-Clubiona japonicola and X3-Tetragnatha japonica) for brown plant hopper (X4-Nilaparvata lugens) and rice spittle bug (X5-Cal-litettix versicolor) was investigated, as well as how interference between and within species occurred, by using a quadratic regression rotational composite design. Six predation models derived from the analysis of interactions among and within predators and preys were developed. The total predatory capacity of spiders on rice insect pests after coexistence for one day can be expressed as follows: Y3 = 32.795 + 2.25X1 + 1.083X2 + 0.5X3 + 10.167X4 + 3.167X5 - 1.67X12 - 2.42X22 - 3.295X32 - 0.045X42 + 0.455X52 - 3.125X1X2 + 0.375X1X3 -0.625X1X4 - 0.375X1X5 + 0.375X2X3 - 0.875X2X4 + 0.125X2X5 + 0.375X3X4 - 0.375X3X5 + 0.125X4X5. The principal efficiency analysis using this model indicated that increases in insect pest density significantly increased predation by predators; this was much greater than the effect of any single predator. X4 had a greater effect than X5; however, X4 and X5 demonstrated little interspecific interference and even promoted each other and increased predation rates as the densities of the two pests increased. Among the three predators, an increase in the density of X, had the greatest effect on the increase in predation, X3 had the second, X2 the third greatest effect. As predator density increased inter- and intra-species interference occurred, which were largely related to the size, activity, niche breadth, niche overlap and searching efficiency of the predators. X2 produced the greatest interference between different individuals and between any other predator species. X3 had the second greatest, which reduced predation levels at high predator densities. Because of these factors, the highest predation rate was obtained at a prey density of 120 per 4 rice-hills. The optimal proportion of the three predators in the multi-predator prey system was X1: X2: X3 = 5.6:1.3:4.1.

Dominant Natural Enemies of Sugarcane Pests and Their Protection and Utilization in Yunnan

This paper discussed and summarized the parasitic characters and the protection and utilization of 7 species of dominant natural enemies of sugarcane pests in Yunnan, China. Sugarcane pests are numerous and there are rich natural enemy resources in Yunnan sugarcane areas. There are more than 283 species of natural enemies against sugarcane pests in Yunnan, among which the dominant natural enemies with protection and utilization value and research significance include Trichogramma, Apanteles flavipes(Cameron) and Sturmiopsis inferens Townsend parasitic on sugarcane borers, Synonycha grandis(Thunberg), Lemnia biplagiata(Swartz), Chilomenes sexmaculata(Fabricius) and Thiallela sp catching and feeding on Ceratovacuna lanigera Zehntner, and Euborellia pallipes Shiraki preying on Saccharicocus sacchari(Cocherell), Dysmicoccus bohinsis Kuw, Trochorhopalus humeralis Chevrolat and Diocalandra sp. There is also one fungal parasite, namely Beauveria bassiana, which is widely distributed in nature, and can parasitize in a variety of sugarcane pests including sugarcane borers, Exolontha serrulata(Gyllenhal), Alissonotum impressicolle Arrow, T. humeralis and Otidognathus rubriceps Chevrola. It has a natural parasitism rate generally around 10% and certain natural inhibition effect on sugarcane pests. Reasonably protecting and utilizing natural enemies and giving full play to the natural regulation of natural enemies on pests are of great significance for protecting the ecological environment, maintaining the ecological balance of sugarcane fields, improving the comprehensive management level of pests, and promoting the sustainable development of sugar industry.

Impact Analysis of Genetically Modified (Bt) Cotton Genotypes on Economically Important Natural Enemies under Field Conditions

Field studies were conducted at Hisar during Kharif, 2009-2010 and 2010-2011 under natural and unsprayed condition. RCH 134 Bt, HS 6 (non Bt), H 1117 and Ganganagar Ageti (non Bt) were selected for the studies. The experiment was laid down in Randomized Block Design replicated thrice having plant spacing 67.5 × 60 cm. Among the bollworms, Erias spp. exhibited positive correlation with rainfall, minimum temperature and relative humidity morning hours significantly at 5 percent level whereas Helicoverpa and Pectinophora displayed positive relations only with evening hours relative humidity significantly while Spodoptera were significantly positive correlated with relative humidity of morning and evening hours. Bollworm complex was negatively correlated with all the weather parameters employed to study although being non-significant in case of rainfall, maximum and minimum of temperature, morning and evening hours of relative humidity. Among the sucking pests, leafhoppers, whitefly, thrips and aphids population showed significantly negative correlation with weather parameters. The comparison of natural bio-agents in cotton hybrids under study revealed that overall mean population of natural enemies were higher in Bt cotton hybrid as compared to non-Bt. These results confirm that use of genetically modified (Bt) cotton in lieu of conventional genotypes could positively impact non-target and beneficial insect species by preserving their host populations.

Effects of sesame nectar on longevity and fecundity of seven Lepidoptera and survival of four parasitoid species commonly found in agricultural ecosystems

Ecological engineering involves the use of plants to promote establishment, survival and efficiency of natural enemies in agricultural systems. Some plant species may be hosts or provide resources to some pest species. We assessed the risks and benefits of sesame （Sesamum indicum L.）, as a nectar source for seven economically important Lepidopteran pest and four parasitoid species in a range of vegetable crop systems. Our results showed that the mean Iongevities of arthropod parasitoids Pteromalus puparum （L.）, Encarsia sophia （Girault ＆ Dodd） and male Microplitis tuberculifer （Wesmael） were significantly extended when fed on sesame flowers compared to the water control. Sesame flowers had no effect on adult Iongevities and fecundities of six out of the seven Lepidoptera pest species tested except Plutella xyllostella （L.） females laid more eggs when fed on sesame flowers. It is likely that the increased fecundity is due to accessibility to nectar at the bottom of corolla because of their smaller body sizes. Our findings provide a first step towards better understanding of the risks and benefits of using sesame to implement ecological engineering for the management of vegetable pests.

Including predator presence in a refined model for assessing resistance of alfalfa cultivar to aphids

The aphid quantity ratio（AQR） is defined as the number of aphids on each cultivar divided by the number of aphids on all cultivars. AQR is based on the correlation between aphid populations and their host plants and is an important tool that has been utilized in evaluating Medicago sativa（alfalfa） cultivar resistance to aphids. However, assessment of alfalfa resistance to aphids can be confused by the presence of aphid predators, causing the assessment of plant resistance to aphids to be based on incorrect aphid population data. To refine the AQR and account for the effect of predators on aphid population assessments, we introduced a parameter ‘α＇, corresponding to the predator quantity ratio, and used αAQR as the ratio to quantify aphid populations. Populations of both aphids（4 species） and their predators（12 species） occurring in 28 M. sativa cultivars were sampled over two years at a research station near Cangzhou, Hebei Province, China. Results showed that the most suitable evaluation period was from May to June, as the aphid population was stable during this period. Compared with the AQR method, the predator population numbers based on the αAQR had a significant inverse relationship with aphid population numbers and the 28 cultivars were clustered into three classes： the resistant class, tolerant class, and susceptible class. In addition, 17 cultivars were reassigned when evaluated using αAQR. All numerical values calculated by αAQR were displayed as a Gaussian distribution, which showed that the 28 cultivars could be clustered into nine groups using a median value（±SE） of 1±0.1. Hence, ongoing alfalfa breeding trials will be assessed using the αAQR to establish a robust system that includes agronomic performance parameters in order to generalize the new method for further studies.

滨海稻区节肢动物天敌种类调查分析

为明确滨海稻区天敌情况,2021~2023年,于滨海稻区调查了水稻节肢类捕食性天敌的种类,结果表明,滨海稻区共捕获水稻节肢类捕食性天敌57种,隶属5目,21科。其中蜘蛛目12科,43种;蜻蜓目1科,2种;脉翅目1科,3种;半翅目3科,3种;鞘翅目4科,7种,以期为稻田害虫生物防治提供科学数据。

宁陵县酥梨节肢动物多样性及主要害虫发生规律研究

【目的】为酥梨害虫的科学防治提供依据。【方法】选取盛果期代表性梨园,分别对梨园内的害虫及其天敌种群、数量进行调查,对主要害虫及天敌在酥梨不同生长季节的发生动态进行分析。【结果】通过网捕、灯诱、性诱、黄板引诱等方法调查宁陵县酥梨梨园内生物种群多样性,结果表明害虫种群共分为8目31种,天敌有8目27种,梨园内生物多样性丰富;应用相对丰富度、优势集中指数、多样性指数、均匀度指数、丰富度指数分析生物多样性状况,结果表明害虫优势种群为梨二叉蚜、梨小食心虫和梨木虱;分析了梨小食心虫和梨木虱的种群发生动态。【结论】实践中应在传统病虫害防治的基础上,充分挖掘天敌对害虫的控制潜能,合理地保护和利用自然天敌。

带药移栽对水稻害虫防控的减药增效作用分析

【目的】以新型、高效、持效期长的杀虫剂三氟苯嘧啶和四唑虫酰胺为例,探究带药移栽对水稻害虫的防控效果及农药减量增效的实践意义。【方法】通过室内模拟秧苗带药移栽分别测定了1.95,5.85和9.75 mg a.i./m^(2)三氟苯嘧啶处理对褐飞虱Nilaparvata lugens和白背飞虱Sogatella furcifera成虫或若虫的毒力和持效期,并在浙江杭州和湖南衡阳两地评估了早、中、晚稻秧苗高剂量带药移栽处理对二化螟Chilo suppressalis和稻飞虱的田间防效以及不同施药模式对稻田寄生蜂种群动态的影响。【结果】室内经5.85和9.75 mg a.i./m^(2)三氟苯嘧啶处理的秧苗在移栽后35 d时使褐飞虱雌成虫和3龄若虫均能保持75%以上的校正死亡率,且5.85 mg a.i./m^(2)剂量处理在移栽后28 d时使白背飞虱雌成虫的校正死亡率大于80%;使用12.75和25.50 mg a.i./m^(2)四唑虫酰胺处理秧苗在移栽后35 d时对早稻二化螟为害的校正防效均在85%以上。综合浙江杭州和湖南衡阳两地中、晚稻田间试验结果表明,应用5.85 mg a.i./m^(2)三氟苯嘧啶和25.50 mg a.i./m^(2)四唑虫酰胺进行秧苗“送嫁药”处理可减少1~2次大田用药和98%以上的农药有效成分用量,同时还保持着与常规喷施相当的防效,并使寄生蜂总种类和总数量分别提高了29.0%~49.7%和61.2%~69.3%。【结论】秧苗移栽前施用防效优良且持效期长的杀虫剂能减少水稻前期的施药次数和用量,产生较好的经济和生态效益。本研究为利用带药移栽技术推行水稻病虫害的绿色防控提供了重要参考。

基于捕食性天敌及害虫种群动态筛选功能植物的研究

新兴的生态调控技术是利用非作物植物进行天敌生境管理的重要措施。为筛选出适宜增效捕食性天敌的功能植物,进而提高天敌对农林生态系统害虫的控制能力,本文通过追踪调查15种功能植物与对照杂草区域内节肢动物群落时序动态,比较了捕食性天敌及植食性害虫的累积量、益害比以及优势天敌类群与主要害虫关联性、时序动态变化。结果显示,绿豆Vigna radiata、紫花苜蓿Medicago sativa、蓖麻Ricinus communis、芥蓝Brassica alboglabra、罗勒Ocimum basilicum、芝麻Sesamum indicum上捕食性天敌累积量、益害比高于其他植物,且与主要害虫的关联性和时序变化关系明确,有益于优势天敌中华通草蛉Chrysoperla sinica、异色瓢虫Harmonia axyridis等种群,可以作为捕食性天敌的生境管理功能植物。本研究为今后进一步更好的筛选出应用于田间保护性生物防治的植物提供基础以及新思路。

江汉平原稻田主要害虫与天敌关系分析

【目的】本研究旨在调查分析江汉平原稻田节肢动物群落的物种组成以及主要害虫与天敌相互作用的关系,为制定水稻害虫绿色防控技术体系提供科学依据。【方法】2019-2020年通过吸虫器法和扫网法在水稻的分蘖期、孕穗期、齐穗期调查江汉平原监利市、潜江市、江陵县等市(县)28块稻田节肢动物物种种类与个体数量,采用主成分分析和灰色关联度分析法分析了各主成分对稻田节肢动物群落的影响以及主要害虫与天敌种群数量之间的关系。【结果】2019-2020年调查的江汉平原稻田节肢动物种类共169种,按照营养取食关系,将稻田节肢动物群落划分为4个亚群落,其中植食类6目33科57种,捕食类7目30科50种,寄生类2目15科44种,中性类5目16科18种。稻田节肢动物群落中对第1主成分贡献大的是白背飞虱Sogatella furcifera和黑尾叶蝉Nephotettix bipunctatus;对第2主成分贡献大的是淡翅小花蝽Orius tantillus和青翅蚁形隐翅虫Paederus fuscipes;对第3主成分贡献大的是稻纵卷叶螟Cnaphalocrocis medinalis和灰飞虱Laodelphax striatellus。与主要害虫稻纵卷叶螟种群数量关联度大的前3位天敌依次为:草间钻头蛛Hylyphantes graminicola>拟环纹豹蛛Pardosa pseudoannulata>三突花蛛Misumenops tricuspidatus。与主要害虫白背飞虱种群数量关联度大的前3位天敌依次为:华丽肖蛸Tetragnatha nitens>黑肩绿盲蝽Cyrtorhinus lividipennis>拟环纹豹蛛。【结论】稻田节肢动物群落构成差异主要是由优势植食性昆虫和优势捕食性天敌数量决定的。捕食动物草间钻头蛛种群数量与稻纵卷叶螟种群数量追随关系最为密切,对稻纵卷叶螟具有一定控制作用,华丽肖蛸的种群数量与白背飞虱种群数量追随关系最为密切,对白背飞虱具有一定控制作用。

美国白蛾天敌昆虫应用研究进展

美国白蛾是一种国际检疫性害虫,原产于北美。由于美国白蛾强大的扩散能力、较长的为害期以及快速繁殖等特性,目前已有35个国家报道了其入侵记录。自1979年美国白蛾在辽宁丹东发现以来,不断地向我国南方地区扩散。因此,根除全部种群已不可能,采取持续有效的生物防控策略是可行的途径。本文总结了国内外美国白蛾的捕食性和寄生性天敌种类,比较了不同地区和不同发生期美国白蛾天敌的多样性,并对利用本地天敌和引进原产地天敌防治美国白蛾的应用技术进行了归纳分析。原产地天敌对美国白蛾具有更强的适应性和攻击性,通过引进原产地天敌可望实现更加持续有效的控制作用。最后展望了天敌昆虫控制美国白蛾的应用前景。

春玉米间作豆科绿肥作物害虫和天敌种群的发生动态

为明确甘肃省河西走廊春玉米(Zea mays)间作豆科绿肥作物害虫和天敌种群的发生动态,建立优良的种植模式以控制玉米害虫,于2019年监测了春玉米间作针叶豌豆(Pisum sativum)、春玉米间作箭筈豌豆(Vicia sativa)和春玉米单作种植模式下害虫和天敌种群的发生动态。结果表明:在整个生长季节内,间作针叶豌豆的春玉米上二斑叶螨(Tetranychus urticae)和玉米蚜(Rhopalosiphum maidis)种群数量分别高达每100株8300.00和1611.33头,棉铃虫(Helicoverpa armigera)种群数量低至每100株40.00头;间作箭筈豌豆的春玉米虽然无二斑叶螨和玉米蚜发生,但棉铃虫种群数量高达每100株66.67头;并且,间作针叶豌豆或箭筈豌豆的春玉米上寄生蜂始见期早、种群数量高。甘肃省河西走廊春玉米间作箭筈豌豆有利于控制二斑叶螨和玉米蚜,但应注意防治棉铃虫;春玉米间作针叶豌豆有利于降低棉铃虫种群数量,但需注意防治二斑叶螨和玉米蚜。

植草带宽度对蜘蛛和步甲群落动态及比邻玉米田害虫发生的影响

农田边界植草带是农田系统各斑块间生物物种迁移和群落演替、物质和能量交换的主要区域,对维持农业生物多样性及提高农田生产力具有重要意义。基于作物-害虫-天敌互作有机整体对植草带宽度的响应,选取不同宽度植草带(2 m、4 m、6 m)及其比邻农田并以对应宽度作物边界作为对照,采用地表陷阱法对蜘蛛和步甲进行取样调查,探究植草带宽度对蜘蛛和步甲种群结构、迁移扩散规律以及对农田害虫控制潜力的影响。结果表明:植草带内蜘蛛和步甲个体数均显著高于对照条带,4 m、6 m植草带的蜘蛛和步甲多度显著高于2 m植草带,且物种丰富度和多度显著高于其对照条带。此外,不同宽度植草带蜘蛛和步甲群落存在较高的异质性,蜘蛛和步甲群落结构差异显著;在4 m和6 m植草带及其比邻玉米田内,蜘蛛和步甲多度在植草带和植草带与比邻玉米田交界处显著高于农田内部,且随距离的增加,蜘蛛物种多度呈显著降低趋势,植草带宽度和距离共同决定蜘蛛和步甲的空间分布;Monte Carlo检验结果表明,植草带宽度、植被Margalef指数对农田中蜘蛛和步甲群落结构的影响均达到显著水平,蜘蛛主要优势科和步甲主要优势种主要分布在6 m植草带比邻玉米田内;4 m、6 m植草带比邻的玉米田中蜘蛛和步甲对玉米害虫的益害比显著高于2 m植草带比邻的玉米田,且4 m、6 m植草带显著增加了玉米籽粒的百粒重及比邻农田的玉米总产量。本研究对植草带涵养捕食性天敌预防害虫发生的最适宽度进行探索,综合考虑植草带耕地占用、天敌涵养和生物控害潜力等因素,确定4 m宽度植草带是具有推广价值的农田边界模式。

不同杀虫剂防治苜蓿蚜虫效果及对捕食性天敌影响

为明确不同杀虫剂对紫花苜蓿蚜虫及其捕食性天敌的影响,本研究比较了吡虫啉、啶虫脒、烯啶虫胺、氟啶虫胺腈、吡蚜酮和螺虫乙酯6种杀虫剂施药后不同时间对苜蓿蚜虫的防治效果及其对捕食性天敌的影响。结果表明,喷药后至10d,6种杀虫剂的防治效果均在85%以上,之后防效均出现不同程度下降,喷药后20d~35d,吡虫啉、啶虫脒、烯啶虫胺和氟啶虫胺腈4种杀虫剂防效为19.17%~40.13%,吡蚜酮和螺虫乙酯防效为58.01%~71.32%,吡蚜酮和螺虫乙酯持续防控效果显著高于前4种杀虫剂。蚜虫和天敌发生动态趋势表明,喷药后蚜虫数量均迅速下降至低水平并保持到4月底;5月上旬吡虫啉、啶虫脒、烯啶虫胺和氟啶虫胺腈4种杀虫剂处理区蚜虫数量开始快速上升,同一调查时间蚜虫数量均显著大于吡蚜酮和螺虫乙酯处理区数量,而天敌数量和益害比却均显著小于吡蚜酮和螺虫乙酯处理区;吡蚜酮和螺虫乙酯防控蚜虫的同时可避免杀伤天敌,自然天敌捕食蚜虫亦抑制蚜虫数量增长,二者协同控制蚜虫危害作用时间长,为苜蓿蚜虫高效绿色防控提供科学依据。

沼液替代化肥对冬小麦田节肢动物群落结构与小麦产量的影响

为了研究等氮条件下沼液按不同比例替代化肥对冬小麦产量和麦田节肢动物群落结构的影响,2021—2022年在安徽农业大学农萃园设置大田试验,试验共设置5个处理:单施化肥、沼液替代20%、50%、80%和100%化肥,分别分析小麦产量和三类节肢动物的变化。结果显示:随着沼液替代化肥量的增多,害虫数量呈现减少趋势,天敌数量呈现先增后减的趋势。当沼液替代20%化肥时,土壤节肢动物密度最高。当沼液替代50%化肥时,多样性指数、均匀度指数以及天敌优势集中性指数最高。当沼液替代化肥达50%及以上时,小麦各产量指标均显著低于单施化肥。结论表明改厕沼液替代化肥比例宜控制在50%到20%之间,可为改厕沼液科学比例替代化肥提供理论参考。

害虫种群的发展与调控

作为自然界中种类和数量最多的动物类群,昆虫与人类生活息息相关。害虫给人类生产生活造成了严重危害,尽管人类长期与其进行斗争,但很难获胜。这主要是因为害虫种群在时空尺度上均易拓展,而人为干扰只是在局部起到一定的害虫种群数量调控作用。事实上除喷施化学药剂、布设诱集装置和采取营林及捕杀等人为干扰措施外,气候、寄主植物和天敌等其他生物也是害虫种群调控中的重要因子。基于害虫种群发生发展现状,在阐明害虫种群自然发展规律的基础上,重点从气候条件、寄主植物和天敌等方面介绍自然条件下害虫种群的抑制因子。通过综述目前常见的几种害虫种群调控途径,认为害虫种群调控需要考虑全部种群分布的区域、作用因子的短期致死率、持续作用时间等,并以最终累积的种群年总死亡率或世代总死亡率为重要指标。综合考虑多种生物和非生物因子,充分利用天敌等自然调控因子的作用,削减各因子之间的不利影响,是更好调控害虫种群的必要途径。

一类具有群体防御行为的庄稼-害虫-天敌模型的动力学分析

研究一类具有群体防御行为的庄稼-害虫-天敌模型的动力学性质.首先,给出了正平衡点的存在条件以及平衡点局部渐近稳定的条件;其次,利用规范型理论和中心流型定理系统分析了Hopf分支的相关性质,包括存在性、稳定性和分支方向等;最后,通过数值模拟验证理论分析的结果.

基于农田生境管理的农作物害虫生态防控研究进展

农业的集约化伴随着非作物生境的丧失,导致了农田生物多样性的锐减,削弱了天敌对农作物害虫的天然控制作用。害虫重发频发和农药残留污染严重威胁人类的食物安全。基于农田生境管理保育农田生物多样性,利用生物之间的平衡作用实现对农作物害虫的生态防控,是破解集约化农田生态与环境问题的关键,也是促进农业绿色可持续发展的根本途径。本文简述了农作物害虫生态防控的发展,系统归纳了农田生境管理的概念、原理、技术及应用进展,重点展望了非作物生境管理领域理论研究、方法技术和组织实践的发展方向,旨在为农作物害虫生态防控相关理论研究及应用实践提供参考。

商河县林业有害生物寄生性天敌昆虫和病毒及主要天敌的应用

1990-2023年通过采集林业有害生物进行饲养及历次普查和灯光诱集,共记述商河县寄生性天敌昆虫4目20科113种,以膜翅目Hymenoptera姬蜂科Ichneumonidae、茧蜂科Braconidae、姬小蜂科Eulophidae、螯蜂科Dryinidae种类最多;病毒有1纲1目1科3种。分别于1998~2023年陆续发表2新属、9新种、6中国新记录种、7山东新记录种;本文新报道汤氏茧蜂Townesilitus sp.为山东新记录属、种,斑足顶姬蜂Acropimpla pictipes(Gravenhorst)为山东新记录种。各类寄生性天敌昆虫和病毒中,杨潜姬蜂Celata populus对台安丝潜叶蜂Fenusella taianensis、杨小舟蛾颗粒体病毒山东毒株MisiGV-SD和黑卵蜂Telenomus sp.等对杨小舟蛾Micromelalopha sieversi有很强寄生控制作用;白蛾聚集盘绒茧蜂Cotesia gregalis、舞毒蛾黑瘤姬蜂Pimpla disparis追寄蝇Exorista spp.对美国白蛾Hyphantria cunea有较高寄生率,其他天敌则对控制一般性有害生物、维护生物多样性、保持生态平衡发挥了重要作用。