利用虫生真菌生物防治柑橘木虱的研究进展

柑橘木虱是柑橘黄龙病的重要传播虫媒。目前对柑橘黄龙病的防治尚缺有效的药剂和抗病品种,加强对柑橘木虱的防治,对控制柑橘黄龙病的蔓延具有重要意义。目前防治柑橘木虱多采用化学防治,杀虫剂的频繁使用造成了农药残留、环境污染、生物多样性被破坏和害虫产生抗药性等诸多问题,生物防治以其高效、低毒、低残留、不易产生抗药性等优点逐渐受到重视。昆虫病原真菌能侵入昆虫寄主体内,导致昆虫发病死亡,具有良好的病害流行潜力及生产应用便利性,利用昆虫病原真菌防治柑橘木虱具有广阔的发展空间。本文总结了用于柑橘木虱生物防治的虫生真菌种类,重点介绍了国内外利用球孢白僵菌、玫烟色棒束孢、淡紫紫孢菌、宛氏拟青霉、蜡蚧菌等虫生真菌在防治柑橘木虱中的应用,并对虫生真菌防治柑橘木虱的发展前景进行了展望,以期为柑橘黄龙病的防控提供借鉴。     

防治果园周边柑橘木虱控制黄龙病效果研究

在新种柑橘园中栽种柑橘无毒苗,定期监测和防治果园内柑橘木虱Diaphorina citri Kuwayama,防治时期为各新梢萌芽期,重点防治期为早夏梢期和早秋梢期;与此同时,调查柑橘园周围柑橘木虱寄主植物,每年2月下旬、5月上旬、8月下旬和11月下旬定期喷药,清除柑橘园周围寄主植物上的柑橘木虱。结果表明,果园内柑橘木虱和黄龙病均得到有效的控制,果园内柑橘木虱种群数量控制在很低的水平,最高为225头/公顷,最低为0;黄龙病发病率也很低,2008年为8‰,实施该技术后,发病率逐年下降,2012年降低到01‰。     

亚洲柑橘木虱与柑橘黄龙病菌互作的研究进展

亚洲柑橘木虱Diaphorina citri Kuwayama作为柑橘产业重要病害柑橘黄龙病的主要传播媒介,已经成为重点防治对象。该害虫与黄龙病之间的互作一直是相关研究的热点,本文就近年来该领域的研究进展做了一个总结,从亚洲柑橘木虱的获菌与传病机制、病原菌与柑橘木虱之间的互作以及病原菌感染寄主植物后对木虱的影响等方面进行了综述。期望为深入开展黄龙病相关研究、寻找防控新途径提供依据。     

佛冈县不同类型橘园柑橘木虱的种群动态

[目的] 明确佛冈县不同类型橘园柑橘木虱的种群动态,为当地柑橘木虱及柑橘黄龙病的防治工作提供科学依据。[方法] 通过2015-2016年的系统调查,对广东省佛冈县砂糖橘园的柑橘木虱种群消长动态进行研究,对比分析了不同处理措施对柑橘木虱种群数量的影响。[结果] 1-3月柑橘木虱发生危害较轻,随着嫩梢增多,其种群数量开始上升,6-9月为种群发生高峰期,期间出现多个发生高峰,10月之后种群数量逐渐进入消退期,种群数量维持在较低水平;2015、2016年佛冈县柑橘木虱的季节性消长动态基本一致,但种群发生量存在明显差别;3种不同类型橘园内柑橘木虱种群发生数量也存在显著差异,常年失管橘园柑橘木虱种群发生数量最高,常规水肥管理橘园次之,二者均显著高于常规水肥管理及化学防治橘园。[结论] 化学防治可在一定程度上控制柑橘木虱的种群数量,及时清理失管橘园对控制柑橘木虱和柑橘黄龙病传播至关重要。     

龙葵上柑橘木虱存活观察与黄龙病检测

柑橘木虱Diaphorina citri是毁灭性病害黄龙病的媒介,其寄主范围比较严格,仅为芸香科内的一些植物。研究发现,在自然状态下,柑橘木虱成虫可在柑橘园中常见茄科Solanaceae杂草-龙葵Solanum nigrum上停留。对比试验显示,木虱成虫在龙葵上的存活期最长可达45 d,而在假臭草Eupatorium catarium、含水海绵和无水海绵上分别为24 d、9 d和2 d;通过实时荧光PCR检测发现部分龙葵叶片中含有黄龙病病原菌。这些非寄主植物可能有助于柑橘木虱躲避不良环境或长距离迁移扩散,成为柑橘木虱和黄龙病的潜在库源。     

亚洲柑橘木虱的起源、分布和扩散能力研究进展

亚洲柑橘木虱Diaphorina citri Kuwayama是柑橘的毁灭性病害—黄龙病(huanglongbing,HLB)的传播媒介,是柑橘生产中最重要的害虫。本文综述了亚洲柑橘木虱的起源、分布和扩散情况,揭示中国亚洲柑橘木虱由南向北的扩散规律,为有效防治木虱、阻止黄龙病进一步蔓延传播、保障我国柑橘产业的健康发展提供依据。     

柑橘木虱抗药性研究进展

柑橘木虱Diaphorina citri Kuwayama主要危害柑橘等芸香科植物,传播柑橘黄龙病病菌。柑橘树感染黄龙病后,叶片黄化,果实早熟脱落,畸形,最终死亡,给柑橘产业带来了极大的损失。柑橘木虱对各种常见的杀虫剂已产生了不同程度的抗药性。本文从柑橘木虱的抗性测定方法、抗药性现状、交互抗性、抗药性机理和抗性治理等方面进行了综述,为今后柑橘木虱的防治提供一定的参考。     

黄龙病病菌在柑橘木虱体内的分布及感染动态

【目的】柑橘木虱Diaphorina citri Kuwayama是传播黄龙病病菌唯一的自然媒介昆虫,本文研究了黄龙病病菌在柑橘木虱各个发育阶段体内的分布以及感染动态,为有效防控柑橘木虱提供科学数据。【方法】利用常规PCR检测柑橘木虱若虫体内的黄龙病病菌,利用q RT-PCR和荧光原位杂交技术分别检测黄龙病病菌在柑橘木虱不同发育虫态体内的含量与分布形式。【结果】常规PCR可以在3-5龄若虫以及成虫体内检测到黄龙病病菌,而q RT-PCR除了3-5龄若虫外,还可以在2龄若虫体内检测到黄龙病病菌。卵和各龄期若虫中黄龙病病菌的含量是随着龄期的变大而不断增多。产卵盛期的成虫木虱体内黄龙病病菌的含量最高,显著高于产卵前期以及产卵后期。荧光原位杂交技术可以检测到4龄、5龄若虫及成虫体内的黄龙病病菌分布形态,病菌在若虫主要分布在U型含菌体内,而在雌雄成虫体内均是散布型分布。【结论】柑橘黄龙病在柑橘木虱的2-5龄若虫及成虫中都有感染,但其含量与分布形式因发育阶段不同而有显著差异。     

柑橘木虱抗药性研究进展

柑橘木虱Diaphorina citri Kuwayama主要危害柑橘等芸香科植物,传播柑橘黄龙病病菌。柑橘树感染黄龙病后,叶片黄化,果实早熟脱落,畸形,最终死亡,给柑橘产业带来了极大的损失。柑橘木虱对各种常见的杀虫剂已产生了不同程度的抗药性。本文从柑橘木虱的抗性测定方法、抗药性现状、交互抗性、抗药性机理和抗性治理等方面进行了综述,为今后柑橘木虱的防治提供一定的参考。     

亚洲柑橘木虱传播黄龙病菌的特性与机制研究进展

黄龙病Huanglongbing(HLB)是世界性的重大柑橘病害,在中国主要由亚洲柑橘木虱Diaphorina citri Kuwayama传播。该害虫的传病特性与机制一直是相关研究热点之一。本文综述了近些年该领域的研究成果,包括亚洲柑橘木虱传播黄龙病的方式、传病过程与机制,以及影响传病效率的因素等方面,为该木虱及黄龙病的防控与深入研究提供参考。     

Asian citrus psyllid,Diaphorina citri,vector of citrus huanglongbing disease

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is an important pest of citrus because it transmits phloem‐limited bacteria [Candidatus Liberibacter spp., notably Ca. L. asiaticus (LAS)] associated with huanglongbing (HLB; citrus greening disease), currently considered the world's most serious disease of citrus. Asian citrus psyllid transmits LAS in a persistent manner and, although the rate of LAS transmission by ACP individuals usually is low, HLB can spread rapidly in a citrus grove and the geographic range of the disease is expanding, threatening citrus industries in new areas. Intensive chemical control of ACP is the primary management strategy currently advocated for HLB, but this strategy is costly, unsustainable, and generally ineffective. The scientific community is searching aggressively for solutions to HLB on many fronts, but it could still be years before solutions are found and implemented. Plant resistance to LAS is one area of research being pursued, whereby traits that confer resistance are identified and incorporated into citrus germplasm through conventional or transgenic methods. It remains to be seen if a solution to HLB can be found that specifically targets ACP, but research on ACP has been stepped up in a number of areas, notably on ACP–LAS–plant interactions, on host plant resistance to ACP, and on molecular methods of silencing ACP genes to induce mortality or to block its ability to transmit HLB‐causing bacteria. Advancements in these and other research areas may depend greatly on a better understanding of basic ACP biology and vector–pathogen–host plant interactions at the molecular, cellular, and community levels. Here, we present an updated review of ACP and HLB with an emphasis on the problem in Florida.     

Influence of limiting and regulating factors on populations of Asian citrus psyllid and the risk of insect and disease outbreaks

Diaphorina citri, known as the Asian citrus psyllid (ACP), is the insect vector of a devastating citrus disease (huanglongbing; HLB), which has caused billions of dollars in damage in Florida since its detection in 2005. Data from long‐term monitoring programs in two Florida citrus groves were used to assess ACP demography and population ecology, which is needed to implement more effective management strategies for HLB. Seasonal patterns and correlations between ACP density estimates and a suite of environmental and community indicators, previously shown to influence ACP demography, were described and interpreted. Data were evaluated for evidence for spatial clustering and density‐dependent recruitment of ACP in a major outbreak event using Taylor power law analysis and by fitting a stochastic Beverton–Holt recruitment model using state‐space approach. Strong evidence for density‐dependent recruitment and spatial clustering was found and should be considered for future modelling work as it can greatly influence ACP populations by affecting their growth rates, dispersal behaviour and morphology, as well as HLB transmission. Observations of ACP density and dispersion in space and time, along with the estimated parameters from the Beverton–Holt model, suggested that intraspecific competition for resources may initiate both local, then widespread dispersal process, thus affecting grove‐wide and area‐wide HLB transmission. When these results were synthesised with those of parallel studies, the removal of several of these regulating factors in a single year could lead to widespread disease of the entire crop in a grove, and likely surrounding groves as well. We provide the first field evidence of the consequences of back‐to‐back ACP colonisation on the rapid spread of the HLB in a grove (a mechanism previously demonstrated in laboratory settings). We stress the importance of proper integrated pest management and area‐wide management to prevent such outbreaks.     

Presence and abundance of Diaphorina citri in Murraya paniculata in urban areas free of huanglongbing in Brazil

Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is the vector of the bacterium Candidatus Liberibacter sp., a quarantine pathogen in citrus production areas such as Australia, Europe, and northeast Brazil, associated with huanglongbing (HLB). The psyllids’ preferred host is Murraya paniculata (L.) Jacq. (Rutaceae), an ornamental plant native to Asia and Oceania, and commonly found in urban areas next to citrus groves around the world. As there are insecticide application restrictions for urban areas, monitoring and use of biological control to suppress ACP are essential for an area-wide HLB management strategy, especially for production areas predominantly composed of small citrus farms. For this, it is necessary to understand the occurrence cycles of ACP and vegetative flush of the ornamental host. This study characterized the occurrence cycles of M. paniculata flush shoot and accumulated rainfall, and the association with ACP presence (proportion of monitored trees) and abundance (per tree) in a Brazilian urban area free of HLB. A 3-year time series was constructed using spectral and co-spectral analysis. Spectral analysis showed the occurrence of at least seven flush shoot cycles of M. paniculata, nearly 10 ACP presence and abundance cycles, and monthly cycles of accumulated rainfall. Cycles of ACP presence were associated with ACP abundance, with ACP presence cycles occurring around 7 days before ACP abundance cycles and the correlation and co-spectral analyses indicated an almost simultaneous occurrence of the main cycles of M. paniculata flush shoots and ACP occurrence. These findings will facilitate the development of an ACP biological control program based on parasitoid releases in urban areas in HLB-free citrus groves.     

Repellency of forty‐one aromatic plant species to the Asian citrus psyllid,vector of the bacterium associated with huanglongbing

Huanglongbing (HLB) is the most devastating citrus disease worldwide. The organism associated with the disease is spread by an insect vector, Diaphorina citri, commonly known as Asian citrus psyllid (ACP). Current management of HLB relies either on physical removal of the infected plants or on chemical control of ACP. Both methods are costly and not overly effective. In addition, public concerns regarding insecticide residues in fruit have greatly increased in recent years. It has been hypothesized that plant volatiles could act as repellents to ACP, thus reduce the incidence of HLB. To test this hypothesis, the repellency of fresh tissues of 41 aromatic plant species to ACP was investigated. The repellency of individual species was determined using a Y‐tube olfactometer. Our results showed that volatiles of five plant species were highly effective in repelling ACP with repellency as much as 76%. Among these, the tree species, Camptotheca acuminate, and the two shrubs, Lantana camara and Mimosa bimucronata, could potentially be planted as a landscape barrier. The two herbs, Capsicum annuum and Gynura bicolor, could potentially be used as interplantings in orchards. This is the first time that the repellency of fresh tissues from a diverse range of plant species to ACP has been determined. Although further field evaluation of various interplanting regimes and landscape barriers are needed to assess their effectiveness, our results showed that these aromatic species, being highly repellent to ACP, offer great potential as more cost‐effective and environmentally sustainable alternatives to the current methods of managing HLB.     

<Superscript>1</Superscript>H NMR analysis of <Emphasis Type="Italic">Citrus macrophylla</Emphasis> subjected to Asian citrus psyllid (<Emphasis Type="Italic">Diaphorina citri</Emphasis> Kuwayama) feeding

The Asian citrus psyllid (ACP) is a phloem-feeding insect that can host and transmit the bacterium Candidatus Liberibacter asiaticus (CLas), which is the putative causative agent of the economically important citrus disease, Huanglongbing (HLB). ACP are widespread in Florida, and are spreading in California; they are the primary mode of CLas transmission in citrus groves. To understand the effects of ACP feeding, different numbers of ACP [0 ACP (control), 5 ACP (low), 15–20 ACP (medium), and 25–30 ACP (high)] were allowed to feed on Citrus macrophylla greenhouse plants. After 7 days of feeding, leaves were collected and analyzed using ¹H NMR. Metabolite concentrations from leaves of trees with ACP feeding had higher variability than control trees. Many metabolites were higher in concentration in the low ACP feeding group relative to control; however, leaves from trees with high ACP feeding had lower concentrations of many metabolites relative to control, including many amino acids such as phenylalanine, arginine, isoleucine, valine, threonine, and leucine. These results suggest ACP density-dependent changes in primary metabolism that can be measured by ¹H NMR. The implications in plant defense are discussed.     

Botanicals,selective insecticides,and predators to control Diaphorina citri （Hemiptera： Liviidae） in citrus orchards

The Asian citrus psyllid （ACP） Diaphorina citri Kuwayama vectors pathogens that cause huanglongbing （HLB） or citrus greening devastating and economically im- portant disease present in most citrus growing regions. Young citrus shoots are required for psyllid reproduction and development. During winter citrus trees produce little or no new growth. Overwintering adults reproduce in spring on newly emerging shoots also attractive to other pests and beneficial insects. Botanicals and relatively selective insecti- cides could help to conserve beneficial insects and reduce pest resistance to insecticides. Sprays of Azadirachtin （Neem）, Tropane （Datura）, Spirotetramat, Spinetoram, and broad- spectrum Imidacloprid were evaluated to control ACP in spring and summer on 10-year-old ＂Kinow＂ Citrus reticulata Blanco trees producing new growth. Psyllid populations were high averaging 5-9 nymphs or adults per sample before treatment application. Nymphs or adults were significantly reduced to 0.5-1.5 per sample in all treatments for 3 weeks, aver- age 61%-83% reduction. No significant reduction in ladybeetles Adalia bipunctata, Ane- glei scardoni, Cheilomenes sexmaculata, and Coccinella septempunctata was observed. Syrphids, spiders and green lacewings were reduced in treated trees except with Tropane. Studies are warranted to assess impact of these predators on ACP and interaction with insecticides. Observed reduction in ACP populations may not be enough considering its reproductive potential and role in the spread of HLB. Follow-up sprays may be required to achieve additional suppression using rotations of different insecticides.     

Differences in Stylet Sheath Occurrence and the Fibrous Ring (Sclerenchyma) between xCitroncirus Plants Relatively Resistant or Susceptible to Adults of the Asian Citrus Psyllid Diaphorina citri (Hemiptera: Liviidae)

The Asian citrus psyllid (ACP, Diaphorina citri, Hemiptera: Liviidae), is the principal vector of the phloem-limited bacteria strongly associated with huanglongbing (HLB), the world’s most serious disease of citrus. Host plant resistance may provide an environmentally safe and sustainable method of controlling ACP and/or HLB. Two xCitroncirus accessions (hybrids of Poncirus trifoliata and Citrus spp.), that are relatively resistant (UN-3881) or relatively susceptible (Troyer-1459) to ACP adults with regard to adult longevity, were compared in relation to ACP feeding behavior and some structural features of the leaf midrib. The settling (putative feeding/probing) sites of ACP adults on various parts of the leaf were not influenced primarily by plant accession. However, fewer ACP stylet sheaths were found in the midrib and fewer stylet sheath termini reached the vascular bundle (phloem and/or xylem) in UN-3881 compared to Troyer-1459 plants. Furthermore, in midribs of UN-3881 leaves the fibrous ring (sclerenchyma) around the phloem was significantly wider (thicker) compared to that in midribs of Troyer-1459 leaves. Our data indicate that feeding and/or probing by ACP adults into the vascular bundle is less frequent in the more resistant (UN-3881) than in the more susceptible (Troyer-1459) accessions. Our results also suggest that the thickness of the fibrous ring may be a barrier to stylet penetration into the vascular bundle, which is important for successful ACP feeding on the phloem and for transmitting HLB-associated bacteria. These results may help in the development of citrus plants resistant to ACP, which in turn could halt or slow the spread of the HLB-associated bacteria by this vector.     

Stylet Morphometrics and Citrus Leaf Vein Structure in Relation to Feeding Behavior of the Asian Citrus Psyllid Diaphorina citri,Vector of Citrus Huanglongbing Bacterium

The Asian citrus psyllid (ACP), Diaphorina citri (Hemiptera: Psyllidae), is the primary vector of the phloem-limited bacterium Candidatus Liberibacter asiaticus (LAS) associated with huanglongbing (HLB, citrus greening), considered the world’s most serious disease of citrus. Stylet morphometrics of ACP nymphs and adults were studied in relation to citrus vein structure and to their putative (histologically verified) feeding sites on Valencia orange leaves. ACP nymphs preferred to settle and feed on the lower (abaxial) side of young leaves either on secondary veins or on the sides of the midrib, whereas adults preferred to settle and feed on the upper (adaxial) or lower secondary veins of young or old leaves. Early instar nymphs can reach and probe the phloem probably because the distance to the phloem is considerably shorter in younger than in mature leaves, and is shorter from the sides of the midrib compared to that from the center. Additionally, the thick-walled ‘fibrous ring’ (sclerenchyma) around the phloem, which may act as a barrier to ACP stylet penetration into the phloem, is more prominent in older than in younger leaves and in the center than on the sides of the midrib. The majority (80–90%) of the salivary sheath termini produced by ACP nymphs and adults that reached a vascular bundle were associated with the phloem, whereas only 10–20% were associated with xylem vessels. Ultrastructural studies on ACP stylets and LAS-infected leaves suggested that the width of the maxillary food canal in first instar nymphs is wide enough for LAS bacteria to traverse during food ingestion (and LAS acquisition). However, the width of the maxillary salivary canal in these nymphs may not be wide enough to accommodate LAS bacteria during salivation (and LAS inoculation) into host plants. This may explain the inability of early instar nymphs to transmit LAS/HLB in earlier reports.     

Odorants for Surveillance and Control of the Asian Citrus Psyllid (Diaphorina citri)

Background

The Asian Citrus Psyllid (ACP), Diaphorina citri, can transmit the bacterium Candidatus Liberibacter while feeding on citrus flush shoots. This bacterium causes Huanglongbing (HLB), a major disease of citrus cultivation worldwide necessitating the development of new tools for ACP surveillance and control. The olfactory system of ACP is sensitive to variety of odorants released by citrus plants and offers an opportunity to develop new attractants and repellents.

Results

In this study, we performed single-unit electrophysiology to identify odorants that are strong activators, inhibitors, and prolonged activators of ACP odorant receptor neurons (ORNs). We identified a suite of odorants that activated the ORNs with high specificity and sensitivity, which may be useful in eliciting behavior such as attraction. In separate experiments, we also identified odorants that evoked prolonged ORN responses and antagonistic odorants able to suppress neuronal responses to activators, both of which can be useful in lowering attraction to hosts. In field trials, we tested the electrophysiologically identified activating odorants and identified a 3-odor blend that enhances trap catches by ∼230%.

Conclusion

These findings provide a set of odorants that can be used to develop affordable and safe odor-based surveillance and masking strategies for this dangerous pest insect.     

Huanglongbing: An overview of a complex pathosystem ravaging the world's citrus

Citrus huanglongbing(HLB) has become a major disease and limiting factor of production in citrus areas that have become infected. The destruction to the affected citrus industries has resulted in a tremendous increase to support research that in return has resulted in significant information on both applied and basic knowledge concerning this important disease to the global citrus industry. Recent research indicates the relationship between citrus and the causal agent of HLB is shaped by multiple elements, in which host defense responses may also play an important role. This review is intended to provide an overview of the importance of HLB to a wider audience of plant biologists. Recent advances on host-pathogen interactions, population genetics and vectoring of the causal agent are discussed.