Population ecology and phenology of Diaphorina citri (Hemiptera: Psyllidae) in two Florida citrus groves

Studies were conducted to assess population densities and phenology of the psyllid Diaphorina citri Kuwayama at two citrus groves in east-central Florida. One grove contained young, irrigated grapefruit trees and the other contained mature, nonirrigated orange trees. The two groves were sampled weekly for eggs, nymphs, and adults on flush shoots; for adults on mature leaves; and for adults captured on yellow sticky card traps. Because infestations of immature D. citri develop strictly on young flush, the abundance of flush was assessed weekly. Overall means of 26.5, 16.8, and 0.27 eggs, nymphs, and adults per flush shoot, respectively, were observed in the young grapefruit trees. In the grove of mature orange trees, overall means of 16.0, 12.7, and 0.31 eggs, nymphs, and adults per flush shoot were observed, respectively. Flush abundance was an inconsistent indicator of the mean density of D. citri per flush shoot. Mean density per shoot by itself was an inconsistent indicator of overall population levels of D. citri at each study site because few shoots were sometimes present when mean densities per shoot were high. May, June, and July were periods of time when immature D. citri were consistently present and most abundant at each study site, but the study indicated large infestations could occur at any time of the year depending on environmental factors and flush availability. Yellow sticky traps were effective for both male and female D. citri and useful for gauging adult population trends.     

Dispersion patterns and sampling plans for Diaphorina citri (Hemiptera: Psyllidae) in citrus

The abundance and spatial dispersion of Diaphorina citri Kuwayama (Hemiptera: Psyllidae) were studied in 34 grapefruit (Citrus paradisi Macfad.) and six sweet orange [Citrus sinensis (L.) Osbeck] orchards from March to August 2006 when the pest is more abundant in southern Texas. Although flush shoot infestation levels did not vary with host plant species, densities of D. citri eggs, nymphs, and adults were significantly higher on sweet orange than on grapefruit. D. citri immatures also were found in significantly higher numbers in the southeastern quadrant of trees than other parts of the canopy. The spatial distribution of D. citri nymphs and adults was analyzed using Iowa's patchiness regression and Taylor's power law. Taylor's power law fitted the data better than Iowa's model. Based on both regression models, the field dispersion patterns of D. citri nymphs and adults were aggregated among flush shoots in individual trees as indicated by the regression slopes that were significantly >1. For the average density of each life stage obtained during our surveys, the minimum number of flush shoots per tree needed to estimate D. citri densities varied from eight for eggs to four flush shoots for adults. Projections indicated that a sampling plan consisting of 10 trees and eight flush shoots per tree would provide density estimates of the three developmental stages of D. citri acceptable enough for population studies and management decisions. A presence-absence sampling plan with a fixed precision level was developed and can be used to provide a quick estimation of D. citri populations in citrus orchards.     

Reduced oviposition by Diaprepes abbreviatus (Coleoptera: Curculionidae) and growth enhancement of citrus by Surround particle film

Regularly applied sprays of a particle film, Surround WP, greatly enhanced the growth of citrus trees on a poorly drained Winder soil at Fort Pierce, FL. After 3 yr of applications every 3 or 4 wk, Surround-treated trees had at least 5 times the mass, 6 times the canopy volume, and approximately 4 times the cross-sectional area of the tree stems at the graft union compared with untreated trees. The larger Surround-treated trees attracted a higher number of adult weevil Diaprepes abbreviatus (L.) and to a lesser extent citrus root weevil, Pachnaeus litus (Germar), per tree, but there was an equivalent number of egg masses per tree compared with the control trees. The number of egg masses per female weevil oviposited on Surround-treated trees was significantly less than either the control trees or trees treated biannually with an entomopathogenic nematode, BioVector. The number of larvae per tree recovered from the roots of excavated trees was greater from trees treated with Surround once every 3 wk compared with control trees. The data suggest that Surround particle film greatly enhanced the growth of citrus trees grown in a poorly drained soil. The reduction in oviposition by D. abbreviatus was insufficient to significantly reduce the number of root weevil larvae per tree feeding on the roots. However, the more vigorous trees resulting from Surround applications may be more resistant or tolerant to root weevil feeding.     

Repellency of a kaolin particle film,Surround, and a mineral oil,Sunspray oil,to silverleaf whitefly (Homoptera: Aleyrodidae) on melon in the laboratory

Surround, a kaolin-based particle film formulation, and Sunspray oil, a mineral oil, were evaluated alone or in combination in choice and no-choice laboratory assays on melon leaves for repellency to adults of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring. In no-choice tests, the number of adults and eggs on leaves did not significantly differ among the three treatments and the water control when materials were applied to either the tipper or lower leaf surface. Significantly fewer adults and eggs were found on treated leaves compared with water when materials were applied to both leaf surfaces. Application of Surround did not affect the oviposition pattern, with 80.2-88.5% eggs oviposited on lower surface. However, whiteflies oviposited more eggs (53.1-63.8%) on the upper compared with the lower surface when Sunspray oil or Surround + Sunspray oil was applied on the lower leaf surface and both leaf surfaces. When whiteflies were allowed to choose among leaves treated with different materials on the same leaf surface(s), significantly fewer adults and eggs were found on treated leaves compared with water-treated leaves, and more adults and eggs were found on leaves when the materials were applied to tipper versus lower or both surfaces. Leaves treated with materials on both leaf surfaces had fewer whiteflies compared with leaves treated on the upper or lower surface. When whiteflies were allowed to choose among leaves treated with materials versus water-treated leaves in a 6:3 or an 8:1 ratio, significantly fewer adults and eggs were found on leaves treated with treatment materials compared with water, regardless of which leaf surface(s) were treated. No significant synergistic or additive effect was detected in Surround + Sunspray oil compared with either material used separately.     

Transmission parameters for Candidatus liberibacter asiaticus by Asian citrus psyllid (Hemiptera: Psyllidae)

The purpose of this investigation was to evaluate acquisition and inoculation (together, transmission) efficiency of Candidatus Liberibacter asiaticus (Las), the pathogen associated with citrus huanglongbing (HLB) by the Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae). In laboratory studies, nymphs reared on Las infected plants were more likely to acquire the bacterium than adults. Acquisition by nymphs ranged from 60 to 100%, whereas acquisition by adults only reached 40% after 5 wk of feeding on Las-infected plants. Similar rates of pathogen acquisition by psyllids after nymphal and adult feeding were observed in the field. Transmission of Las from parent to offspring (transovarial) occurred at a rate of 2-6%. One year after psyllid inoculations, successful transmission by individual D. citri ranged from 4 to 10%, whereas groups of 100 or more D. citri transmitted the pathogen at a rate of approximately 88%. In addition, the proportion of Las-positive adult psyllids, determined using quantitative real-time polymerase chain reaction, decreased over time when held on healthy plants. Due to the low rate of pathogen acquisition and long time period required for successful inoculation by adult D. citri, experiments designed to determine the latent period required for replication and successful inoculation of Las by D. citri did not result in Las-infected plants after >1 yr of incubation after inoculation. Collectively, these results indicate that adult D. citri which acquire the HLB pathogen as adults are poor vectors of the pathogen compared with adults that acquired the pathogen as nymphs.     

Action of particle films on the biology and behavior of pear psylla (Homoptera: Psyllidae)

Particle films with different properties have been developed for arthropod pest control. Two basic film types are hydrophobic and hydrophilic films. The hydrophilic film formulations differ in the amount and kind of spreader-sticker that is incorporated into the kaolin particles. The effects of particle film type (hydrophobic versus hydrophilic) and formulation (Surround versus Surround WP) on the biology and behavior of pear psylla, Cacopsylla pyricola (Foerster), were investigated on pear in a series of laboratory studies. Scanning electron microscopy determined that the number of particles that attached to the front tibia of adult psylla differed by particle formulation but the particle sizes were fairly uniform and ranged from 3.6 to 4.5 microm in diameter. Adults had difficulty grasping particle film-treated leaves, and this effect was influenced by film type and leaf surface. Choice and no-choice tests indicated that adult settling and oviposition were very low, regardless of film type or formulation. Under no-choice conditions, adult mortality was low, in part, because the adults were able to feed through all 3% particle films, but at reduced rates. However, the mortality of adults sprayed with 3% particle film solutions ranged from 22.2 to 62.5% within 72 h after treatment, and mortalities differed most between the hydrophilic formulations. Nymphs born on particle film-treated foliage incurred high mortalities ranging from 58.9 to 82.0% by the time they reached the fifth instar and were affected most by particle film type. Nymphal development was not affected by particle film type or formulation. Egg fertility and nymphal hatch also were unaffected by particle films. These studies determined that there are a number of biological effects particle films have on pear psylla beyond the deterrence of adult settling and oviposition.     

亚洲柑橘木虱成虫和5龄若虫在感染黄龙病的柑橘上的取食行为及获菌效率比较

【目的】亚洲柑橘木虱Diaphorina citri是柑橘的毁灭性病害——黄龙病亚洲种‘Candidatus Liberibacter asiaticus’(‘C las’)的主要传播媒介。本研究的目的是明确木虱成虫和5龄若虫的取食行为、获菌效率是否有差异,以及寄主感染黄龙病是否对5龄若虫取食产生影响。【方法】利用直流型刺吸电位仪(DC-EPG Giga-4)记录柑橘木虱成虫和5龄若虫在携带黄龙病的酸橘Citrus reticulata cv.Sunki嫩梢上10 h的取食行为,用qPCR单头检测其获得黄龙病病原菌的效率,并比较5龄若虫在感病和健康植株嫩梢上的取食行为。【结果】柑橘木虱成虫与5龄若虫在感染黄龙病的酸橘上的取食行为有显著差异。5龄若虫比成虫更快地开始在韧皮部和木质部进行吸食,口针在韧皮部的总过程以及吸食时间显著长于成虫。此外,5龄若虫和成虫在EPG测定(同时饲菌)10 h后获菌率分别为37.5%和20.0%,若虫明显高于成虫。寄主植物感染黄龙病对5龄若虫的取食行为有一定的影响,表现在感病植株上的刺探次数、唾液分泌次数和韧皮部吸食次数都显著少于健康植株,而两者分泌唾液和韧皮部吸食时间没有显著差异。另外,在感病植株上首次韧皮部取食出现时间较在健康植株上要早。【结论】在同等时间下,柑橘木虱5龄若虫比成虫在感染黄龙病的酸橘上的取食能力更强、取食量更大、获菌率更高,原因可能是若虫需要更多的营养物质供其生长发育所致。寄主感染黄龙病对木虱5龄若虫的取食有利,使其更快地开始取食,而且更改取食位点次数变少,推测可能与黄龙病菌破坏了植物的防御有关。     

园艺矿物油乳剂对亚洲柑橘木虱成虫刺吸行为的影响

目的】亚洲柑橘木虱Diaphorina citri是传播柑橘最重要病害黄龙病(huanglongbing, Candidatus Liberibacter asiaticus)的媒介昆虫,树冠喷施园艺矿物油(horticultural mineral oil, HMO)可以减少其在柑橘上的取食和产卵。本研究旨在探索植物组织内残留的园艺矿物油如何影响亚洲柑橘木虱成虫的取食行为。【方法】采用直流型刺吸电位仪(DC-EPG Giga-8)记录亚洲柑橘木虱成虫12 h内在喷施不同浓度(0.25%, 0.5%, 1%和2%, v/v)HMO(nC24)乳剂和清水(对照)时柑橘嫩叶上的刺探和取食行为并转换为波形信号,分析比较各处理的波形参数。【结果】不同浓度HMO乳剂处理显著提高了亚洲柑橘木虱成虫在柑橘叶片上的C波(路径波)持续时间百分比,显著减少了E2波(韧皮部吸食汁液)持续时间百分比,而对D(口针第一次接触韧皮部组织), E1(韧皮部出现唾液分泌) 和G(木质部吸食汁液) 波持续时间百分比没有显著影响。HMO处理组C波的每成虫波形累积时间(WDI)显著长于对照组,而各浓度处理之间没有显著差异,但D波WDI明显短于对照组。随着HMO浓度的增加, E1, E2和G波WDI显著下降,2% HMO处理组E1, E2和G波WDI明显低于其他浓度处理组。HMO乳剂处理明显减少了刺探次数;在HMO处理中,每成虫刺探次数和每成虫各波形次数均显著少于对照组,其中以1%和2% HMO乳剂处理最少。HMO乳剂处理组np波 (非刺探波)、D波、E2波的每成虫单次波形持续时间(WDE)均短于对照组,其中2% HMO乳剂处理后,D, E1和E2波WDE显著短于其他浓度处理和对照。同时,2% HMO乳剂处理推迟了从口器接触叶片到第1次开始刺探的时间和从口器接触叶片到第1次刺探到韧皮部的时间。【结论】结果表明,2% HMO乳剂显著减少亚洲柑橘木虱成虫在柑橘叶片上的取食次数和有效取食时间,同时还缩短了其在韧皮部分泌唾液和吸食汁液时间,因此可推荐矿物油用于柑橘黄龙病和亚洲柑橘木虱的综合防治体系。同时初步推断矿物油的作用机制可能是其进入植物气孔阻止植物挥发性物质的释放,抑制或掩盖柑橘叶片表面的挥发性物质从而减少了亚洲柑橘木虱在寄主上取食。     

薇苷菊乙醇提取物对桔全爪螨种群的控制作用

研究薇苷菊(Mikaniamicrantha)乙醇提取物对桔全爪螨(Panonychuscitri)种群的控制作用,并比较其与常用杀螨剂哒螨灵的效果.在实验室用0.1、0.2、0.4g·L^-13个浓度提取物分别喷布桔全爪螨卵、幼螨和若螨,除了01g·L^-1浓度处理对卵没有效果外,该处理幼螨、若螨存活率以及另2个浓度处理3个螨态的存活率都显著下降.在非选择性试验条件下,用这3个浓度的提取物处理叶片饲养的桔全爪螨雌螨繁殖量显著减少,寿命也显著缩短.在田间用这3个浓度的提取物在20d内连喷2次,桔全爪螨卵、幼螨和若螨的存活率都低于对照,干扰作用控制指数分别为0518、0.292、0.277,即对种群增长控制的效果分别为4.82%、70.8%、72.3%,比15%哒螨灵乳油2000倍处理更有效控制桔全爪螨的田间种群.田间试验结果还表明,提取物处理的叶片比对照和哒螨灵处理的浓绿,而且对桔全爪螨的天敌较安全     

Description and Biology of A New Species of Cybocephalus Erichson (Coleoptera: Nitidulidae), A Predator of Australian Citrus Whitefly

Cybocephalus aleyrodiphagus sp.n., a predator of Australian citrus whitefly, Orchamoplatus citri (Takahashi), is described from adults and larvae collected from southern New South Wales (where it appears to be the major natural enemy of O. citri ) and South Australia. Eggs of C. aleyrodiphagus are laid singly near egg circles of O. citri and larvae feed on eggs, crawlers and nymphs. Adults feed on all immature stages of O. citri. Reproductive, but not non-reproductive, females contain greater quantities of stearic, oleic and linoleic acid than males indicating the possible presence of a sex pheromone. In southern New South Wales, C. aleyrodiphagus sp.n. overwinters as non-reproductive adults and produces two adult generations during December-January and March-May. the sex ratio is close to 1:1 during October-December (overwintered adults) but male biased (2.2:1) during January-July (new generation adults). Trends of abundance for C. aleyrodiphagus correspond well with those for O. citri nymphs/pupae indicating a functional response of the predator to prey, despite disruption by foraging ants.     

Distribution and sampling of the whiteflies Aleurothrixus floccosus, Dialeurodes citri, and Parabemisia myricae (Homoptera: Aleyrodidae) in citrus in Spain

From 1993 to 1995 data sets were collected from four citrus groves in Valencia, Spain, to determine the distribution patterns of eggs and nymphs of Aleurothrixus floccosus (Maskell), Dialeurodes citri (Ashmead), and Parabemisia myricae (Kuwana) on leaves, and to develop reliable sampling plans for estimating densities of immature whiteflies. A. floccosus showed higher aggregation than the other two species. The dispersion index b from the Taylor power law did not vary between different developing stages for A. floccosus and D. citri, reaching overall values of 1.70 and 1.53, respectively. In P. myricae, b was 1.60 for eggs and N1, and 1.46 for the remaining nymphs. The minimum number of leaves to estimate the population density with a coefficient of variation of 0.25 for densities above 10 immature whiteflies per leaf was 40 for D. citri and P. myricae, and 250 for A. floccosus. Binomial sampling programs for the three species were rejected for pest management purposes due to the high sample sizes required. The enumerative procedure of counting the number of insects per leaf appears to be the most suitable method for D. citri and P. myricae. For A. floccosus an index of occupation (from 0 to 10) linearly related to the proportion of the leaf undersurface occupied by this insect was found to be reliable and time-saving. Examining 150 leaves with this index achieves the desired relative variation level of 0.25 for most population densities usually found in commercial groves.     

nC22矿物油及其与吡虫啉混用对柑橘木虱的室内毒力评价

【目的】室内评价nC22矿物油单独使用,以及与吡虫啉混用对柑橘木虱Diaphorina citri的毒力,并筛选nC22矿物油对吡虫啉防治柑橘木虱具有增效作用的混配比例,为矿物油防治柑橘木虱的应用提供科学依据。【方法】使用nC22矿物油以及阳性对照nC23和nC28矿物油,采用浸渍法和喷雾法分别检测矿物油对柑橘木虱卵和低龄若虫、高龄若虫、成虫的致死作用,以处理后第7天(卵)和第1天(若虫和成虫)的LC 50值评估毒力。将nC22矿物油与吡虫啉以不同配比混配,测定混配液对低龄若虫的毒力,使用交互测定法、共毒因子(co-toxicity factor,CTF)法和共毒系数(co-toxicity coefficient,CTC)法评价矿物油对吡虫啉的增效作用。【结果】单独使用时,nC22矿物油对卵的LC 50值低于nC23和nC28矿物油;对低龄若虫和高龄若虫的LC 50值与nC23矿物油相当,都低于nC28矿物油;对成虫的LC 50值与nC28矿物油相当,都低于nC23矿物油。与吡虫啉混用时,nC22矿物油与吡虫啉混配比例为3∶7,4∶6和7∶3时,矿物油对吡虫啉有增效作用:交互测定法中柑橘木虱低龄若虫的实际死亡率位于等效线的上方,CTF值分别为34.807,22.655和40.798,CTC值分别为187.410,183.876和222.936。3种混配液中7∶3的混配比例对吡虫啉的增效作用最强。【结论】nC22矿物油对柑橘木虱的毒力高于进口nC23矿物油及传统nC28矿物油,且以适当混配比例混用时nC22矿物油对吡虫啉具有显著增效作用,理论上可大幅减少化学杀虫剂的使用量,可进一步通过田间试验进行验证。     

Effects of hydrophilic and hydrophobic kaolin-based particle films on pea aphid (Homoptera: Aphididae) and its entomopathogen Pandora neoaphidis (Entomophthorales: Entomophthoraceae)

Hydrophobic and hydrophilic kaolin-based particle films are effective for control of insect pests in certain agricultural crops. How these products interact with potential biological control agents is not well documented. This study was conducted to evaluate the effects of the hydrophobic (M96-018) and hydrophilic (Surround WP) kaolin-based particle films (Engelhard Corporation, Iselin, NJ) on pea aphid, Acyrthosiphon pisum (Harris), on peas (Pisum spp.), and on the fungal aphid pathogen Pandora neoaphidis (Remaudière and Hennebert) Humber. Over two field seasons (2001 and 2002) in northern Idaho, applications of M96-018 significantly reduced the rate of pea aphid increase on pea, but Surround WP, tested only in 2001, did not reduce aphid population growth rate. Neither particle film treatment was as effective as a standard application of esfenvalerate (DuPont Asana). In the laboratory, particle films suppressed pea aphid populations by up to 30%. M96-018 seemed to have some repellent activity based on aphid distributions after treating plants. When applied along with P. neoaphidis conidia, M96-018 but not Surround WP caused higher percentage of infection mortality of pea aphids by P. neoaphidis than occurred on controls treated only with P. neoaphidis conidia. P. neoaphidis conidia deposited on glass slides coated with M96-018, produced more germ tubes and secondary conidia than those deposited on untreated glass slides or slides treated with Surround WP. This result suggests that greater infection of pea aphids on plants treated with M96-018 is in part a result of a direct enhancement of fungal germination by the particle film.     

Particle film affects black pecan aphid (Homoptera: Aphididae) on pecan

Three species of aphids attack pecan foliage, Carya illinoensis (Wang.) K. Koch, and cause economic damage. We tested a kaolin-based particle film against one of these aphid species, black pecan aphid, Melanocallis caryaefoliae (Davis). Effect of particle film on host selection, adult mortality, and production of nymphs by M. caryaefoliae was tested on seedling pecans in the laboratory. Fewer M. caryaefoliae adults selected treated foliage compared with untreated foliage. A higher percentage of adults that did select treated foliage were recovered from upper leaf surfaces compared with the percentage of adults recovered from upper leaf surfaces of untreated leaves. Observations with a microscope revealed an accumulation of particle film on aphid body parts, especially on tarsi, and strongly suggests that aphid mobility was restricted. Adult mortality was higher on treated foliage and led to an overall decrease in production of nymphs on those seedlings. In addition, we measured spectral properties of treated seedling pecan foliage. Light reflectance by treated foliage was increased and absorptance decreased compared with control foliage whereas transmittance of light through control and particle film-treated leaves was similar. We did not detect any phytotoxic effect on pecan due to application of particle film.     

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.     

Predation of Galendromus helveolus (Acari: Phytoseiidae) on Brevipalpus californicus (Acari: Tenuipalpidae)

The false spider mite, Brevipalpus californicus (Banks), is a major citrus pest in Texas. This phytophagous mite causes damage to fruit, leaves and stems of citrus, and is also a vector of citrus leprosis virus. Galendromus helveolus (Chant) is one of the most prevalent predacious mite species found on Texas citrus. The predation potential of G. helveolus on different stages of B. californicus was evaluated in the laboratory. An individual immature G. helveolus mite consumed an average of 30.7 eggs, 53.6 larvae, or 22.7 nymphs of B. californicus before developing to an adult. An individual adult female G. helveolus consumed an average of 164.8 eggs, 369.6 larvae, or 80.9 nymphs of B. californicus. Both immature and adult G. helveolus never fed on adult stage of B. californicus and never completed development. The development times of the immature stages of G. helveolus were 4.5, 4.1 and 4.6 days when fed on eggs, larvae and nymphs of B. californicus, respectively. When G. helveolus fed on the larval stage of B. californicus, the adults had the longest longevity (18.5 days) and the highest fecundity (14.0 eggs/female).     

Sexual transmission of a plant pathogenic bacterium, Candidatus Liberibacter asiaticus, between conspecific insect vectors during mating

Candidatus Liberibacter asiaticus is a fastidious, phloem-inhabiting, gram-negative bacterium transmitted by Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae). The bacterium is the presumed causal agent of huanglongbing (HLB), one of the most destructive and economically important diseases of citrus. We investigated whether Las is transmitted between infected and uninfected D. citri adults during courtship. Our results indicate that Las was sexually transmitted from Las-infected male D. citri to uninfected females at a low rate (<4%) during mating. Sexual transmission was not observed following mating of infected females and uninfected males or among adult pairs of the same sex. Las was detected in genitalia of both sexes and also in eggs of infected females. A latent period of 7 days or more was required to detect the bacterium in recipient females. Rod shaped as well as spherical structures resembling Las were observed in ovaries of Las-infected females with transmission electron microscopy, but were absent in ovaries from uninfected D. citri females. The size of the rod shaped structures varied from 0.39 to 0.67 μm in length and 0.19 to 0.39 μm in width. The spherical structures measured from 0.61 to 0.80 μm in diameter. This investigation provides convincing evidence that a plant pathogenic bacterium is sexually transmitted from male to female insects during courtship and established evidence that bacteria persist in reproductive organs. Moreover, these findings provide an alternative sexually horizontal mechanism for the spread of Las within populations of D. citri, even in the absence of infected host trees.     

Three homopteran pests of citrus as prey for the convergent lady beetle: suitability and preference

The convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), is an important predator of soft-bodied insect pests in many regions of the United States, but generally uncommon in Florida citrus. Certain citrus producers in Florida recently initiated releases of commercially available H. convergens from California against the Asian citrus psyllid Diaphorina citri Kuwayama, vector of Huanglongbing or citrus greening disease. However, there is little information on potential efficacy of this predator against the psyllid or other pests of citrus. Preference, development, and reproduction by H. convergens was evaluated on freshly collected nymphs of D. citri, brown citrus aphid Toxoptera citricida Kirkaldy, green citrus aphid Aphis spiraecola Patch, and frozen eggs of the flour moth Ephestia kuehniella Zeller. Larvae preferred D. citri over T. citricida in two-way choice tests and consumed more D. citri or A. spiraecola than T. citricida in no-choice tests. Adults consumed equal numbers of all three species in both tests. Development times of larvae at 25.5±0.05°C on A. spiraecola were longer than on the other three diets. Larval survival and pupation times did not differ among diets. Females lived longer than males irrespective of diet, and longevity of both genders was greatly increased on E. kuehniella compared with D. citri and A. spiraecola. Life table analysis indicated that H. convergens should increase on all three species, with a greater potential on psyllids than aphids. Further studies are warranted to assess establishment and persistence of this potential biological control agent in the Florida citrus environment.     

Development of Iphiseiodes quadripilis (Banks) (Acari: Phytoseiidae) on pollen or mite diets and predation on Aculops pelekassi (Keifer) (Acari: Eriophyidae) in the laboratory

Development and reproduction of Iphiseiodes quadripilis (Banks) were evaluated on single food diets of pollen (Malephora crocea Jacquin [ice plant] or Quercus sp. [oak]), spider mites, [Eutetranychus banksi (McGregor) or Panonychus citri (McGregor) (Acari: Tetranychidae)], or the citrus rust mite Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae). Experiments were conducted in an environmental chamber at 28 degrees +/- 1 degrees C, 14:10 (L:D) daylength, and 45% RH. I. quadripilis completed development and laid viable eggs that subsequently hatched on diets of either ice plant or oak pollen or eggs and motile stages of E. banksi. P. citri was acceptable as prey, but survival of larvae to adults was only 36%, whereas survival on E. banksi, ice plant pollen, and oak pollen was 48, 60, and 68%, respectively. The webbing produced by P. citri seemed to inhibit foraging behavior of I. quadripilis larvae and nymphs. Larvae of I. quadripilis developed only to the second nymphal instar on a diet of P. oleivora alone or water alone. Starved I. quadripilis females and deutonymphs were observed preying on the pink citrus rust mite, Aculops pelekassi (Keifer) (Eriophyidae). During 4-min observation trials, two series of I. quadripilis fed on 1.8 +/- 0.47 and 3.5 +/- 0.45 A. pelekassi motile stages after being starved for 6 and 24 h, respectively. I. quadripilis females did not prey on P. oleivora in arenas containing both rust mite species.     

Toxicity of insecticidal soaps to the Asian citrus psyllid and two of its natural enemies

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is an important pest of citrus because it transmits plant pathogens responsible for a serious disease of citrus known as huanglongbing. Conventional insecticides are frequently used to manage ACP. Insecticidal soaps (hereafter ‘soaps’) are an insect control option labelled for commercial use as well as for use by homeowners and organic growers. Soaps have been shown to be toxic to some insect pests and therefore might be an alternative to conventional pesticides for control of ACP, but the efficacy of soaps against ACP was largely unknown. Our objective was to test whether different concentrations of two insecticidal soaps, M‐Pede and Safer Insecticidal Soap Concentrate, caused mortality of ACP adults, nymphs and eggs. In addition, we tested whether these soaps were toxic to two natural enemies of ACP, adults of the lady beetle Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) and the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae). Direct sprays of M‐Pede or Safer Insecticidal Soap were acutely toxic to ACP adults (regardless of gender) and nymphs when applied in solutions of 0.8–2% in water. Insecticidal soaps were non‐toxic to eggs at rates of up to 2%. Residues of soap were less toxic to adult ACP than direct sprays, even when applied at concentrations of up to 4%. M‐Pede or Safer soap at high concentrations (for example, 2% v/v in water) may be an effective alternative to conventional pesticides to manage adult and nymphal ACP, although multiple applications may be needed if a target population includes eggs. A 2% concentration of either soap applied as a direct spray was non‐toxic to adult C. sanguinea but acutely toxic to adult T. radiata. Soaps therefore may be compatible with biological control of ACP by adult coccinellids but not the parasitoid T. radiata.