Infection with 'Candidatus Liberibacter asiaticus' improves the fecundity of Diaphorina citri aiding its proliferation: A win-win strategy.

The evolution of insect vector-pathogen relationships has long been of interest in the field of molecular ecology. One system of special relevance, due to its economic impacts, is that between Diaphorina citri and 'Candidatus Liberibacter asiaticus' (CLas), the cause of the severe Asian form of huanglongbing. CLas-positive D. citri are more fecund than their CLas-negative counterparts, boosting opportunities for pathogens to acquire new vector hosts. The molecular mechanism behind this life-history shift remains unclear. Here, we found that CLas promoted ovarian development and increased the expression of the vitellogenin receptor (DcVgR) in ovaries. DcVgR RNAi significantly decreased fecundity and CLas titer in ovaries, extended the preoviposition period, shortened the oviposition period and blocked ovarian development. Given their importance in gene regulation, we explored the role of miRNAs in shaping these phenotypes and their molecular triggers. Our results showed that one miRNA, miR-275, suppressed DcVgR expression by binding to its 3' UTR. Overexpression of miR-275 knocked down DcVgR expression and CLas titer in ovaries, causing reproductive defects that mimicked DcVgR knockdown phenotypes. We focused, further, on roles of the Juvenile Hormone (JH) pathway in shaping the observed fecundity phenotype, given its known impacts on ovarian development. After CLas infection, this pathway was upregulated, thereby increasing DcVgR expression. From these combined results, we conclude that CLas hijacks the JH signalling pathway and miR-275, thereby targeting DcVgR to increase D. citri fecundity. These changes simultaneously increase CLas replication, suggesting a pathogen-vector host mutualism, or a seemingly helpful, but cryptically costly life-history manipulation.

Blood typing and transfusion therapy in a patient with A2 subtype acute myeloid leukemia M2: A case report.

BACKGROUND: Acute myeloid leukemia (AML) is one of the most common types of leukemia in adults. However, AML is relatively rare in the population overall, accounting for only about 1 percent of all cancers. Treatment for AML can be very effective for some patients, yet it leaves others with serious and even life-threatening side effects. Chemotherapy is still the primary treatment for most AML, but over time, leukemia cells become resistant to chemotherapy drugs. In addition, stem cell transplantation, targeted therapy, and immunotherapy are currently available. At the same time, with the progression of the disease, the patient may have corresponding complications, such as coagulation dysfunction, anemia, granulocytopenia, and repeated infection, so transfusion supportive therapy will be involved in the overall treatment regime. To date, few articles have reported on blood transfusion treatment options for patients with ABO subtypes AML-M2. Blood transfusion therapy is an important supportive treatment for AML-M2, and accurate determination of patients' blood type is one of the most important steps in the treatment process. In this study, we explored blood typing and supportive treatment strategies for a patient with A2 subtype AML-M2 to provide the basis for treatment for all patients. CASE SUMMARY: In order to determine the blood type of the patient, serological and molecular biological methods were used for reference tests, and the genetic background was studied to determine the patient's final blood type and select the appropriate blood products for infusion treatment. According to the results obtained by serological and molecular biological methods, the blood type of the patient was A2 subtype; the genotype was A02/001; the irregular antibody screening was negative, and anti-A1 was found in the plasma. According to the overall treatment plan, active anti-infection, elevated cells, component blood transfusion support, and other rescue and supportive treatments were given, and the patient successfully passed the stage of myelosuppression after chemotherapy. Re-examination of bone marrow smears showed that AL was in complete remission of bone marrow signs, and minimal residual leukemia lesions suggested no cells with obvious abnormal immunophenotype (residual leukemia cells < 10-4). CONCLUSION: The infusion of patients with A2 subtype AML-M2 with A irradiated platelets and O washing red blood cells can meet the needs of clinical treatment.

Susceptibility of Diaphorina citri to Irradiation with UV-A and UV-B and the Applicability of the Bunsen-Roscoe Reciprocity Law.

Populations of Diaphorina citri decline with elevation and, in a study in Bhutan, were rarely found above 1200 m ASL. The impact of ultraviolet (UV) radiation, particularly UV-B, on immature stages of the psyllid was proposed as limiting factor. As no studies have been undertaken on the influences of UV radiation on the development of D. citri, we examined the effects of UV-A and UV-B on different stadia of the psyllid. In addition, compliance with the Bunsen-Roscoe reciprocity law was examined. Irradiation with UV-A marginally reduced egg hatch and the survival times of emerging nymphs. Early instar nymphs were little affected by this waveband, but the survival of adults was reduced at the higher doses used. With UV-B, egg hatch and the survival times of early and late instar nymphs declined in proportion to UV-B dose. A dose of 57.6 kJ m-2 d-1 reduced the survival time of only adult females. Female fecundity was reduced at high UV-A and UV-B doses but increased at low doses. The Bunsen-Roscoe law held true for eggs and early instar nymphs for different durations and irradiances of UV-B. Eggs and nymphs had ED50 values for UV-B lower than the daily fluxes of this wavelength experienced worldwide. Thus, UV-B could be a factor causing the psyllid to be scarce at high elevations.

Spatial Distribution and Temporal Dynamics of Candidatus Liberibacter Asiaticus in Different Stages of Embryos, Nymphs and Adults of Diaphorina citri.

Huanglongbing, a globally devastating citrus disease, is associated with Candidatus Liberibacter asiaticus (CLas) and is mainly transmitted by Diaphorina citri. Verification of the distribution and dynamics of CLas in D. citri is critical to understanding CLas transmitted by vectors in nature. Here, the distribution and titers of CLas in different sexes and tissues of D. citri adults were investigated by fluorescence in-situ hybridization (FISH) and quantitative real-time PCR (qRT-PCR). Results showed that CLas had widespread distribution in the brain, salivary glands, digestive system, and reproductive system of both females and males, indicating a systemic infection of CLas in D. citri. Moreover, CLas fluorescence intensity and titers were significantly increased in both the digestive system and the female reproductive system with development and there was a marked decreased in both the salivary glands and the male brain, but there was no significant change in the female brain or the male reproductive system. Furthermore, the distribution and dynamics of CLas in embryos and nymphs were investigated. CLas was observed in all laid eggs and subsequent first-second-instar nymphs, indicating that a high percentage of embryos and nymphs resulting from infected D. citri mothers were infected with CLas.

Change of termite hindgut metabolome and bacteria after captivity indicates the hindgut microbiota provides nutritional factors to the host.

The gut-dwelling microbiota is an indispensable part of termites. It is influenced by a series of factors, such as diet and captivity. The objectives of this study were to study the metabolic functions of hindgut microbiota and to investigate the influence of captivity on the hindgut microbiota. The dampwood termite Hodotermopsis sjostedti was reared in the laboratory for 6 months. We conducted the metabolome analysis of the fat body from the freshly-collected workers (FBF), the hindgut fluid of the freshly-collected workers (HFF), and the hindgut fluid of laboratory-maintained workers. In addition, the 16S rRNA genes from the hindgut bacteria in the freshly-collected and laboratory-maintained workers were sequenced. According to our results, the concentrations of metabolites associated with amino acid biosynthesis, vitamin biosynthesis, fatty acid biosynthesis, and cofactor biosynthesis were higher in HFF compared with those in FBF, suggesting that the hindgut microbiota provides nutritional factors to the host. However, after captivity, the concentrations of metabolites in the hindgut associated with amino acid biosynthesis, nucleotide sugar metabolism, vitamin biosynthesis, and carbon metabolism decreased, while those associated with the steroid hormone biosynthesis and ovarian steroidogenesis increased. Meanwhile, the 16S amplicon study revealed that the abundance of certain bacteria changed after captivity, such as uncultured Termite Group 1 bacterium, Candidatus Symbiothrix dinenymphae, and unclassified Desulfovibrio. Our findings show that captivity influences the hindgut microbiota and shed light on the metabolic potential of the hindgut microbiota.

Preliminary Report on the Acquisition, Persistence, and Potential Transmission of Citrus tristeza virus by Diaphorina citri.

Citrus tristeza virus (CTV) is one of the most important citrus tree viruses: a graft-transmissible virus that can be vectored by several aphid species. Diaphorina citri is the insect vector of "Candidatus Liberibacter spp.", a bacterium associated with citrus Huanglongbing (HLB). However, no detailed description of the relationship between CTV and D. citri has been reported. In this study, D. citri adults collected from CTV-infected "Shatangju" mandarin, "Newhall" sweet orange, and "fingered citron" trees in different orchards yielded CTV-positive rates of 40%, 65%, and 95%, respectively, upon detection by conventional PCR. Illumina HiSeq sequencing followed by de novo assembly recovered the primary full CTV genome from the RNA of 30 D. citri adults sampled from CTV-positive citrus plants. Molting and adult emergence did not affect the presence or titers of CTV within the D. citri; however, the persistence of CTV in psyllids varied among different host plant species. Groups of 10 D. citri (from a population 85% CTV-positive) were shown to potentially transmit CTV to two citrus species, "Shatangju" mandarin and "Eureka" lemon, yielding 58.33% and 83.33% CTV-positive plants, respectively. No transmission of CTV to orange jasmine plants occurred. Thus, this study reports on the ability of D. citri to acquire and transmit CTV, making D. citri as a vector of two important citrus pathogens, warranting further attention and investigation.

The first complete mitochondrial genome sequence of Cacopsylla citrisuga (Yang & Li), a new insect vector of Huanglongbing in Yunnan Province, China.

Cacopsylla citrisuga (Yang & Li) is an important pest-threatening Citrus and Poncirus plants (Rutaceae) and a newly identified insect vector of citrus Huanglongbing. The complete mitochondrial genome of C. citrisuga was 14,906 bp in length, with 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs). The phylogenetic trees inferred from Bayesian inference and maximum likelihood analyses confirmed C. citrisuga as a member of the genus Cacopsylla. Our phylogenetic analyses suggested that the Cacopsylla is paraphyletic, and confirmed C. citrisuga as a member of clade-I under Cacopsylla. The complete mitochondrial genome of C. citrisuga will provide important information for the phylogeny and evolution analysis of Cacopsylla.

Genome Sequence Resource of 'Candidatus Liberibacter asiaticus' from Diaphorina citri Kuwayama (Hemiptera: Liviidae) from La Réunion.

'Candidatus Liberibacter asiaticus' is an insect-transmitted, phloem-restricted α-proteobacterium associated with huanglongbing. Here, we provide the whole genome sequence of 'Ca. L. asiaticus' strain ReuSP1 from its insect vector Diaphorina citri (Hemiptera: Liviidae) collected in La Réunion. The genome is composed of 1,230,064 bp and has a 36.5% G+C content. This study reports the first 'Ca. L. asiaticus' genome sequence from La Réunion, which will add to 'Ca. L. asiaticus' genome resources and help elucidate our understanding of the introduction pathway into La Réunion.

Host Plant-Mediated Interactions Between 'Candidatus Liberibacter asiaticus' and Its Vector Diaphorina citri Kuwayama (Hemiptera: Liviidae).

The Diaphorina citri Kuwayama (Hemiptera: Liviidae) also known as Asian citrus psyllid transmits 'Candidatus Liberibacter asiaticus' (CLas) associated with the citrus Huanglongbing (HLB). Minimizing Asian citrus psyllid populations is one of the most important methods for HLB control. The development and survival of Asian citrus psyllid were evaluated on CLas+ and CLas- plants of Citrus reticulata Blanco. cv. Mashuiju (Sapindales: Rutaceae) or Citrus sunki Hort. ex Tanaka (Sapindales: Rutaceae) to assess the effects of CLas infection on vector populations. The development times were unaffected between CLas+ and CLas- plants for eggs and first to third instar nymphs but decreased for fourth instars, fifth instars, and total nymphal life on CLas+ plants. The survival rates of eggs and first and second instar nymphs were significantly lower, while those of third to fifth instar nymphs were significantly higher on CLas+ plants. However, overall nymphal survival did not differ between CLas+ and CLas- plants. The pre-oviposition period of Asian citrus psyllid on CLas+ plants decreased, while oviposition period increased, resulting in significantly higher fecundity and population trend index compared with those on CLas- plants, illustrating an overall fitness benefit of CLas infection to Asian citrus psyllid. On the other hand, the longevity and resistance to starvation and lower temperatures of adults from CLas+ plants were significantly lower than those from CLas- plants suggesting that there may be a fitness cost for Asian citrus psyllid on CLas+ plants. The development time of eggs and nymphs and adult longevity were always shorter on C. reticulata regardless of infection status. This knowledge of host plant, pathogen, and vector interactions is useful for developing Asian citrus psyllid-HLB management programs.

Host and environmental factors influencing 'Candidatus Liberibacter asiaticus' acquisition in Diaphorina citri.

BACKGROUND: Diaphorina citri is a vector of 'Candidatus Liberibacter asiaticus' (CLas) associated with citrus Huanglongbing. In this study, the infection and titers of CLas in the psyllid, were monitored for life cycle stage, sex, host-plant CLas titer, host-plant genotype, and ambient temperature. RESULTS: Acquisition efficiency of CLas by D. citri was highest in nymphs reared at 25 °C on a host plant with high CLas titers but was independent of the host genotypes assessed and of vector sex. We further observed that D. citri nymphs acquired CLas more rapidly than adults based on acquisition access periods (AAPs). CLas did not multiply in the alimentary canal, hemolymph, and salivary glands of adults for 18 days after a 3-day AAP as adult. However, CLas multiplication was detected in hemolymph and salivary gland of adults after the bacterium was acquired by nymphs. Eighty percent of salivary glands of adults contained CLas 18 days after a 3-day AAP as nymph compared to 10% 18 days after a 3-day AAP as adults. CONCLUSION: Different factors tested herein influenced CLas acquisition efficiency of D. citri, CLas multiplication and spread inside the psyllid. These observations serve to better understand mechanisms of CLas infection in D. citri. © 2018 Society of Chemical Industry.

Population diversity of Diaphorina citri (Hemiptera: Liviidae) in China based on whole mitochondrial genome sequences.

BACKGROUND: Diaphorina citri (Asian citrus psyllid; ACP) transmits 'Candidatus Liberibacter asiaticus' associated with citrus Huanglongbing (HLB). ACP has been reported in 11 provinces/regions in China, yet its population diversity remains unclear. In this study, we evaluated ACP population diversity in China using representative whole mitochondrial genome (mitogenome) sequences. Additional mitogenome sequences outside China were also acquired and evaluated. RESULTS: The sizes of the 27 ACP mitogenome sequences ranged from 14 986 to 15 030 bp. Along with three previously published mitogenome sequences, the 30 sequences formed three major mitochondrial groups (MGs): MG1, present in southwestern China and occurring at elevations above 1000 m; MG2, present in southeastern China and Southeast Asia (Cambodia, Indonesia, Malaysia, and Vietnam) and occurring at elevations below 180 m; and MG3, present in the USA and Pakistan. Single nucleotide polymorphisms in five genes (cox2, atp8, nad3, nad1 and rrnL) contributed mostly in the ACP diversity. Among these genes, rrnL had the most variation. CONCLUSION: Mitogenome sequences analyses revealed two major phylogenetic groups of ACP present in China as well as a possible unique group present currently in Pakistan and the USA. The information could have significant implications for current ACP control and HLB management. © 2018 Society of Chemical Industry.

Phylogeography of Diaphorina citri (Hemiptera: Liviidae) and its primary endosymbiont, 'Candidatus Carsonella ruddii': an evolutionary approach to host-endosymbiont interaction.

BACKGROUND: In insects, little is known about the co-evolution between their primary endosymbionts and hosts at the intraspecific level. This study examined co-diversification between the notorious agricultural pest Diaphorina citri and its primary endosymbionts (P-endosymbiont), 'Candidatus Carsonella ruddii' at the population level. RESULTS: Maximum likelihood, haplotype network, principal components and Bayesian clustering identified three lineages for D. citri and its P-endosymbiont: a Western clade containing individuals from Pakistan, Bhutan (Phuentsholing), Vietnam (Son La), USA, Myanmar and China (Ruili, Yunnan); a Central clade, with accessions originating from Southwest China, Bhutan (Tsirang) and Bangladesh; and an Eastern clade containing individuals from Southeast Asia, and East and South China. A more diverse genetic structure was apparent in the host mitochondrial DNA than their P-endosymbionts; however, the two sets of data were strongly congruent. CONCLUSION: This study provides evidence for the co-diversification of D. citri and its P-endosymbiont during the migration from South Asia to East and Southeast Asia. We also suggest that the P-endosymbiont may facilitate investigations into the genealogy and migration history of the host. The biogeography of D. citri and its P-endosymbiont indicated that D. citri colonized and underwent a secondary dispersal from South Asia to East and Southeast Asia. © 2018 Society of Chemical Industry.

A new sesquiterpene lactone glucoside and other constituents from Inula salsoloides with insecticidal activities on striped flea beetle (Phyllotreta striolata Fabricius).

A new sesquiterpene, eupatolide 13-O-ß-d-glucopyranoside (eupatolide-II, 1), lactone glucoside, along with 15 known compounds, were isolated from the whole plant of Inula salsoloides (Asteraceae). Dichloromethane extract and compounds 1-11 were used to investigate insecticidal activities against vegetable important pest, striped flea beetle (Phyllotreta striolata Fabricius). None of the samples show any toxicity under concentration of 500 times, while compound 1 and the extract had toxic effect when the concentration increased to 250 times. But the corrected mortality of compound 1 and the extract were only 44.83 and 13.80%, respectively. Compound 11 (inulasalene) showed repellency effect in the no-choice test, and the repellency rate was 70%. Compounds 1 and 3 (inulasalsolide) showed the antifeeding rates of 65.22 and 47.06%, respectively. Compound 10 (11ß,13-dihydrogeneupatolide) showed strong attractive effects on the adults, while the difference of injured area between the treatment and control was also not significant.

Analyses of Mitogenome Sequences Revealed that Asian Citrus Psyllids (Diaphorina citri) from California Were Related to Those from Florida.

Asian citrus psyllid (ACP, Diaphorina citri Kuwayama) transmits "Candidatus Liberibacter asiaticus" (CLas), an unculturable alpha-proteobacterium associated with citrus Huanglongbing (HLB). CLas has recently been found in California. Understanding ACP population diversity is necessary for HLB regulatory practices aimed at reducing CLas spread. In this study, two circular ACP mitogenome sequences from California (mt-CApsy, ~15,027 bp) and Florida (mt-FLpsy, ~15,012 bp), USA, were acquired. Each mitogenome contained 13 protein coding genes, 2 ribosomal RNA and 22 transfer RNA genes, and a control region varying in sizes. The Californian mt-CApsy was identical to the Floridian mt-FLpsy, but different from the mitogenome (mt-GDpsy) of Guangdong, China, in 50 single nucleotide polymorphisms (SNPs). Further analyses were performed on sequences in cox1 and trnAsn regions with 100 ACPs, SNPs in nad1-nad4-nad5 locus through PCR with 252 ACP samples. All results showed the presence of a Chinese ACP cluster (CAC) and an American ACP cluster (AAC). We proposed that ACP in California was likely not introduced from China based on our current ACP collection but somewhere in America. However, more studies with ACP samples from around the world are needed. ACP mitogenome sequence analyses will facilitate ACP population research.

Genetic diversity of Diaphorina citri and its endosymbionts across east and south-east Asia.

BACKGROUND: Diaphorina citri is the vector of 'Candidatus Liberibacter asiaticus', the most widespread pathogen associated huanglongbing, the most serious disease of citrus. To enhance our understanding of the distribution and origin of the psyllid, we investigated the genetic diversity and population structures of 24 populations in Asia and one from Florida based on the mtCOI gene. Simultaneously, genetic diversity and population structures of the primary endosymbiont (P-endosymbiont) 'Candidatus Carsonella ruddii' and secondary endosymbiont (S-endosymbiont) 'Candidatus Profftella armatura' of D. citri were determined with the housekeeping genes. RESULT: AMOVA analysis indicated that populations of D. citri and its endosymbionts in east and south-east Asia were genetically distinct from populations in Pakistan and Florida. Furthermore, P-endosymbiont populations displayed a strong geographical structure across east and south-east Asia, while low genetic diversity indicated the absence of genetic structure among the populations of D. citri and its S-endosymbiont across these regions. CONCLUSION: The 'Ca. C. ruddii' is more diverse and structured than the D. citri and the 'Ca. P. armatura' across east and south-east Asia. Multiple introductions of the psyllid have occurred in China. Management application for controlling the pest is proposed based on the genetic information of D. citri and its endosymbionts. © 2017 Society of Chemical Industry.

The Complete Mitochondrial Genome Sequence of Bactericera cockerelli and Comparison with Three Other Psylloidea Species.

Potato psyllid (Bactericera cockerelli) is an important pest of potato, tomato and pepper. Not only could a toxin secreted by nymphs results in serious phytotoxemia in some host plants, but also over the past few years B. cockerelli was shown to transmit "Candidatus Liberibacter solanacearum", the putative bacterial pathogen of potato zebra chip (ZC) disease, to potato and tomato. ZC has caused devastating losses to potato production in the western U.S., Mexico, and elsewhere. New knowledge of the genetic diversity of the B. cockerelli is needed to develop improved strategies to manage pest populations. Mitochondrial genome (mitogenome) sequencing provides important knowledge about insect evolution and diversity in and among populations. This report provides the first complete B. cockerelli mitogenome sequence as determined by next generation sequencing technology (Illumina MiSeq). The circular B. cockerelli mitogenome had a size of 15,220 bp with 13 protein-coding gene (PCGs), 2 ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and a non-coding region of 975 bp. The overall gene order of the B. cockerelli mitogenome is identical to three other published Psylloidea mitogenomes: one species from the Triozidae, Paratrioza sinica; and two species from the Psyllidae, Cacopsylla coccinea and Pachypsylla venusta. This suggests all of these species share a common ancestral mitogenome. However, sequence analyses revealed differences between and among the insect families, in particular a unique region that can be folded into three stem-loop secondary structures present only within the B. cockerelli mitogenome. A phylogenetic tree based on the 13 PCGs matched an existing taxonomy scheme that was based on morphological characteristics. The available complete mitogenome sequence makes it accessible to all genes for future population diversity evaluation of B. cockerelli.

The complete mitochondrial genome sequence of Diaphorina citri (Hemiptera: Psyllidae).

The first complete mitochondrial genome (mitogenome) sequence of Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae) from Guangzhou, China, is presented. The circular mitogenome is 14,996 bp in length with an A + T content of 74.5%, and contains 13 protein-coding genes (PCGs), 22 tRNA genes (tRNAs), two rRNA genes and an AT-rich control region. Synteny was identical to the ancestral insect mitogenomes. All PCGs start with 'ATN' codons. Eleven PCGs use the complete termination codons ('TAA' or 'TAG'), while the remaining two (cox2 and nad5) use a single 'T' as the stop codon. All tRNAs have the typical cloverleaf structure, except for trnTrp which lacks the variable arm and trnSer (AGN) which lacks the dihydrouridine arm. A phylogenetic tree, including 12 members of Sternorrhyncha, was constructed based on the 13 PCGs sequences. The resulting phylogenetic tree matched the established taxonomic scheme based on morphology.

[Controlling effects of plant extracts and pesticides on Myzus persicae and Lipaphis erysimi populations].

This paper studied the controlling effects of Xanthium sibiricum and Syngonium podophyllum ethanol extracts, mobile oil emulsion and 0.3% azadirachtin EC on Myzus persicae and Lipaphis erysimi populations both in laboratory and in field. The results showed that in laboratory, X. sibiricum extract was the key deterrent to Myzus persicae, while sprayed it with S. podophyllum extract and with petroleum spray oil or 0.3 % azadirachtin EC, the deterrent effect could be improved. As for pterigota Lipaphis erysimi, the extracts of the two plants were the main deterrents, and their interference effect was non-linear. In field, S. podophyllum extract had a stronger deterrent effect when sprayed independently. L. erysimi population could be successfully controlled by the mixtures of plant extracts and insecticides, with an efficiency of 95.7%. The best treatment against M. persicae population was X. sibiricum extract, with an efficiency of 87%, while S. podophyllum extract mixed with 0.3% azadirachtin EC, and X. sibiricum extract mixed with 0.3% azadirachtin EC had an efficiency of >80%.

[Control effects of Mikania micrantha alcohol extract on citrus red mite Panonychus citri].

This study showed that spraying 0.2 and 0.4 g x L(-1) Mikania micrantha alcohol extracts on Panonychus citri could significantly decrease the survival rates of P. citri eggs, larvae and nymphs, and 0.1 g x L(-1) M. micrantha alcohol extract could also significantly decrease the survival rates of larvae and nymphs. In a no-choice test, both the fecundity and the longevity of female P. citri fed on the leaves treated with all three test concentrations 0.1, 0.2 and 0.4 g x L(-1) of M. micrantha alcohol extracts were significantly reduced, compared with those fed on alcohol-treated leaves. In a field experiment, the efficacy of M. micrantha alcohol extracts at three test concentrations was compared with water, alcohol, and 15% Pyridaben, an acaricide widely used in commercial control of red mite in sweet orange orchards. The survival rates of P. citri eggs, larvae and nymphs in all three M. micrantha treatments were lower than the control, and the interference index of population control (IIPC) was 0.518, 0.292 and 0.277, respectively, while the IIPC for the Pyridaben treatment was 0.945, with a control efficacy of only 5.52%. M. micrantha extract had an increased control effect with its increasing concentration, and was safer to natural enemies than 15% Pyridaben. The leaves in the three M. micrantha treatments were less damaged, and their color was much deeper than that of the other three treatments. Therefore, M. micrantha alcohol extract provided a better control of citrus red mite populations than Pyridaben.

[Bioassay on oviposition repellency of non-preferable plant extracts against citrus red mite Panonychus citri].

The oviposition repellency of the alcohol extracts from 50 species of non-preferable plants and azadirachtin against citrus red mite (Panonychus citri) was determined using laboratory bioassays. In choice tests, the extracts from 42 of the 50 plant species and 1% azadirachtin (2000 x) significantly reduced oviposition 1d after treatment. The repellency effect of the extracts from the 42 plant species was better than that of azadirachtin. Mikania micrantha extract had the best result, with an Interference Index of Population Control (IIPC) of 0.087 1 d after treatment, and significantly reduced oviposition for 9 d, while the extracts from Sesbania cannabina, Allium tuberosum, Paederia scandens, Duranta erecta and Dicranopteris pedata also had good effects, with an oviposition repellency of over 70% 1 d after treatment, and significantly reduced oviposition for 4-6 d. The effect became weaker as time went on. None of the extracts showed significant oviposition attraction.