Intra‐population genetic variation in diapause incidence of adult‐diapausing Tetranychus pueraricola (Acari: Tetranychidae)

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Biological parameters of the predatory mite Cheletomimus bakeri (Acari: Cheyletidae) feeding on Tetranychus cinnabarinus (Acari: Tetranychidae)

Developmental periods of egg, larva and nymphal stages and fecundity as well as predation of Cheletomimus bakeri (Acari: Cheyletidae) feeding on Tetranychus cinnabarinus (Acari: Tetranychidae) were evaluated at different temperatures (15, 20, 25, 30 and 35°C) at 65 ± 10% relative humidity and 16 L: 8D in the laboratory. The development periods of C. bakeri from egg through adult decreased significantly when the temperature was increased from 20°C to 35°C. Egg and total development periods of C. bakeri at 20, 25, 30 and 35°C were 13.86, 7.98, 5.07, 4.08 days and 58.66, 41.51, 21.21, 22.92 days, respectively. The highest numbers of total and daily egg production were found at 20°C and 30°C, respectively. Net reproductive rate (R₀ = 13.29), mean generation time (T = 88.30), gross reproductive rate (GRR = 17.46) and doubling time (DT = 23.66) were the highest at 20°C. The intrinsic rate of increase (r_m = 0.0592) and finite capacity for increase (λ = 1.061) for C. bakeri were the highest at 30°C. Predation of C. bakeri increased throughout the range of prey densities. The highest consumption number of C. bakeri feeding on T. cinnabarinus males per day was 4.63, 4.70 and 4.60 when confined to 40, 80 and 160 individuals, respectively. Our data suggest that C. bakeri does not appear to have much promise for the control of spider mites because of the characteristics of the predator such as slow development period, poor searching capacity and low intrinsic rate of increase.     

Host-plant acceptance and performance of Tetranychus urticae (Acari, Tetranychidae)

Abstract: Tetranychus urticae is a serious pest of several crops worldwide. It performs differentially on diverse host‐plant species. Because dispersion is mainly passive, the process of host‐plant selection should be viewed in terms of host‐plant acceptance and not in terms of host finding. The objectives of this study were to investigate: (1) the acceptance of strawberry (S) in comparison with onion (O), leek (L) and parsley (P) by T. urticae; and (2) the suitability of these host plants for the performance of T. urticae, in terms of fecundity and survival. Host‐plant acceptance was measured through females that settled on a test plant or females that left for another host plant. In another experiment, for a duration of 5 days, individual newly mated females were assigned to discs of each host plant and the fecundity, the maximum number of offspring obtained from one female that settled on the disc, the survival and the percentage of females that oviposited at least one egg were analysed. A choice test to measure the preference of females for different host plants was performed. Movements took place towards (S) from the three plants: (O), (L) and (P). Mites significantly moved to other places in the Petri dishes from leek‐origin discs. Dispersal of T. urticae from (S) to other host‐plant discs was similar for all plants. Mean fecundity was higher on (S) than on the other plants. The maximum number of offspring per female was highest on (S), lowest on (L) and (O), and intermediate on (P). Survival of females and percentage of females that laid at least one egg were independent of the host plant. The choice test showed that oviposition was higher on (S) and (P) and very poor on (L) and (O) and that more females settled on (S) and (P). Although mites migrated from parsley to strawberry, the first host plant has a higher acceptance of T. urticae in terms of maximum number of offspring per female than onion and leek, and a lower performance in terms of fecundity than strawberry. Parsley could be a good candidate for an associate plant in a strawberry crop; however, it needs more research under field conditions.     

Host plant-mediated interactions between Tetranychus urticae and Eotetranychus carpini borealis (Acari: Tetranychidae)

Competitive interactions between Tetranychus urticae and Eotetranychus carpini borealis were investigated under laboratory and greenhouse conditions. When placed first to colonize red raspberry leaves, T. urticae caused extinction of E. carpini borealis populations. E. carpini borealis had detrimental effects on T. urticae but did not cause T. urticae population extinction. The area used by E. carpini borealis for egg deposition decreased with an increase in the number of T. urticae eggs. Red raspberry showed an induced response to T. urticae and E. carpini borealis feeding after two weeks of infestation. Population growth of each species was reduced on plants that were previously infested by conspecifics but inducible response by one species had no effects on the other species.     

Population Dynamics of Tetranychus Kanzawai (Acari: Tetranychidae) on Hydrangea

The seasonal occurrence of Tetranychus kanzawai Kishida populations on hydrangea (Hydrangea macrophylla) was studied at two different localities in Ibaraki, Japan, during a three-year period. There were two types of seasonal population trends: one with a population peak from May to June, and the other with the spring peak in June and the autumn peak in September–October. Each year the populations on hydrangea plants abruptly declined just after the spring peak. Predators showed a delayed density-dependent numerical response. The population crashed even in the absence of predators, suggesting that the predators had nothing to do with the June decline. Furthermore, the rate of development from larva to adult and the fecundity in adult females on detached hydrangea leaves decreased markedly just prior to the abrupt decline in density in June. Consequently, seasonal changes in plant quality (perhaps influenced by secondary compounds) seem to contribute to the drastic decline of T. kanzawai density on hydrangea in June.     

Gene flow among Tetranychus urticae (Acari: Tetranychidae) populations in Greece

Polymorphism of four enzymatic loci has been examined in 27 populations of Tetranychus urticae in relation to their geographical distribution and to two ecological parameters: open field vs. greenhouse habitats, and species of the colonized host plant. Genetic differentiation was significantly correlated to geographical distance in both types of habitat. Mite density and distribution of infested plants appear to be important factors for the population structure of T. urticae . In open field, T. urticae specimens from citrus trees were genetically more similar to other 'citrus' samples collected in different localities than they were from mites collected in the same locality on other plant species.     

Acaricidal activities of extracts of Kochia scoparia against Tetranychus urticae, Tetranychus cinnabarinus, and Tetranychus viennensis (Acari: Tetranychidae)

Extracts of an annual herbaceous plant, Kochia scoparia (L.) Schrad (Macrophomina), were bioassayed to determine their acaricidal activities against Tetranychus urticae Koch, Tetranychus cinnabarinus (Boisduval), and Tetranychus viennensis Zacher (Acari: Tetranychidae) in the laboratory. Extracts had both contact and systemic toxicity to these mites. Three solvents were tested for preparing crude extracts: petroleum ether, chloroform, and methanol. Methanol was the most effective solvent, extracting 3.11-4.53% of the acaricide. Petroleum ether was the least effective solvent, extracting 1.25-1.54%. However, extracts with chloroform resulted in the highest mite mortality (78.86%), and ultrasound-assisted extraction required the least time (10 min). Concentrated extracts were prepared using chloroform, methyl acetate, or distilled water as a solvent. Mite mortalities from the concentrated extracts by methyl acetate or distilled water were significantly lower than those by chloroform. The mean lethal concentrations (LC50) of the extracts by chloroform, methyl acetate, and distilled water to the mites were 0.71 +/- 0.06, 2.08 +/- 0.16 and 8.75 +/- 0.062 mg/ml, respectively. After liquid chromatography and thin layer chromatography, the concentrated extracts by chloroform were separated into seven groups of isolated fractions and tested for acaricidal activity.     

Novel and selective acetylcholinesterase inhibitors for Tetranychus cinnabarinus (Acari: Tetranychidae)

The carmine spider mite, Tetranychus cinnabarinus (Acari: Tetranychidae), is an economically important and extremely polyphagous herbivorous pest, with the title of “resistance champion” among arthropods. Anticholinesterase insecticides such as organophosphate and carbamate account for more than one-third of global insecticide sales. The non-target toxicity and resistance problem of organophosphate and carbamate have become of growing concern, which may be due to the fact that they target the ubiquitous catalytic serine residue of acetylcholinesterase (AChE) in mammals, birds, and beneficial insects. In this study, the structural differences between T. cinnabarinus AChE and human AChE, at or near the catalytic pocket, were illustrated. From the SPECS chemical lead-compound database, 55 AChE inhibitor candidates were screened for high affinity for T. cinnabarinus AChE, but low affinity for human AChE, using the DOCK 6 and AutoDock Vina software. Three of the fifty-five candidates had inhibitory activity greater than that of the reversible AChE inhibitor eserine, with no observed inhibitory activities against human AChE. Two of the three had toxicity to T. cinnabarinus comparable to that of natural insecticidal pyrethrins. However, their potency is low compared with that of etoxazole, and further work is needed to optimize their potency. The selectivity of the three compounds over human and mite AChE may be due to their interaction with the mite-specific residues, as analyzed by Cyscore. The three compounds are potential lead compounds for development of novel acaricides against T. cinnabarinus with reduced toxicity to non-target species and a low propensity for resistance.     

Photoperiodic control of reproductive arrest in the oak-inhabiting spider mite Schizotetranychus brevisetosus (Acari: Tetranychidae)

Experimental and Applied Acarology - Populations of Schizotetranychus brevisetosus Ehara (Acari: Tetranychidae), which live on the evergreen oak (Quercus glauca), survive the coldest months as...     

Divergent methylation pattern in adult stage between two forms of Tetranychus urticae (Acari: Tetranychidae)

The two‐spotted spider mite, Tetranychus urticae Koch has two forms: green form and red form. Understanding the molecular basis of how these two forms established without divergent genetic background is an intriguing area. As a well‐known epigenetic process, DNA methylation has particularly important roles in gene regulation and developmental variation across diverse organisms that do not alter genetic background. Here, to investigate whether DNA methylation could be associated with different phenotypic consequences in the two forms of T. urticae, we surveyed the genome‐wide cytosine methylation status and expression level of DNA methyltransferase 3 (Tudnmt3) throughout their entire life cycle. Methylation‐sensitive amplification polymorphism (MSAP) analyses of 585 loci revealed variable methylation patterns in the different developmental stages. In particular, principal coordinates analysis (PCoA) indicates a significant epigenetic differentiation between female adults of the two forms. The gene expression of Tudnmt3 was detected in all examined developmental stages, which was significantly different in the adult stage of the two forms. Together, our results reveal the epigenetic distance between the two forms of T. urticae, suggesting that DNA methylation might be implicated in different developmental demands, and contribute to different phenotypes in the adult stage of these two forms.     

Genetic Differentiation in Tetranychus Urticae (Acari: Tetranychidae) from greenhouses in France

The polymorphism of 4 enzymatic systems of 21 Tetranychus urticae samples collected in southern France was analyzed in order to ascertain genetic differentiation within and between greenhouses. Genetic structure was investigated in relation to mite density, geographic distribution of greenhouses and the colonized host plant. We found that mite density and distribution of infested plants influence gene flow within greenhouses. Between greenhouses isolation by distance was significant. Differentiation did not appear to be associated with the colonized plant species.     

姜黄素类化合物对朱砂叶螨的生物活性

分别用玻片浸渍法和叶片浸渍法测定了从姜黄中分离的姜黄素(curcumin,CCM)、去甲氧基姜黄素(demethoxycurcumin,DMC)和双去甲氧基姜黄素(bisdemethoxycurcumin,BDMC) 3种天然姜黄素类化合物对朱砂叶螨Tetranychus cinnabarinus Boisduval的成螨、若螨、卵的触杀活性以及对成螨产卵的抑制作用。结果表明：3种化合物对朱砂叶螨的生物活性大小依次为BDMC>DMC>CCM。3种化合物对朱砂叶螨成螨触杀活性最高者为BDMC,处理24 h和48 h其LC₅₀分别为1.18和0.51 mg/mL。对若螨触杀活性的大体趋势与对成螨的相同,其中处理48 h,BDMC对若螨的LC₅₀最小,为2.48 mg/mL。3种化合物对朱砂叶螨卵的触杀毒力也同样表现为BDMC>DMC>CCM。3种单体化合物都表现出一定的对朱砂叶螨雌成螨的产卵抑制作用。对姜黄素类化合物构效关系的初步研究,明确了甲氧基在姜黄素模板上对杀螨活性的贡献,对于开发具经济价值的叶螨类杀螨剂或者筛选先导化合物模板,具有一定的参考价值。     

迷迭香油和花椒油对朱砂叶螨的生物活性

【目的】明确室内条件下迷迭香油和花椒油对朱砂叶螨Tetranychus cinnabarinus (Boisduval)的生物活性。【方法】采用熏蒸法和驱避法测定迷迭香油和花椒油对5日龄朱砂叶螨雌成螨的熏蒸活性、产卵抑制活性和驱避活性;并采用EthoVision XT6分析亚致死浓度下两种精油对雌成螨行为的影响。【结果】分别将5日龄雌成螨熏蒸处理12, 24和48 h后,迷迭香油对朱砂叶螨的致死率均显著高于花椒油处理组（P＜0.05）,且随着熏蒸时间的延长或精油浓度的升高,其熏蒸活性均增强;不同浓度的迷迭香油处理朱砂叶螨雌成螨24 h后的产卵抑制率均显著高于花椒油处理组（P＜0.05）。迷迭香油和花椒油处理朱砂叶螨雌成螨24 h的LC₃₀分别为6.731和120.142 μL/L;迷迭香油对朱砂叶螨雌成螨的驱避活性明显高于花椒油处理组。两种精油亚致死浓度处理朱砂叶螨雌成螨后,其自发运动方式发生了明显变化,移动频率在LC₁₀ 时呈现最高;且迷迭香油对朱砂叶螨雌成螨自发运动能力的影响比花椒油处理的影响更为明显。【结论】迷迭香油对朱砂叶螨的生物活性明显高于花椒油,因此,迷迭香油对朱砂叶螨的生物防治具有较高的应用价值。本研究为绿色蔬菜植物源杀螨剂的研究提供了科学依据。     

Isolation, characterization, inheritance and linkage of microsatellite markers in Tetranychus kanzawai (Acari: Tetranychidae)

We isolated and characterized seven microsatellite markers in Tetranychus kanzawai (Acari: Tetranychidae). We also examined the conformity of the isolated markers to Mendelian laws and analyzed linkage among the microsatellite loci. All microsatellite markers fit expected 1:1 disomic segregation ratio and hence were inherited in a Mendelian manner. Significant pairwise linkage was detected in three pairs of microsatellite loci. These isolated microsatellite markers may become a powerful tool for the study of behavioral ecology, population genetics, and genome mapping of T. kanzawai.     

Acaricidal activity of Juglans regia leaf extracts on Tetranychus viennensis and Tetranychus cinnabarinus (Acari: Tetranychidae)

Leaf extracts of the walnut, Juglans regia L., were evaluated under laboratory conditions to determine their acaricidal activity on the mites Tetranychus cinnabarinus (Boisduval) and Tetranychus viennensis Zacher (Acari: Tetranychidae). Extracts had both contact and systemic toxicity to these mites. The four solvents tested for preparing crude extracts were petroleum ether, chloroform, ethyl acetate, and methanol. Methanol was the most efficient solvent, with an extraction rate from 17.06 + 0.80 to 20.27 +/- 0.28%. Petroleum ether was the least effective solvent, with extraction rates from 2.30 +/- 0.13 to 2.71 +/- 0.13%. However, the crude extracts with petroleum ether resulted in the highest mite mortality (79.04 +/- 0.52%) in a slide dip bioassay. Mites mortalities from the concentrated extracts prepared by chloroform, ethyl acetate, methanol, or distilled water were significantly lower than petroleum ether. The mean lethal concentrations (LC50) of the extracts from petroleum ether, chloroform, ethyl acetate, methanol, and distilled water to the two mite species were 0.73 +/- 0.04, 1.66 +/- 0.28, 4.96 +/- 0.35, 7.45 +/- 0.67, and 9.91 +/- 0.32 mg/ml, respectively. After liquid chromatography and thin-layer chromatography, the concentrated extracts of petroleum ether were separated into eight fractions and tested for acaricidal activity. Fraction 6 produced significantly higher mite mortality rates than the other groups, killing approximately 90% of both species.     

Toxicity of plant essential oils to Tetranychus urticae (Acari: Tetranychidae) and Phytoseiulus persimilis (Acari: Phytoseiidae)

Fifty-three plant essential oils were tested for their toxicity against eggs and adults of Tetranychus urticae Koch as well as adults of Phytoseiulus persimilis Athias-Henriot, by using a filter paper diffusion bioassay without allowing direct contact. Responses varied according to oil type and dose, and mite species. In a plastic container (4.5 by 9.5 cm) bioassay at 14 x 10(-3) microl/ml air, caraway seed, citronella java, lemon eucalyptus, pennyroyal, and peppermint oils gave > 90% mortality against adult T. urticae, whereas 82 and 81% mortality was observed with sage and spearmint oils, respectively. With the exception of sage oil, the other six essential oils were highly effective against T. urticae eggs at 9.3 x 10(-3) microl/ml air. Against adult P. persimilis, these six test oils caused > 90% mortality at 7.1 x 10(-3) microl/ml air. Particularly peppermint oil at 4.7 x 10(-3) microl/ml air was highly toxic. In an acrylic cage (30 by 30 by 40 cm ) test, lemon eucalyptus, pennyroyal, peppermint, and spearmint oils were highly effective against adult T. urticae at 1.4 x 10(-3) microl/ml air. These results indicate that the mode of delivery of these essential oils was largely a result of action in the vapor phase via the respiratory system. The essential oils described herein merit further study as potential fumigants for T. urticae control.     

Genetic distinctness between two forms of Tetranychus urticae Koch (Acari: Tetranychidae) detected by electrophoresis

The genetic relatedness between the green and red forms of the two-spotted spider mite, Tetranychus urticae Koch, was analysed using an allozyme marker, MDH, detected by polyacrylamide gel electrophoresis. Cross experiments showed that each of the two forms had form-specific alleles for MDH. Furthermore, there was no overlapping in the alleles for MDH between the field populations of the two forms, suggesting that no gene flow would occur between them in the field.