Resistance status of the carmine spider mite,Tetranychus cinnabarinus and the twospotted spider mite,Tetranychus urticae to selected acaricides on strawberries

The carmine spider mite, Tetranychus cinnabarinus (Boisduval) and the twospotted spider mite, Tetranychus urticae Koch, are serious pests of strawberries and many other horticultural crops. Control of these pests has been heavily dependent upon chemical acaricides. Objectives of this study were to determine the resistance status of these two pest species to commonly used acaricides on strawberries in a year‐round intensive horticultural production region. LC₉₀ of abamectin for adult carmine spider mites was 4% whereas that for adult twospotted spider mites was 24% of the top label rate. LC_90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 0.5%, 0.5%, 1.4% and 83% of their respective highest label rates for carmine spider mite eggs, 0.7%, 2.7%, 12.1% and 347% of their respective highest label rates for the nymphs. LC_90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respective highest label rates for twospotted spider mite eggs, 3%, 13%, 432,214% and 15% of their respective highest label rates for the nymphs. Our results suggest that T. cinnabarinus have developed resistance to bifenazate and that the T. urticae have developed resistance to hexythiazox. These results strongly emphasize the need to develop resistance management strategies in the region.     

On gene flow between Tetranychus urticae Koch, 1836 and Tetranychus cinnabarinus (Boisduval) Boudreaux, 1956 (Acari: Tetranychidae): Sononomy between the two species

It was found that the reproductive separation between the two-spotted spider mite (Tetranychus urticae Koch) and the carmine spider mite (Tetranychus cinnabarinus (Boisduval) is far from complete. Hybrid strains were established which possessed the morphological characteristics of T. cinnabarinus, but which were homozygous for a marker gene originating from T. urtica. In addition, short-day treatment leads to diapause not only in the species from cold climates (T. urticae), but also in a population of T. cinnabarinus. It is questioned whether T. cinnabarinus deserves ranking at species level.

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Résumé Ce travail montre que l'isolement reproductif entre Tetranychus uriticae Koch et Tetranychus cinnabarinus (Boisduval), est loin d'être complet. L'auteur a obtenu des souches hybrides présentant les caractéristiques morphologiques de T. cinnabarinus, mais homozygotes pour un gêne marqueur provenant de T. urticae. De plus, une diminution de la photopériode entraîne l'entrée en diapause des espèces provenant de régions à climat froid (T. urticae), mais aussi d'une population de T. cinnabarinus.Il est finalemant proposé de considérer Tetranychus cinnabarinus (Boisduval) Boudreaux, 1956, comme un synonyme de Tetranychus urticae Koch, 1836.

     

Effects of host interaction with Wolbachia on cytoplasmic incompatibility in the two‐spotted spider mite Tetranychus urticae

The endosymbiotic bacterium Wolbachia pipientis infects a wide range of arthropods and induces a variety of reproductive anomalies, including cytoplasmic incompatibility (CI). Three populations of the two‐spotted spider mite, Tetranychus urticae, were investigated in the present study. Based on gene sequencing, they had different host genetic backgrounds but were infected with the same Wolbachia strain. We also examined the CI level relative to host background, male age, Wolbachia density, and Ankyrin (ANK) gene expression in T. urticae. The results of the present study suggest that: (1) CI differences between populations appear to be a result of host genetic background; (2) male age is not a factor determining intensity of CI; (3) Wolbachia density in males may serve as threshold factor necessary for the CI to occur in T. urticae, after which other factors become important in determining the strength of CI; and (4) hosts may modulate CI intensity through modulation of ANK gene expression in males. Our results describe a new type of interaction between Wolbachia and its hosts, and the effect of the interactions on CI. Further investigations on the functions of Wolbachia ankyrin gene products and their host targets, particularly with respect to host reproductive manipulation, are also imperative.     

Spider-Mite Problems and Control in Taiwan

Problems with spider mites first appeared in Taiwan in 1958, eight years after the importation of synthetic pesticides, and the mites evolved into major pests on many crops during the 1980s. Of the 74 spider mite species recorded from Taiwan 10 are major pests, with Tetranychus kanzawai most important, followed by T. urticae, Panonychus citri, T. cinnabarinus, T. truncatus and Oligonychus litchii. Most crops suffer from more than one species. Spider mites reproduce year-round in Taiwan. Diapause occurs only in high-elevation areas. Precipitation is the most important abiotic factor restricting spider-mite populations. Control is usually accomplished by applying chemicals. Fifty acaricides are currently registered for the control of spider mites. Acaricide resistance is a serious problem, with regional variation in resistance levels. Several phytoseiid mites and a chrysopid predator have been studied for control of spider mites with good effect. Efforts to market these predators should be intensified so that biological control can be a real choice for farmers.     

Effect of the extract and compound from Solanum nigrum Linn on Tetranychus cinnabarinus

The carmine spider mite Tetranychus cinnabarinus (Boisduval) is a serious pest affecting various glasshouse vegetables, fruits and crops and causes significant damage to crop yields and quality by piercing and sucking foliar tissues. The control of this mite primarily involves the application of synthetic chemical pesticides. In this study, a Solanum nigrum L. extract was evaluated for its potential acaricidal activity against adult female T. cinnabarinus in laboratory conditions, and the S. nigrum extract showed marked efficacy in controlling the carmine spider mite both in vitro and in potted seedlings. Furthermore, the active compound, a phytostanol ester (β‐sitosterol‐3‐O‐heptadeca‐8Z, 11Z‐dienoate), was isolated from the petroleum ether‐soluble fraction of S. nigrum extract via repeated column chromatography and identified based on its physiochemical properties and spectral data. At 7 days after treatment in a potted seedling experiment, the LC₅₀ values of the S. nigrum extract and active compound were found to be 4.70 and 1.85 g/l, respectively. All of these results demonstrated that the S. nigrum extract and its active component exhibit the potential for use as new natural acaricides for controlling carmine spider mites.     

Herbivore performance and plant defense after sequential attacks by inducing and suppressing herbivores

It is well known that herbivore-induced plant defenses alter host plant quality and can affect the behavior and performance of later arriving herbivores.Effects of sequential attacks by herbivores that either suppress or induce plant defenses are less well studied.We sequentially infested leaves of tomato plants with a strain of the phytophagous spider mite Tetranychus urticae that induces plant defenses and the closely related Tetranychus evansi, which suppresses plant defenses.Plant quality was quantified through oviposifion of both spider mite species and by measuring proteinase inhibitor activity using plant material that had been sequentially attacked by both herbivore species.Spider-mite oviposifion data show that T.evansi could suppress an earlier induction of plant defenses by T.urticae,and T.urticae could induce defenses in plants previously attacked by T.evansi in 1 day.Longer attacks by the second species did not result in further changes in oviposifion.Proteinase inhibitor activity levels showed that T.evansi suppressed the high activity levels induced by T.urticae to constitutive levels in 1 day,and further suppressed activity to levels similar to those in plants attacked by T.evansi alone.Attacks by T.urticae induced proteinase inhibitor activity in plants previously attacked by T.evansi,eventually to similar levels as induced by T.urticae alone.Hence,plant quality and plant defenses were significantly affected by sequential attacks and the order of attack does not affect subsequent performance,but does affect proteinase inhibitor activity levels.Based on our results,we discuss the evolution of suppression of plant defenses.     

Dispersal of diapausing Tetranychus urticae and T. kanzawai

The spider mites Tetranychus urticae Koch and Tetranychus kanzawai Kishida (Acari: Tetranychidae) overwinter mostly as mated adult diapausing females. Their overwintering survival depends in part on their dispersal towards suitable habitats. We investigated the dispersal behaviour of diapausing females of T. urticae and T. kanzawai with respect to factors known to affect the dispersal of non‐diapausing mites: light, population density, gravity, and humidity. In general, diapausing females of T. urticae showed a stronger tendency to disperse than did those of T. kanzawai under all test conditions. High population density promoted the dispersal of diapausing T. urticae, but not of T. kanzawai. Dispersal of diapausing females of both species was not significantly affected by gravity, humidity, or whether feeding damage was caused by conspecifics or heterospecifics. On plants, more T. urticae than T. kanzawai moved downward. We propose that dispersal after the onset of diapause may be an important life‐history strategy in T. urticae, but not in T. kanzawai.     

Preliminary evaluation of <Emphasis Type="Italic">Cladosporium cladosporioides</Emphasis> (Fresen.) de Vries in laboratory conditions,as a potential candidate for biocontrol of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> Koch

A survey for natural entomopathogenic fungi of two spotted spider mite (Tetranychus urticae) adults was made in Erzurum, Turkey, during the period 2006. Tetranychus urticae (65.8%) infected with a strain of the fungus Cladosporium cladosporioides were found. Thirteen isolates of C. cladosporioides were assessed against T. urticae, in a single dose (8 × 10⁶ conidia ml ⁻¹), laboratory bioassay on bean leaflets. The total mortality percentage caused by C. cladosporioides isolates varied from 50.95 to 74.76% and LT₅₀ values ranged from 2.34 to 3.90 days. The results revealed that isolates of C. cladosporioides were effective against two spotted spider mite. This is the first record of natural infection of T. urticae by C. cladosporioides.     

Lethal activity of beauvericin,a Beauveria bassiana mycotoxin,against the two‐spotted spider mites,Tetranychus urticae Koch

The entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin is known to produce a broad range of secondary metabolites. Beauvericin, a cyclic hexadepsipeptide, is the best known mycotoxin produced by B. bassiana; however, reports discussing the insecticidal activity of beauvericin per se are limited. In this study, we assessed the lethal activity of beauvericin against Tetranychus urticae Koch (Acarina: Tetranychidae). In addition, screening for suitable application of the mycotoxin against T. urticae on greenhouse strawberries is discussed. Beauvericin was able to control successfully T. urticae where concentrations of 10, 100 and 1,000 µg/g recorded mortalities of 84%, 100% and 100%, respectively, against motile stages. Furthermore, beauvericin inhibited egg hatching up to 83.3%, 69.3% and 53.3%, respectively, using the same concentrations under laboratory conditions. Under greenhouse conditions, the efficacy recorded was 52.6%, 85.7%, 72.4% and 72.4% at 1, 3, 7 and 10 days post‐inoculation, respectively. Beauvericin was efficacious under greenhouse conditions since the application increased strawberry yields while showing no phytotoxicity and ecotoxicological risk. Resistance to beauvericin was not detected initially at the unselected strain of T. urticae. Yet, the laboratory selection of populations of T. urticae exposed to beauvericin resulted in relatively resistant T. urticae strain that displayed no cross‐resistance to cyflumetofen and bifenazate. The acaricidal activity of beauvericin documented in this study would increase the efficacy of integrated pest management strategies.     

Optimum release times for biological control of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) by Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseidae) on the strawberry in greenhouses

The effectiveness of the predatory mite Phytoseiulus persimilis Athias‐Henriot (Acari: Phytoseidae) in controlling the two‐spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) was evaluated in commercial strawberry greenhouses in two areas of Korea. Optimum release times for P. persimilis were investigated by case studies. Control effects of the two‐spotted spider mite by release of the predatory mite were shown. There was mostly good control by the release of P. persimilis when there were fewer than 0.9 T. urticae per leaf. We recommend it would be ideal to release P. persimilis twice in December and once in February for very early strawberry harvest, and three times from February to March (after overwintering) for early harvest.     

Salivary proteins of spider mites suppress defenses in Nicotiana benthamiana and promote mite reproduction

Spider mites (Tetranychidae sp.) are widely occurring arthropod pests on cultivated plants. Feeding by the two‐spotted spider mite T. urticae, a generalist herbivore, induces a defense response in plants that mainly depends on the phytohormones jasmonic acid and salicylic acid (SA). On tomato (Solanum lycopersicum), however, certain genotypes of T. urticae and the specialist species T. evansi were found to suppress these defenses. This phenomenon occurs downstream of phytohormone accumulation via an unknown mechanism. We investigated if spider mites possess effector‐like proteins in their saliva that can account for this defense suppression. First we performed an in silico prediction of the T. urticae and the T. evansi secretomes, and subsequently generated a short list of candidate effectors based on additional selection criteria such as life stage‐specific expression and salivary gland expression via whole mount in situ hybridization. We picked the top five most promising protein families and then expressed representatives in Nicotiana benthamiana using Agrobacterium tumefaciens transient expression assays to assess their effect on plant defenses. Four proteins from two families suppressed defenses downstream of the phytohormone SA. Furthermore, T. urticae performance on N. benthamiana improved in response to transient expression of three of these proteins and this improvement was similar to that of mites feeding on the tomato SA accumulation mutant nahG. Our results suggest that both generalist and specialist plant‐eating mite species are sensitive to SA defenses but secrete proteins via their saliva to reduce the negative effects of these defenses.     

Evaluation of a damage threshold for two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), in hop culture

Damage caused by two‐spotted spider mites (Tetranychus urticae) at harvest to yield, quality (measured in percentage α‐acids content) and cone infestation was assessed on hop cvs Hallertauer Magnum, Hallertauer Tradition and Perle. Acaricide‐untreated hop plants with known levels of T. urticae infestation were compared with neighbouring acaricide‐treated plants. Although in 24 of the 36 experimental harvests the untreated hop plants had spider mite infestations of > 100 mites leaf^?1, yields and α‐acids content from the untreated plants were significantly lower than the treated plants in only four instances. However, although mite infestation of cones from untreated hops were significantly higher than acaricide‐treated plants in 27 of the 36 cases, in only one instance did that cause economic loss. Spider mite infestation levels of c. 90 mites leaf^?1 are tolerable at harvest time with little or no risk of causing economic loss to hop growers.     

Survey of natural enemies of spider mites (Acari: Tetranychidae) in citrus orchards in eastern Spain

Field surveys were conducted from 2004 to 2007 to determine the species composition and relative abundance of natural enemies associated with colonies of either the citrus red mite, Panonychus citri, or the two spotted spider mite, Tetranychus urticae, in Valencian citrus orchards (eastern Spain). Fourteen species were recorded, six phytoseiid mites and eight insect predators. Two of them are reported for the first time on citrus in Spain and two more are first reports as predators associated with T. urticae. The community of predators associated with T. urticae and P. citri was almost identical, and the Morisita–Horn index of similarity between both natural enemy complexes was close to one, suggesting that predators forage on both pest species. Quantifying the presence of many known spider mites predators in Valencian citrus orchards is an important first step towards spider mite control. A challenge for future studies will be to establish conservation and/or augmentation management strategies for these predators, especially to improve T. urticae biological control.     

Genetic structure of a phytophagous mite species affected by crop practices: the case of Tetranychus urticae in clementine mandarins

Tetranychus urticae Koch is a cosmopolitan mite considered as the most polyphagous species among spider mites. This mite is a key pest of clementine mandarins in Eastern Spain, where Spanish clementine production concentrates. Crop management practices can affect the population dynamics of this mite and, consequently, its impact on the orchard. Microsatellite markers were used to study mite population genetics from two commercial orchards which had been managed differently following Integrated Pest Management (IPM) or Organic Pest Management (OPM) schemes during four consecutive years. A multiplex system including 20 microsatellite loci was designed specifically and allowed an efficient and inexpensive genotyping of individual mites. We found that the IPM population had a stronger fluctuation of population structure and higher genetic diversity compared to OPM population. Thus, our study concludes that crop management has an impact on the population genetics of T. urticae which may be related to the alternation of some acaricides under IPM.     

Behavioural response and winter survival of mated and unmated diapausing females of the Tetranychus atlanticus-urticae complex (Acari, Tetranychidae)

Behavioural responses were studied in mated and unmated females of a Dutch strain of the spider mite Tetranychus urticae which were destined to enter diapause. Observations were confined to the period between acquirement of the winter coloration by the females (a few days after the last moult) and their entering of artificial hibernation sites offered to the mites on the host leaves. Unmated females were found to stay longer on the leaf surface than mated females; they entered the hibernation sites significantly later than mated females. The delay in the search for hibernation sites shown by unmated females may be seen as a behavioural adaptation to enhance the chance of being fertilized before hibernation. Winter survival of mated and unmated diapausing females of the same strain of mites was studied both in the laboratory at a constant temperature of 2±1°C and outdoors under natural climatic conditions in Amsterdam during the winter of 1990–1991. Survival was high under both conditions for mated as well as unmated females; no significant differences in survival were found between both types of female. Observations on post-diapause females of Tetranychus atlanticus (a mite belonging to the T. urticae complex) sampled from strawberry fields near Moscow in spring, showed that at most 10% of the females of this natural spider mite population were unmated. Both mated and unmated females had survived winter temperatures of -28 to -30°C.     

Investigations on the Tetranychus urticae complex in north west Europe (Acari: Tetranychidae)

Two species of spider mite occur in greenhouses in the Netherlands. Tetranychus urticae Koch is usually green, can live on many plants, but cannot build up large populations on carnations; it may have a diapausing stage which is very resistant to cold. No biological races of T. urticae were found. T. cinnabarinus Boisd. is carmine-coloured, often found on carnations, and does not have a diapause. It is not resistant to cold.The two species do not interbreed. Growers of carnations have only T. cinnabarinus to deal with, and can arrange control measures accordingly.

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Zusammenfassung Untersuchungen der Morphologie, der Wirtspflanzenwahl, der Überwinterungsweise und Kreuzingsexperimente haben gezeigt, daß in Gewächshäusern Hollands zwei Spinnmilben-Arten auftreten, nämlich Tetranychus urticae Koch und T. cinnabarinus Boids. Darüberhinaus wurde Material von Spinnmilben je einer Lokalität in Deutschland, der Schweiz und Belgien verwendet. T. urticae ist meistens grün gefärbt, lebt an einem großen Wirtspflanzenkreis, kann aber an Nelken (Dianthus caryophyllus L.) keine Populationen bilden. Diese Art geht unter dem Einfluß verschiedener biologischer Faktoren in Diapause. Während dieser Periode ist sie sehr kälteresistent. Der Winter wird an geschützten Orten verbracht. Kreuzungen zwischen Populationen verschiedener Herkunft ergaben stets eine normale Nachkommenschaft. Zucht-experimente mit diesen Populationen auf verschiedenen Wirtspflanzen ergaben keinen Hinweis für das Bestehen von biologischen Rassen bei T. urticae. T. cinnabarinus ist karminrot gefärbt und wird am häufigsten auf Nelken gefunden, obwohl in Laboratoriumsversuchen die Entwicklung an Buschbohnen (Phaseolus vulgaris L.) schneller verläuft. Diese Art tritt überhaupt nicht in Diapause ein, bleibt den Winter über an den Blättern und ist gegenüber Kältebedingungen entschieden weniger resistent als T. urticae. Kreuzungen zwischen Populationen verschiedener Herkunft ergaben immer eine normale Nachkommenschaft.Das Ausbleiben von Bastardierungen, das in Kreuzungsexperimenten zwischen den beiden Arten gefunden wurde, erbrachte den strengsten Nachweis, daß in den Gewächshäusern zwei verschiedene Arten vorkommen.Da T. cinnabarinus hauptsächlich auf Gewächshäuser mit Nelken beschränkt ist und T. urticae sich andererseits an diesen Pflanzen nicht vermehrt, haben es die Nelkenanbauer lediglich mit T. cinnabarinus zu tun, und es ergibt sich eine Möglichkeit, Nelken frei von Spinnmilbenbefall zu halten.

     

Genetic variations in a population of herbivorous mites Tetranychus urticae in the production of the induced volatiles by kidney bean plants

Abstract

This study tested whether a population of herbivorous mites Tetranychus urticae exhibits genetic variation in the production of induced plant volatiles in kidney bean plants (Phaseolus vulgaris L.). We selected two T. urticae genotypes based on their dispersal behavior (early- and late-disperser) in two plant lines (Line-1 and Line-2). In both lines, plants infested by the early-disperser produced large amounts of induced volatiles after the spider mite population peaked on the plants, whereas those infested by the late-disperser emitted the largest amount of induced volatiles at the population peak. The possible manipulation of the production of herbivore-induced plant volatiles by herbivores is discussed.     

Various effects of ethanolic extract of Mentha pulegium on the two-spotted spider mite,Tetranychus urticae (Tetranychidae)

Ethanolic extract of Mentha pulegium was evaluated against the adults of important arthropod pest species, the two-spotted spider mite, Tetranychus urticae. Potential acaricidal impact of plant was determined by contact application. Phytotoxicity was recorded after 24 h. The value of LC₅₀ was 59,149 mg L^?1. Also, LT₅₀ values were 27.42, 25.56 and 19.79 h for 35,000, 50,000 and 100,000 mg L^?1, respectively. Also, results showed that this ethanolic extract had impact on repellency of T. urticae. All of the tested concentrations were similar in the repellency test. On the other hand, the used concentrations (1000, 4000, 6000 and 8000 mg L^?1) affected on the oviposition of mite females. These extract doses significantly decreased the egg laying on the treated surface. The current study indicated that this ethanolic extract can be used as a safe acaricide on T. urticae.