Arrestment responses of the predatory mite, Phytoseiulus persimilis, to steep odour gradients of a kairomone

ABSTRACT. The response of the predatory mite, Phytoseiulus persimilis Athias-Henriot, to steep gradients of a volatile kairomone emitted by its prey, Tetranychus urticue Koch, was studied in a vertical air flow chamber. The orientation to wind direction was eliminated by using an olfactometer that had an air stream approaching the predator from below a gauze screen upon which the predator walked. The steep gradient of odour was obtained by putting a cylinder filled with prey-infested leaves vertically below the screen. Starved predators were arrested in the odour patch by walking more slowly and tortuously than well-fed predators. The latter mites did not show a significant ortho- or klinokinetic response to the presence of odour. Both well-fed and starved predators showed a chemotactic response to steep gradients at the border of the circular odour patch. Predators that happened to walk out of the patch, frequently turned back to it. This response is presumably based on idiothetic information about the predator's immediately previous walking directions, because it occurred in the odour-free zone after passing the steep gradient of prey odour. Right-about turns can help the predator to stay in static odour plumes with steep gradients at the borders. This type of plume is present only close to the odour source. Further away from the source the odour plume tends to move to and fro due to variation in wind direction. For the predator to keep track of these snaking plumes the right-about turns are unlikely to be of any value because the response is of short duration and because the response to a moving plume appeared to be inadequate; by moving the cylinder below the screen (and consequently the odour patch) it was found that the predator turned back even if the odour gradient was made to pass the predator in the same direction as that of the predator's movement.     

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.     

Interactions of two natural enemies of Tetranychus urticae,the fungal entomopathogen Beauveria bassiana and the predatory mite,Phytoseiulus persimilis

The effect of either untreated or treated adults of the spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) by Beauveria bassiana (Bals.) Vuillemin (Ascomycota: Hypocreales) DEBI008 at 1×10⁶ (conidia/ml) was investigated on developmental stages and life table parameters of Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) under laboratory conditions. Four time intervals (0, 24, 48 and 72 h post-inoculation of spider mites) were considered for studying the predator characteristics as different treatments. Duration of each life stage, longevity, reproduction rate, intrinsic rate of natural increase (r _m ), net reproductive rate (R ₀), mean generation time (T) and finite rate of increase (λ) of the P. persimilis were calculated on both untreated and B. bassiana treated spider mite adults. Data analysis showed that longevity and fecundity of predatory mites fed on untreated and treated mites (time interval 0) were higher in comparison with other time intervals after inoculation. The entomopathogenic fungus adversely affected longevity and fecundity of the predatory mite. Fertility life table parameters of predatory mites fed on T. urticae treated by B. bassiana at different time intervals showed that T, R ₀, λ and r _m are strongly affected by the fungus presence and these parameters had significant differences among time treatments. The least r _m value was observed in the time interval of 72 h post-inoculation. The fitness of T. urticae was affected by B. bassiana 24, 48 and 72 h post-inoculation of mite adults, and consequently it caused decreased longevity of P. persimilis and accordingly a decrease in the intrinsic rate of natural increase of the predator.     

Interactions in a trirophic acarine predator-prey metapopulation system: effects of Tetranychus urticae on the dispersal rates of Phytoseiulus persimilis (Acarina: Tetranychidae, Phytoseiidae)

The dispersal behaviour of the predatory mite Phytoseiulus persimilis Athias-Henriot between bean plants was studied in a greenhouse. The aim of the study was to estimate the rate of predator emigration affected by different densities of Tetranychus urticae Koch and different numbers of between-plant connections (bridges). The results show that predators emigrate from a plant almost exclusively as a response to the local prey density whereas the loss rate (the per capita rate at which predators disappear from the system) also depends on the prey density on the surrounding plants, provided they are connected to the central plant by bridges. © Rapid Science Ltd. 1998     

Vertical dispersal of the two-spotted spider mite Tetranychus urticae, and the predatory mite Phytoseiulus persimilis on dwarf hops

1 The pattern of dispersion within plants of the two-spotted spider mite, Tetranychus urticae, and its predator, the phytoseiid Phytoseiulus persimilis, was studied on the dwarf hop variety First Gold from May to September in 1997 and 1998. 2 Spider mite populations developed on the lower leaves initially but, by late July, as the numbers of mites increased, most were found towards the top of plants. From early August, the numbers of spider mites decreased most rapidly on the upper parts of plants. 3 Where P. persimilis was released, the predator maintained the numbers of T. urticae below those found on non-release plots throughout the season. 4 By early August, the predator’s pattern of dispersion was similar to that of the pest. 5 Predators spread to non-release plots by 20 June in 1997 and 24 July in 1998 and eventually became more numerous than on the plots where they had been released.     

Mating and prey stage affecting life history,reproduction and life table of the predacious mite Phytoseiulus macropilis (Banks) (Acari: Phytoseiidae)

Abstract

Two factors were examined to determine their effect on the life history, reproduction and life table parameters in the predacious mite Phytoseiulus macropilis (Banks) in the laboratory. The factors studied included multiple mating and various prey stages of Tetranychus urticae Koch. When females fed on mixed actives (protonymphs and deutonymphs) of T. urticae, the fecundity of females mated more than once was 1.7 times higher than in females mated only once, also oviposition period and adult longevity was longer. The adult longevity and life span of P. macropilis were similar when fed on mixed actives, eggs (0 – 24-h-old) and (0 – 48-h-old) of T. urticae, while both periods were increased and reproduction was higher when fed on older eggs (72 – 96-h-old) of T. urticae. The total number of eggs deposited by females was significantly higher on eggs of (various ages) than on mixed actives of T. urticae. Life table parameters showed that a diet of (72 – 96-h-old) eggs of T. urticae provided the longest generation time (11.066 days) and female longevity (33.54 days) as well as the highest intrinsic rate of natural increase (rm = 0.36755) and greatest total fecundity which resulted in the highest net reproductive rate (Ro = 58.4136) value. The adult female consumed daily an average of 6.8 mixed actives of T. urticae during its life cycle, while it was increased to 13.6 during the oviposition period. The daily (72 – 96-h-old) eggs of T. urticae consumed by female P. macropilis during its life cycle and adult longevity was significantly higher than that recorded on either (0 – 24-h-old) or (0 – 48-h-old) eggs of T. urticae.     

Effects of host-plant species on diapause induction of the Kanzawa spider mite, Tetranychus kanzawai

In many herbivorous arthropods, incidence of diapause, which is considered to reflect the timing of diapause, changes depending on the host plants they utilize. Several theoretical studies suggest that the optimal timing of diapause induction depends on life‐history traits; if the development time of the arthropod is short, fecundity is high, or survival rate remains high throughout the season, the optimal timing of diapause induction would be shifted toward the end of the season. For herbivorous arthropods, these life history traits may change among their host plants. Here we examined whether a population of the Kanzawa spider mite, Tetranychus kanzawai Kishida (Acari: Tetranychidae), shows the predicted pattern of diapause induction on two host plants, the kidney bean [Phaseolus vulgaris (Leguminosae)] and Japanese Orixa [Orixa japonica (Rutaceae)], on which the mites show different performances. Rearing conditions were controlled in two ways. In the first experiment, day length and temperature were kept constant throughout the mite lifetime at either of three conditions from mid October to early November. In the second experiment, the conditions were changed from 20 °C and L11.5:D12.5 at immature stages to 18 °C and L11:D13 at adult stage in order to better approximate field conditions. In the first experiment, diapause incidence on P. vulgaris was lower than on O. japonica. This tendency became stronger in the second experiment, suggesting a difference in the timing of diapause induction among host plants. On the other hand, P. vulgaris was proven to allow high performance, i.e., greater lifetime fecundity and shorter development times, although it had no effect on the survival rate. The relationship between diapause incidence and performance is consistent with the prediction of theoretical studies that a short development time or high fecundity delays the timing of diapause induction.     

Geographic variation of diapause intensity in the spider mite Tetranychus urticae

Abstract. Eight strains of the spider mite Tetranychus urticae, originating from different localities in western and central Europe, with latitudes ranging from 40.5 to 60^oN, displayed marked differences in the period of chilling at 4^oC required for diapause termination under a diapause-maintaining short-day photoperiodic regime at 19^oC, to which the mites were transferred after the cold period. The higher the latitude from which the strains originated the longer was the period of chilling required for diapause termination, suggesting the presence of a gradient in diapause intensity, diapause being deeper the more northern the origin of the strains. Two strains originating from higher altitudes appeared to have a much deeper diapause than expected from their latitudinal origin. In addition, these two mountain strains showed mutual differences in diapause intensity, notwithstanding the fact that they originated from similar latitudes and altitudes; local climatic conditions probably act as strong selective forces with regard to diapause depth. All strains appeared to be sensitive to photoperiod during the period of diapause development. Diapause was quickly completed by a long-day photoperiod (LD 17:7 h), but was maintained by a short-day photoperiod (LD 10:14h). However, even under the latter regime sensitivity to photoperiod gradually diminished and eventually disappeared, thus leading to ‘spontaneous’ termination of diapause. The length of the period of diapause development, as measured by the sensitivity to photoperiod of diapausing mites, varied between strains; it was shorter in the southern strains and longer in the northern strains. The results indicate great variation in diapause intensity between strains, which is probably genetically determined and may have adaptive significance for this widespread species. When young females which had just entered diapause were kept for ever longer periods of time under the diapause inducing short-day regime at which they had been reared, before being transferred to the cold room, the duration of the period of chilling required for diapause termination was found to decrease proportionally in all three strains tested. These results suggest that intensification of diapause does not occur in T. urticae; diapause intensity seems to be highest at the beginning of diapause and to diminish gradually during diapause development.     

Inter- and intra-population variations in diapause attribute of the two-spotted spider mite,Tetranychus urticae Koch,in Japan

Populations of the two-spotted spider mite, Tetranychus urticae Koch collected from various localities and from various host plants in Japan showed wide variations in diapause attribute. Diapause percentages at 18°C/9L15D varied from nearly 100% in the north to 0% in the south-west. At intermediate latitudes the mites showed wide inter-population variations. Populations on herbaceous hosts in vinyl- or glass-houses gave significantly lower incidence of diapause than those on roses and deciduous fruit trees. Presence of winter hosts and better host quality under protected environments seemed to favour non-diapausing mites. The temperature threshold for diapause expression also varied widely among local populations. Northern populations consistently had higher and less variable thresholds than populations at intermediate latitudes with thresholds between 15 and 18°C. Inbred lines derived from a population in Kyoto exhibited a wide variation in diapause percentage at 18°C. These results show that diapause in T. urticae is a quantitative threshold trait and that populations in central Japan consist of a variety of genotypes with different diapause traits. This might provide a genetic source for adaptation to local and temporal variations in environmental conditions.     

Functional response of Nesidiocoris tenuis (Hemiptera: Miridae) to the two-spotted spider mite,Tetranychus urticae

We examined the functional response of Nesidiocoris tenuis to varying densities of the two-spotted spider mite, Tetranychus urticae and found that the data fit a Type II response, with the attack rate (a) increasing with increased predator size. N. tenuis can be considered as a potential biological control agent of this pest in tomato.     

Comparative effects of form, colour, and pheromone of twospotted spider mite quiescent deutonymphs on male guarding behaviour

Abstract. Effects of form, colour, and pheromone of twospotted spider mite, Tetranychus urticae (Koch), quiescent deutonymphs on adult male guarding behaviour were tested independently and in combination using no-choice and sequential-presentation bioassays. Significantly more males approached yellow stimuli sources than non-yellow sources in all bioassays, suggesting that males orient visually to yellow carotenoid pigments of quiescent deutonymphs. The form and extract (pheromone) of quiescent deutonymphs did not increase male approach frequency. All three cues elicited male arrestment; contrasts of 2 × 3 factorial bioassay data showed that male tactile and/or visual perception of form increased arrestment frequency more than did contact chemoperception of extract, while extract perception caused more arrestments than did visual perception of colour. All three cues prolonged arrestment duration and increased frequency of intermale conflicts near stimuli sources, but form had greater impact than did other cues on the numbers of conflicts observed during coguarding incidents. Significant interactions among stimuli were observed, indicating that presence of multiple stimuli had a synergistic effect on the duration of male response. Males approached and were arrested by all three stimuli combined as often as by quiescent deutonymphs, but arrestments caused by quiescent deutonymphs were longer than those elicited by artificial stimuli. This difference suggests that either additional cues or differences in pheromone release rates are involved in eliciting and prolonging male T. urticae guarding behaviour.     

Diapause‐inducing signals prolong nymphal development in the two‐spotted spider mite Tetranychus urticae

Female two‐spotted spider mite Tetranychus urticae are grown under different photoperiods and the photoperiodic regulation of diapause is examined. The photoperiodic response curve for diapause induction was of the long day–short day type, with critical day lengths (CDLs) of 2 and 12.5 h; diapause was induced between these CDLs. The preimaginal period is significantly longer in diapausing females than in non‐diapausing females; moreover, a significant positive correlation is detected between diapause incidence and deutonymphal period. Diapause incidence is high when long‐night photoperiods are applied against a background of continuous darkness in the stages including the deutonymph; this stage appears to be the most sensitive to photoperiod. These observations suggest that diapause‐inducing conditions inhibit nymphal development, particularly in the deutonymphal stage when photoperiodic time measurement for determination of reproduction or diapause is carried out.     

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.     

Comparative toxicity of some acaricides to the predatory mite, Phytoseiulus persimilis and the twospotted spider mite, Tetranychus urticae

The relative toxicity of someacaricides to the predatory mite, Phytoseiulus persimilis and the twospottedspider mite, Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae) wasevaluated in laboratory. Five of theacaricides tested, including bifenazate,acequinocyl, chlorfenapyr, flufenoxuron andfenbutatin oxide, were much less toxic to adultfemales and immatures of P. persimilisthan to those of T. urticae, and adultfemale predators treated with these fiveacaricides produced 84±96% as many eggs as didcontrol females. Etoxazole did not seriouslyaffect the survival and reproduction of adultfemale predators but caused high mortalityrates in eggs and larvae of P.persimilis. Milbemectin and fenazaquin werevery toxic to adult females and immatures ofP. persimilis. Adult female predatorssurvived on a diet of spider mites treated withbifenazate, acequinocyl, chlorfenapyr,flufenoxuron and fenbutatin oxide, and theirfecundity, prey consumption and the sex ratioof the progeny were not substantially affected. Based on the results, bifenazate, acequinocyl,chlorfenapyr, flufenoxuron and fenbutatin oxideappeared to be the promising candidates for usein integrated mite management programs whereP. persimilis is the major naturalenemy.     

Phytochemical,acaricidal and biological activity of Dodonaea viscosa L. against the two spotted spider mite Tetranychus urticae Koch

Alcohol extract, saponins and flavones fractionated from Dodonaea viscosa leaves were tested for their acaricidal activity against the adult females of Tetranychus urticae Koch. It was found that crude alcohol extract was more potent than the isolates obtained. At LC₅₀ and LC₉₀ levels, the crude extract ranked the first. All the biotic factors are significantly affected. The fecundity was seriously reduced however, the hatchability of eggs was not affected. Two flavonoids were identified as Querectin 3–0-glucose 7-0-rhamnoside and the other as Querectin 3-0 arabinose 7-0 rhammoside from the ethyl acetate fraction of the alcohol extract.     

Post-embryonic development of the two-spotted spider mite Tetranychus urticae with special reference to the differentiation of the female reproductive system

Summary

The spider mite, Tetranychus urticae passes through four active stages in its life cycle: larva, protonymph, deutonymph, adult. The duration at 23°C and 40–60% relative humidity is 10–12 days. Each of the movable stages is followed by a resting phase (= chrysalis) where moulting processes are prepared. The general internal anatomy of the developmental stages does not differ from that of the adults. The gonadial rudiment of the female larva is an undifferentiated cell mass situated between the nervous system and the anus. In the nymphochrysalis, development of oocytes starts as indicated by synaptonemal complexes occuring in cells which are interconnected via cytoplasmic bridges. Cells exhibiting extranuclear material appear during the protonymphal stage. The presumptive uterus and vagina are formed during the deutochrysalis stage and consist of an undifferentiated tube, the distal portion of which is lined by a fine cuticle. The ovary of the deutonymph contains different cell types. Oogonia and growing oocytes are found in the cranial germ region. Oocytes, nurse cells and cells with large lobed nuclei can be observed in the caudal previtellogenic region. Oocytes protrude through the ovarian surface and invade ovarian pouches covered only by the basement membrane whereby each is connected to a tri-nucleate nurse cell via a cytoplasmic bridge. Oocytes increase in size but do not form yolk droplets. The uterus and vagina are differentiated during the late deutonymphal stage and copulation may take place as indicated by the presence of sperm in the lumen of the seminal receptacle.

The results are compared to previously published information on the female reproductive system of T. urticae and discussed with reference to co-operation of ovarian cell types and their origin.     

New report of Neozygites sp. infecting red spider mite Tetranychus urticae infesting French bean from Eastern Plateau and Hill region,India

An anamorphic entomopathogenic fungus Neozygites sp. belonging to the Family Neozygitaceae was found infecting the tetranychid mites Tetranychus urticae Koch (Acari: Tetranychidae) of French bean (Phaseolus vulgaris L.) for the first time in Eastern Plateau and Hill region of India in the month of October 2011. The report of entomopathogenic fungus could be of help in managing acaricide resistant mites.     

Toxicity and ovicidal activity of different plant extracts on two-spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae)

The acaricidial, persistent and ovicidal activities of four methanolic extracts of Anisosciadium orientale DC., Scaligeria meifolia Boiss., Trigonella elliptica Boiss. and Ptelea viscosa L. were assessed against the two-spotted spider mite, Tetranychus urticae Koch, in a bioassay under laboratory conditions. All the extracts exhibited significant adult female mite mortality as compared to control and S. meifolia extract showed highest toxicity based on the LC₅₀ when compared with the other extracts tested. In the persistence test, the mites were exposed to 1, 24, 48 and 72 h old residues of 50% lethal concentration of methanolic extracts. The results showed that the lethal concentration effects of plant extracts fade within two or three days. S. meifolia caused high ovicidal activity (45.84%) followed by A. orientale (41.40%), T. elliptica (40.11%) and P. viscosa (37.66%). The results suggest that the methanolic extracts of A. orientale, S. meifolia, T. elliptica and P. viscosa have the potential to be used in mite pest management.