Effect of biologically active plants used as netst material and the derived benefit to starling nestlings

Summary The European starling Sturnus vulgaris preferentially incorporates fresh sprigs of particular plant species for use as nesting material. Chemicals found in these plants may act to reduce pathogen and ectoparasite populations normally found in nest environments. The present experiments were performed to test this Nest Protection Hypothesis. In the fild, we experimentally determined that wild carrot Daucus carota, a plant species preferred as nest material, effectively reduced the number of hematophagous mites found within nests relative to control nests without green vegetation. Chicks from nests containing wild carrot had higher levels of blood hemoglobin than chicks from control nests. However, there were no differences in weight or feather development. In the laboratory, we found that wild carrot and fleabane, Erigeron philadelphicus, (also preferred by starlings as nest material) substantially reduced the emergence of feeding instars of mites, while garlic mustard, Alliaria officinalis, (commonly available but not preferred) had little effect on the emergence of mites. We infer that preferred plant material may act to inhibit feeding or otherwise delay reproduction of mites, thereby reducing risk of anemia to developing nestlings.     

Heat tolerance of strawberry tarsonemid mite Phytonemus pallidus

The heat tolerance of the strawberry tarsonemid mite Phytonemus pallidus ssp. fragariae was studied in northern Sweden by treating adult mites in hot water at temperatures 44°C, 46°C and 48°C. During the summer, the shortest exposure times required to kill all adult mites at these temperatures were 6, 2.5 and 1.25 min, respectively. It is concluded that hot‐water treatment of strawberry runners for 6.5 min at 46°C would suffice to kill all tarsonemid mites on infested runners. This exposure time includes the time needed to raise the temperature of the plant material to that of the water bath. In the autumn, from the middle of September and later, the mites became successively much more heat tolerant as they prepared for hibernation. It is expected that longer exposure periods are needed to kill mites on frigoplants.     

In situ observation of the <Emphasis Type="Italic">Cardinium</Emphasis> symbionts of <Emphasis Type="Italic">Brevipalpus</Emphasis> (Acari: Tenuipalpidae) by electron microscopy

Brevipalpus (Acari: Tenuipalpidae) mites are important pests on a variety of host plant species. The mites damage their hosts directly by feeding and some species also serve as vectors of plant viruses. Among more than 200 described Brevipalpus species, three are recognized as vectors of plant viruses: B. phoenicis, B. californicus and B. obovatus. These species occur worldwide in subtropical and tropical regions. Brevipalpus mites reproduce mostly by thelytokous parthenogenesis and this condition was attributed to a bacterial endosymbiont, recently characterized as a member of the genus Cardinium. The same symbiont infects many other arthropods and is capable of manipulating their host reproduction in various ways. Generally the presence of Cardinium is determined by molecular, PCR based, techniques. In the current work we present visual evidence for the presence of these bacteria by transmission electron microscopy as a complement of previous detection by PCR. Cardinium is easily identified by the presence of a unique array of microtubule-like structures (ML) in the cell. Symbionts have been observed in several organs and eggs from different populations of all three Brevipalpus species known as vector of plant viruses. Cardinium cells were always immersed directly within the cytoplasm of infected cells. Bacteria were observed in all females of all instars, but were absent from all males examined. Females from some Brevipalpus populations were observed to be uninfected by Cardinium. This observation confirmed previous PCR-based results that these populations were aposymbiotic. The observed distribution of the bacteria suggests that these bacteria could have other functions in the mite biology beside feminization.     

A method for both mass and individual rearing of fungivorous astigmatid mites (Acari)

Several species of common fungi were assessed as food for fungivorous astigmatid mites. Hypocrea nigricans, Botrytis cinerea and Flammulina velutipes were generally good food sources for most mites examined. Fungal mycelia growing on PDA (potato dextrose agar) medium were not only nutritionally adequate but the system also maintained high humidity through the water-based agar medium. Among acarid mites, most species of Rhizoglyphinae could be reared easily with the method. Although filter-feeding histiostomatid mites do not feed directly on hyphae, some species were successfully maintained with the same method through multiple generations. Presumably, these mites obtained sufficient nutrition from the agar medium and fungal metabolites leaching into it. Most species ultimately produced dispersing heteromorphic deutonymphs on these media. Individual mites were also maintained in isolation within glass rings on fungal colonies. Using this technique, we were able to compare developmental periods, fecundity and survival periods of mites reared under different conditions.     

Interactions in a tritrophic acarine predator-prey metapopulation system III: effects of Tetranychus urticae (Acari: Tetranychidae) on host plant condition

Spider mites are serious pests on many economically important plant species, because they may reduce plant productivity and, at high mite densities, overexploit and even kill the host plants. We have conducted a series of greenhouse experiments to quantify the effects of two-spotted spider mites (Tetranychus urticae) on host plants (Phaseolusvulgaris). The average amount of chlorophyll per cm² leaf area was used as a measure of plant condition. It was shown that chlorophyll concentration decreases with plant age and intensity of spider mite feeding. Damage caused by spider mites was assessed visually, using the Leaf Damage Index (LDI) defined by, and a mathematical relationship between the visual measurements and the amount of chlorophyll/cm² was fitted to data. The relationship may serve as a short-cut to estimate overall plant injury, expressed as the relative loss of chlorophyll/cm² leaf area caused by spider mites (D). D takes values between 0 (no injury) and 1 (all leaves dead). A highly significant positive relationship between the instantaneous spider mite density and D was found, even though D is expected to reflect the cumulated density of mites (mite-days). A model of plant growth incorporating information about plant age and D predicts that plant area has a maximum when plant age is about 60 days, and that plant area decreases exponentially with an increase in D. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pollen consumption by flower mites in three hummingbird-pollinated plant species

Laboratory studies suggest that pollen consumption by flower mites may decrease the male fitness of the plant by reducing the available pollen for dispersal. Here we assessed pollen consumption by flower mites under natural conditions in three plant species with long-lived, protandrous flowers, Moussonia deppeana (Gesneriaceae), Lobelia laxiflora and L. cardinalis (Lobeliaceae). Total pollen mass was measured after 24 and 48 h in flowers exposed to flower mites and excluded from hummingbirds, flowers exposed to mites and hummingbird visitation, and in flowers recently opened with dehisced anthers. Compared with recently opened flowers, pollen availability was reduced about half in the presence of flower mites and the same effect was observed in the three plant species. Our results suggest that flower mites are removing a great deal of pollen and the reduction of pollen implies the possibility of direct impact on pollen transfer.     

Impact and management of the eriophyoid mite Trisetacus juniperinus on the evergreen cypress Cupressus sempervirens

Abstract 1 In the Mediterranean region, the eriophyoid mite Trisetacus juniperinus causes considerable damage to the evergreen cypress, Cupressus sempervirens L., particularly in nurseries and young stands, disturbing the apical growth of the tree. 2 The impact of mites on survival and apical growth of two commercial clones of cypress (Agrimed and Bolgheri), as well as the results of differently timed pesticide applications to suppress mite population on newly grafted trees, were evaluated. 3 Mites easily infested clonal scions from rootstocks that were previously infested in the nursery, inducing tip deformation and disturbance of the growth. Apical growth was significantly lower in infested than in control trees 2 years following the graft. 4 Deformed apical buds were left early by mites, which dispersed in the crown and may have incurred high mortality. This is interpreted as a defensive reaction of the cypress to the mite attack, which involves costs resulting in reduced apical growth in both clones. However, mites partly overcame tree defences in the Bolgheri clone. 5 Healthy rootstock and graft material should be used to limit damage and maintain plant growth because natural infestations rarely occur. In case of attack, a pesticide should be applied as soon as possible because precocious mite infestation has a log‐lasting effect on tree growth, with considerable economic damage.     

Interactions in a tritrophic acarine predator-prey metapopulation system V: Within-plant dynamics of Phytoseiulus persimilis and Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae)

To investigate the relative contributions of bottom-up (plant condition) and top-down (predatory mites) factors on the dynamics of the two-spotted spider mite (Tetranychus urticae), a series of experiments were conducted in which spider mites and predatory mites were released on bean plants. Plants inoculated with 2, 4, 8, 16, and 32 adult female T. urticae were either left untreated or were inoculated with 3 or 5 adult female predators (Phytoseiulus persimilis) one week after the introduction of spider mites. Plant area, densities of T. urticae and P. persimilis, and plant injury were assessed by weekly sampling. Data were analysed by a combination of statistical methods and a tri-trophic mechanistic simulation model partly parameterised from the current experiments and partly from previous data. The results showed a clear effect of predators on the density of spider mites and on the plant injury they cause. Plant injury increased with the initial number of spider mites and decreased with the initial number of predators. Extinction of T. urticae, followed by extinction of P. persimilis, was the most likely outcome for most initial combinations of prey and predators. Eggs constituted a relatively smaller part of the prey population as plant injury increased and of the predator population as prey density decreased. We did not find statistical evidence of P. persimilis having preference for feeding on T. urticae eggs. The simulation model demonstrated that bottom-up and top-down factors interact synergistically to reduce the density of spider mites. This may have important implications for biological control of spider mites by means of predatory mites.     

PCR-based identification of the pathogenic bacterium, Acaricomes phytoseiuli, in the biological control agent Phytoseiulus persimilis (Acari: Phytoseiidae)

The predatory mite, Phytoseiulus persimilis is an important biological control agent of herbivorous spider mites. This species is also intensively used in the study of tritrophic effects of plant volatiles in interactions involving plants, herbivores, and their natural enemies. Recently, a novel pathogenic bacterium, Acaricomes phytoseiuli, has been isolated from adult P. persimilis females. This pathogen causes a characteristic disease syndrome with dramatic changes in longevity, fecundity, and behavior. Healthy P. persimilis use spider mite-induced volatiles to locate prey patches. Infection with A. phytoseiuli strongly reduces the attraction to herbivore-induced plant volatiles. The loss of response to herbivore-induced plant volatiles along with the other disease symptoms can have a serious impact on the success of biological control of spider mites. In this study, we have developed a molecular tool (PCR) to detect the pathogenic bacterium in individual predatory mites. PCR primers specific for A. phytoseiuli were developed based on 16S ribosomal DNA of the bacterium. The PCR test was validated with DNA extracted from predatory mites that had been exposed to A. phytoseiuli. A survey on different P. persimilis populations as well as other predatory mite species from several companies that rear predatory mites for biological control revealed that the disease is widespread in Europe and is restricted to P. persimilis. The possibility that the predatory mites get infected via their prey Tetranychus urticae could be eliminated since the PCR test run on prey gave a negative result.     

Do domatia mediate mutualistic interactions between coffee plants and predatory mites?

Many plant species possess structures on their leaves that often harbour predatory or fungivorous mites. These so‐called domatia are thought to mediate a mutualistic interaction; the plant gains protection because mites decimate plant pathogenic fungi or herbivores, whereas the mites find shelter in the domatia. We tested this hypothesis using two species of coffee (Coffea spp.) plants that posses domatia consisting of small cavities at the underside of the leaves, and which often harbour mites. We assessed densities of domatia, of the predatory mite Iphiseiodes zuluagai Denmark and Muma (Acari: Phytoseiidae) and of herbivorous mites Oligonychus ilicis (McGregor) (Acari: Tetranychidae) and Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) on Coffea arabica L. (Rubiaceae) and Coffea canephora Pierre in the field. Over a period of 50 days, C. arabica harboured on average 7.5 times more predatory mites and 0.4–0.66 fewer prey mites than C. canephora. Hence, the higher density of predatory mites on C. arabica could not be explained by higher densities of prey. However, the density of domatia on C. arabica was on average 1.65 times higher than on C. canephora, and within each species, leaves with higher densities of domatia also harboured more predators. This suggests a positive effect of domatia on predatory mites. In the laboratory, survival of adult female predatory mites on leaves of C. arabica with open domatia was indeed significantly higher than on leaves with closed domatia. Hence, predatory mites benefited from the domatia. However, plants with higher densities of domatia did not harbour fewer herbivores. Taken together, our study only provides partial evidence for a mutualistic interaction between coffee plants and predatory mites, mediated by domatia.     

Plants,mites and mutualism: leaf domatia and the abundance and reproduction of mites on Viburnum tinus (Caprifoliaceae)

Associations between mites and leaf domatia have been widely reported, but little is known about their consequences for either plants or mites. By excising domatia from leaves of the laureltinus, Viburnum tinus L. (Caprifoliaceae), in the garden and laboratory, we showed that domatia alter the abundance, distribution, and reproduction of potential plant mutualists. Over 4 months, leaves with domatia on six garden shrubs had 2–36 times more predatory and microbivorous mites, and more mite eggs than leaves without domatia. However, this effect varied among plants and was weaker on one shrub with few mites on its leaves. Domatia also influenced the distribution of mites on leaves. A significantly higher fraction of mites, representing all life stages, was found in vein axils of leaves with domatia than in vein axils on leaves without domatia. Single-leaf experiments in the laboratory showed that domatia enhanced reproduction by the predatory mite, Metaseiulus occidentalis, especially at low relative humidity (30–38%). When domatia were removed, oviposition was reduced significantly only at low relative humidity, suggesting that domatia provide mites with refuge from environmental extremes on the leaf surface. Moreover, the use of domatia by predatory mites may reduce the impact of some plant enemies. In two experiments where prey consumption was measured, M. occidentalis ate significantly higher percentages of the eggs of the two-spotted spider mite (Tetranychus urticae). Our results are consistent with the viewpoint that mite-domatia associations are mutualistic. By directly aiding and abetting the third trophic level, plants with leaf domatia may increase the efficiency of some predaceous and microbivorous mites in consuming plant enemies.     

Control of the broad mite (Polyphagotarsonemus latus (Banks)) on organic greenhouse sweet peppers (Capsicum annuum L.) with the predatory mite, Neoseiulus cucumeris (Oudemans)

The predatory mite Neoseiulus cucumeris (Oudemans) (Acarina: Phytoseiidae) successfully controlled the broad mite Polyphagotarsonemus latus (Banks) (Acarina: Tarsonemidae) on two varieties of greenhouse-grown sweet peppers (Capsicum annuum L.). A survey of pre-plant seedlings showed that nurseries were a source of infestation for the broad mite. The predatory mites were released twice (on day 1 and 5, or 15 days later) on each plant, every second plant or every fourth plant. Broad mite populations were evaluated by sampling young leaves from the top of the plant. The effect of the broad mite on plant height, dry mass and yield was evaluated. Additionally, since N. cucumeris is known to control thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), blue sticky traps and flower sampling were used to evaluate changes in thrips populations. All three release rates of N. cucumeris significantly (P<0.05) controlled broad mite populations, but when the predatory mites were released only on every fourth plant, the overall height and yield of the plants were adversely affected by broad mites. Releasing N. cucumeris on each or every second plant was as efficacious in controlling broad mites as sulfur treatments in terms of plant height, dry mass and yield. Plants treated with sulfur, however, had significantly higher thrips populations and fruit damage.     

Diversity of phytoseiid mites (Acari: Mesostigmata: Phytoseiidae) in the Atlantic Forest of São Paulo

The objective of this study was to evaluate the diversity of Phytoseiidae in the Atlantic Forest of São Paulo State, Brazil, and to estimate the possible role of this ecosystem as a reservoir for mites of this family. Samples were taken from 187 plant species belonging to 73 plant families in three vegetation types of the Atlantic Forest, from February 2001 to October 2002. In total, 1102 specimens of 54 species belonging to 20 genera of the three phytoseiid subfamilies were found. Most specimens (93%) and species (91%) belonged to the Amblyseiinae. The majority of species found belong to taxonomic groups largely composed of generalist predators (especially Amblyseius and Euseius). In general, the more abundant mites were found on a diversity of plant species, but a few of the abundant species were found on only a small number of plant species. Only nine of the mites encountered during this study are of known agricultural importance. The results obtained suggest the importance of the wide plant diversity in the region to sustain a wide diversity of phytoseiids. The extensive clearance of the Brazilian Atlantic Forest is a threat to the diversity of these mites, important predators of mite pests.     

Phoretic dispersal on bumblebees by bromeliad flower mites (Mesostigmata, Melicharidae)

Nectarivorous flower mites (Mesostigmata: Melicharidae) live mostly on hummingbird-pollinated plants in the New World. We observed Proctolaelaps sp. living on Neoregelia johannis (Bromeliaceae) in a coastal rain forest site in south-eastern Brazil. Flower anthesis of this bromeliad lasted a single day. We recorded mites moving into, feeding from, presumably mating and reproducing, and exiting bromeliad flowers within just a single day. We observed three ant species predating flower mites on bromeliads. The main visitor was the bumblebee Bombus morio, which always landed on the inflorescence to access nectar inside the bromeliad flowers. We found Proctolaelaps sp. mites on 47% of 38 bumblebees inspected, with each Bombus hosting 2 mites on average; only adults and mostly female mites (93%) usually found on the bumblebees’ gula region of the head. This is the first study to document nectarivorous flower mites living on a melittophilous host plant using bumblebees for phoretic dispersal.     

Behaviours of phoretic mites (Acari) associated with Ips pini and Ips grandicollis (Coleoptera: Curculionidae) during host‐tree colonization

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Host Selection by the Herbivorous Mite Polyphagotarsonemus latus (Acari: Tarsonemidae)

This study examined the host-selection ability of the broad mite Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae). To make long-distance-shifts from one host plant patch to another, broad mites largely depend on phoretic association with whiteflies. However, the host plants of whiteflies and broad mites are not necessarily the same. We determined the host-preference and acceptance of free-moving and phoretic broad mites using two behavioral bioassays. We used a choice test to monitor host selection by free-moving mites. In the case of phoretic mites, we compared their rate of detachment from the phoretic vector Bemisia tabaci placed on leaves taken from various host plants. The suitability of the plant was further determined by monitoring mite’s fecundity and its offspring development. We compared the mites’ responses to young and old cucumber (Cucumis sativus cv. ‘Kfir’) leaves (3rd and 8–9th leaf from the apex, respectively), and two tomato (Solanum lycopersicum cvs. ‘M82’ and ‘Moneymaker’). Free-moving mites of all stages and both sexes preferred young cucumber leaves to old cucumber leaves and preferred young cucumber rather than young tomato leaves, demonstrating for the first time that broad mites are able to choose their host actively. As for phoretic mated females, although eventually most of the mites abandoned the phoretic vector, the rate of detachment from the whitefly vector was host dependent and correlated with the mites’ fitness on the particular host. In general, host preference of phoretic female mites resembled that of the free-moving female. Cues used by mites for host selection remain to be explored.     

Relationship between dispersal and fecundity ofTetranychus urticae Koch (Acari: Tetranychidae) exposed to flucythrinate

The effects of the synthetic pyrethroid flucythrinate on dispersal and fecundity of the two-spotted spider mite,Tetranychus urticae Koch, was investigated using a vial exposure technique that allowed treatment of mites without incidental treatment of host plant and allowed determination of the actual dose received by the mites. Flycythrinate elicited both immediate and delayed dispersal. Immediate dispersal within 120 min posttreatment was more sensitive than delayed dispersal and fecundity at 24, 48, and 72 h posttreatment. The lowest flucythrinate concentrations elicited immediate dispersal without subsequent inhibition of fecundity, providing support for the hypothesis that pyrethroid-induced mite population outbreaks can result from dispersal of healthy mites to areas of low competition. Delayed dispersal, however, was observed only in mites that had reduced fecundity. No significant increases in egg production were observed; however, mites exposed to the lowest concentrations of flucythrinate showed a trend toward increased fecundity at 48 and 72 h posttreatment. Since the mites were treated rather than the host plant, it appeared that the dispersal associated with flucythrinate was manifested primarily through a general stimulation of locomotor activity rather than directional locomotor response.Contribution from the Missouri Agricultural Experiment Station, Columbia, MO, Journal Series No. 10037.     

Interactions in a tritrophic acarine predator-prey metapopulation system IV: effects of host plant condition on Tetranychus urticae (Acari: Tetranychidae)

Feeding by spider mites can cause severe injury to a host plant and lead to a decreasing per capita growth rate and an increasing per capita emigration rate. Such density-dependent responses to local conditions are important in a metapopulation context because they allow the herbivores to colonize new host plants and thereby prolong the time until regional (metapopulation) extinction. In order to include density-dependent responses of the two-spotted spider mite (Tetranychus urticae) in a realistic metapopulation model, a series of greenhouse experiments was conducted with the purpose to quantify how the condition of bean plants (Phaseolus vulgaris) influences the demographic parameters of T. urticae. Plant age per se reduced the growth rate of the spider mites only slightly, whereas the growth rate declined significantly as the plants were injured by the mites. The relationships between plant condition (expressed by the plant injury index D) and the birth and loss (death + emigration) rates of the mites were quantified so as to predict population growth as a function of D. Maximum per capita growth rate (r) was estimated to be c. 0.21 day⁻¹. The growth rate is expected to be negative when D exceeds 0.8. When mites were allowed to emigrate to neighbouring plants via bridges, the per capita emigration rate increased almost exponentially with D. The proportion of eggs in the population decreased with D while the numerical ratio between immatures to adults and the sex ratio did not change with D. Overall, immatures and adults constituted 74% and 26%, respectively, of the active mites and c. 46% of the adults were males. The bridges that connected a donor plant with the surrounding recipient plants were responsible for the majority of the emigrations from donor plants. Most mites stopped after having crossed a single bridge, but a few crossed two bridges while none crossed three bridges within 24 h. The significance of the results for biological control is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The quantitative assessment of arthropod predation rates by electrophoresis

The development of an electrophoretic technique for the quantitative assessment of specific prey material in the gut of a predator is described. Panonychus ulmi and Tetranychus urticae were used as test prey species. Samples prepared from these mites were electrophoresed on polyacrylamide concentration gradient slab gels, which were then treated to reveal esterase activity. The relationship of intensity of a stained band with sample concentration and staining time was not linear for some esterases. Possible causes of this non-linearity were identified but could not readily be eliminated. However, quantitative assessment of prey material is possible after the preparation of a calibration curve.     

Induced defence in detached uninfested plant leaves: effects on behaviour of herbivores and their predators

Summary Induction of plant defence against herbivores may include the attraction by volatile infochemicals of natural enemies of the herbivore. The emitted volatiles that mediate this attraction may also affect the behaviour of the herbivore itself. In this paper we investigate the response of the herbivorous spider miteTetranychus urticae and the predatory mitePhytoseiulus persimilis towards volatiles whose production is induced in detached Lima bean leaves. Detached uninfested Lima bean leaves were incubated on wet cotton wool on which bean leaves infested with spider mites (T. urticae) were present simultaneously or had been present previously. These treatments induce the production of volatile infochemicals in the uninfested bean leaf tissue: predatory mites are attracted and spider mites are deterred. These are the first data on the response of predators and herbivores to plant volatiles whose production was induced in detached uninfested leaves.