Plants with spider-mite prey attract more predatory mites than clean plants under greenhouse conditions

Although many predators and parasitoids are known to respond to odours produced by plants infested with their prey under laboratory conditions, there are actually few studies that show that this response leads to higher numbers of predators or parasitoids on the plants under natural conditions. Here we study the response of predatory mites (Phytoseiulus persimilis Athias-Henriot, Acari, Phytoseiidae) to odours from cucumber plants infested with two-spotted spider mites (Tetranychus urticae Koch, Acari, Tetranychidae) in greenhouse release experiments, where predators were released in the centre of a hexagon of cucumber plants. Forty to 57% of all predators released were recaptured on plants within 7 h. Of these, an average of 79.5% were found on infested plants, indicating that these attract about 4 times as many predators as do clean plants. Hence, the blind predatory mites were guided to the plants with prey by herbivore-induced odours produced by the plant, as was indicated by olfactometer experiments, where it was found that P. persimilis preferred odours from infested cucumber plants to odours from clean cucumber plants. The long-range searching behaviour of P. persimilis is discussed.     

Absence of odour-mediated avoidance of heterospecific competitors by the predatory mite Phytoseiulus persimilis

Arthropods use odours associated with the presence of their food, enemies and competitors when searching for patches. Responses to these odours therefore determine the spatial distribution of animals, and are decisive for the occurrence and strength of interactions among species. Therefore, a logical first step in studying food web interactions is the analysis of behaviour of individuals that are searching for patches of food. We followed this approach when studying interactions in an artificial food web occurring on greenhouse cucumber in the Netherlands. In an earlier paper we found that one of the predators of the food web, the predatory mite Phytoseiulus persimilis Athias-Henriot, used to control spider mites, discriminates between odours from plants with spider mites, Tetranychus urticae Koch, and plants with spider mites plus conspecific predators. The odours used for discrimination are produced by adult prey in response to the presence of predators, and probably serve as an alarm pheromone to warn related spider mites. Other predator species may also trigger production of this alarm pheromone, which P. persimilis could use in turn to avoid plants with heterospecific predators. We therefore studied the response of the latter to odours from plants with spider mites and 3 other predator species, i.e. the generalist predatory bug Orius laevigatus (Fieber), the polyphagous thrips Frankliniella occidentalis and the spider-mite predator Neoseiulus californicus (McGregor). Both olfactometer and greenhouse release experiments yielded no evidence that P. persimilis avoids plants with any of the 3 heterospecific predators. This suggests that these predators do not elicit production of alarm pheromones in spider mites, and we argue that this is caused by a lack of coevolutionary history. The consequences of the lack of avoidance of heterospecific predators for interactions in food webs and biological control are discussed.     

Attraction of a generalist predator towards herbivore-infested plants

The occurrence and strength of interactions among natural enemies and herbivores depend on their foraging decisions, and several of these decisions are based on odours. To investigate interactions among arthropods in a greenhouse cropping system, we studied the behavioural response of the predatory bug Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) towards cucumber plants infested either with thrips (Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)) or with spider mites (Tetranychus urticae Koch (Acari: Tetranychidae)). In greenhouse release-recapture experiments, the predatory bug showed a significant preference for both thrips-infested plants and spider mite-infested plants over clean plants. Predatory bugs preferred plants infested with spider mites to plants with thrips. Experience with spider mites on cucumber leaves prior to their release in the greenhouse had no effect on the preference of the predatory bugs. However, this experience did increase the percentage of predators recaptured. Y-tube olfactometer experiments showed that O. laevigatus was more attracted to odours from plants infested with spider mites than to odours from clean plants. Thus, O. laevigatus is able to perceive odours and may use them to find plants with prey in more natural conditions. The consequences of the searching behaviour for pest control are discussed.     

Olfactory response of predatory mites to vegetative and reproductive parts of coconut palm infested by <Emphasis Type="Italic">Aceria guerreronis</Emphasis>

The phytophagous mite Aceria guerreronis Keifer is an important pest of coconut worldwide. A promising method of control for this pest is the use of predatory mites. Neoseiulus baraki (Athias-Henriot) and Proctolaelaps bickleyi Bram are predatory mites found in association with A. guerreronis in the field. To understand how these predators respond to olfactory cues from A. guerreronis and its host plant, the foraging behavior of the predatory mites was investigated in a Y-tube olfactometer and on T-shaped arenas. The predators were subjected to choose in an olfactometer: (1) isolated parts (leaflet, spikelet or fruit) of infested coconut plant or clean air stream; (2) isolated parts of non-infested or infested coconut plant; and (3) two different plant parts previously shown to be attractive. Using T-shaped arenas the predators were offered all possible binary combinations of discs of coconut fruit epidermis infested with A. guerreronis, non-infested discs or coconut pollen. The results showed that both predators were preferred (the volatile cues from) the infested plant parts over clean air. When subjected to odours from different infested or non-infested plant parts, predators preferred the infested parts. Among the infested plant parts, the spikelets induced the greatest attraction to predators. On the arenas, both predators preferred discs of coconut fruits infested with A. guerreronis over every other alternative. The results show that both predators are able to locate A. guerreronis by olfactory stimuli. Foraging strategies and implications for biological control are discussed.     

Spider Mites Avoid Plants with Predators

While searching for food, prey can use cues associated with their predators to select patches with a reduced predation risk. In many cases, odours indicate the presence of both food and predators. Spider mites are known to use odours to locate food and mates, but also to avoid interspecific competitors. We studied the response of the two-spotted spider mite, Tetranychus urticae, to cues associated with the presence of their predators, the phytoseiid Phytoseiulus persimilis. We found that the spider mites strongly avoid plants defended by this predator, but do not avoid plants with another predatory mite, Neoseiulus californicus. Since P. persimilis is commonly used in the greenhouse where our strain of T. urticae was collected and strains of this pest are known to adapt to greenhouse environments, we hypothesize that there has been selection on the pest to recognize its enemy. We further hypothesize that there has been no selection to recognize N. californicus, as it has not been used against two-spotted spider mites in the greenhouse where our spider mites were collected. We discuss the implications of avoidance of predation by spider mites and non-lethal effects of predators for biological control of this pest in greenhouses.     

Odour-mediated preference and prey preference of Macrolophus caliginosus between spider mites and green peach aphids

Abstract  A comparative study between direct prey preference and odour-mediated preference of the predatory mirid bug, Macrolophus caliginosus , was conducted. We used a Y-tube olfactometer to determine the attraction of the predator to herbivore-induced volatiles from Myzus persicae or Tetranychus urticae -infested sweet pepper plants over clean plants and to direct prey odours over clean air. The mirid bugs showed a stronger response to odours from infested plants than to odours from clean plants. The mirids did, however, not seem to exploit odours emitted directly from the prey themselves. Our results further demonstrated that M. caliginosus prefers M. persicae to T. urticae in a direct two-choice consumption test. This preference was, however, not reflected in a similar odour-mediated preference between plant volatiles induced by either of the two preys. Two hypotheses are suggested for this neutral response of the mirids to herbivore-induced volatiles from a preference prey or a non-preference prey.     

Infochemical-mediated intraguild interactions among three predatory mites on cassava plants

Carnivorous arthropods exhibit complex intraspecific and interspecific behaviour among themselves when they share the same niche or habitat and food resources. They should simultaneously search for adequate food for themselves and their offspring and in the meantime avoid becoming food for other organisms. This behaviour is of great ecological interest in conditions of low prey availability. We examined by means of an olfactometer, how volatile chemicals from prey patches with conspecific or heterospecific predators might contribute to shaping the structure of predator guilds. To test this, we used the exotic predatory mites Typhlodromalus manihoti and T. aripo, and the native predatory mite Euseius fustis, with Mononychellus tanajoa as the common prey species for the three predatory mite species. We used as odour sources M. tanajoa-infested cassava leaves or apices with or without predators. T. manihoti avoided patches inhabited by the heterospecifics T. aripo and E. fustis or by conspecifics when tested against a patch without predators. Similarly, both T. aripo and E. fustis females avoided patches with con- or heterospecifics when tested against a patch without predators. When one patch contained T. aripo and the other T. manihoti, females of the latter preferred the patch with T. aripo. Thus, T. manihoti is able to discriminate between odours from patches with con- and heterospecifics. Our results show that the three predatory mite species are able to assess prey patch profitability using volatiles. Under natural conditions, particularly when their food sources are scarce, the three predatory mite species might be involved in interspecific and/or intraspecific interactions that can substantially affect population dynamics of the predators and their prey.     

Evaluation of the predatory mite <Emphasis Type="Italic">Phytoseiulus macropilis</Emphasis> (Acari: Phytoseiidae) as a biological control agent of the two-spotted spider mite on strawberry plants under greenhouse conditions

The predatory mite Phytoseiulus macropilis is a potential biological control agent of the two-spotted spider mite (TSSM) Tetranychus urticae on strawberry plants. Its ability to control TSSM was recently assessed under laboratory conditions, but its ability to locate and control TSSM under greenhouse conditions has not been tested so far. We evaluated whether P. macropilis is able to control TSSM on strawberry plants and to locate strawberry plants infested with TSSM under greenhouse conditions. Additionally, we tested, in an olfactometer, whether odours play a role in prey-finding by P. macropilis. The predatory mite P. macropilis required about 20 days to achive reduction of the TSSM population on strawberry plants initially infested with 100 TSSM females per plant. TSSM-infested plants attract an average of 27.5 ± 1.0% of the predators recaptured per plant and uninfested plants attracted only 5.8 ± 1.0% per plant. The predatory mites were able to suppress TSSM populations on a single strawberry plant and were able to use odours from TSSM-infested strawberry plants to locate prey in both olfactometer and arena experiments. Hence, it is concluded that P. macropilis can locate and reduce TSSM population on strawberry plants under greenhouse conditions.     

Influence of species of host plants on the predation of thrips by Neoseiulus cucumeris, Iphiseius degenerans and Orius laevigatus

A leaf-disc bioassay was used to compare the predation levels of two species of predatory mites (Neoseiulus cucumeris (Oudemans) and Iphiseius degenerans (Berlese)) and a predatory bug (Orius laevigatus (Fieber)), on the thrips Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouché), feeding on a range of susceptible plant species from twelve plant families. The predatory bug, O. laevigatus, reduced the number of thrips to a greater extent than the predatory mites and all three predators showed greater levels of predation on F. occidentalis than on H. haemorrhoidalis. The level of predation caused by each predator varied among the species of plants; the variation was greater on the plant hosts of H. haemorrhoidalis than of F. occidentalis.     

Combining plant- and soil-dwelling predatory mites to optimise biological control of thrips

The efficiency of a natural enemy combination compared to a single species release for the control of western flower thrips (WFT) Frankliniella occidentalis (Pergande) on cucumber plants was investigated. Since a large part of F occidentalis seems to enter the soil passage, a joint release of the plant-inhabiting predatory mite Amblyseius cucumeris (Oudemans) that feeds on thrips first-instar larvae and the soil-dwelling predatory mite Hypoaspis aculeifer (Canestrini) that preys on thrips pupae in the ground might offer a promising approach for a holistic control strategy. Therefore, two sets of experiments were conducted in cooperation with a commercial vegetable grower where the plants in plots were infested with a defined number of larval and adult F occidentalis. Two species of natural enemies were released either synchronously or solely, and their efficacy was compared to control plots devoid of antagonists. In both experiments, the predatory mites were released twice with a density of 46 A. cucumeris/m2, and 207 H. aculeifer/m2 (low-density) in the first experiment and 528 H. aculeifer/m2 (high-density) in the second one. Population growth of all arthropod species on the plants and in the soil was quantified at regular intervals and included all soil-dwelling mites and alternative preys present in the substrate. The results showed that H. aculeifer alone had a significant impact on thrips population development only when released at high-densities, but competence was lower compared to the other antagonist treatments. The impact of A. cucumeris alone and A. cucumeris & H. aculeifer combined was similar. Thus, the pooled exploitation of natural enemies did not boost thrips control compared to the single species application of A. cucumeris (non-additive effect), which could be explained by resource competition between both predatory mite species. Species number and population size in the soil of the experimental plots both showed a high variability, a possible consequence of their interaction with released soil-dwelling predatory H. aculeifer mites. The impact of resource competition and presence of alternative preys on thrips biological control is exhaustively discussed. From our study, we can extract the subsequent conclusions: (1) the combined use of H. aculeifer and A. cucumeris cannot increase thrips control on cucumber compared to the release of A. cucumeris alone, but the overall reliability of thrips biological control might be enhanced, (2) the availability of alternative preys seemed to affect the thrips predation rate of H. aculeifer, and (3) the impact of naturally occurring soil predatory mites on the control of WFT seemed to be partial.     

Biological Control of the Bulb Mite, Rhizoglyphus robini , by the Predatory Mite, Hypoaspis aculeifer , on Lilies: Predator-Prey Dynamics in the Soil, under Greenhouse and Field Conditions

We tested the capacity of the soil-dwelling predatory mite, Hypoapsis aculeifer , to control mites attacking lily bulbs. Experiments in the greenhouse and in the field showed that in the absence of predatory mites populations of the bulb mite, Rhizoglyphus robini , on lily bulbs increased, whereas the release of predatory mites either slowed down the increase - as observed in the field - or caused the bulb mites populations to decrease - as observed in the greenhouse. In all cases the population of predatory mites increased as long as bulb mite densities were not too low. However, within the first week after predator release there was usually a sharp decline to 10-40% of the original number released. Greenhouse experiments on intact lily bulbs in pots, boxes and 1 m 2 plots with peat soil showed that when released in a ratio of 1 predator to 2 or 5 prey, the predatory mite, Hypoaspis aculeifer , suppressed populations of bulb mites to less than 10 individual per bulb within 6 weeks. Elimination of bulb mites was observed only when the predator-to-prey ratio at release was equal to 3:1. Field experiments in 2 m 2 plots with intact bulbs in rather compact sandy soil showed that when released in ratio of 1 predator to 1 or 2 prey, the predatory mite, H. aculeifer , did not cause the population of bulb mites to decrease, but it did reduce their population growth. The initial predator-to-prey ratios required to achieve suppression (ca 1:2) or elimination (3:1) in the soil environment are much higher than those required for bulb mite elimination when lily bulb scales were embedded in a medium of vermiculite (ca 1:20). Among the possible causes are: (1) the initial losses of predators in the greenhouse and even more so in the field due to mortality and/or emigration from the experimental plots; (2) the lower temperatures in the greenhouse and especially in the field, which slow down the growth and predation processes and thereby delay prey extinction; and (3) the spatial complexity of the soil environment which creates refuges for the bulb mites.     

Odour-mediated responses of a predatory mirid bug and its prey, the two-spotted spider mite

It has been shown that many natural enemies of herbivorous arthropods use herbivore induced plant volatiles (HIPVs) to locate their prey. Herbivores can also exploit cues emitted by plants infested with heterospecifics or conspecifics. A study was conducted to test whether green bean HIPVs as well as odours emitted directly by spider mites influenced the orientation behaviour of the predatory mirid bug, Macrolophus caliginosus and its prey, Tetranychus urticae in a Y-tube olfactometer. Our results show that both spider mites and M. caliginosus preferred spider mite infested green bean plants to uninfested plants. For M. caliginosus this response was mediated by HIPVs whereas for T. urticae it was mediated through a composite response to both HIPVs and odours emitted directly by the conspecifics (and their associated products). The results may be of use in practical biocontrol situations, through e.g., plant breeding for improved HIPV production, conditioning of mass-reared predators to appropriate cues, and employment of “push–pull-strategies” by using HIPVs.     

How predatory mites find plants with whitefly prey

We investigated the searching behaviour of two species of predatory mites, Typhlodromips swirskii (Athias-Henriot) and Euseius scutalis (Athias-Henriot), both known to feed on immature stages of the whitefly Bemisia tabaci Gennadius. When released in a greenhouse inside a circle of cucumber plants that were alternatingly clean or infested with immature whiteflies, the mites took several days to find plants. Both species were recaptured significantly more on plants with whiteflies. This suggests that the mites are able to discriminate between plants with and without whiteflies. The predators may either have been attracted to plants with whiteflies from a distance or arrested on plants with whiteflies. Typhlodromips swirskii that had previously fed on whitefly immatures on cucumber leaves were significantly attracted by volatiles from cucumber plants with whiteflies in a Y-tube olfactometer. This suggests that the mites use volatile cues to discriminate between infested and clean plants. However, this response waned rapidly; if predators, experienced as above, were starved for 3–4 h in absence of cucumber leaves, they no longer preferred volatiles of infested plants to clean plants. Furthermore, T. swirskii that had no experience with immature whiteflies on cucumber plants also did not prefer odours of infested plants to those of clean plants. Because the release experiment with this species in the greenhouse was done with inexperienced predators, this suggests that the aggregation of mites on plants with whiteflies was mainly caused by differential arrestment of mites on plants with prey and clean plants. For T. swirskii, this was in agreement with the finding that the fraction of predators on plants with prey increased with time to levels higher than 70%. A less clear trend was found for E. scutalis, for which the fraction of predators on plants with prey stabilized soon after release to levels from 54–70%. Hence, the predatory mites may find plants with prey by random searching, but they are subsequently arrested on these plants. An earlier study showed that 87% of all whiteflies released in a set-up as used here were recaptured within 1 day. Hence, the effectiveness with which predatory mites locate plants with whiteflies is low compared with that of their prey. We expect this to generate spatial patterns in the dynamics of predator and prey and this may have consequences for biological control of whiteflies with predatory mites.     

Pollen as Food for the Predatory Mites Iphiseius Degenerans and Neoseiulus Cucumeris (Acari: Phytoseiidae): Dietary Range and Life History

Although all known phytoseiid mites (Acari: Phytoseiidae) are predators of mites or small insects, many readily feed and reproduce on pollen as well. This ability to feed on food from plant origin increases their survival during periods when prey is locally sparse, but might occur at the expense of the ability to utilize food as efficiently as specialized predators. In this study we compare two predatory mite species used as biological control agents against thrips, Neoseiulus cucumeris and Iphiseius degenerans, with respect to (1) the range of pollen species that may serve as food sources for a sustained oviposition; and (2) the life history and expected intrinsic growth rates on some suitable pollen diets. The results show that I. degenerans is, compared to N. cucumeris, able to utilize a larger proportion of approx. 25 pollen species tested, but does not show equally high ovipositional rates as N. cucumeris. Consequently, the highest intrinsic growth rate for I. degenerans (0.21 day ^–1) will be surpassed by N. cucumeris.     

Review Behaviour and indirect interactions in food webs of plant-inhabiting arthropods

With the increased use of biological control agents, artificial food webs are created in agricultural crops and the interactions between plants, herbivores and natural enemies change from simple tritrophic interactions to more complex food web interactions. Therefore, herbivore densities will not only be determined by direct predator–prey interactions and direct and indirect defence of plants against herbivores, but also by other direct and indirect interactions such as apparent competition, intraguild predation, resource competition, etc. Although these interactions have received considerable attention in theory and experiments, little is known about their impact on biological control. In this paper, we first present a review of indirect food web interactions in biological control systems. We propose to distinguish between numerical indirect interactions, which are interactions where one species affects densities of another species through an effect on the numbers of an intermediate species and functional indirect interactions, defined as changes in the way that two species interact through the presence of a third species. It is argued that functional indirect interactions are important in food webs and deserve more attention. Subsequently, we discuss experimental results on interactions in an artificial food web consisting of pests and natural enemies on greenhouse cucumber. The two pest species are the two-spotted spider mite Tetranychus urticae and the western flower thrips, Frankliniella occidentalis. Their natural enemies are the predatory mite Phytoseiulus persimilis, which is commonly used for spider mite control and the predatory mites Neoseiulus cucumeris and Iphiseius degenerans and the predatory bug Orius laevigatus, all natural enemies of thrips. First, we analyse the possible interactions between these seven species and we continue by discussing how functional indirect interactions, particularly the behaviour of arthropods, may change the significance and impact of direct interactions and numerical indirect interactions. It was found that a simple food web of only four species already gives rise to some quite complicated combinations of interactions. Spider mites and thrips interact indirectly through resource competition, but thrips larvae are intraguild predators of spider mites. Some of the natural enemies used for control of the two herbivore species are also intraguild predators. Moreover, spider mites produce a web that is subsequently used by thrips to hide from their predators. We discuss these and other results obtained so far and we conclude with a discussion of the potential impact of functional indirect and direct interactions on food webs and their significance for biological control.     

Review: predatory soil mites as biocontrol agents of above- and below-ground plant pests

Biological pest control is becoming increasingly important for sustainable agriculture. Although many species of natural enemies are already being used commercially, efficient biological control of various pests is still lacking, and there is a need for more biocontrol agents. In this review, we focus on predatory soil mites, their role as natural enemies, and their biocontrol potential, mainly in vegetable and ornamental crops, with an emphasis on greenhouse systems. These predators are still underrepresented in biological control, but have several advantages compared to predators living on above-ground plant parts. For example, predatory soil mites are often easy and affordable to mass rear, as most of them are generalist predators, which also means that they may be used against various pests and can survive periods of pest scarcity by feeding on alternative prey or food. Many of them can also endure unfavourable conditions, making it easier for them to establish in various crops. Based on the current literature, we show that they have potential to control a variety of pests, both in greenhouses and in the field. However, more research is needed to fully understand and appreciate their potential as biocontrol agents. We review and discuss several methods to increase their efficiency, such as supplying them with alternative food and changing soil/litter structure to enable persistence of their populations. We conclude that predatory soil mites deserve more attention in future studies to increase their application in agricultural crops.

     

A key volatile infochemical that elicits a strong olfactory response of the predatory mite <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>, an important natural enemy of the two-spotted spider mite <Emphasis Type="Italic">Tetranychus urticae</Emphasis>

Herbivore-induced plant volatiles (HIPVs) emitted from lima bean leaves infested with the two-spotted spider mites Tetranychus urticae strongly attract the predatory mites Neoseiulus californicus. Among these HIPVs, methyl salicylate and linalool can attract the predators. Three green-leaf volatiles (GLVs) of (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate and (E)-2-hexenal, found in the odor blends from T. urticae-infested leaves and physically damaged leaves, can also attract the predators. To search for a strong predator attractant, the olfactory responses of N. californicus to each synthetic compound or their combinations were investigated in a Y-tube olfactometer. When presented a choice between a mixture of the five compounds (i.e. the two HIPVs and the three GLVs) and T. urticae-infested leaves, N. californicus did not discriminate between these odor sources. The same trend was observed when either a mixture of the two HIPVs or methyl salicylate vs. T. urticae-infested leaves were compared. In contrast, the predators preferred T. urticae-infested leaves to linalool, each of the three GLVs, or a mixture of the three GLVs. These results indicated that methyl salicylate is a strong predator attractant, and its potential attractiveness almost equaled that of the blend of HIPVs from T. urticae-infested leaves.     

Attraction of Phytoseiulus persimilis (Acari: Phytoseiidae) towards volatiles from various Tetranychus urticae-infested plant species

Plants infested with the spider mite Tetranychus urticae Koch, may indirectly defend themselves by releasing volatiles that attract the predatory mite Phytoseiulus persimilis Athias-Henriot. Several plants from different plant families that varied in the level of spider mite acceptance were tested in an olfactometer. The predatory mites were significantly attracted to the spider mite-infested leaves of all test plant species. No differences in attractiveness of the infested plant leaves were found for predatory mites reared on spider mites on the different test plants or on lima bean. Thus, experience with the spider mite-induced plant volatiles did not affect the predatory mites. Jasmonic acid was applied to ginkgo leaves to induce a mimic of a spider mite-induced volatile blend, because the spider mites did not survive when incubated on ginkgo. The volatile blend induced in ginkgo by jasmonic acid was slightly attractive to predatory mites. Plants with a high degree of direct defence were thought to invest less in indirect defence than plants with a low degree of direct defence. However, plants that had a strong direct defence such as ginkgo and sweet pepper, did emit induced volatiles that attracted the predatory mite. This indicates that a combination of direct and indirect defence is to some extent compatible in plant species.     

Disentangling mite predator‐prey relationships by multiplex PCR

Gut content analysis using molecular techniques can help elucidate predator‐prey relationships in situations in which other methodologies are not feasible, such as in the case of trophic interactions between minute species such as mites. We designed species‐specific primers for a mite community occurring in Spanish citrus orchards comprising two herbivores, the Tetranychidae Tetranychus urticae and Panonychus citri, and six predatory mites belonging to the Phytoseiidae family; these predatory mites are considered to be these herbivores’ main biological control agents. These primers were successfully multiplexed in a single PCR to test the range of predators feeding on each of the two prey species. We estimated prey DNA detectability success over time (DS₅₀), which depended on the predator‐prey combination and ranged from 0.2 to 18 h. These values were further used to weight prey detection in field samples to disentangle the predatory role played by the most abundant predators (i.e. Euseius stipulatus and Phytoseiulus persimilis). The corrected predation value for E. stipulatus was significantly higher than for P. persimilis. However, because this 1.5‐fold difference was less than that observed regarding their sevenfold difference in abundance, we conclude that P. persimilis is the most effective predator in the system; it preyed on tetranychids almost five times more frequently than E. stipulatus did. The present results demonstrate that molecular tools are appropriate to unravel predator‐prey interactions in tiny species such as mites, which include important agricultural pests and their predators.     

捕食螨化学生态研究进展

捕食螨是重要的生物防治因子。早在20世纪70年代就发现了捕食螨的性信息素,许多研究证明植物挥发物在捕食螨向猎物定位过程中发挥着至关重要的作用,影响捕食螨寻找猎物的植物挥发物来源于未受害植物、机械损伤植物、猎物危害植物、非猎物危害植物。人工合成的植物挥发物组分对捕食螨具有引诱作用,但引诱活性低于虫害诱导植物释放的挥发性混合物。捕食螨的饲养条件、饥饿程度、学习与经验行为等会影响捕食螨对植物挥发物的反应。介绍了信息素与植物挥发物对捕食螨的作用,并讨论了目前存在的问题和研究前景。