Functionally different predators break down antipredator defenses of spider mites

Prey that lives with functionally different predators may experience enhanced mortality risk, because of conflicts between the specific defenses against their predators. Because natural communities usually contain combinations of prey and functionally different predators, examining risk enhancement with multiple predators may help to understand prey population dynamics. It is also important in an applied context: risk enhancement with multiple biological control agents could lead to successful suppression of pests. We examined whether risk enhancement occurs in the spider mite Tetranychus kanzawai Kishida (Acari: Tetranychidae) when exposed to two predator species: a generalist ant, Pristomyrmex punctatus Mayr (Hymenoptera: Formicidae), and a specialist predatory mite, Neoseiulus womersleyi Schicha (Acari: Phytoseiidae). We replicated microcosms that consisted of spider mites, ants, and predatory mites. Spider mites avoided generalist ants by staying inside their webs on leaf surfaces. In contrast, spider mites avoided specialist predatory mites that intruded into their webs by exiting the web, which obviously conflicts with the defense against ants. In the presence of both predators, enhanced mortality of spider mites was observed. A conflict occurred between the spider mites’ defenses: they seemed to move out of their webs and be preyed upon by ants. This is the first study to suggest that risk enhancement occurs in web‐spinning spider mites that are exposed to both generalist and specialist predator species, and to provide evidence that ants can have remarkable synergistic effects on the biological control of spider mites using specialist predatory mites.     

Amblyseius andersoni Chant (Acari: Phytoseiidae), a successful predatory mite on Rosa spp

Roses on commercial nurseries commonly suffer from attacks by the two-spotted spider mite, Tetranychus urticae, which have a negative influence on growth and quality. The aim of this project is to find natural enemies that are well adapted to roses, and may improve biological control. At different sites such as a plant collection garden, public parks and field boundaries, leaves were sampled from roses to identify the indigenous species of predatory mites. Amblyseius andersoni was amongst other species frequently found, which suggests that this species thrives well on roses. The possibility for biological control of spider mites with A. andersoni was investigated both in container roses outdoors and in glasshouses. In plots of outdoor roses artificially infested with spider mites, the following treatments were carried out: spider mites alone (untreated plot), Amblyseius andersoni Amblyseius andersoni and ice plants, Neoseiulus californicus, Neoseiulus californicus and ice plants. There were four replications of the treatments. The ice plants, Delosperma cooperi, were added to some treatments to supply pollen as extra food for the predatory mites. Natural enemies such as Chrysoperla spp., Conwentzia sp., Orius sp., Stethorus punctillum, and Feltiella acarisuga occurred naturally and contributed to the control of spider mites. After one month the spider mites were eradicated in all treatments. At the end of the trial, predatory mites were collected from all plots for identification. The ratio of Amblyseius andersoni to Neoseiulus californicus was approximately 9:1. There was no obvious effect of the ice plants on the number of predatory mites. On a nursery, where new roses are bred and selected, Amblyseius andersoni was released in three glasshouses after one early treatment with bifenazate against two-spotted spider mite Tetranychus urticae. In two of these glasshouses Neoseiulus californicus was also released. Samples, which were taken in the summer months showed that the spider mites were kept at a very low level. Amblyseius andersoni was found, even if spider mites were absent. Rose plants infested with spider mites, that were brought in to the glasshouses later developed spider mite 'hotspots'. Phytoseiulus persimilis was introduced in the hot spots and contributed to the control along with Neoseiulus californicus, Amblyseius andersoni and naturally occurring Feltiella acarisuga. These observations showed that Amblyseius andersoni is a good candidate for preventing spider mite outbreaks, as it easily survives without spider mites. This predatory mite is able to survive on other food, including thrips and fungal spores.     

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.     

Differences among plant species in acceptance by the spider mite Tetranychus urticae Koch

Abstract:  The spider mite Tetranychus urticae Koch has a broad range of host plants. However, the spider mite does not accept all plants to the same degree because of differences in nutritive and toxic constituents. Other factors, such as the induction of secondary metabolites, the morphology of a leaf surface and the presence of natural enemies, also play an important role in plant acceptance. We compared plants from various families in their degree of acceptance by the spider mite, to get an indication of the plant's direct defence. Glycine max (soybean), Humulus lupulus (hop), Laburnum anagyroides (golden chain) and Nicotiana tabacum (tobacco) were highly accepted by the spider mites. Different glandular hair densities among tobacco cultivars did not affect their suitability towards spider mites significantly. Solanum melalonga (eggplant), Robinia pseudo-acacia (black locust), Vigna unguiculata (cowpea) and Datura stramonium (thorn apple) were accepted by the spider mites to a lesser degree. Vitis vinifera (grapevine) was poorly accepted by the spider mite. It might be that the food quality of the leaves was not high enough to arrest the spider mites. Also, Capsicum annuum (sweet pepper) and especially Ginkgo biloba (ginkgo) were poorly accepted by the spider mite, probably because of the presence and concentration of certain of the secondary metabolites in the leaves. The spider mites accepted all the plants belonging to the Fabaceae for feeding, but those belonging to the Solanaceae showed a larger variance in spider mite acceptance varying from well accepted (tobacco) to poorly accepted (sweet pepper).     

Oviposition-site shift in phytophagous mites reflects a trade-off between predator avoidance and rainstorm resistance

Predators can reduce prey population densities by driving them to undertake costly defences. Here, we report on a remarkable example of induced antipredator defence in spider mites that enhances the risk to rainstorms. Spider mites live on the undersides of host plant leaves and usually oviposit on the leaf undersurface. When they are threatened by predatory mites, they oviposit on three-dimensional webs to avoid egg predation, although the cost of ovipositing on webs has not yet been clearly determined. We prepared bean plants harbouring spider mite (Tetranychus kanzawai) eggs on either leaf surfaces or webs and exposed them to rainstorms outdoors. We found that fewer eggs remained on webs than on leaf surfaces. We then examined the synergistic effect of wind and rain by simulating both in the laboratory. We conclude that ovipositing on webs comes at a cost, as eggs are washed off the host plants by wind and rain. This may explain why spider mite populations decrease drastically in the rainy season, although they inhibit leaf undersides where they are not directly exposed to rainfall.     

Pest species diversity enhances control of spider mites and whiteflies by a generalist phytoseiid predator

To test the hypothesis that pest species diversity enhances biological pest control with generalist predators, we studied the dynamics of three major pest species on greenhouse cucumber: Western flower thrips, Frankliniella occidentalis (Pergande), greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and two-spotted spider mites, Tetranychus urticae Koch in combination with the predator species Amblyseius swirskii Athias-Henriot. When spider mites infested plants prior to predator release, predatory mites were not capable of controlling spider mite populations in the absence of other pest species. A laboratory experiment showed that predators were hindered by the webbing of spider mites. In a greenhouse experiment, spider mite leaf damage was lower in the presence of thrips and predators than in the presence of whiteflies and predators, but damage was lowest in the presence of thrips, whiteflies and predators. Whitefly control was also improved in the presence of thrips. The lower levels of spider mite leaf damage probably resulted from (1) a strong numerical response of the predator (up to 50 times higher densities) when a second and third pest species were present in addition to spider mites, and (2) from A. swirskii attacking mobile spider mite stages outside or near the edges of the spider mite webbing. Interactions of spider mites with thrips and whiteflies might also result in suppression of spider mites. However, when predators were released prior to spider mite infestations in the absence of other pest species, but with pollen as food for the predators, we found increased suppression of spider mites with increased numbers of predators released, confirming the role of predators in spider mite control. Thus, our study provides evidence that diversity of pest species can enhance biological control through increased predator densities.     

Potential lethal and non-lethal effects of predators on dispersal of spider mites

Predators can affect prey dispersal lethally by direct consumption or non-lethally by making prey hesitate to disperse. These lethal and non-lethal effects are detectable only in systems where prey can disperse between multiple patches. However, most studies have drawn their conclusions concerning the ability of predatory mites to suppress spider mites based on observations of their interactions on a single patch or on heavily infested host plants where spider mites could hardly disperse toward intact patches. In these systems, specialist predatory mites that penetrate protective webs produced by spider mites quickly suppress the spider mites, whereas generalist predators that cannot penetrate the webs were ineffective. By using a connected patch system, we revealed that a generalist ant, Pristomyrmex punctatus Mayr (Hymenoptera: Formicidae), effectively prevented dispersal of spider mites, Tetranychus kanzawai Kishida (Acari: Tetranychidae), by directly consuming dispersing individuals. We also revealed that a generalist predatory mite, Euseius sojaensis Ehara (Acari: Phytoseiidae), prevented between-patch dispersal of T. kanzawai by making them hesitate to disperse. In contrast, a specialist phytoseiid predatory mite, Neoseiulus womersleyi Schicha, allowed spider mites to escape an initial patch, increasing the number of colonized patches within the system. Our results suggest that ants and generalist predatory mites can effectively suppress Tetranychus species under some conditions, and should receive more attention as agents for conservation biological control in agroecosystems.     

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.     

Plant-related factors influence the effectiveness of Neoseiulus fallacis (Acari: Phytoseiidae), a biological control agent of spider mites on landscape ornamental plants

The predatory mite Neoseiulus fallacis (Garman) was evaluated as a biological control agent of herbivorous mites on outdoor-grown ornamental landscape plants. To elucidate factors that may affect predator efficiency, replicated tests were conducted on 30 ornamental plant cultivars that varied in relationship to their generalized morphology (e.g., conifers, shade trees, evergreen shrubs, deciduous shrubs, and herbaceous perennials), production method (potted or field grown), canopy density, and the prey species present on each. Plant morphological grouping and foliar density appeared to be the most influential factors in predicting successful biological control. Among plant morphological groups, N. fallacis was most effective on shrubs and herbaceous perennials and less effective on conifers and shade trees. N. fallacis was equally effective at controlling spider mites on containerized (potted) and field grown plants, and there was no difference in control of mites on plants with Tetranychus spp. versus those with Oligonychus or Schizotetranychus spp. Moderate to unsuccessful control of spider mites by N. fallacis occurred mostly on tall, vertical plants with sparse canopies. Acceptable spider mite control occurred in four large-scale releases of N. fallacis into production plantings of Abies procera, Thuja occidentalis 'Emerald', Malus rootstock, and Viburnum plicatum 'Newport'. These data suggest that N. fallacis can be an effective biological control agent of multiple spider mite species in a range of low-growing and selected higher growing ornamental plants.     

Euseiusfinlandicus (Acari: Phytoseiidae) as a potential biocontrol agent against Tetranychus urticae (Acari: Tetranychidae): life history and feeding habits on three different types of food

Life history and reproductive parameters of the generalist predatory mite Euseius (Amblyseius) finlandicus (Oudemans) were studied in the laboratory at 25 +/- 1 degrees C, with a 16L:8D photoperiod and 60 +/- 15% RH, to investigate its response to different food sources: an eriophyid mite Aceria sp., tulip pollen Tulipa gesnerana L., and two-spotted spider mite Tetranychus urticae Koch. Total developmental time of the immature stages was the shortest on eriophyid mites, followed by pollen, and then spider mites. Fecundity was highest on pollen (43.69 eggs; 1.63 eggs/female/day), then eriophyid mites (39.73 eggs; 1.37 eggs/female/day) and lowest on spider mites (18.16 eggs; 0.80 eggs/female/day). Intrinsic rate of increase (Rm), net reproductive rate (Ro) and finite rate of increase (lambda) followed the same pattern [pollen (0.168, 27.96 and 1.183, respectively), eriophyid mites (0.153, 20.81 and 1.167), spider mites (0.110, 9.44 and 1.119)]. Mean generation time (days) was the shortest on pollen (19.90), followed by eriophyid mites (20.02), and then spider mites (20.59). Average spider mite larvae consumed by E. finlandicus during immature stages were 9.18 for males and 11.85 for females. Adult E. finlandicus females consumed an average of 166.38 spider mite protonymphs during adult stage compared to an average of 66.55 by males. The number of prey protonymphs consumed per day by females was highest in the oviposition period, lower in the pre-oviposition period and the lowest in the post-oviposition period. The eriophyid mite as a prey recorded the shortest developmental time, while pollen as food recorded the highest oviposition rate in E. finlandicus. The potential of this predator as a biocontrol agent against T. urticae is discussed.     

Positive association between thrips and spider mites in seedling cotton

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Herbivorous mites as ecological engineers: indirect effects on arthropods inhabiting papaya foliage

We examined the potential of a leaf roller to indirectly influence a community of arthropods. Two mite species are the key herbivores on papaya leaves in Hawaii: a spider mite, Tetranychus cinnabarinus Boisduval, and an eriophyid mite, Calacarus flagelliseta, which induces upward curling of the leaf margin at the end of the summer when populations reach high densities. A survey and three manipulative field experiments demonstrated that (1) leaf rolls induce a consistent shift in the spatial distribution of spider mites and their predators, the coccinellid Stethorus siphonulus Kapur, the predatory mites Phytoseiulus spp., and the tangle-web building spider Nesticodes rufipes Lucas; (2) the overall abundance of spiders increases on leaves with rolls; (3) the specialist predators Stethorus and Phytoseiulus inhabit the rolls in response to their spider mite prey; and (4) the spider inhabits the rolls in response to the architecture of the roll itself. This study shows the importance of indirect effects in structuring a terrestrial community of herbivores.     

The role of glandular and non-glandular trichomes in the negative interactions between strawberry cultivars and spider mite

In tropical countries, spider mite (Tetranychus urticae Koch) is a major pest of strawberries. This pest is mainly controlled by the application of pesticides. Use of pest-resistant cultivars is a healthy and environment-friendly alternative to pesticide use. This paper describes the role of glandular and non-glandular trichomes in the interaction between strawberry cultivars and spider mite. The methodology used in this study was based on two bioassays. First, the thumbtack bioassay of Weston and Snyder was used to differentiate strawberry cultivars in terms of the distance travelled by the mites. Second, different types of trichomes present on the abaxial surface of the strawberry leaves were identified and counted. The results of this study showed a significantly negative correlation between the distance travelled by the spider mites and the density of glandular trichomes on the strawberry plant. The cultivars Camino Real and Dover had the highest densities of glandular trichomes and the shortest distance travelled by the mites. In contrast, the cultivars Ventana and Toyonoka had the lowest density of glandular trichomes and the longest distance travelled by the spider mites. The high density of glandular trichomes might have been responsible for the spider mite non-preference to the Camino Real and Dover strawberry cultivars, whereas the non-glandular trichomes minimally contributed to this non-preference. The results of this study affirm the role of glandular trichomes in negative interactions between strawberry and spider mites.     

Predators induce interspecific herbivore competition for food in refuge space

Resource competition among herbivorous arthropods has long been viewed as unimportant because herbivore populations are controlled by predators. Although recently resurrected as an organizing force in arthropod communities on plants, there is still general agreement that resource competition among herbivores is reduced by predators. Here we show the reverse: predators induce interspecific resource competi-tion among herbivores. We found that thrips larvae ( Frankliniella occidentalis ) use the web produced and inhabited by the spider mite Tetranychus urticae as a refuge from predation by the phytoseiid mite Neoseiulus cucumeris . Thrips larvae prefer clean plant parts, but move into the web upon perceiving volatile cues associated with thrips and predators. This behaviour leads to lower predation risk, but also to reduced developmental rate and lower production of thrips larvae due to competition with spider mites. In addition, thrips larvae consume spider-mite eggs. Thus, predators induce interspecific competition and intraguild predation among herbivores within refuge space, even when host plants have an overall green appearance.     

Biocontrol of Two-spotted Spider Mite Tetranychus urticae on Dwarf Hops by the Phytoseiid Mites Phytoseiulus persimilis and Neoseiulus californicus

Two female Phytoseiulus persimilis and their offspring eliminated two-spotted spider mite Tetranychus urticae from hop leaf discs faster than two female Neoseiulus californicus and their offspring at 25°C. A combination of one female of each species and their offspring eliminated spider mites faster than the N. californicus alone, but slower than P. persimilis alone. Air relative humidities of 55% and 93% had no effect on predation. Both predator species cannibalised eggs and juveniles when spider mite numbers were low. In field experiments in 1996, fewer spider mites were recorded where P. persimilis was released, irrespective of the presence of N. californicus. Pest numbers on cv. 'First Gold' were lower than on cv. 'Herald'. No differences were recorded between the numbers of spider mite eggs in predator release treatments on 'First Gold', but fewer active stages of spider mites were recorded on plots with P. persimilis than controls soon after the time of peak pest population densities. On 'Herald', fewer spider mite active stages and eggs were recorded where predators were released than on untreated controls.     

Evaluation of airborne methyl salicylate for improved conservation biological control of two-spotted spider mite and hop aphid in Oregon hop yards

The use of synthetic herbivore-induced plant volatiles (HIPV) to attract natural enemies has received interest as a tool to enhance conservation biological control (CBC). Methyl salicylate (MeSA) is a HIPV that is attractive to several key predators of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and hop aphid, Phorodon humuli (Schrank) (Homoptera: Aphididae). A 2-year study was conducted to evaluate the recommended commercial use of MeSA in hop yards in Oregon. Slow-release MeSA dispensers were stapled to supporting poles in 0.5 ha plots and these plots were compared to a paired non-treated plot on each of three farms in 2008 and 2009. Across both years, there was a trend for reduced (range 40–91%) mean seasonal numbers of T. urticae in five of the six MeSA-baited plots. Stethorus spp., key spider mite predators, tended to be more numerous in MeSA-baited plots compared to control plots on a given farm. Mean seasonal densities of hop aphid and other natural enemies (e.g., Orius spp. and Anystis spp.) were similar between MeSA-treated and control plots. Variability among farms in suppression of two-spotted spider mites and attraction of Stethorus spp. suggests that the use of MeSA to enhance CBC of spider mites in commercial hop yards may be influenced by site-specific factors related to the agroecology of individual farms or seasonal effects that require further investigation. The current study also suggests that CBC of hop aphid with MeSA in this environment may be unsatisfactory.     

Intraguild predation of Orius tristicolor by Geocoris spp. and the paradox of irruptive spider mite dynamics in California cotton

It is paradoxical when a community of several natural enemies fails to control a pest population when it can be shown experimentally that single members of the natural enemy community are effective control agents when tested individually. This is the case for spider mites, Tetranychus spp., in California cotton. Spider mites exhibit irruptive population dynamics despite that fact that experiments have shown that there are at least four predators (Galendromus occidentalis, Frankliniella occidentalis, Orius tristicolor, and Geocoris spp.) that, when tested singly, can suppress mite populations. One possible explanation for the paradox is intraguild predation, wherein one predator consumes another. Here, I evaluate the hypothesis that intraguild predation is a strong interaction among spider mite predators. I report manipulative field experiments, focal observations of freely foraging predators in the field, and population survey data that suggest that the minute pirate bug O. tristicolor, is subject to strong predation by other members of the predator community, and in particular by Geocoris spp. These results, combined with the results of prior work, suggest that pervasive intraguild predation among spider mite predators may explain the pest status of Tetranychus spp. in cotton.     

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 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.     

Efficacy and persistence of rosemary oil as an acaricide against twospotted spider mite (Acari: Tetranychidae) on greenhouse tomato

Efficacy of rosemary, Rosmarinus officinalis L., essential oil was assessed against twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), as well as effects on the tomato, Lycopersicum esculatum Mill., host plant and biocontrol agents. Laboratory bioassay results indicated that pure rosemary oil and EcoTrol (a rosemary oil-based pesticide) caused complete mortality of spider mites at concentrations that are not phytotoxic to the host plant. The predatory mite Phytoseiulus persimilis Athias-Henriot is less susceptible to rosemary oil and EcoTrol than twospotted spider mite both in the laboratory and the greenhouse. Rosemary oil repels spider mites and can affect oviposition behavior. Moreover, rosemary oil and rosemary oil-based pesticides are nonpersistent in the environment, and their lethal and sublethal effects fade within 1 or 2 d. EcoTrol is safe to tomato foliage, flowers, and fruit even at double the recommended label rate. A greenhouse trial indicated that a single application of EcoTrol at its recommended label rate could reduce a twospotted spider mite population by 52%. At that rate, EcoTrol did not cause any mortality in P. persimilis nor did it affect their eggs. In general, EcoTrol was found to be a suitable option for small-scale integrated pest management programs for controlling twospotted spider mites on greenhouse tomato plants.