Effect of spinosad and predatory mites on control of Frankliniella occidentalis in three strawberry cultivars

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major pest of strawberry, Fragaria × ananassa Duchesne (Rosaceae). Spinosad is highly efficacious against F. occidentalis, and spinosad is believed to be compatible in an integrated pest management program. This study determined whether F. occidentalis could be controlled with predatory mites [Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) (both Acari: Phytoseiidae), and Hypoaspis miles (Berlese) (Acari: Laelapidae)] and spinosad in strawberry. In the glasshouse, three strawberry cultivars (Camarosa, Camino Real, and Albion) were sprayed once with spinosad at the recommended rate (80 ml 100 l^?1 rate, 0.096 g a.i. l^?1) or with water (control). Thrips adults were released onto plants 24 h after spraying and predatory mites released 6 days later. Spinosad significantly reduced thrips numbers compared with water. All three mite species reduced F. occidentalis numbers, and spinosad had no effect on predatory mites. Though H. miles could not be counted, the numbers of thrips in treatments with H. miles were lower than those in treatments without the mite. Thrips numbers were lowest on Camino Real and highest on Camarosa. These results suggest that the use of Camino Real with spinosad applications followed by releases of predatory mites can significantly reduce thrips numbers.     

Use of spinosad and predatory mites for the management of Frankliniella occidentalis in low tunnel‐grown strawberry

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a major pest of strawberry. The efficacy of three species of predatory mites, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) (both: Acari: Phytoseiidae), and Hypoaspis miles (Berlese) (Acari: Laelapidae), and their compatibility with spinosad for the control of this thrips was evaluated in commercial strawberry in spring. Low tunnel‐grown strawberry was treated with ‘water then mites’, ‘spinosad then mites’, or ‘mites then spinosad’. Predatory mites were released as single‐, two‐ and three‐species combinations. Overall, spinosad‐treated plants had fewer thrips than water‐treated plants (control). In all treatment regimes, each species of predatory mite reduced the number of thrips relative to those plants that received no mites. Predatory mites were most effective in reducing thrips when released after spinosad was applied. Any multiple‐species combination of predatory mites reduced thrips numbers more than single‐species releases. The two‐species combination of T. montdorensis (foliage inhabiting) and H. miles (soil dwelling) was the most effective in suppressing thrips. The next most effective combination was a three‐species release. Of multiple‐species combinations, the two‐species combination of T. montdorensis and N. cucumeris was the least effective in suppressing thrips numbers. The spinosad and mites only temporarily reduced the numbers of F. occidentalis. This suggests that further application of predatory mites, spinosad, or both is required to maintain F. occidentalis populations below an economically damaging level.     

Comparison of the predation capacities of two soil-dwelling predatory mites,Gaeolaelaps aculeifer and Stratiolaelaps scimitus (Acari: Laelapidae), on three thrips species

Soil-dwelling predatory mites are natural enemies of various soil pest insects and mites. Both Gaeolaelaps aculeifer (Canestrini) and Stratiolaelaps scimitus (Womersley) are commercialized natural enemies of thrips, but there is little information on the predation rate of these predatory mites on different thrips species. We compared their predation capacities on three thrips species, Frankliniella occidentalis, F. intonsa, and Thrips palmi, which are major pests of various horticultural plants. The predatory rate of G. aculeifer was higher than that of S. scimitus. Both predator species fed on more T. palmi thrips than F. occidentalis or F. intonsa thrips, which may be attributable to the smaller body size of T. palmi than the other thrips. Predation rates of female adults were 2.6–2.8 times higher than those of deutonymphs in both species. Predation rates were not separated according to the various developmental stages (i.e., second instar larva, pupa, or adult) of thrips; however, deutonymphs fed on fewer adults than larvae or pupae of F. occidentalis. Our results suggest that both G. aculeifer and S. scimitus are active predators that can prey during any of their developmental stages and on any species of thrips tested.     

Prey suitability of western flower thrips,Frankliniella occidentalis,and onion thrips,Thrips tabaci,for the predatory mite Amblyseius swirskii

Western flower thrips, Frankliniella occidentalis, and onion thrips, Thrips tabaci, are both important polyphagous pests of vegetables and ornamentals in greenhouses. Difficulties in biological control of these pests have prompted a search for new natural enemies. Most recently, the predatory mite Amblyseius swirskii has been commercialised as biological control agent of whiteflies and thrips. However, little is known about the suitability of thrips as prey for A. swirskii. We therefore assessed prey acceptance and life history of A. swirskii when feeding on F. occidentalis and T. tabaci at 25±1°C. Amblyseius swirskii juveniles preyed upon first larval instars of both F. occidentalis and T. tabaci but suffered from high mortality (67 and 78%). Developmental time (egg to adult) of A. swirskii was 7.8 days with either prey species. Adult A. swirskii females readily accepted first larval instars of both thrips species, which were attacked in <20 min on a leaf and <10 min in an artificial cage. Oviposition rates (0.92 and 0.99 eggs/female/day) and offspring sex ratios (63 and 70% females) were similar with F. occidentalis and T. tabaci as prey. Less than one-third of juveniles reaching adulthood and oviposition rates below one egg/female per day resulted in relatively low intrinsic rates of increase (r _m) (0.056 and 0.024 per day with F. occidentalis and T. tabaci, respectively). Altogether, our study suggests that the recently reported superiority of A. swirskii to the widely used Neoseiulus cucumeris in suppression of thrips is due to other traits than its population growth capacity with thrips as prey.     

Predatory mites avoid ovipositing near counterattacking prey

Attacking prey is not without risk; predators may endure counterattackby the prey. Here, we study the oviposition behaviour of a predatory mite(Iphiseius degenerans) in relation to its prey, thewesternflower thrips (Frankliniella occidentalis). This thrips iscapable of killing the eggs of the predator. Thrips and predatory mites - apartfrom feeding on each other - can also feed and reproduce on a diet of pollen.Because thrips may aggregate at pollen patches, such patches may be risky foroviposition by the predatory mites. We found that, in absence of thrips,predatory mites lay their eggs close to pollen, but further away when thripsarepresent. Predatory mite eggs near pollen were killed more frequently by thripsthan when they were deposited further away. The oviposition behaviour of thepredatory mite was also studied in absence of thrips, but in presence of thealarm pheromone of thrips. This pheromone is normally secreted upon contactwithpredators or competitors. When applied close to the pollen, predatory mitesoviposited significantly further away from it. When the alarm pheromone wasapplied away from the food source, most eggs were found near the pollen. Theseresults indicate that female predatory mites show flexible ovipositionbehaviourin response to the presence of their counterattacking prey.     

Generalist-feeding subterranean mites as potential biological control agents of immature corn rootworms

Predatory mites are important components of subterranean food webs and may help regulate densities of agricultural pests, including western corn rootworms (Chrysomelidae: Diabrotica virgifera virgifera). Implementing conservation and/or classical biocontrol tactics could enhance densities of specialist or generalist predatory mites and lead to pest suppression, but first relevant mite species must be identified and their predatory capabilities evaluated. We conducted lab assays to quantify consumption of immature rootworms and oviposition rates of various mite species. Our study indicates that rootworms are a sub-optimal food source for the mite taxa tested. However, all mite species fed upon rootworms to some degree, although consumption by nematophagous Eviphis ostrinus was extremely low. Predators consumed more rootworm larvae than eggs, and mite size was correlated with prey consumption, with larger predators eating more prey. Four mite taxa (Gaeolaelaps sp., S. miles, Gl. americana, and G. aculeifer) had detrimental effects on survival of rootworm larvae, and the latter two species also had negative impacts on densities of pest eggs. Although it is unlikely that any of these mite species by itself has a major impact on rootworm control, the community of generalist soil-dwelling mites may play an important role in regulating immature rootworm populations in the field.     

Oviposition patterns in a predatory mite reduce the risk of egg predation caused by prey

Abstract 1. Predatory arthropods lay their eggs such that their offspring have sufficient prey at their disposal and run a low risk of being eaten by conspecific and heterospecific predators, but what happens if the prey attacks eggs of the predator? 2. The egg distribution and time allocation of adult female predatory mites Iphiseius degenerans as affected by predation of their eggs by prey, the western flower thrips Frankliniella occidentalis, were studied on sweet pepper plants. The predatory mites attack the first instar of thrips but all active stages of thrips are capable of killing the eggs of the predator; however the predatory mite is used for biological control of thrips. 3. The majority of predatory mite eggs was laid on the underside of leaves in hair tufts (domatia). During the experiment, females spent increasing amounts of time in flowers where they fed on pollen and thrips larvae. The risk of predation on predator eggs by thrips was lower on leaves than in flowers where the majority of thrips resides. Moreover, predation risk was higher outside leaf domatia than inside. 4. This suggests that predators avoid ovipositing in places with abundant prey to prevent their eggs from being eaten by thrips.     

Combined releases of entomopathogenic nematodes and the predatory mite Hypoaspis aculeifer to control soil-dwelling stages of western flower thrips Frankliniella occidentalis

The effect of the predatory miteHypoaspis aculeifer Canestrini (Acarina:Laelapidae) on soil-dwelling stages of thewestern flower thrips (WFT) Frankliniellaoccidentalis Pergande (Thysanoptera: Thripidae)and the influence of combined releases of H.aculeifer and two entomopathogenic nematodes(EPNs) Heterorhabditis bacteriophora Poinar(Rhabditida: Heterorhabditidae) (strain HK3,HK3) and Steinernema feltiae Filipjev(Rhabditida: Steinernematidae) (Nemaplus®,SFN) were investigated in pot trials usingseedlings of green beans (Phaseolus vulgarisL.). Ten H. aculeifer adults per pot and 400infective juveniles (IJs) cm^–2 soil, of the twoEPN strains were used. In comparison withuntreated control, H. aculeifer reduced theproportion of adult F. occidentalis emergenceby 46%, while SFN and HK3 led to a reductionin adult thrips emergence by 46% and 61%,respectively. Significant differences in adultWFT emergence were found between combinedtreatments of EPNs and H. aculeifer, andindividual applications of EPNs and/or H.aculeifer, with significantly lower adultthrips emergence in the combined treatments.These findings highlight the potential for acombined use of EPNs with H. aculeifer for thecontrol of soil-dwelling stages of thrips.     

Simple mass‐rearing technique of a predatory mite Gaeolaelaps aculeifer (Canestrini) (Acari: Laelapidae)

We developed a simple mass‐rearing technique for a soil‐dwelling predatory mite Gaeolaelaps aculeifer. The rearing container consists of two (inner and outer) plastic boxes. The inner box contains rice husks, and is placed inside the outer box which contains a small amount of water. This system is useful to keep high humidity within the inner box and to prevent mites escaping from the box. The prey mite Tyrophagus putrescentiae was also reared in a similar way using rice bran and provided to G. aculeifer once a week. Rearing condition within the inner box were maintained at 25 ± 1°C, 95 ± 5% relative humidity. In this double box system, G. aculeifer was rapidly grown and overpopulated within two weeks while another predatory mite Stratiolaelaps scimitus require four weeks rearing period. This technique help farmers improve biological control efficacy of soil pests in greenhouse as well as open field cultivation.     

Rate of consumption of Western flower thrips pupae by the soil-dwelling mite Hypoaspis sclerotarsa (Acari: Laelapidae)

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), are one of the most serious pests of horticultural crops worldwide. Despite one third of its lifecycle being in the soil, the potential for biological control of WFT in the soil is poorly understood and requires further elucidation. A number of studies report that polyphagous predatory mites prey on pupal stages of WFT in the soil, but little has been done on consumption rates. Therefore, we designed a laboratory study to examine the rate of consumption of WFT pupae in potting media, by the soil-dwelling mite Hypoaspis sclerotarsa (Costa). Five predator densities were evaluated (0, 2, 4, 6 and 8) against four densities of WFT prey (5, 10, 15 and 20 pupae). Pupal consumption was assessed at 2 hourly intervals over a six-hour period. The study confirmed that H. sclerotarsa did consume WFT pupae and that the rate of consumption increased with increasing density of H. sclerotarsa. The rate of consumption also increased with the density of WFT pupae. However, this was not consistent because, as the numbers of WFT pupae increased, so did the ratio of WFT pupae remaining to those consumed, increase. This paper is the first report of H. sclerotarsa in Kenya, and of its potential as a biocontrol agent of WFT. Further studies are now needed to understand interaction of foliar and soil dwelling predatory mites (H. sclerotarsa) for control of WFT under field conditions.     

Prey preference of Orius sauteri between Western Flower Thrips and spider mites

Prey preference of polyphagous predators plays an important role in the suppression of various species of pest insects. In this study, the prey preference of Orius sauteri (Poppius) (Heteroptera: Anthocoridae) between deutonymphs of Tetranychus urticae Koch (Acari: Tetranychidae) and second instars of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and the influence of spider mite density on the preference were examined in the laboratory in three-dimensional set-ups at 25 ± 1 °C and 70 ± 5% r.h. The results showed that the predatory bug in the presence of equal densities of the two prey species had a clear preference for thrips (preference index β: 0.86 ± 0.02), consuming 7.2 thrips larvae and 1.5 spider mite deutonymphs during the experimental periods of 6 h. The number of thrips consumed by O. sauteri did not change when the density ratio of thrips to spider mites was decreased from 1:1 to 1:5. Predation on spider mites increased when their ratio to thrips increased, but the disproportionate predation (i.e., the functional response) of O. sauteri towards spider mites resulted in a linear increase in the preference for F. occidentalis . The possible implications of these findings for the suppression of spider mites by O. sauteri in relation to the recent invasion of F. occidentalis into China are discussed.     

Biocontrol of the shore fly Scatella tenuicosta with Hypoaspis miles and H. aculeifer in peat pots

Hypoaspis miles Berlese and H. aculeiferCanestrini (Acari: Laelapidae) were usedagainst Scatella tenuicosta Collin(Diptera: Ephydridae) at the rates of 7, 14and 36 mites per 0.3-l peat pot (1000, 2000 and5000 per net-m² of peat) with mint (Mentha piperita L.) as the crop. The predatorswere applied either one day (preventivecontrol) or nine days after (curative control)exposing the pots to the flies in thegreenhouse. Based on the number of flies thatemerged from the pots, the control efficacy of preventive H. aculeifer treatments at therate of 36 mites per pot was 84–100% and 92–97% (range over four replicate blocks)after two and three weeks, respectively, fromthe application. The control efficacy ofcurative treatments was 93–100% and 83–94% after two and three weeks, respectively,from the application. Preventive treatmentswith H. miles applied at the rate of 36per pot controlled the flies by 92–100% and 68–97% two and three weeks, respectively, afterthe application. Curative treatments with 36H. miles per pot were less effective (–53–68% and –16–65%, respectively). All treatments with lower mite rates with eitherspecies were ineffective. Due to moreconsistent reduction of fly numbers by Hypoaspis aculeifer, the species was concluded to be a better biocontrol agent ofshore flies in short-term greenhouse cropsgrown in peat pots, probably due to its higherpredation capacity in comparison to H. miles.     

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.     

Implications of alternative prey on biocontrol of pests by arthropod predators in strawberry

A range of naturally occurring predator species or commercially produced predators can be used in biocontrol strategies for pests. However, multiple potential prey species or other alternative food sources are often present for predatory insects at any one time. The availability of this ‘alternative’ prey may affect specific pest control by predators and thus influence the release rates of predators required for economic pest control. Strawberry aphid (Chaetosiphon fragaefolii), western flower thrips (Frankliniella occidentalis) and European tarnished plant bug (Lygus rugulipennis) are important and damaging pests in strawberry. In this study, laboratory, glasshouse and field experiments were undertaken to assess the effects of the availability of multiple prey species on biocontrol of specific pests. Results indicated that two of the predators tested showed preferences for prey species such that biocontrol of a particular pest was often less effective when a combination of pest species was present than would have been expected from results of experiments with single prey species alone. The experiments indicated that Orius laevigatus preferred C. fragaefolii to F. occidentalis or to L. rugulipennis, and preferred L. rugulipennis to F. occidentalis. Chrysoperla carnea was shown to prefer C. fragaefolii to L. rugulipennis, and C. fragaefolii over F. occidentalis. Therefore, it is important to consider the effects of alternative prey on suppression of pest species when deciding on management strategies and release rates of predators.     

Interaction between life stages in a phytoseiid predator: western flower thrips prey killed by adults as food for protonymphs of Amblyseius cucumeris

Alternative feeding strategies are important in determining the lifestyle of polyphagous spider mite prodators, and could play a key role in their use for biocontrol of prey such as thrips. The small size of Amblyseius cucumeris relative to western flower thrips, Frankliniella occidentalis, limits its survival and development when this prey is the only food available. We show that when A. cucumeris nymphs were reared either alone or with a gravid female on live larvae of F. occidentalis as the only source of food, survival was increased and development was accelerated by the presence of the adult. Similar performance by predator nymphs reared alone on freshly killed thrips larvae indicated that those nymphs reared on live prey with an adult were benefiting from feeding on prey killed by the adult. Variation of the period when an adult female was present with the nymph showed that food provided as a result of the adult's preying activities was beneficial until approximately one third through nymphal development, after which protonymphs became independent predators, with good survival and rapid development when provided only with live F. occidentalis larvae. The results are discussed in relation to adult dispersal in specialist as opposed to generalist phytoseiids, and its potential manipulation in using A. cucumeris for thrips biocontrol.     

Candidate natural enemies for control of Rhizoglyphus robini Claparède (Acari: Astigmata) in lily bulbs: exploration in the field and pre-selection in the laboratory

To find suitable candidates for biological control of the bulb mite, Rhizoglyphus robini Claparède (Acari: Astigmata) on lilies, exploration was undertaken in areas where the bulb mite is an established pest (The Netherlands, Taiwan and Japan). Among the predators, found in association with R. robini in the field and under storage conditions, mesostigmatic mites predominate. The most abundant species were Hypoaspis aculeifer (Canestrini), Lasioseius bispinosus Evans and Parasitus fimetorum (Berlese). These predators appeared to feed and reproduce on a diet of exclusively R. robini and they were able to control the bulb mite in small-scale population experiments initiated with a 1:20 predator-prey ratio. Under laboratory conditions corresponding to lily bulb propagation (lily scales mixed with vermiculite and stored at 23°C and >90% RH) the laelapid mite, H. aculeifer, was the most effective predator; the ascid predator, L. bispinosus, was much less effective, but being relatively small and being successful in attacking the juvenile stages of the bulb mite it may be better able to search for bulb mites hidden inside the lily bulb. The parasitid predator, P. fimetorum, failed to control the bulb mite when vermiculite was used as a medium, but turned out to suppress this prey when peat was used instead. Various strains of H. aculeifer or closely related species were compared with respect to their impact and performance on bulb mites as prey: two Dutch strains, one obtained from Breezand and the other from 'tZand, a Taiwanese strain, a German strain that in contrast to the previously mentioned strains was not collected from lily bulbs, but from agricultural areas near Bremen and, in addition, a Canadian strain of a related species (Hypoaspis miles Berlese), known to control sciarid fly larvae. These comparative experiments showed that H. miles died out without noticeable impact on the bulb mite population whereas all strains of H. aculeifer were able to suppress the bulb mites to very low numbers. However, the numerical responses of the H. aculeifer strains differed in that those collected in association with the pest (Breezand > Taiwan > 'tZand) were superior to the strain from Bremen. These results do not provide support to the Hokkanen and Pimentel hypothesis, which states that predators forming an evolutionary new association with the pest are often more effective in biological control.     

Provision of astigmatid mites as supplementary food increases the density of the predatory mite Amblyseius swirskii in greenhouse crops,but does not support the omnivorous pest,western flower thrips

Astigmatid mites can be used as prey for mass rearing of phytoseiid predators, but also as a supplemental food source to support predator populations in crops. Here we evaluated the potential of six species of astigmatid mites (living or frozen) as alternative food for the predatory mite Amblyseius swirskii Athias-Henriot in greenhouse crops. All prey mites tested were suitable for predator oviposition. In general, oviposition was greater when prey mites were reared on dog food with yeast than when they were reared on wheat bran with yeast. Amongst prey items provided as frozen diet, larvae of Thyreophagus entomophagus (Laboulbene), Acarus siro L. and Lepidoglyphus destructor (Schrank) that had been reared on dog food with yeast, resulted in the highest oviposition rates of A. swirskii. T. entomophagus larvae as frozen diet resulted in the shortest preimaginal developmental time of A. swirskii. On chrysanthemum plants, we found that the greatest increase in predator density occurred when living mites of T. entomophagous were used as a food source. This increase was greater than when predators were fed cattail pollen, a commonly used supplemental food. Effects on predators of providing living A. siro and L. destructor, or frozen larvae of T. entomophagous as food, were comparable with provision of pollen. Use of supplemental food in crops can be a risk if it is also consumed by omnivorous pests such as western flower thrips, Frankliniella occidentalis Pergande. However, we showed that both frozen and living mites of T. entomophagous were unsuitable for thrips oviposition. Hence, we believe that provision of prey mite species increases A. swirskii density, supporting biological control of thrips and other pests in greenhouse crops.

     

Host-plant-mediated interaction between populations of a true omnivore and its herbivorous prey

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), are competitors with twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), for plant resources and potential predators on spider mites when the opportunity arises. Which interaction predominates may depend on relative population densities and individual species’ responses to the plants on which they co‐occur. We examined interactions between populations of thrips and spider mites on several cultivars of two bedding plants: impatiens (Impatiens wallerana Hook.f) cultivars ‘Impulse Orange’ and ‘Cajun Carmine’, and ivy geranium [Pelargonium peltatum (L.) L’Her ex Aiton] cultivars ‘Sybil Holmes’ and ‘Amethyst 96’. Four combinations of thrips and mite numbers were studied: thrips alone, mites alone, and two densities of thrips and mites together. We compared population numbers after 4 weeks. Overall, mite numbers increased more rapidly than thrips did, but both species increased more rapidly on impatiens than on ivy geraniums. Between impatiens cultivars, thrips and mites increased more slowly on ‘Cajun Carmine’ (i.e., it was more resistant) than on ‘Impulse Orange’. On ivy geraniums, spider mites increased more slowly on ‘Sybil Holmes’ than on ‘Amethyst 96’ but the reverse was the case for thrips. Regardless of plant species or cultivar, thrips had a strong negative effect on spider mites whenever they co‐occurred, suppressing mite population growth by around 50% compared to when mites were alone. However, the effect of spider mites on western flower thrips depended on the quality of the plant species. On impatiens, thrips co‐occurring with spider mites increased slightly more than thrips alone did, while on ivy geranium mites had a small negative effect on thrips. Contrary to expectations, thrips had a larger negative impact on spider mites on plants that were more susceptible to thrips than they did on plants more resistant to thrips. We suggest that host plants mediate the interaction between an omnivore and its herbivorous prey not only by altering individual diet choice but by changing the relative population dynamics of each species.     

Interactions in the biological control of western flower thrips Frankliniella occidentalis (Pergande) and two-spotted spider mite Tetranychus urticae Koch by the predatory bug Orius insidiosus Say on beans

An omnivore shows preference to its preys and thus its control efficiency could be altered in different mix infestation system. The efficiency of Orius insidiosus for biocontrol of either Frankliniella occidentalis or Tetranychus urticae alone or for the two pests in combinations was studied on beans. When only mites or thrips were offered as prey, 1 or 2 O. insidiosus could considerably suppress pest populations at an initial density of 20, 40, and 80 adult female mites, and 100 and 160 thrips larvae, respectively. A single O. insidiosus was able to reduce mite populations by 52.9, 38.7, and 25.8% at initial densities of 20, 40, and 80 mites, respectively, two bugs achieved control levels of 60.6, 63.1, and 38.4%. Releases of 1 and 2 O. insidiosus resulted in corrected mortalities of 62.5 and 87.9%, and 46.3 and 71.9% in F. occidentalis at initial larval densities of 100 and 160, respectively. When two pests were simultaneously offered, the efficiency of O. insidiosus in controlling T. urticae markedly decreased. Furthermore, mite control decreased with increasing T. urticae densities and was also affected by the density of O. insidiosus. The presence of mites at initial densities of 20–80 females did not significantly influence thrips control by O. insidiosus. The presence of F. occidentalis resulted in higher oviposition by O. insidiosus females than the presence of mites, indicating that thrips are a more suitable resource than T. urticae for O. insidiosus. The implications for biocontrol of F. occidentalis and T. urticae are discussed.     

Predation capacity,development and reproduction of the southern African flower bugs Orius thripoborus and Orius naivashae (Hemiptera: Anthocoridae) on various prey

The little-studied species Orius thripoborus (Hesse) and Orius naivashae (Poppius) (Hemiptera: Anthocoridae) have potential as biological control agents of thrips pests in southern Africa, but may also hold promise for the control of other harmful arthropods. In this study, the predation capacity, development, reproduction and growth rates of both predatory species on the key pests Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), Tetranychus urticae Koch (Acari: Tetranychidae) and Myzus persicae nicotianae Blackman (Hemiptera: Aphididae) were examined under laboratory conditions. Female adults of O. thripoborus and O. naivashae fed on 24 and 18 F. occidentalis 2nd instars, and 15 and 21 T. urticae eggs per day, respectively. Developmental and reproductive parameters of both Orius species were most favorable on F. occidentalis. Their intrinsic rates of increase (r_m) were highest when fed on F. occidentalis, averaging 0.123 and 0.131 females/female/day for O. thripoborus and O. naivashae, respectively. On the other prey, O. thripoborus showed significantly higher r_m-values than O. naivashae. Overall, r_m-values on M. persicae nicotianae were higher than on T. urticae, although differences were only significant for O. thripoborus. For O. naivashae, the estimated intrinsic rates of increase on the tested non-thrips prey were slightly negative. Our findings indicate the potential of both Orius spp. as biocontrol agents of thrips, whereas only O. thripoborus appears to hold promise for the suppression of aphids and spider mites as well.