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Abstract: The ectoparasitic mite Varroa destructor is a major honey bee pest, and its control using pathogen-based biopesticides would resolve many of the problems, such as contamination and pesticide resistance, experienced with chemical control. A biopesticide, formulated with commercially-prepared conidia of a strain of Beauveria bassiana isolated from V. destructor was tested against the mites in bee colonies in southern France. The impact of treatment on hive survivorship, weight and mite infestation levels were very different from those of previous experiments using laboratory-prepared conidia: bee hives treated with the biopesticide died at a higher rate, lost more weight, and had higher mite densities at the end of the study than control hives. The biopesticide was subsequently found to be contaminated with bacteria. Two strains of bacteria were identified, by biotyping and sequencing data of the 16S rRNA and rpoB regions, and while the strains were distinct both were Pseudomonas sp. belonging to the P. fluorescens group. In dual cultures B. bassiana growth was slowed or suppressed when bacterial cfu density was about equal or greater than that of B. bassiana. Experiments using caged adult bees showed that bees ingesting diet and sugar solution treated with B. bassiana and kept at 30°C had significantly lower survival times than those treated with one of the bacterial strains, but the opposite was true at 33°C. Because one arthropod (honey bees) was treated for infestation by another (V. destructor), the impact of bacterial contamination was likely more noticeable than in most uses of biopesticides, such as treating plants against phytophagous insects. To reduce such risk in biopesticide development, a systematic screening for bacterial contamination prior to field application is recommended. [Copyright &y& Elsevier]

Abstract: Tetranychus urticae Koch (Acari: Tetranychidae) is an important pest of citrus that can also feed on most plant species occurring in the ground cover associated with this crop. To determine the effect of managing the ground cover on the biological control of this mite, we have studied the dynamics of both tetranychid and phytoseiid mites in four commercial citrus orchards under three different ground cover management strategies: (1) bare soil, (2) resident wild cover and (3) a sown cover of Festuca arundinacea Schreb. (Poaceae). The results obtained provide evidence that both bottom-up and top-down regulation processes related to the nature of the ground cover affected the tetranychid mite populations in citrus orchards (Panonychus citri (McGregor), Tetranychus evansi Baker & Pritchard and T. urticae). Best results were obtained with the ground cover of F. arundinacea, which did not allow the establishment of T. evansi, and offered a better regulation of both P. citri and T. urticae than either bare soil or the resident wild cover. We hypothesize that the selection of a host race of T. urticae specialized in F. arundinacea when this plant was used as a cover crop could partly explain the results obtained. Further trap cropping effects could also be relevant (bottom-up regulation). [Copyright &y& Elsevier]

Abstract: Tetranychus urticae Koch (Acari: Tetranychidae) is a key pest of citrus that can also feed on most plant species occurring in the ground cover associated with this crop. To determine the effect of the management of the ground cover on the biological control of this mite, we have studied the dynamics of both tetranychid and phytoseiid mites in four commercial clementine mandarin orchards under three different ground cover management strategies: (1) bare soil, (2) resident wild cover and (3) a sown cover of Festuca arundinacea Schreb. (Poaceae). Our results provide evidence that the management of ground cover can affect both Tetranychid and Phytoseiid mite populations. We hypothesize that both natural enemies (top-down mechanisms) and plant resources (bottom-up mechanisms, discussed in a previous paper) play important regulatory roles. T. urticae specialist phytoseiid mites were consistently found in the F. arundinacea cover and this may explain the better regulation of Tetranychid mite populations on trees grown in association with this cover crop. In contrast, the more regular provision of alternative food (pollen) in the wild cover relative to the F. arundinacea cover, could explain the higher abundance of generalist pollen feeder phytoseiids in the former. As a result, more efficient T. urticae-specialized phytoseiids could suffer increased competition from generalist pollen feeders in the wild cover. This fact, in combination with periods of prey scarcity, could result in their disappearance from the agroecosystem, resulting in an inadequate control of Tetranychid mites in trees grown in association with a wild cover. [Copyright &y& Elsevier]

Abstract: To improve the biological control of persea mite (Oligonychus perseae) in Israeli avocado orchards we evaluated two approaches: (1) Augmentative inundative releases in commercial orchards of Neoseiulus californicus, an exotic spider mite predator, and (2) Conservation of Euseius scutalis, the prevalent indigenous phytoseiid predator found in avocado orchards, by pollen provisioning. The latter was done at three spatial scales; leaf discs, seedlings and trees. Neoseiulus californicus releases led to a significant reduction in persea mite population densities. Nonetheless, most of the recovered predators consisted of E. scutalis. The leaf disc experiment showed that E. scutalis can significantly reduce persea mite populations even though it cannot penetrate or tear the mite nests. The seedling experiments demonstrated that E. scutalis can suppress persea mite when pollen is available and provisioning maize pollen substantially increased E. scutalis populations. Field trials revealed that conservation of E. scutalis using Rhodes grass (Chloris gayana) as a windborne pollen provisioning cover crop (WPPCC) was highly effective, compared to repeated artificial pollen applications. Densities of phytoseiid populations were significantly higher on trees adjacent to the Rhodes grass patches than on distant trees, whereas persea mite populations on trees adjacent to these patches were consistently lower. In this study, we show that the use of Rhodes grass as a WPPCC for conservation of E. scutalis is both effective and sustainable. While our results indicate that E. scutalis has potential for mite control, future studies are needed to demonstrate the efficacy of this approach in commercial orchards. [Copyright &y& Elsevier]

Abstract: The coconut mite Aceria guerreronis Keifer resides beneath the perianth of coconut fruits where it feeds on the tender meristematic tissue. A. guerreronis is one of the most important coconut pests but knowledge of its population dynamics is scant. We quantified seasonal and fruit age-related population fluctuations of A. guerreronis and its predator Neoseiulus paspalivorus DeLeon in Benin. N. paspalivorus was the most common and abundant beneath the bracts compared with other predators, which were very scarce and were largely found outside the bracts. Both percent fruit occupation and abundance of A. guerreronis and N. paspalivorus varied across sampling months as well as among coconut plantations and fruit age classes. Both parameters peaked in the middle of the rainy season and at the end of the dry season. Fruit age at which A. guerreronis and N. paspalivorus started to colonize the fruits was 0.9 and 1.2months, respectively. The two species reached their peak abundance (1512 A. guerreronis and 2.3 N. paspalivorus per fruit) on 3months-old fruits. Peak percent fruit occupation by A. guerreronis (∼70%) occurred after 4.3months, which was ∼0.7months earlier than that by N. paspalivorus (∼22%). Difficulties encountered by the predators in accessing the area beneath the perianth on the very young fruits allowed A. guerreronis a head-start in population build-up leading to strongly diverging population curves as a function of fruit age (higher population increase compared to N. paspalivorus). Protecting the very young fruits from A. guerreronis colonization should be a key issue for developing successful control strategies of this pest. [ABSTRACT FROM AUTHOR]

Abstract: When multiple predator species are introduced to control a single prey species, predator species may act synergistically if the rate of mortality of the prey exceeds the rate of mortality from all single predator species combined. Alternatively, the release of multiple predator species may yield a lower than expected prey mortality due to competitive interactions (including intraguild predation) amongst predators. The question of whether and when multiple natural enemies interact to produce lower or higher prey mortality than each predator species acting alone depends on the details of predator–predator interactions. In this study, we investigated whether combined releases of Phytoseiulus persimilis and Neoseiulus californicus provide better biological control of Tetranychus cinnabarinus on strawberry than releases of each predator species alone. Experiments were conducted in two commercial strawberry fields (Fragaria ananassa Duch. cv. ‘Camarosa’). The release of P. persimilis alone and the combined release of N. californicus and P. persimilis reduced the numbers of T. cinnabarinus on strawberry equally. The densities of T. cinnabarinus in the treatment with N. californicus alone were significantly higher than in the other treatments, and this was the only treatment in which the economic injury level was surpassed. The densities of P. persimilis in absence of N. californicus were similar to those in presence of N. californicus. Hence, there was no significant adverse effect of the presence of N. californicus on the densities of P. persimilis. The densities of N. californicus in the absence of P. persimilis were lower than the densities in the presence of P. persimilis, but this difference was not significant. We conclude that, compared to releases with P. persimilis alone, there is no advantage to releasing N. californicus, either alone or in combination with P. persimilis. [Copyright &y& Elsevier]

Abstract: The eriophyid mite, Aceria salsolae de Lillo and Sobhian, is being evaluated as a prospective classical biological control agent of invasive alien tumbleweeds, including Salsola tragus, S. collina, S. paulsenii and S. australis, in North America. Previous laboratory experiments to determine the host specificity of the mite indicated that it could sometimes persist and multiply on some nontarget plants, including Bassia hyssopifolia and B. scoparia. These are both European plants whose geographic range overlaps that of the mite, but the mite has never been observed on them in the field. A field experiment was conducted in Italy to determine if the mite would infest and damage these plants under natural outdoor conditions. The results indicate that this mite does not attain significant populations on these nontarget plants nor does it significantly damage them. Salsola tragus was heavily infested by A. salsolae, and plant size was negatively correlated to the level of infestation. Although S. kali plants were also infested, their size did not appear to be affected by the mites. The other nontarget plants were not as suitable for the mite in the field as in previous laboratory experiments. We conclude that there would be no significant risk to nontarget plants as a result of using A. salsolae as a biological agent to control Salsola species in North America. [Copyright &y& Elsevier]

Abstract: Rhodacaridae are cosmopolitan mites mentioned as predators, although nothing is known about their potential as biological control agents. One of the objectives of the work reported in this paper was to evaluate the potential of Protogamasellopsis posnaniensis (Acari: Rhodacaridae) as predator of representative species of insects of the families Sciaridae (Bradysia matogrossensis (Lane)) and Thripidae (Frankliniella occidentalis (Pergande)), of mites of the family Acaridae (Tyrophagus putrescentiae (Schrank) and Rhizoglyphus echinopus (Fumouze & Robin) and of nematodes of the family Rhabditidae (Protorhabditis sp.). Another objective was to determine the biological cycle of P. posnaniensis when fed the prey on which it performed best in the preceding predation test. The study was conducted in a laboratory where the experimental units were maintained at 25±1°C, 97±3% RH and in the dark. Although the predator was able to kill all prey species considered in this study, the most favorable prey were T. putrescentiae, F. occidentalis and Protorhabditis sp. Survivorship of the predator in predation tests was always 98% or higher. Life table biological parameters when the predator was fed T. putrescentiae were: R o =109.29; T =19.06 days; λ =1.28 e r m =0.32 female/female/day. Despite preying upon larvae of B. matogrossensis, eggs of the former can also be killed by the latter. The results indicated that P. posnaniensis is a promising biological control agent, deserving additional studies on its possible use for the control of soil pests. [Copyright &y& Elsevier]

Abstract: Generalist phytoseiids are often observed for long periods on plants in the absence of prey, feeding on alternative foods and reaching high population levels. The persistence of generalist predatory mites on plants with a scarcity or absence of prey is a requirement for successful biocontrol strategies of herbivore mites. The importance of pollen as an alternative food for the support of generalist predatory mite populations is widely recognized. However, on grape the presence of pollen is often limited and thus other food sources should contribute towards generalist predatory mite persistence on perennial plants. Previous field observations reported the relationships between the population increases of generalist phytoseiids with late-season spread of grape downy mildew (GDM) Plasmopara viticola. In this study, we test the hypothesis that GDM could be a suitable food source for the predatory mites Amblyseius andersoni and Typhlodromus pyri. In the laboratory we compared the development times, oviposition rates and life-table parameters of predatory mites feeding on pollen or GDM mycelium and spores. Grape downy mildew supported the survival, development and oviposition of T. pyri and A. andersoni. Life-table parameters showed that GDM was a less suitable food source than pollen for both phytoseiid species and that it was more favorable for A. andersoni than for T. pyri. Implications for predator–prey interactions and conservation biological control in vineyards are discussed. [Copyright &y& Elsevier]

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

Abstract: Biological control of spider mites on crops grown in arid environments is a serious problem, which is difficult to solve with the currently commercially available predatory mites (Acari: Phytoseiidae). In phytoseiids the degree of adaptation to low humidity underlies considerable intraspecific variability allowing the screening for a dry resistant strain within a given species. We considered the generalist predator Neoseiulus californicus an ideal species for such a screening due to its well-known plasticity in life history, and behavioural and ecological traits. Within the frame of a multi-institutional project on the identification and mass rearing of a dry adapted N. californicus strain, we evaluated life history parameters such as adult female survival, oviposition and offspring sex ratio, egg hatchability and development, and juvenile survival and development of eight strains at three to four humidity levels (64.0–75.6% at 25°C). Strains came from Hérault/France (FR), Tuscany/Italy (FL), Valencia/Spain (SP), La Cruz/Chile (CH), Sicily/Italy (SI) and California/USA (BOKU, ISZA, ARO). The influence of low humidity on life history traits decreased during ontogeny, with the egg being the most sensitive to dry ambient conditions. The high variability of the N. californicus strains in their performance at the lowest humidity tested (64.0%) allowed to classify the strains into three distinct groups. (1) Egg hatch probabilities were nearly zero in the FL, SP and ISZA strains (0.07–0.01). (2) The second group with the FR, CH and ARO strains was characterized by low egg survival (0.14–0.18) but high juvenile survival probabilities (0.69–0.82). (3) Among the eight evaluated strains the BOKU and SI strains had the highest egg (0.37 and 0.38) and juvenile survival probabilities (0.96 and 0.83). We conclude that BOKU and to a somewhat lesser degree SI are the most promising N. californicus strains for arid environments and should henceforth be evaluated on different crops in semi-field and field trials. [Copyright &y& Elsevier]

Abstract: An emulsifiable formulation of Beauveria bassiana conidia was applied alone or together with pyridaben 15% EC at ∼5% of its labeled application rate for control of citrus red mite Panonychus citri in three citrus orchards (Trials 1–3) of Taizhou, Zhejiang, southeastern China during the mild, rainy season of autumn 2006. Aqueous dilutions (150l/ha) of two fungal rates (1.5 and 3.0×1013 conidia/ha in Trials 1 and 2; 1.2×1012 and 1.2×1013 in Trial 3) or the low chemical rate (562.5mg AI/ha) were sprayed to plots in randomized blocks (40-m-long row of trees per plot, three plots per treatment) with mean density of 17.8, 15.0 and 12.0 mites per leaf in Trials 1–3, respectively. Based on percent density declines and relative efficacies estimated by sampling all plots at 3–5 day intervals, the two fungal rates in each trial gave significant control and the fungal/chemical combinations always resulted in better control. The pyridaben-inclusive sprays of ⩾1.5×1013 conidia/ha applied twice at 15-day interval provided excellent mite control for 35 days, yielding overall mean efficacies of 83.2–92.3% and mite density declines of 73.8–91.2%. In contrast, the relative efficacy in a standard pyridaben treatment (11.25g AI/ha) reached 83.8% on day 3 but decreased from 72.0% on day 5 to 4.1% on day 15. Field conditions, featured with the records of ∼20°C and >95% RH for 216 and 300h in Trials 1 and 2 (35 days) and 52h in Trial 3 (15 days), were favorable. The effects of local weather on the trials in topographically different hillside orchards are discussed. Conclusively, combined application of the fungal formulation with pyridaben at the low rate is a potential alternative for sustainable control of the mite pest in orchards of southern China. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Two closely related teasels (Dipsacales: Dipsacaceae, Dipsacus spp.) of European origin have become invasive weeds in the United States. Common teasel (Dipsacus fullonum L.) and cutleaf teasel (Dipsacus laciniatus L.) have likely been in North America for more than two centuries, having been introduced along with cultivated teasel [D. sativus (L.) Honckney], an obsolete crop plant. There are few records of American insects or pathogens attacking Dipsacus spp. Invasive teasels have recently begun to spread rapidly throughout much of their current range, for reasons that are not yet known. Common and/or cut-leaf teasel have been listed as noxious in five US states and as invasive in 12 other states and four national parks. Because the family Dipsacaceae is an exclusively Old World family, classical biological control is an important component of the overall management strategy of this weed in the US. Field surveys for natural enemies of D. fullonum and D. laciniatus in their native ranges and literature reviews of natural enemies of plants in the family Dipsacaceae have yielded 102 species of insects in six orders, as well as 27 fungi from 10 orders, three mites, one nematode, and two viruses. Due to the biennial nature of these weeds, a strategy to assign highest priority to biological control candidates attacking first-year (rosette) plants has been established. Candidates selected for further study based on this strategy include Chromatomyia ramosa (Hendel) (Diptera: Agromyzidae), Longitarsus strigicollis Wollaston (Coleoptera: Chrysomelidae), Epitrimerus knautiae Liro (Acarina: Eriophyiidae), Euphydryas desfontainii (Godart) (Lepidoptera: Nymphalidae), Erysiphe knautiae Duby (Erysiphales: Erysiphaceae), and Sphaerotheca dipsacearum (Tul. and C. Tul.) (Erysiphales: Erysiphaceae). [Copyright &y& Elsevier]

Abstract: Ectoparasitic mites of the genus Psoroptes cause mange in a wide range of domestic and wild vertebrate hosts. The mite infestation may be localised in the ear of the host, or be more generalised over the body. In the latter case, infestation may be debilitating and often fatal, particularly in domesticated cattle, sheep and goats. At present, control depends on the use of organophosphate or pyrethroid plunge dips or injectable endectocides. A series of in vivo bioassays are described here to further evaluate the use of an entomopathogenic fungus, Metarhizium anisopliae (Metschnikoff) as a biological control agent for Psoroptes mites. Mites were obtained from the ears of rabbits (Psoroptes ovis (Hering) syn. Psoroptes cuniculi). High levels of mortality (>94%) were observed in all life-cycle stages when exposed to a 1×108 conidiaml−1 suspension; there were no significant differences in infection between the different life-cycle stages. The treatment of eggs, however, had no effect on hatch rate. The horizontal transmission of the pathogen was considered by placing live uninfected mites in experimental chambers with an infected cadaver, but preventing direct contact using a mesh cage which would allow the passage of conidia but exclude direct physical contact. None of the uninfected mites showed signs of mycosis-induced mortality, indicating that direct contact with the cadaver was required for infection. Uninfected live mites were then brought into direct contact with an infected cadaver by a single touch of the mite to the cadaver (<1s), or indirectly by allowing the live uninfected mite to walk over a piece of filter paper from which an infected cadaver had been removed. Both treatments resulted in fungal infection in approximately 40% of the live mites. The implications of these results for the transmission of M. anisopliae between infected Psoroptes mites, when used as a biological control agent, on an infected host is discussed. [Copyright &y& Elsevier]

Abstract: The predatory mites Phytoseiulus persimilis and Amblyseius cucumeris are commonly used in commercial greenhouses for augmentative biological control of spider mites and thrips, respectively. One disincentive for growers to use biological control is the cost of manually distributing predators. Therefore, we tested the efficiency of two types of mechanical blowers for dispensing predatory mites. One blower had a metering device to control the flow of material (MBWMD); the other had no metering device (MBWOMD). Predator survival was measured at various distances after dispensing them with blowers. Survival also was compared with a manual-sprinkling method. When blowers were held horizontally, the distribution of predators was uneven for both blowers. For P. persimilis, 77% were found at 1.52 and 2.44m with the MBWOMD, whereas 75% were located at 2.44, 3.35, and 4.27m with the MBWMD. For A. cucumeris, 97% were found at 1.52, 2.44, and 3.35m with the MBWOMD, while 81% landed at 2.44 and 3.35m with the MBWMD. Percentages of live P. persimilis found using the MBWMD, MBWOMD, and manual-sprinkling were 31±4, 49±3, and 68±8%, respectively. For A. cucumeris, percentages of survival were 61±4, 79±4, and 83±7%, respectively. The MBWOMD dispensed P. persimilis 22 and 44 times faster than the MBWMD and manual-sprinkling, respectively. Mechanical blowers have the advantage of better coverage, substantially less labor, and estimated total costs to growers that are approximately half that of the manual release method. [Copyright &y& Elsevier]

Abstract: The behavior of the two-spotted spider mite, Tetranychus urticae Koch and the predatory mite Phytoseiulus persimilis A.-H. was investigated in laboratory experiments with transgenic Bt-eggplants, Solanum melongena L., producing the Cry3Bb toxin and corresponding isogenic, non-transformed eggplants. In bitrophic experiments, dual-choice disc tests were conducted to reveal the effects of transgenic eggplants on host plant preference of T. urticae. Adult spider mite females were individually placed on leaf discs (2cm diameter) and were observed during five days. Females occurred significantly more frequently on transgenic halves on which also significantly more T. urticae eggs were found. The effects of a Cry3Bb-eggplant fed prey on the feeding preference of P. persimilis were investigated in tritrophic experiments. Sixteen spider mite females, eight of which had been taken from transgenic and eight from isogenic eggplants, were offered to well-fed females of P. persimilis and numbers of respective spider mites consumed were registered 12h later when the predators were offered new spider mites again. This procedure was repeated six times. The results revealed that predatory mites consumed significantly less Bt-fed spider mites than prey that had been raised on control eggplants. These results indicate that eggplants expressing the Cry3Bb toxin for resistance against the Colorado potato beetle are more preferred by spider mites but are less preferred by their predator P. persimilis. Possible consequences of these findings for biological control of spider mites on eggplants are discussed. [Copyright &y& Elsevier]

Abstract: The commercially available strains of Phytoseiulus persimilis Athias-Henriot, the biological control agent of Tetranychus urticae Koch, perform poorly in the Western Mediterranean, probably because they are not well adapted to local climatic conditions. For that reason, efforts are being focused on the development of a biological control programme using native phytoseiid mites. Four species of red spider mites can be found in vegetable crops in eastern Spain: T. urticae, Tetranychus turkestani Ugarov and Nikolski, Tetranychus ludeni Zacher and the recently introduced Tetranychus evansi Baker and Pritchard. To evaluate their potential role as biological control agents, the present study evaluates the life-history of local populations of Neoseiulus californicus (McGregor) and P. persimilis when fed on T. urticae, T. turkestani, T. evansi, and T. ludeni in the laboratory. Results indicate that N. californicus and P. persimilis are able to feed and complete their development on the four tested red spider mite species. The predators may exhibit a particularly high capacity for population increase when fed on T. urticae, T. turkestani, and T. ludeni, thus may be able to provide effective control of these species in the field. When fed T. evansi, however, predator performance was poor; significant increase in development and preoviposition times, and a reduction in oviposition period and fecundity were recorded. The resultant low capacity for population growth suggests poor ability of the two tested predators to suppress T. evansi populations on commercial crops. It is unlikely therefore that P. persimilis and N. californicus, now being widely used to control T. urticae in greenhouse crops in Central Europe, will be able to halt any spread of T. evansi to greenhouse crops in temperate areas. [Copyright &y& Elsevier]

We evaluated economically feasible release rates of the western predatory mite, Galendromus occidentalis, for spider mite control in organically and conventionally managed commercial cotton fields. An important feature of the experimental design was the evaluation of predatory mite releases at a large spatial scale; the majority of plots were near 2 ha. Predatory mite releases did not enhance the density of the western predatory mite, and populations of western predatory mites remained very low throughout the growing season. However, predatory mite releases did appear to reduce the seasonal abundance of spider mites. Nevertheless, spider mite densities exceeded economic thresholds in many of the release plots, and neither early releases (3–6 nodes per plant) or late releases (>7 nodes per plant) enhanced seed cotton yields. We discuss some potential factors that could have limited the impact of the released predatory mites. [Copyright &y& Elsevier]

• Bottom-up factors alter plant quality and potentially biological control agents. • We tested these factors on a mite introduced to control Lygodium microphyllum. • In shade house studies, bottom-up factors limited populations of the mite. • Field surveys validated findings where mites were highly established. • Bottom-up factors help shape agent distributions in the field. The efficacy of biological control as a tool to manage invasive plants relies on widespread agent establishment, yet achieving such establishment remains a central challenge to the field. One potential explanation for patchy distributions of agents is the role of 'bottom-up' factors that influence plant quality and, in turn, local agent establishment. We investigated the roles of two bottom-up factors, soil fertilization and inundation, on establishment of the leaf galling mite Floracarus perrepae (Acariformes; Eriophyidae), an agent introduced to control the noxious vine Lygodium microphyllum (Lygodiaceae; Old World climbing fern) found in both upland and inundated habitats in Florida, USA. We conducted a series of shade house experiments to quantify bottom-up factors under controlled settings, and then validated these finding using a regional survey of 19 L. microphyllum infestations. Our shade house experiments demonstrated positive effects of fertilizer and negative effects of soil inundation on F. perrepae populations. Our regional survey showed no difference in leaf percent N between sites with or without F. perrepae galls. However, when we restricted our analysis to the area of the state where the mite had established, sites with galls had 33% higher leaf N than sites without galls, and nearly all inundated sites lacked galls. Bottom-up factors determine local mite establishment, but regionally, other factors (e.g., genetic factors underlying plant susceptibility) are likely at play. Our study demonstrates both the consequences and limitations of bottom-up factors to shape distributions of biological control agents in the field and has important implications for effective management of invasive plants. [ABSTRACT FROM AUTHOR]

There is increasing interest in the possibility of using eriophyid mites as biological control agents of invasive alien weeds; however their small size and our lack of knowledge about their general biology present challenges to evaluating their risk to nontarget plants. Aceria salsolae has been proposed as a candidate agent for Russian thistle (Salsola tragus) in the USA. During host specificity testing this mite could sometimes persist on five nontarget species under laboratory no-choice conditions. We conducted a series of no-choice laboratory experiments and a field experiment to try to delineate the physiological and ecological host ranges of this mite and assess its risk to nontarget plants. In the laboratory, A. salsolae increased exponentially on S. tragus , multiplying about 80 fold in 5 weeks. Low levels of reproduction were observed on some plants of Atriplex coronata , Bassia hyssopifolia , B. prostrata , Kochia scoparia and Suaeda calceoliformis in the laboratory during 5 weeks, but mean mite densities remained low (less than 6 fold increase vs. 80 fold on S. tragus). In a field experiment in which plants were inoculated with mites in June and then harvested when they began to produce seed, mites persisted on A. coronata for up to 9 weeks after inoculation, but at extremely low densities, and with no evidence of reproduction. No mites persisted on A. truncata , B. hyssopifolia, or S. calceoliformis. Mite densities were lower on all plants in the field than in the laboratory, probably due to increased mortality and the opportunity to disperse by wind. No signs of damage were observed on any of the nontarget plants in the laboratory or the field experiments. We conclude that this mite is not likely to multiply on any of these plants under field conditions, and that it is not expected to pose a risk to any nontarget plants in the contiguous USA. [ABSTRACT FROM AUTHOR]

• Natural enemies can regulate populations of Brevipalpus yothersi. • Phytoseiid and cheyletid predators were evaluated for control of Brevipalpus yothersi. • Amblyseius largoensis suppressed Brevipalpus yothersi on citrus plants. • Predatory mites can be important in IPM programs tailored to manage citrus leprosis. Citrus leprosis is a serious viral disease of citrus transmitted by Brevipalpus mites. The disease is present in South America, Central America, and Mexico, but not in the United States. One of its primary vectors, however, is present in Florida and other southern states. Non-viruliferous Brevipalpus yothersi (Acari: Tenuipalpidae) are present in Florida and could facilitate the spread of the disease if citrus leprosis viruses (CiLVs) are introduced into the state. In preparation for the possible incursion of CiLVs, we evaluated the biological control potential of four predatory mite species (Neoseiulus longispinosus , N. californicus , Amblyseius largoensis ; Acari: Phytoseiidae) and Hemicheyletia bakeri (Acari: Cheyletidae) that are naturally associated with Brevipalpus spp. in citrus. In laboratory no-choice assays, the phytoseiid mites preyed mostly upon immature stages of B. yothersi , while H. bakeri preyed mainly on adults. In dual choice assays, all predators preferred Tetranychus urticae (Acari: Tetranychidae) over B. yothersi , but A. largoensis consumed more B. yothersi than the other three predators. A greenhouse experiment was performed to evaluate the potential of A. largoensis and H. bakeri to suppress B. yothersi populations on citrus trees. Four predator release treatments consisting of single or combined releases of A. largoensis and H. bakeri at a 1:10 (predator: B. yothersi) ratio were tested. Releases of A. largoensis alone or in combination with H. bakeri effectively suppressed B. yothersi and reduced damage to citrus plants. Release of H. bakeri alone, however, had no suppressive effect on B. yothersi populations. Overall, our results show that A. largoensis could be an efficient biological control agent of B. yothersi and could play an important role in citrus IPM programs tailored to manage citrus leprosis. [ABSTRACT FROM AUTHOR]