A morphologically specialized soldier caste improves colony defense in a neotropical eusocial bee

Division of labor among workers is common in insect societies and is thought to be important in their ecological success. In most species, division of labor is based on age (temporal castes), but workers in some ants and termites show morphological specialization for particular tasks (physical castes). Large-headed soldier ants and termites are well-known examples of this specialization. However, until now there has been no equivalent example of physical worker subcastes in social bees or wasps. Here we provide evidence for a physical soldier subcaste in a bee. In the neotropical stingless bee Tetragonisca angustula, nest defense is performed by two groups of guards, one hovering near the nest entrance and the other standing on the wax entrance tube. We show that both types of guards are 30% heavier than foragers and of different shape; foragers have relatively larger heads, whereas guards have larger legs. Low variation within each subcaste results in negligible size overlap between guards and foragers, further indicating that they are distinct physical castes. In addition, workers that remove garbage from the nest are of intermediate size, suggesting that they might represent another unrecognized caste. Guards or soldiers are reared in low but sufficient numbers (1-2% of emerging workers), considering that <1% usually perform this task. When challenged by the obligate robber bee Lestrimelitta limao, an important natural enemy, larger workers were able to fight for longer before being defeated by the much larger robber. This discovery opens up opportunities for the comparative study of physical castes in social insects, including the question of why soldiers appear to be so much rarer in bees than in ants or termites.

Contrasting Effects of Ethylene Biosynthesis on Induced Plant Resistance against a Chewing and a Piercing-Sucking Herbivore in Rice

Ethylene is a stress hormone with contrasting effects on herbivore resistance. However, it remains unknown whether these differences are plant- or herbivore-specific. We cloned a rice 1-aminocyclopropane-1-carboxylic acid (ACC) synthase gene, OsACS2, whose transcripts were rapidly up-regulated in response to mechanical wounding and infestation by two important pests: the striped stem borer (SSB) Chilo suppressalis and the brown planthopper (BPH) Nilaparvata lugens. Antisense expression of OsACS2 (as-acs) reduced elicited ethylene emission, SSB-elicited trypsin protease inhibitor (TrypPI) activity, SSB-induced volatile release, and SSB resistance. Exogenous application of ACC restored TrypPI activity and SSB resistance. In contrast to SSB, BPH infestation increased volatile emission in as-acs lines. Accordingly, BPH preferred to feed and oviposit on wild-type (WT) plants—an effect that could be attributed to two repellent volatiles, 2-heptanone and 2-heptanol, that were emitted in higher amounts by as-acs plants. BPH honeydew excretion was reduced and natural enemy attraction was enhanced in as-acs lines, resulting in higher overall resistance to BPH. These results demonstrate that ethylene signaling has contrasting, herbivore-specific effects on rice defense responses and resistance against a chewing and a piercing-sucking insect, and may mediate resistance trade-offs between herbivores of different feeding guilds in rice.

Per-field land use and land cover data set of the Haean catchment, South Korea

Detailed data on land use and land cover constitute important information for Earth system models, environmental monitoring and ecosystem services research. Global land cover products are evolving rapidly; however, there is still a lack of information particularly for heterogeneous agricultural landscapes. We censused land use and land cover field by field in the agricultural mosaic catchment Haean in South Korea. We recorded the land cover types with additional information on agricultural practice. In this paper we introduce the data, their collection and the post-processing protocol. Furthermore, because it is important to quantitatively evaluate available land use and land cover products, we compared our data with the MODIS Land Cover Type product (MCD12Q1). During the studied period, a large portion of dry fields was converted to perennial crops. Compared to our data, the forested area was underrepresented and the agricultural area overrepresented in MCD12Q1. In addition, linear landscape elements such as waterbodies were missing in the MODIS product due to its coarse spatial resolution. The data presented here can be useful for earth science and ecosystem services research.

Flying capacity of Psyttalia concolor and Chrysoperla carnea under a UV-absorbing net (Bionet®) in presence and absence of crop.

Field studies were conducted in walk-in tunnels to determine the flying capacity in the presence and absence of crop, of the parasitoid Psyttalia concolor and the predator Chrysoperla carnea under a UV-absorbent net (Bionet®). Yellow sticky cards were used for insect recovery but neither P. concolor nor C. carnea were very attracted to them, thus captures were too low to permit any meaningful comparisons. Bionet® did not seem to affect the mobility of any natural enemy irrespective of the trap location and monitoring hour. Climatic conditions inside nets were very extreme (average temperatures very high and relative humidity very low) threatening insect survival. New experiments are being developed, trying to find new attractants that permit a significant capture of both natural enemies.

Influence of new integrated pest management strategies on aphidophagous predators in horticultural crops

El 1 de enero de 2014 entró en vigor la Directiva Europea 2009/128/CE sobre uso sostenible de plaguicidas y el Real Decreto 1311/2012 por el cual se traspone dicha normativa comunitaria al ámbito nacional. Estos reglamentos establecen el marco legal por el que las explotaciones agrícolas deben cumplir los principios generales de la Gestión Integrada de Plagas (GIP). Los principios de la GIP dan preferencia a aquellos métodos de control que sean sostenibles y respetuosos con el medio ambiente, dando prioridad al control biológico, al físico y a otros de carácter no químico. Sin embargo, el uso de insecticidas selectivos con los enemigos naturales es necesario en ocasiones para el adecuado manejo de las plagas en cultivos hortícolas. Por ello, el objetivo general de esta Tesis ha sido aportar conocimientos para la mejora del control de plagas en cultivos hortícolas, mediante la integración de estrategias de lucha biológica, física y química. La primera de las líneas de investigación de esta Tesis se centró en el estudio del efecto de la presencia dos depredadores, larvas Chrysoperla carnea y adultos de Adalia bipunctata, en la dispersión del virus de transmisión no persistente Cucumber mosaic virus (CMV) y del virus de transmisión persistente Cucurbit aphid-borne yellows virus (CABYV), transmitidos por el pulgón Aphis gosypii en cultivo de pepino. La tasa de transmisión de CMV fue baja para los dos tiempos de evaluación ensayados (1 y 5 días), debido al limitado movimiento de su vector A. gossypii. Las plantas que resultaron infectadas se localizaron próximas a la fuente de inóculo central y la presencia de ambos enemigos naturales no incrementó significativamente el porcentaje de plantas ocupadas por pulgones ni la tasa de transmisión de CMV. Los patrones de distribución de A. gossypii y de CMV tan solo fueron coincidentes en las proximidades de la planta central infectada en la que se liberaron los insectos. En los ensayos con CABYV, la presencia de C. carnea y de A. bipunctata respectivamente provocó un incremento significativo de la dispersión de A. gossypii tras 14 días, pero no tras 7 días desde la liberación de los insectos. La reducción en el número inicial de pulgones en la planta central infectada con CABYV fue siempre mayor tras la liberación de C. carnea en comparación con A. bipunctata. Sin embargo, la tasa de transmisión de CABYV y su distribución espacial no se vieron significativamente modificadas por la presencia de ninguno de los depredadores, ni tras 7 días ni tras 14 días desde el inicio de los ensayos. Al igual que se estudió el efecto de la presencia de enemigos naturales en el comportamiento de las plagas y en la epidemiología de las virosis que transmiten, en una segunda línea de investigación se evaluó el posible efecto del consumo de pulgones portadores de virus por parte de los enemigos naturales. Este trabajo se llevó a cabo en el Laboratorio de Ecotoxicología del Departamento de Entomología de la Universidade Federal de Lavras (UFLA) (Brasil). En él se evaluó la influencia en los parámetros biológicos del enemigo natural Chrysoperla externa al alimentarse de Myzus persicae contaminados con el virus de transmisión persistente Potato leafroll virus (PLRV). El consumo de M. persicae contaminados con PLRV incrementó significativamente la duración de la fase larvaria, reduciendo también la supervivencia en comparación a otras dos dietas a base de M. persicae no contaminados con el virus y huevos del lepidóptero Ephestia kuehniella. La duración de la fase de pupa de C. externa no difirió significativamente entre las dietas a base de pulgones contaminados con PLRV y pulgones no contaminados, pero ambas fueron menores que con la dieta con huevos de E. kuehniella. Sin embargo, ni la supervivencia en la fase de pupa ni los parámetros reproductivos de los adultos emergidos mostraron diferencias significativas entre las dietas evaluadas. Por el contrario, la supervivencia de los adultos durante los 30 primeros días desde su emergencia sí se vio significativamente afectada por la dieta, siendo al término de este periodo del 54% para aquellos adultos de C. externa que durante su fase larvaria consumieron pulgones con PLRV. Dentro de la GIP, una de las estrategias de carácter físico que se emplean para el control de plagas y enfermedades en cultivos hortícolas protegidos es el uso de plásticos con propiedades fotoselectivas de absorción de la radiación ultravioleta (UV). Por ello, la tercera línea de investigación de la Tesis se centró en el estudio de los efectos directos e indirectos (mediados por la planta) de condiciones especiales de baja radiación UV sobre el crecimiento poblacional del pulgón A. gossypii y los parámetros biológicos del enemigo natural C. carnea, así como sobre las plantas de pepino en las que se liberaron los insectos. Los ensayos se realizaron en jaulones dentro de invernadero, utilizándose en el primero de ellos plantas de pepino sanas, mientras que en el segundo las plantas de pepino fueron previamente infectadas con CABYV para estudiar de qué manera afectaba la incidencia del virus en las mismas condiciones. Las condiciones de baja radiación UV (bajo plástico Térmico Antivirus®) ejercieron un efecto directo en las fases iniciales del cultivo de pepino, promoviendo su crecimiento, mientras que en fases más avanzadas del cultivo indujeron un aumento en el contenido en nitrógeno de las plantas. Las plantas de pepino que fueron sometidas a mayor intensidad de radiación UV (bajo plástico Térmico Blanco®) al inicio del cultivo mostraron un engrosamiento significativo de las paredes de las células epidérmicas del haz de las hojas, así como de la cutícula. El uso del plástico Térmico Antivirus®, utilizado como barrera fotoselectiva para crear condiciones de baja radiación UV, no alteró con respecto al plástico Térmico Blanco® (utilizado como control) el desarrollo poblacional del pulgón A. gossypii ni los parámetros biológicos evaluados en el depredador C. carnea. En el segundo experimento, realizado con plantas infectadas con CABYV, la incidencia de la virosis enmascaró las diferencias encontradas en experimento con plantas sanas, reduciendo aparentemente la influencia de las distintas condiciones de radiación UV. Por último, para el desarrollo de las estrategias de GIP es importante estudiar los posibles efectos secundarios que los plaguicidas pueden tener en los enemigos naturales de las plagas. Es por ello que en la Tesis se evaluaron la toxicidad y los efectos subletales (fecundidad y fertilidad) de flonicamida, flubendiamida, metaflumizona, spirotetramat, sulfoxaflor y deltametrina en los enemigos naturales C. carnea y A. bipunctata. Los efectos secundarios fueron evaluados por contacto residual tanto para larvas como para adultos de ambos enemigos naturales en condiciones de laboratorio. Flonicamida, flubendiamida, metaflumizona y spirotetramat fueron inocuos para larvas de último estadio y adultos de C. carnea y A. bipunctata. Por este motivo, estos insecticidas se presentan como buenos candidatos para ser incorporados dentro de programas de GIP en combinación con estos enemigos naturales para el control de plagas de cultivos hortícolas. Sulfoxaflor fue ligeramente tóxico para adultos de C. carnea y altamente tóxico para larvas de último estadio de A. bipunctata. Para A. bipunctata, sulfoxaflor y deltametrina fueron los compuestos más dañinos. Deltametrina fue también el compuesto más tóxico para larvas y adultos de C. carnea. Por tanto, el uso de deltametrina y sulfoxaflor en programas de GIP debería tomarse en consideración cuando se liberasen cualquiera de estos dos enemigos naturales debido al comportamiento tóxico que mostraron en condiciones de laboratorio. ABSTRACT On 1 January 2014 came into effect the Directive 2009/128/EC of the European Parliament about sustainable use of pesticides and the Royal Decree 1311/2012 that transposes the regulation to the Spanish level. These regulations establish the legal framework that agricultural holdings must adhere to in order to accomplish the general principles of Integrated Pest Management (IPM). The guidelines of IPM give priority to sustainable and eco-friendly pest control techniques, such as biological and physical measures. Nevertheless, the use of pesticides that are selective to natural enemies is sometimes a necessary strategy to implement accurate pest management programs in horticultural protected crops. Therefore, the general objective of this Thesis was to contribute to the improvement of pest management strategies in horticultural crops, by means of the integration of biological, physical and chemical techniques. The first research line of this Thesis was focused on the evaluation of the effects of two aphidophagous predators, Chrysoperla carnea larvae and Adalia bipunctata adults, on the spread of the non-persistently transmitted Cucumber mosaic virus (CMV, Cucumovirus) and the persistently transmitted Cucurbit aphid-borne yellows virus (CABYV, Polerovirus), by the aphid vector Aphis gossypii in a cucumber crop under greenhouse conditions. The CMV transmission rate was generally low, both after 1 and 5 days, due to the limited movement of its aphid vector A. gossypii. Infected plants were mainly located around the central virusinfected source plant, and the percentage of aphid occupation and CMV-infected plants did not differ significantly in absence and presence of natural enemies. The distribution patterns of A. gossypii and CMV were only coincident close to the central plant where insects were released. In the CABYV experiments, the presence of C. carnea larvae and A. bipunctata adults induced significant A. gossypii dispersal after 14 days but not after 7 days. The reduction in the initial aphid population established in the central plant was always higher for C. carnea than for A. bipunctata. Nevertheless, CABYV spread was not significantly modified by the presence of each predator either in the short term (7 days) or in the long term (14 days). Furthermore, the percentage of CABYV-infected plants did not significantly differ when each natural enemy was present in any evaluation period. It is important to evaluate the influence that natural enemies have on pest dynamics and on the spread of viral diseases, but it should be also taken into account the possible effect on the performance of natural enemies when they feed on preys that act as vectors of viruses. Thus, in a second research line developed in the Laboratory of Ecotoxicology, Department of Entomology, of the Universidade Federal de Lavras (UFLA) (Brazil), it was evaluated the performance of Chrysoperla externa under the condition of consuming Myzus persicae acting as vector of Potato leafroll virus (PLRV). The diet composed of PLRV-infected M. persicae significantly increased the length and reduced the survival rate, of the larval period in regard to the other two diets, composed of non-infected M. persicae and Ephestia kuehniella eggs. The lengths of the pupal stage were not significantly different between the aphid diets, but both were significantly shorter than that of E. kuehniella eggs. Neither pupal survival nor reproductive parameters revealed significant differences among the diets. Nevertheless, the adult survival curves during the first 30 days after emergence showed significant differences, reaching at the end of this interval a value of 54% for those C. externa adults fed on PLRVinfected aphids during their larval period. According to the IPM guidelines, one of the physical strategies for the control of pests and diseases in horticultural protected crops is the use of plastic films with photoselective properties that act as ultraviolet (UV) radiation blocking barriers. In this sense, the third research line of the Thesis dealt with the study of the direct and plant-mediated influence of low UV radiation conditions on the performance of the aphid A. gossypii and on the biological parameters of the natural enemy C. carnea, as well as on the cucumber plants where insects were released. The experiments were conducted inside cages under greenhouse conditions, using for the first one healthy cucumber plants, while for the second experiment the cucumber plants were previously infected with CABYV in order to assess the influence of the virus in the same conditions. The low UV radiation conditions (under Térmico Antivirus® plastic film) seemed to exert a direct effect in the early stages of cucumber plants, enhancing their growth, and in an increasing nitrogen content at further developmental stages. The higher UV radiation exposure (under Térmico Blanco® plastic film) in the early stages of the cucumber crop induced the thickening of the adaxial epidermal cell walls and the cuticle of leaves. The use of Térmico Antivirus® plastic film as a photoselective barrier to induce low UV radiation conditions did not modify, in regard to Térmico Blanco® plastic film (used as control), neither the population development of A. gossypii nor the studied biological parameters of the predator C. carnea. In the second experiment, done with CABYV-infected cucumber plants, the incidence of the virus seemed to mask the direct and plant-mediated influence of the different UV radiation conditions. In last term, for the development of IPM strategies it is important to study the potential side effects that pesticides might have on natural enemies. For this reason, in the Thesis were tested the toxicity and sublethal effects (fecundity and fertility) of flonicamid, flubendiamide, metaflumizone, spirotetramat, sulfoxaflor and deltamethrin on the natural enemies C. carnea and A. bipunctata. The side effects of the active ingredients of the insecticides were evaluated with residual contact tests for the larvae and adults of these predators under laboratory conditions. Flonicamid, flubendiamide, metaflumizone and spirotetramat were innocuous to last instar larvae and adults of C. carnea and A. bipunctata. Therefore, these pesticides are promising candidates for being incorporated into IPM programs in combination with these natural enemies for the control of particular greenhouse pests. In contrast, sulfoxaflor was slightly toxic to adults of C. carnea and was highly toxic to last instar larvae of A. bipunctata. For A. bipunctata, sulfoxaflor and deltamethrin were the most damaging compounds. Deltamethrin was also the most toxic compound to larvae and adults of C. carnea. In accordance with this fact, the use of sulfoxaflor and deltamethrin in IPM strategies should be taken into consideration when releasing either of these biological control agents, due to the toxic behavior observed under laboratory conditions.

Compatibilidad de Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) y Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), importantes enemigos naturales de la mosca blanca Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) en cultivos hortícolas, con nuevas barreras físicas selectivas y modernos plaguicidas

Los programas de Gestión Integrada de Plagas (GIP) promueven el uso de estrategias de control que sean respetuosas con el medio ambiente, sin embargo el uso de insecticidas en los cultivos hortícolas sigue siendo necesario para el control de determinadas plagas, como es el caso de la mosca blanca Bemisia tabaci (Gennadius). Por ello, el objetivo de esta tesis es el estudio de la integración de las tres estrategias de control más empleadas hoy en día para el control de plagas: el control biológico, el físico y el químico. Una primera parte de este trabajo ha consistido en el estudio de los efectos letales y subletales de once insecticidas, aplicados a la dosis máxima de campo, sobre los enemigos naturales Eretmocerus mundus Mercet y Amblyseius swirskii Athias-Henriot, mediante ensayos de laboratorio y persistencia (laboratorio extendido). Para la evaluación de la toxicidad de los insecticidas sobre los estados de vida más protegidos de estos enemigos naturales, se trataron bajo la Torre de Potter las pupas de E. mundus y los huevos de A. swirskii. Además, se llevaron a cabo ensayos de contacto residual para determinar los efectos letales y subletales de estos insecticidas sobre el estado adulto de ambas especies de enemigos naturales. Para ello, los pesticidas se aplicaron sobre placas de cristal (laboratorio) o sobre plantas (laboratorio extendido: persistencia). Los resultados mostraron que los insecticidas flonicamida, flubendiamida, metaflumizona, metoxifenocida, spiromesifen y spirotetramat eran compatibles con el estado de pupa de E. mundus (OILB 1: Inocuos). Sin embargo, abamectina, deltametrina y emamectina fueron categorizadas como ligeramente tóxicas (OILB 2) al causar efectos deletéreos. Los dos pesticidas más tóxicos fueron spinosad y sulfoxaflor, los cuales redujeron significativamente la emergencia de las pupas tratadas (OILB 4: Tóxicos). Flonicamida, flubendiamida, metoxifenocida y spiromesifen fueron compatibles con el estado adulto de E. mundus (OILB 1: Inocuos). Abamectina, deltametrina, emamectina, metaflumizona y spiromesifen pueden ser recomendados para su uso en programas de GIP, si se usan los plazos de seguridad apropiados, de acuerdo con la persistencia de cada uno de estos insecticidas, antes de la liberación del enemigo natural. Al contrario, spinosad y sulfoxaflor no resultaron ser compatibles (OILB D: Persistentes), aunque la realización de ensayos adicionales es necesaria para ver los efectos de los mismos en campo. Todos los insecticidas estudiados, excepto el spirotetramat (OILB 2: Ligeramente tóxico), fueron selectivos para el estado de huevo de A. swirskii (OILB 1: Inocuos). Flonicamida, flubendiamida, metaflumizona, metoxifenocida, spiromesifen, spirotetramat y sulfoxaflor, fueron compatibles con el estado adulto de A. swirskii (OILB 1: Inocuos). Abamectina, deltametrina, emamectina y spinosad pueden ser recomendados para su uso en programas de GIP, si se usan los plazos de seguridad apropiados, de acuerdo con la persistencia de cada uno de estos insecticidas, antes de la liberación del enemigo natural. Entre las nuevas estrategias de la GIP, los plásticos y mallas fotoselectivas han demostrado ser una herramienta importante para el control de plagas y enfermedades en cultivos hortícolas protegidos. Por ello, en una segunda parte de este trabajo, se estudiaron tanto los efectos directos, como la combinación de efectos directos y mediados por planta y plaga de ambientes pobres en luz UV, en presencia o ausencia del Virus del rizado amarillo del tomate (TYLCV), sobre E. mundus. En primer lugar, se realizó un ensayo al aire libre para la evaluación de la capacidad de vuelo de E. mundus en cajas tipo túnel (1 x 0,6 x 0,6 m) cubiertas con distintas barreras absorbentes de luz UV. Se detectó un efecto directo en la capacidad de orientación de E. mundus, debido a que este parasitoide utiliza estímulos visuales para localizar a sus huéspedes, únicamente en las barreras que bloqueaban más del 65% de la luz UV (malla G). En segundo lugar, bajo condiciones de invernadero, se evaluó la combinación de efectos directos y mediados por planta y plaga sobre E. mundus, usando plantas de tomate sanas o infectadas con el TYLCV y cajas (30 x 30 x 60 cm) cubiertas con los distintos plásticos fotoselectivos. En este caso, no se observó ningún efecto en la capacidad benéfica del parasitoide cuando este estaba en contacto con plantas de tomate infestadas con ninfas de B. tabaci, lo que demuestra que este insecto usa estímulos táctiles para encontrar a sus huéspedes a cortas distancias. Además, las diferentes condiciones de radiación UV estudiadas tuvieron cierto impacto en la morfología, fisiología y bioquímica de las plantas de tomate, infestadas o no con el virus de la cuchara, detectándose pequeñas alteraciones en alguno de los parámetros estudiados, como el peso fresco y seco, el contenido en H y el espesor de las cutículas y de las paredes celulares de la epidermis foliar. Por último, no se observaron efectos de la radiación UV mediados por planta, ni en B. tabaci ni en su parasitoide, E. mundus. En una tercera parte, se evaluaron los efectos de una malla tratada con bifentrin sobre ambos enemigos naturales, en ensayos de laboratorio, semicampo y campo. Las mallas tratadas fueron diseñadas originariamente para el control de mosquitos vectores de la malaria, y actualmente se está trabajando para su uso en agricultura, como una nueva estrategia de control de plagas. En ensayos de laboratorio, cuando adultos de E. mundus y A. swirskii se expusieron por contacto durante 72 horas con la malla tratada (cajas de 6 cm diámetro), se registró una alta mortalidad. Sin embargo, en el ensayo de preferencia, estos enemigos naturales no fueron capaces de detectar la presencia de bifentrin y, en aquellos individuos forzados a atravesar la malla tratada, no se observó mortalidad a corto plazo (72 horas). En estudios de semicampo, llevados a cabo bajo condiciones de invernadero en cajas de 25 x 25 x 60 cm de altura, la capacidad benéfica de E. mundus no se vio afectada. Finalmente, en ensayos de campo llevados a cabo en invernaderos comerciales (4000m2) en Almería, A. swirskii no se vio afectado por la presencia en el cultivo de la malla tratada con bifentrin y los niveles de infestación de B. tabaci y F. occidentalis detectados bajo dicha malla, fueron inferiores a los del control. Por último, se ha evaluado la composición de la microflora bacteriana de tres especies de parasitoides, E. mundus, Eretmocerus eremicus Rose & Zolnerowich y Encarsia formosa Gahan, y la influencia de la misma en su susceptibilidad a insecticidas. Se llevó a cabo una extracción total de ADN de los insectos y la región variable V4 del ARNr se amplificó usando cebadores universales bacterianos. Para identificar las secuencias de los géneros bacterianos presentes en los parasitoides, se realizó una Next Generation sequencing (Illumina sequencing). Una vez identificados los géneros bacterianos, el gen ADNr 16S de las Actinobacterias se amplificó del ADN extraído de los insectos, usando cebadores universales bacterianos y específicos de Actinobacterias, y los productos de la Nested PCR fueron clonados para identificar todas las especies del género Arthrobacter. Tres bacterias (A. aurescens Phillips, A. nicotinovarans Kodama, Yamamoto, Amano and Amichi y A. uratoxydans Stackebrandt, Fowler, Fiedler and Seiler), próximas a las especies de Arthrobacter presentes en los parasitoides, se obtuvieron de la colección bacteriana del BCCMTM/LMG y se midió su actividad esterasa. Finalmente, se realizaron ensayos con antibióticos (tetraciclina) y de contacto residual con insecticidas (abamectina) para determinar la influencia de las especies de Arthrobacter en la susceptibilidad de E. mundus a insecticidas. Los resultados muestran que este género bacteriano puede afectar a la toxicidad de E. mundus a abamectina, mostrando la importancia de la comunidad microbiana en enemigos naturales, factor que debe ser considerado en los estudios de evaluación de los riesgos de los insecticidas. ABSTRACT Integrated Pest Management (IPM) programs promote the use of control strategies more respectful with the environment; however the use of insecticides in vegetable crops is still needed to control certain pests, such as the whitefly Bemisia tabaci (Gennadius). Therefore, the objective of this work is to study the integration of the three most commonly used pest control strategies nowadays: biological, physical and chemical control. Firstly, the lethal and sublethal effects of eleven insecticides, applied at their maximum field recommended concentration, on the parasitic wasp Eretmocerus mundus Mercet and the predator Amblyseius swirskii Athias-Henriot has been assessed in the laboratory and in persistence tests (extended laboratory). To test the effects of pesticides on the most protected life stage of these natural enemies, E. mundus pupae and A. swirskii eggs were sprayed under a Potter precision spray tower. Laboratory contact tests were therefore conducted to determine the lethal and sublethal effects of these pesticides on the adult stage of these natural enemies. In the residual contact tests the pesticides were applied on glass plates (laboratory) or plants (extended laboratory: persistence). The study showed that the insecticides flonicamid, flubendiamide, metaflumizone, methoxyfenozide, spiromesifen and spirotetramat were selective for E. mundus pupae (IOBC 1: Harmless). Nevertheless, abamectin, deltamethrin and emamectin were categorized as slightly harmful (IOBC 2) due to the deleterious effects caused. The two most harmful pesticides were spinosad and sulfoxaflor, which significantly reduced the adult emergence from treated pupae (IOBC 4: Harmful). Flonicamid, flubendiamide, methoxyfenozide and spiromesifen were compatible with E. mundus adults (IOBC 1: Harmless). Base on the duration of the harmful activity, abamectin, deltamethrin, emamectin, metaflumizone and spirotetramat could be recommended for use in IPM programs if appropriate safety deadlines are used before the natural enemy release. On the contrary, spinosad and sulfoxaflor were not compatible (IOBC D: persistent), although additional studies are required to determine their effects under field conditions. All the pesticides tested, except spirotetramat (IOBC 2: Slightly harmful), were selective for A. swirskii eggs (IOBC 1: Harmless). Flonicamid, flubendiamide, metaflumizone, methoxyfenozide, spiromesifen, spirotetramat and sulfoxaflor were compatible with A. swirskii adults (IOBC 1: Harmless). However, abamectin, deltamethrin, emamectin and spinosad could be recommended for use in IPM programs if appropriate safety deadlines are used before the natural enemy release. Among new IPM strategies, UV-absorbing photoselective plastic films and nets have been shown to be an important tool for the control of pests and diseases in horticultural protected crops. Because of that, we secondly studied the plant and pest insect-mediated and/or the direct effects on E. mundus under different UV radiation conditions, in presence or absence of the Tomato Yellow Leaf Curl Virus (TYLCV). In the first experiment, performed outdoors, the flight activity of E. mundus was studied in one-chamber tunnels (1 x 0.6 x 0.6 m) covered with different photoselective barriers. Because E. mundus uses visual cues for host location at a long distance, a direct effect on its host location ability was detected, but only in the UV-absorbing barriers blocking more than 65% of the UV light (G net). In a second experiment, the direct and plant and pest insect-mediated effects of different UV radiation conditions on E. mundus were studied, inside cages (30 x 30 x 60 cm) covered with the different UVplastic films and under greenhouse conditions, using healthy or TYLCV-virus infected tomato plants. In this case, not any effect on the beneficial capacity of this parasitoid was detected, proving that he uses tactile cues at a short distance of the host. Moreover, the different UV radiation conditions studied had a certain direct impact in the morphology, physiology and biochemistry of tomato plants infested or not with the TYLCV, and small alterations in some parameters such as fresh and dry weight, H percentage and cuticle and cell wall thickness of epidermal cells of the leaves, were detected. Finally, none plant-mediated UV effects neither in the whitefly B. tabaci nor in their parasitic wasp were found. Thirdly, the effects of a bifenthrin treated net were evaluated in different laboratory, semi-field and field experiments on the natural enemies studied. Treated nets were developed long time ago aiming at the control of the mosquitoes vectors of malaria, and nowadays, there is a great interest on assessing the possibility of their use in agriculture. In laboratory assays, a high mortality was recorded when E. mundus and A. swirskii adults were exposed by contact to the bifenthrin treated net for 72 hours in small cages (12 cm diameter). However, these natural enemies were not able to detect the presence of bifenthrin in a dual-choice test and no short-term mortality (72 hours) was recorded in those individuals that went through the treated net. In semi-field assays, performed under greenhouse conditions with cages of 25 x 25 x 60 cm high, the beneficial capacity of E. mundus was not affected. Finally, in field assays carried out in commercial multispan greenhouses (4000 m2) in Almería, A. swirskii was not affected by the presence of the bifenthrin treated net in the crop and the B. tabaci and F. occidentalis infestation levels were significantly lower than in the control. Finally, the composition of the microflora present in three species of parasitoids, E. mundus, Eretmocerus eremicus Rose & Zolnerowich and Encarsia formosa Gahan, and its influence in their susceptibility to insecticides, have been assessed. A total DNA extraction was performed on insects and universal bacterial primers were used to amplify the variable V4 region of the rRNA. A Next Generation sequencing (Illumina sequencing) was performed to identify the sequences of the bacterial genera present in the parasitic wasps. Once, the bacterial genera were identified, 16S rDNA gene of Actinobacteria were amplified from insects DNA extracts using the universal bacterial and actinobacterial primers, and the nested PCR products, were cloned to identify the Arthrobacter species. Three bacteria (A. aurescens Phillips, A. nicotinovarans Kodama, Yamamoto, Amano and Amichi and A. uratoxydans Stackebrandt, Fowler, Fiedler and Seiler), having the closest match with the Arthrobacter species present in the parasitic wasps, were obtained from the BCCMTM/LMG bacteria collection and its esterase activity was measured. Finally, antibiotic and residual contact tests were done to determine the influence of Arthrobacter species in the susceptibility of E. mundus to pesticides (abamectin). The results suggest that this bacterial genus can affect the toxicity of E. mundus to abamectin, which in turn supports the importance of the microbial community in natural enemies that it should be considered as a factor in risk assessment tests of pesticides.

INFLUENCE OF A NATIVE INSECTARY PLANT, CHAMAECRISTA FASCICULATA (MICHX.) ON ORGANIC FIELD CORN AND ARTHROPOD COMMUNITIES

Increasing plant diversity in conventionally monoculture agrosystems has been promoted as a method to enhance beneficial arthropod density and efficacy, suppress herbivory and provide a range of ecosystem services. I investigated the pest suppressive potential and economic impact of plant diversification in organic field corn. The experiment consisted of two treatments, corn grown in monoculture (C) and bordered by strips of partridge pea (PP). Pest and natural enemy populations, corn damage, yield, and profits were compared among treatments. Natural enemy and herbivore arthropod populations were affected by treatment and distance from plot border. Corn damage due to pests was also affected by treatment and location, but did not significantly affect yield. Yield in monoculture plots was generally greater than in PP but did not result in greater profit. Pest and natural enemy arthropod abundances were elevated in partridge pea treatment borders, but these populations did not consistently diffuse into plot interiors. The potential causes and implications of findings are discussed.

Natural history of an ant-plant-butterfly interaction in a Neotropical savanna

Non-myrmecophilous lepidopteran larvae using plants bearing ant attractants such as extrafloral nectaries are good models for studying morphological and behavioural mechanisms against ant predation. Udranomia spitzi (Hesperiidae) is a butterfly whose larvae feed on leaves of Ouratea spectabilis (Ochnaceae), a plant with extrafloral nectaries. We described the early stages of U. spitzi, and used field observations and experiments to investigate the defensive strategies of caterpillars against predatory ants. Larvae pass through five instars and pupation occurs inside larval leaf shelters. Ant-exclusion experiments revealed that the presence of ants did not affect significantly caterpillar survival. Predation experiments showed that vulnerability to ant predation decreased with increase in larval size. The present study showed that predatory ants are not as relevant as demonstrated for other systems, and also illustrates how observational data and field experiments can contribute to a better understanding of the biology and ecology of a species of interest.

Adaptation to enemy shifts: rapid resistance evolution to local Vibrio spp. in invasive Pacific oysters

One hypothesis for the success of invasive species is reduced pathogen burden, resulting from a release from infections or high immunological fitness (low immunopathology) of invaders. Despite of strong selection exerted on the host, the evolutionary response of invaders to newly acquired pathogens has rarely been considered. The two independent and genetically distinct invasions of the Pacific oyster Crassostrea gigas into the North Sea represent an ideal model system to study fast evolutionary responses of invasive populations. By exposing both invasion sources to ubiquitous and phylogenetically diverse pathogens (Vibrio spp.) we demonstrate that within a few generations hosts adapted to sympatric pathogen communities. However, this local adaptation only became apparent in selective environments, i.e. at elevated temperatures reflecting patterns of disease outbreaks in natural populations. Resistance against sympatric and allopatric Vibrio spp. strains was dominantly inherited in crosses between both invasion sources, resulting in an overall higher resistance of admixed individuals than pure lines. Therefore we suggest that a simple genetic resistance mechanism of the host is matched to a common virulence mechanism shared by local Vibrio strains. This combination might have facilitated a fast evolutionary response that can explain another dimension of why invasive species can be so successful in newly invaded ranges.

Particle and gaseous emissions from compressed natural gas and ultralow sulphur diesel-fuelled buses at four steady engine loads

Exhaust emissions from thirteen compressed natural gas (CNG) and nine ultralow sulphur diesel in-service transport buses were monitored on a chassis dynamometer. Measurements were carried out at idle and at three steady engine loads of 25%, 50% and 100% of maximum power at a fixed speed of 60 kmph. Emission factors were estimated for particle mass and number, carbon dioxide and oxides of nitrogen for two types of CNG buses (Scania and MAN, compatible with Euro 2 and 3 emission standards, respectively) and two types of diesel buses (Volvo Pre-Euro/Euro1 and Mercedez OC500 Euro3). All emission factors increased with load. The median particle mass emission factor for the CNG buses was less than 1% of that from the diesel buses at all loads. However, the particle number emission factors did not show a statistically significant difference between buses operating on the two types of fuel. In this paper, for the very first time, particle number emission factors are presented at four steady state engine loads for CNG buses. Median values ranged from the order of 1012 particles min-1 at idle to 1015 particles km-1 at full power. Most of the particles observed in the CNG emissions were in the nanoparticle size range and likely to be composed of volatile organic compounds The CO2 emission factors were about 20% to 30% greater for the diesel buses over the CNG buses, while the oxides of nitrogen emission factors did not show any difference due to the large variation between buses.