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Sphaerophoria rueppellii is a commercially available syrphid used for control of numerous agricultural and ornamental aphid pests. Previous research has shown that prey species can affect some of the biological traits of beneficial insects, which might affect their success and establishment, but such effects are completely unknown for this predator. The present work explored the effects of two polyphagous aphid species which are common agricultural pests in vegetables and cereal crops (Myzus persicae and Rhopalosiphum padi, respectively) and one ornamental pest (Aphis nerii), on some fitness-related parameters of S. rueppellii, when fed exclusively with one of these species during the larval stage. Fecundity and fertility of females was higher when they were fed with R. padi and showed the lowest values with A. nerii. Egg-to-adult survival and adult’s wing length were also shorter when syrphid larvae ate the latter species, which might be related to the aphid’s host plant toxicity, the ornamental Nerium oleander. These results will help to improve the use of this predator with regards to the targeted aphid pest and the affected plants., Sphaerophoria rueppellii es un sírfido comercializado para el control de numerosas plagas agrícolas y ornamentales de pulgón. Investigaciones previas han mostrado que la especie de la que se alimentan los insectos beneficiosos puede afectar a algunos de sus parámetros biológicos, lo que a su vez puede condicionar su éxito y establecimiento; sin embargo, estos efectos son totalmente desconocidos para este depredador de pulgón. El presente trabajo ha estudiado los efectos de dos especies polífagas de pulgón que constituyen plagas agrícolas comunes en cultivos hortícolas y de cereales (Myzus persicae y Rhopalosiphum padi, respectivamente) y de una plaga ornamental (Aphis nerii), en algunos parámetros relacionados con la eficacia biológica de S. rueppellii, cuando este depredador se alimenta exclusivamente con una de estas especies durante su fase larvaria. La fecundidad y fertilidad de las hembras adultas fue superior cuando se alimentaron con R. padi, y alcanzaron su valor más bajo con A. nerii. La supervivencia de huevo a adulto y la longitud alar de éstos también fueron menores cuando las larvas de sírfido se alimentaron con este último pulgón, lo cual puede estar relacionado con la toxicidad que tiene su planta huésped, la especie ornamental Nerium oleander. Estos resultados ayudarán a mejorar el manejo de este depredador en función de la especie de pulgón plaga y del tipo de planta.

Sphaerophoria rueppellii is a commercially available syrphid used for control of numerous agricultural and ornamental aphid pests. Previous research has shown that prey species can affect some of the biological traits of beneficial insects, which might affect their success and establishment, but such effects are completely unknown for this predator. The present work explored the effects of two polyphagous aphid species which are common agricultural pests in vegetables and cereal crops (Myzus persicae and Rhopalosiphum padi, respectively) and one ornamental pest (Aphis nerii), on some fitness-related parameters of S. rueppellii, when fed exclusively with one of these species during the larval stage. Fecundity and fertility of females was higher when they were fed with R. padi and showed the lowest values with A. nerii. Egg-to-adult survival and adult’s wing length were also shorter when syrphid larvae ate the latter species, which might be related to the aphid’s host plant toxicity, the ornamental Nerium oleander. These results will help to improve the use of this predator with regards to the targeted aphid pest and the affected plants., Sphaerophoria rueppellii es un sírfido comercializado para el control de numerosas plagas agrícolas y ornamentales de pulgón. Investigaciones previas han mostrado que la especie de la que se alimentan los insectos beneficiosos puede afectar a algunos de sus parámetros biológicos, lo que a su vez puede condicionar su éxito y establecimiento; sin embargo, estos efectos son totalmente desconocidos para este depredador de pulgón. El presente trabajo ha estudiado los efectos de dos especies polífagas de pulgón que constituyen plagas agrícolas comunes en cultivos hortícolas y de cereales (Myzus persicae y Rhopalosiphum padi, respectivamente) y de una plaga ornamental (Aphis nerii), en algunos parámetros relacionados con la eficacia biológica de S. rueppellii, cuando este depredador se alimenta exclusivamente con una de estas especies durante su fase larvaria. La fecundidad y fertilidad de las hembras adultas fue superior cuando se alimentaron con R. padi, y alcanzaron su valor más bajo con A. nerii. La supervivencia de huevo a adulto y la longitud alar de éstos también fueron menores cuando las larvas de sírfido se alimentaron con este último pulgón, lo cual puede estar relacionado con la toxicidad que tiene su planta huésped, la especie ornamental Nerium oleander. Estos resultados ayudarán a mejorar el manejo de este depredador en función de la especie de pulgón plaga y del tipo de planta.

Predictable effects of resource availability on plant growth-defense strategies provide a unifying theme in theories of direct anti-herbivore defense, but it is less clear how resource availability modulates plant indirect defense. Ant-plant-hemipteran interactions produce mutualistic trophic cascades when hemipteran-tending ants reduce total herbivory, and these interactions are a key component of plant indirect defense in most terrestrial ecosystems. Here we conducted an experiment to test how ant-plant-hemipteran interactions depend on nitrogen (N) availability by manipulating the presence of ants and aphids under different N fertilization treatments. Ants increased plant flowering success by decreasing the densities of herbivores, and the effects of ants on folivores were positively related to the density of aphids. Unexpectedly, N fertilization produced no changes in plant N concentrations. Plants grown in higher N grew and flowered more, but aphid honeydew chemistry stayed the same, and neither the density of aphids nor the rate of ant attraction per aphid changed with N addition. The positive effects of ants and N addition on plant fitness were thus independent of one another. We conclude that N was the plant's limiting nutrient and propose that addition of the limiting nutrient is unlikely to alter the strength of mutualistic trophic cascades.

Predictable effects of resource availability on plant growth-defense strategies provide a unifying theme in theories of direct anti-herbivore defense, but it is less clear how resource availability modulates plant indirect defense. Ant-plant-hemipteran interactions produce mutualistic trophic cascades when hemipteran-tending ants reduce total herbivory, and these interactions are a key component of plant indirect defense in most terrestrial ecosystems. Here we conducted an experiment to test how ant-plant-hemipteran interactions depend on nitrogen (N) availability by manipulating the presence of ants and aphids under different N fertilization treatments. Ants increased plant flowering success by decreasing the densities of herbivores, and the effects of ants on folivores were positively related to the density of aphids. Unexpectedly, N fertilization produced no changes in plant N concentrations. Plants grown in higher N grew and flowered more, but aphid honeydew chemistry stayed the same, and neither the density of aphids nor the rate of ant attraction per aphid changed with N addition. The positive effects of ants and N addition on plant fitness were thus independent of one another. We conclude that N was the plant's limiting nutrient and propose that addition of the limiting nutrient is unlikely to alter the strength of mutualistic trophic cascades.

In plant-ant-hemipteran interactions, ants visit plants to consume the honeydew produced by phloem-feeding hemipterans. If genetically based differences in plant phloem chemistry change the chemical composition of hemipteran honeydew, then the plant's genetic constitution could have indirect effects on ants via the hemipterans. If such effects change ant behavior, they could feed back to affect the plant itself. We compared the chemical composition of honeydews produced by Aphis nerii aphid clones on two milkweed congeners, Asclepias curassavica and Asclepias incarnata, and we measured the responses of experimental Linepithema humile ant colonies to these honeydews. The compositions of secondary metabolites, sugars, and amino acids differed significantly in the honeydews from the two plant species. Ant colonies feeding on honeydew derived from A. incarnata recruited in higher numbers to artificial diet, maintained higher queen and worker dry weight, and sustained marginally more workers than ants feeding on honeydew derived from A. curassavica. Ants feeding on honeydew from A. incarnata were also more exploratory in behavioral assays than ants feeding from A. curassavica. Despite performing better when feeding on the A. incarnata honeydew, ant workers marginally preferred honeydew from A. curassavica to honeydew from A. incarnata when given a choice. Our results demonstrate that plant congeners can exert strong indirect effects on ant colonies by means of plant-species-specific differences in aphid honeydew chemistry. Moreover, these effects changed ant behavior and thus could feed back to affect plant performance in the field.

In plant-ant-hemipteran interactions, ants visit plants to consume the honeydew produced by phloem-feeding hemipterans. If genetically based differences in plant phloem chemistry change the chemical composition of hemipteran honeydew, then the plant's genetic constitution could have indirect effects on ants via the hemipterans. If such effects change ant behavior, they could feed back to affect the plant itself. We compared the chemical composition of honeydews produced by Aphis nerii aphid clones on two milkweed congeners, Asclepias curassavica and Asclepias incarnata, and we measured the responses of experimental Linepithema humile ant colonies to these honeydews. The compositions of secondary metabolites, sugars, and amino acids differed significantly in the honeydews from the two plant species. Ant colonies feeding on honeydew derived from A. incarnata recruited in higher numbers to artificial diet, maintained higher queen and worker dry weight, and sustained marginally more workers than ants feeding on honeydew derived from A. curassavica. Ants feeding on honeydew from A. incarnata were also more exploratory in behavioral assays than ants feeding from A. curassavica. Despite performing better when feeding on the A. incarnata honeydew, ant workers marginally preferred honeydew from A. curassavica to honeydew from A. incarnata when given a choice. Our results demonstrate that plant congeners can exert strong indirect effects on ant colonies by means of plant-species-specific differences in aphid honeydew chemistry. Moreover, these effects changed ant behavior and thus could feed back to affect plant performance in the field.

The green shield scale, Pulvinaria psidii Maskell, was found at high levels on red ginger (Alpinia purpurata K. Schum.) at IIHR Farm, Bangalore in June 2006. Following the release of the Australian ladybird beetle, Cryptolaemus montrouzieri Mulsant @10 / plant, the scale population declined from 174.60 scales / shoot on 15 June to 1.40 / shoot on 1 September in 2006. The population of C. montrouzieri ranged from 3.40 to 10.34 per shoot during the study period. Since no other natural enemies were recorded, the reduction in the population of P. psidii in the red ginger biocontrol plot was attributed mainly to the action of C. montrouzieri.