Omnivorous Predator Research Articles

Responses of soil micro-food web to long-term fertilization in a wheat–maize rotation system

Soil microbes and nematodes are important components of soil biota that strongly affect agricultural productivity and sustainability. Currently, our knowledge on the response of soil biota to agricultural management is restricted. This study aimed to identify the relationship between microbial and nematode communities and explore the resource path that flows within the soil micro-food web under different fertilization practices in a winter-wheat/summer-maize rotation system. The experiment was a randomized complete block design with three replicates for each treatment that included unfertilized control; inorganic N, P and K fertilizer (NPK); NPK plus manure; and NPK plus maize straw. Soil samples were taken at a 0–20cm depth when wheat and maize were harvested. The results showed that organic manure or maize straw combined with NPK fertilizers had positive effects on the soil microbial and nematode communities. For example, the incorporation of straw increased the fungal biomass. Long-term inorganic fertilization might restrain nematode biomass accumulation especially in fungivorous nematodes. The analysis of the metabolic footprints of nematodes suggested that the incorporation of straw could enhance the carbon resource flow into the soil food web by enhancing nematode biomass. Structural equation modeling analysis suggested that the bottom–up control from the microbial community to the nematode community was more obvious in the wheat season in comparison with the maize season. In addition, a relatively stronger predation relationship was found between omnivores–predators and bacterivores rather than fungivores. Our study suggests that organic management combined with NPK fertilization could effectively enhance the association between microbial and nematode communities, while a crop rotation system with maize may have a negative influence on the structure of the soil micro-food web.

Direct effects of elevated temperature on a tri-trophic system: Salix, leaf beetles and predatory bugs

The net effect of climatic change on biotic interactions will depend on how each interacting species is individually affected. Elevated temperatures are predicted to have differential effects on species across trophic levels, due to asymmetric sensitivity to temperature changes. In this study, we examined the direct effects of three temperature regimes (16, 20 and 24 °C) that reflect present and, potentially, future climate conditions on the response of Salix spp. plants, an important bioenergy crop, and its most damaging herbivore (Phratora vulgatissima) and an efficient natural enemy (the omnivorous predator Orthotylus marginalis). We found that plant growth, herbivore oviposition and enemy egg-foraging rate correlated positively with temperature. In the event of elevated temperatures following global climatic changes, these species could potentially respond in tandem. Still, the strength of responses varied among species, with herbivore and natural enemy exhibiting a similar and steeper rate of response relative to plants. Additionally, the herbivore’s response was influenced by plant quality with altered oviposition rates depending on whether it was fed the (previously determined) resistant Salix dasyclados or susceptible S. viminalis. This indicates that host plant chemistry has the potential to mediate differential responses to temperature. Together, our results suggest that indirect effects of elevated temperatures, leading to a disruption of trophic associations, may be less likely or less severe in this tri-trophic system.

Dynamics of soil nematode communities in wheat fields under different nitrogen management in Northern China Plain

The temporal dynamics of nematode abundance and community composition were monitored in a nitrogen (N) fertilization experiment during the main growth stages of winter wheat in Northern China Plain. A randomized complete block design was used with four levels of N fertilization (50, 100, 150 and 300 kg N ha−1 y−1 denoted as N1, N2, N3 and N4, respectively). The results showed that winter wheat aboveground biomass increased but soil pH decreased with elevating N fertilization. Total nematode abundance reached the highest values at the shooting stage of wheat, and was significantly increased by the N fertilization. On the contrary, nematode generic richness declined with increasing N fertilization. The relative abundance of bacterivores showed minor changes among different fertilization treatments whereas that of fungivores was suppressed by the N4 treatment. Plant parasites were the most abundant under the N2 treatment. The relative abundance of omnivores–predators declined with increasing N fertilization. The results indicate that trophic groups have distinctive responses to different levels of N fertilization, and N fertilization may induce an abundant but simple nematode community in the winter wheat field of North China Plain. Our findings also highlight the potential of adequate N application to reduce plant parasites and to control agriculture pests.

Responses of Soil Nematode Abundance and Diversity to Long-Term Crop Rotations in Tropical China

A field experiment was carried out from 2003 to 2013 in the Wanzhong Farm of the Hainan Island, China, to determine the effects of two long–term banana rotations on the abundance and trophic groups of soil nematode communities in the island. The experiment was set out as a randomized complete block design with three replications of three treatments: banana–pineapple rotation (AB), banana–papaya rotation (BB) and banana monoculture (CK) in a conventional tillage system. Soil samples were taken at depths of 0–10, 10–20 and 20–30 cm, and nematodes were extracted by a modified cotton–wool filter method and identified to the genus level. Nematode ecological indices of Shannon–Weaver diversity (H′), dominance index (λ), maturity index (MI), plant parasite index (PPI), structure index (SI), enrichment index (EI), and channel index (CI) were calculated. A total of 28 nematode genera with relative abundance over 0.1% were identified, among which Tylenchus and Paratylenchus in the AB, Thonus in the BB, Tylenchus and Helicotylenchus in the CK were the dominant genera. The rotation soils favored bacterivores, fungivores and omnivores–predators with high colonizer–persister (c–p) values. Soil food web in the rotation systems was highly structured, mature and enriched as indicated by SI, MI and EI values, respectively. Higher abundance of bacterivores and lower values of CI suggested that the soil food web was dominated by a bacterial decomposition pathway in rotation soils. Nematode diversity was much higher after a decade of rotation. Soil depth had significant effects on the abundance of soil nematodes, but only on two nematode ecological indices (λ and MI).

Colonisation rate and adaptive foraging control the emergence of trophic cascades.

Ecological communities are assembled and sustained by colonisation. At the same time, predators make foraging decisions based on the local availabilities of potential resources, which reflects colonisation. We combined field and laboratory experiments with mathematical models to demonstrate that a feedback between these two processes determines emergent patterns in community structure. Namely, our results show that prey colonisation rate determines the strength of trophic cascades - a feature of virtually all ecosystems - by prompting behavioural shifts in adaptively foraging omnivorous fish predators. Communities experiencing higher colonisation rates were characterised by higher invertebrate prey and lower producer biomasses. Consequently, fish functioned as predators when colonisation rate was high, but as herbivores when colonisation rate was low. Human land use is changing habitat connectivity worldwide. A deeper quantitative understanding of how spatial processes modify individual behaviour, and how this scales to the community level, will be required to predict ecosystem responses to these changes.

Nitrogen and water limitations in tomato plants trigger negative bottom-up effects on the omnivorous predator Macrolophus pygmaeus

Omnivorous Heteroptera predators play important roles in biological control of a wide range of pest insects. Their predation could be influenced by various biotic or abiotic factors. Here we examined the effects of nitrogen and water inputs to tomato plants (Solanum lycopersicum L.) on the predation strength of the omnivore Macrolophus pygmaeus Wagner (Hemiptera: Miridae) on eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). We tested the hypothesis that a change in plant status, manipulated by sub-optimal nutrients and water inputs, may influence predation on E. kuehniella by the predator M. pygmaeus. Nitrogen and water restrictions depressed the predation of E. kuehniella eggs by M. pygmaeus. Moreover, we observed a 30 % reduction in predator longevity on plants under low water inputs. Therefore, the negative bottom-up effect of nitrogen and water limitations (in tomato plants) toward M. pygmaeus may be detrimental for mirid predator-based IPM programs in tomato crops.

Beyond Predation: The Zoophytophagous Predator Macrolophus pygmaeus Induces Tomato Resistance against Spider Mites.

Many predatory insects that prey on herbivores also feed on the plant, but it is unknown whether plants affect the performance of herbivores by responding to this phytophagy with defence induction. We investigate whether the prior presence of the omnivorous predator Macrolophus pygmaeus (Rambur) on tomato plants affects plant resistance against two different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI), may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators.

Pollen suitability for the development and reproduction of Amblydromalus limonicus (Acari: Phytoseiidae)

Plant pollen is considered a food of high nutritional quality for several natural enemies, such as predatory insects and mites. In periods of prey absence or scarcity, omnivorous predators often exploit plant pollen as an alternative food. In the case of predators feeding on mixed diets, pollen may be consumed supplementary to the main prey. However, genetic variation may translate into quality differences in pollen derived from distinct plant species. We herein assessed the nutritional suitability of the pollen of four anemophilous plant species [cattail—Typhalatifolia (L.), pine, corn, and olive] for the predatory mite Amblydromaluslimonicus (Garman & McGregor) (Acari: Phytoseiidae), a phytoseiid mite with great potential for controlling thrips and whiteflies in greenhouse crops. Juvenile development and survival were not affected by the different pollens. Nevertheless, significant differences in adult performance (longevity and egg production) resulted in considerable effects of pollen species on the calculated intrinsic rates of increase (rm) for this predator. Cattail followed by olive pollen resulted in the highest rm values (0.2340 and 0.2001 day−1, respectively), while the lowest values were recorded for corn and pine pollen. Our results show that all pollens tested may be used as alternative food for sustaining the population of A. limonicus in the field. Recorded differences among pollens highlight the need for a careful consideration of the quality of pollen used in laboratory rearings and in field applications.

Impact of processed earwigs and their faeces on the aroma and taste of 'Chasselas' and 'Pinot Noir' wines

The abundance of the European earwig Forficula auricularia L. (Dermaptera, Forficulidae) in European vineyards increased considerably over the last few years. Although earwigs are omnivorous predators that prey on viticultural pests such as grape moths, they are also known to erode berries and to transfer fungal spores. Moreover, they are suspected to affect the human perception of wines both directly by their processing with the grapes and indirectly by the contamination of grape clusters with their faeces. In this study we artificially contaminated grapes with F. auricularia adults and/or their faeces and determined the impact on aroma and taste of white 'Chasselas' and red 'Pinot noir' wines. Whereas the addition of five living adults/kg grapes affected the olfactory sensation of 'Chasselas' wines only marginally, 0.6 gram of earwig faeces/kg grapes had a strong effect on colour, aroma and the general appreciation of 'Chasselas' wines. Faeces-contaminated wines were less fruity and less floral, the aroma was described as faecal and they were judged to be of lower quality. The contamination of 'Pinot noir' grapes with four different densities of living earwig adults (e.g. 0, 5, 10 and 20 individuals/kg grapes) showed that only wines contaminated with more than 10 earwigs/kg grapes smelled and tasted significantly different than the uncontaminated control wine. Earwig-contaminated 'Pinot noir' wines were judged to be of lower quality. The descriptors “animal”, “reductive”, “vegetal”, “acidic”, “bitter” and “tannic” characterised their sensory perception. In conclusion, our results show that there is a real risk of wine contamination by F. auricularia . In particular, earwig faeces and earwig adults at densities above a threshold of 5 to 10 individuals/kg grapes have the potential to reduce the quality of wines. The evolution of earwig populations in vineyards should therefore be monitored carefully in order to anticipate problems during vinification.

Evidence that the house finch (Carpodacus mexicanus) uses scent to avoid omnivore mammals

The detection of predator chemical cues is an important antipredatory behaviour as it allows an early assessment of predation risk without encountering the predator and therefore increases survival. For instance, since chemical cues are often by-products of metabolism, olfaction may gather information not only on the identity but also about the diet of predators in the vicinity. Knowledge of the role of olfaction in the interactions of birds with their environment, in contexts as important as predator avoidance, is still scarce. We conducted two two-choice experiments to explore 1) whether the house finch Carpodacus mexicanus can detect the chemical cues of a marsupial predatory mammal, the common opossum (Didelphis marsupialis), and 2) whether its response to such cues is influenced by the recent diet of this omnivorous predator, as this would increase the accuracy with which the risk of predation is assessed. House finches avoided the area of the apparatus containing the scent of the predator, and this effect did not depend on the recent diet (bait used to lace the traps) of the predator. Our results provide clear evidence that house finches detect and use the chemical cues of predators to assess the level of predation risk of an area and avoid it.

Can Interactions Between an Omnivorous Hemipteran and an Egg Parasitoid Limit the Level of Biological Control for the Tomato Pinworm?

Relationships between the omnivorous predator Nesidiocoris tenuis (Reuter) and the egg parasitoid Trichogramma achaeae Nagaraja and Nagarkatti were studied in the laboratory (no-choice and choice assays, and functional responses) and in a greenhouse experiment. Both natural enemies are utilized in the biological control of tomato pinworm on greenhouse-grown tomato crops. Three different food items were offered to the predator: nonparasitized prey, prey parasitized for less than 4 d by T. achaeae, and prey parasitized for more than 4 d by the parasitoid. There were significant differences in consumption of food types, with highest consumption for nonparasitized prey, followed by parasitized (<4 d) and then parasitized (>4 d), both in no-choice and choice trials. At the same time, the predator causes a significant mortality in the prey (over 80%) regardless of previous parasitism, resulting in a very coincidental intraguild predation detrimental to the parasitoid. It has also been observed that there was a change in the functional response by the predator from Type II in presence of nonparasitized prey to Type I when there was a combination of parasitized and nonparasitized prey. This represents an increase of instantaneous search rate (a') and a decrease of handling time (Th), which indicates a change in feeding behavior on the two prey types. Under greenhouse conditions, the intraguild predation reduced the percentage of parasitism by T. achaeae in just over 20%. However, when both natural enemies were present, a better control of pest Tuta absoluta (Meyrick) was achieved than in the case of application of any of them alone.

Plant‐sex‐biased tritrophic interactions on dioecious willow

Plant sex effects on herbivores are well studied, but little is known about these effects on predators and predator–herbivore dynamics. Here we take a holistic approach to study, simultaneously, plant sex effects on herbivore and predator preference and performance, as well as population densities and predation pressure in the field. For dioecious Salix cinerea (grey willow) we found that male plants represented higher host plant quality than females for an omnivorous predator (Anthocoris nemorum, common flower bug), while host plant quality for its herbivorous prey (Phratora vulgatissima, blue willow beetle) was not sex‐biased. The herbivore strongly preferred the host plant sex (female) that was suboptimal for the predator, which in turn followed its prey to female plants, leading to plant‐sex‐biased predation. These results provide new insight into the far‐reaching effects of plant sex on insect communities, and open up novel opportunities for improving biocontrol of the herbivore in Salix short rotation coppice.

Community, trophic structure and functioning in two contrasting Laminaria hyperborea forests

Worldwide kelp forests have been the focus of several studies concerning ecosystem dysfunction in the past decades. Multifactorial kelp threats have been described and include deforestation due to human impact, cascading effects and climate change. Here, we compared community and trophic structure in two contrasting kelp forests off the coasts of Brittany. One has been harvested five years before sampling and shelters abundant omnivorous predators, almost absent from the other, which has been treated as preserved from kelp harvest. δ15N analyses conducted on the overall communities were linked to the tropho-functional structure of different strata featuring these forests (stipe and holdfast of canopy kelp and rock). Our results yielded site-to-site differences of community and tropho-functional structures across kelp strata, particularly contrasting in terms of biomass on the understorey. Similarly, isotope analyses inferred the top trophic position of Marthasterias glacialis and Echinus esculentus which may be considered as strong interactors in the sub-canopy. We interrogate these patterns and propose a series of probable and testable alternative hypotheses to explain them. For instance, we propose that differences of trophic structure and functioning result from confounded effects of contrasting wave dissipation depending on kelp size-density structure and community cascading involving these omnivorous predators. Given the species diversity and complexity of food web highlighted in these habitats, we call for further comprehensive research about the overall strata and tropho-functional groups for conservation management in kelp forests.

New parasitoid-predator associations: female parasitoids do not avoid competition with generalist predators when sharing invasive prey.

Optimal habitat selection is essential for species survival in ecosystems, and interspecific competition is a key ecological mechanism for many observed species association patterns. Specialized animal species are commonly affected by resource and interference competition with generalist and/or omnivorous competitors, so avoidance behavior could be expected. We hypothesize that specialist species may exploit broad range cues from such potential resource competitors (i.e., cues possibly common to various generalist and/or omnivorous predators) to avoid costly competition regarding food or reproduction, even in new species associations. We tested this hypothesis by studying short-term interactions between a native larval parasitoid and a native generalist omnivorous predator recently sharing the same invasive host/prey, the leaf miner Tuta absoluta. We observed a strong negative effect of kleptoparasitism (food resource stealing) instead of classical intraguild predation on immature parasitoids. There was no evidence that parasitoid females avoided the omnivorous predator when searching for oviposition sites, although we studied both long- and short-range known detection mechanisms. Therefore, we conclude that broad range cue avoidance may not exist in our biological system, probably because it would lead to too much oviposition site avoidance which would not be an efficient and, thus, beneficial strategy. If confirmed in other parasitoids or specialist predators, our findings may have implications for population dynamics, especially in the current context of increasing invasive species and the resulting creation of many new species associations.

Use of plant resources by an omnivorous predator and the consequences for effective predation

Plant-provided food may enhance survival and establishment of omnivorous predators on target crops but on the other hand they may adversely affect predation rates and thus their potential for biological control of target pests. However, it is not known how predation is affected by plant food quality and prey density. The omnivorous predator Macrolophus pygmaeus is commonly used in augmentative releases in greenhouse crops. Experiments have shown its ability to utilize plant resources; eggplant and pepper plant leaves are the most and least suitable, respectively. In this study we searched the effects of floral resources (pollen or flower) of eggplant or pepper plant on the predation rate of M. pygmaeus. We used experiments in dishes (leaves) and cages (plants) under a range of densities of its prey, the aphid Myzuspersicae. We did not find evidence that the consumption rates and the type of the functional responses of M. pygmaeus were affected by the plant leaf (eggplant vs pepper plant) or the increase in the spatial scale (leaf vs plant). However, the presence of pollen or a flower of eggplant and to a lesser extent of pepper plant reduced the plateau of the functional response to aphid density and increased the handling time per prey. The extent of prey feeding replacement by flower resources was dependent on the interaction between plant species and prey density. It seems that there is a constant rate of prey consumption replacement at intermediate and high prey densities on eggplant but only at intermediate prey densities on pepper plant. These results indicate the interactions between plant and prey resources in diets of omnivores and may be useful for its efficacy in pest control on eggplant and pepper plant.

Sugars as complementary alternative food for the establishment of Nesidiocoris tenuis in greenhouse tomato

AbstractNesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is an omnivorous generalist predator which is augmentatively released and conserved for control of whiteflies (Hemiptera: Aleyrodidae) and Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in tomato crops. Eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) are often provided as factitious prey to improve the establishment of N. tenuis after its release. We first tested different amounts of E. kuehniella eggs per plant to optimize N. tenuis establishment and then investigated whether the amount of eggs that optimized N. tenuis establishment might be reduced by adding sugars (hydrocapsules filled with 0.5 m sucrose) under walk‐in cage and commercial greenhouse conditions. These experiments demonstrated that the addition of sugar to the diet of N. tenuis could half the amount of E. kuehniella eggs required to establish N. tenuis. Under greenhouse conditions, the progeny of N. tenuis per plant did not differ significantly between E. kuehniella alone or the half amount of E. kuehniella plus hydrocapsules. These results demonstrated that the sugar could partially substitute for E. kuehniella eggs improve establishment of N. tenuis and suggest that natural sugars such as nectar and honeydew might also beneficial.

Redescription of the Little-known Ciliate Apoamphisiella vernalis (Stokes, 1887) Berger, 2006 (Ciliophora, Hypotricha) from the Atlantic Forest, Brazil.

Apoamphisiella Foissner, 1997 is a genus of hypotrichous ciliates reported to occur in various locations in the world, but that seems particularly widespread in the Americas. In this study, the first record of Apoamphisiella vernalis for Brazil is presented based on a population from the Atlantic Forest of the Minas Gerais state. A redescription of A. vernalis made from light and scanning electron microscopy observations unveils a unique combination of diagnostic features for this species, namely the presence of green cortical granules, one contractile vacuole lacking collecting canals, and the rear end of both left and right marginal cirral rows located at same level. Moreover, A. vernalis is found to be an omnivorous predator, feeding on arcelline testate amoebae, rotifers, and other organisms.

Phylogenetic structures of soil nematode communities along a successional gradient in an unreclaimed copper mine tailings site

Analysis of the phylogenetic structure of biological communities by examining the extent to which community members are more closely related (phylogenetically clustered) or less closely related (phylogenetically overdispersed) than expected by chance has recently been proven to be a promising approach to gain insight into the factors governing the community assembly. However, to date there aren't any studies that have quantitatively examined the community structure of soil nematodes in a phylogenetic framework, despite their crucial roles in soil food webs and nutrient cycling processes. Here, we explored the phylogenetic structures of soil nematode communities along a successional gradient in an unreclaimed copper (Cu) mine tailings site to reveal the potential determinants of the soil nematode community assembly. Unexpectedly, we found little evidence that the phylogenetic distance of the co-occurring soil nematodes increased along this gradient. In contrast, phylogenetic structures of the soil nematode communities along the gradient appeared to show a weak tendency toward clustering (i.e. nematodes tend to co-occur with other closely related nematodes more often than expected by chance). On the other hand, when different soil nematode groups characterized by feeding habits were taken into account separately, we unveiled contrasting phylogenetic community structures: bacterial-feeding (BF), plant-feeding (PF), and omnivore-predator (OP) nematode communities tended to be phylogenetically clustered; whereas, fungal-feeding (FF) nematode communities exhibited a tendency toward phylogenetic overdispersion. Moreover, the net relatedness indices of nematode communities characterized by different feeding habits were shown to be correlated with distinct soil chemical properties (such as diethylene triamine pentaacetic acid extractable Cu for BF and cation exchange capacity for FF), indicating that the assembly processes of these communities were not neutral and might have been largely driven by the respective soil chemical properties. Collectively, our results provided novel insight into the factors driving the assembly of soil nematode communities, highlighting the potential for future studies on nematodes to benefit from a community phylogenetics approach.

Testing the enemies hypothesis in peach orchards in two different geographic areas in eastern China: the role of ground cover vegetation.

Many studies have supported the enemies hypothesis, which suggests that natural enemies are more efficient at controlling arthropod pests in polyculture than in monoculture agro-ecosystems. However, we do not yet have evidence as to whether this hypothesis holds true in peach orchards over several geographic locations. In the two different geographic areas in eastern China (Xinchang a town in the Shanghai municipality, and Hudai, a town in Jiangsu Province) during a continuous three-year (2010–2012) investigation, we sampled arthropod pests and predators in Trifolium repens L. and in tree canopies of peach orchards with and without the ground cover plant T. repens. No significant differences were found in the abundances of the main groups of arthropod pests and predators in T. repens between Hudai and Xinchang. The abundance, richness, Simpson's index, Shannon-Wiener index, and Pielou evenness index of canopy predators in ground cover areas increased by 85.5, 27.5, 3.5, 16.7, and 7.9% in Xinchang, and by 87.0, 27.6, 3.5, 17.0 and 8.0% in Hudai compared to those in the controls, respectively. The average abundance of Lepidoptera, Coleoptera, Homoptera, true bugs and Acarina canopy pests in ground cover areas decreased by 9.2, 10.2, 17.2, 19.5 and 14.1% in Xinchang, and decreased by 9.5, 8.2, 16.8, 20.1 and 16.6% in Hudai compared to that in control areas, respectively. Our study also found a higher density of arthropod species resources in T. repens, as some omnivorous pests and predators residing in T. repens could move between the ground cover and the orchard canopy. In conclusion, ground cover in peach orchards supported the enemies hypothesis, as indicated by the fact that ground cover T. repens promoted the abundance and diversity of predators and reduced the number of arthropod pests in tree canopies in both geographical areas.

The predatory mirid Dicyphus maroccanus as a new potential biological control agent in tomato crops

The first record of the omnivorous predator Dicyphus maroccanus Wagner (Hemiptera: Miridae) inhabiting tomato crops in the Valencia region (East Coast of Spain) was in 2009. Since then, D. maroccanus has often been found preying on the eggs of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in this area. To evaluate this predator’s potential as a biological control agent, its life-history traits in the presence and absence of prey [(eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)] on tomato plants were studied under laboratory conditions. Immature stages that preyed on eggs of E. kuehniella developed successfully. However, no nymph completed development on the plant without the addition of E. kuehniella eggs. To reach adulthood, male and female D. maroccanus nymphs consumed 267 and 312 E. kuehniella eggs, respectively. The net reproductive rate (R0) was estimated to be 34.52 female eggs per female, the generation time (T) was 40.48 days, and the estimated intrinsic rate of increase (rm) was 0.0868 females per female per day at 25 °C. In a second experiment, the capacity to detect plants infested or not infested with T. absoluta was studied using a Y-tube olfactometer. Female D. maroccanus were strongly attracted to the odor of T. absoluta-infested plants. In a third experiment, the capacity of D. maroccanus to control T. absoluta on tomato plants was investigated under extended laboratory conditions. Dicyphus maroccanus significantly reduced the number of T. absoluta-infested leaves in over 90 % of cases relative to control conditions. These results suggest that D. maroccanus could play a significant role in T. absoluta management. The potential of this zoophytophagous predator as a biocontrol agent on tomato crops is discussed.