Potential Biological Control Agent Research Articles

Assemblage of Ceutorhynchinae Weevils Associated With Brassicaceae in Quebec (Canada) Agroecosystems.

Ceutorhynchinae Gistel (Coleoptera: Curculionidae) are a highly diverse phytophagous group of weevils in which the most species rich genus, Ceutorhynchus Germar (Coleoptera: Curculionidae), is mainly associated with Brassicaceae. Some Ceutorhynchinae, such as the invasive cabbage seedpod weevil (CSW), Ceutorhynchus obstrictus (Marsham), are important pests of cultivated Brassicaceae, and others are natural enemies of weeds and potential biological control agents. This study aims to characterize Ceutorhynchinae assemblages in canola growing regions of Quebec. Ceutorhynchinae were sampled in areas adjacent to canola fields or other crops in six administrative regions of Quebec during the summers of 2019 and 2020. A total of 25 Ceutorhynchinae species were collected and identified. Canonical analysis and multivariate regression tree analysis revealed that the assemblage of Ceutorhynchinae varied regionally and was either dominated by the invasive canola pest CSW or by the native weevil Ceutorhynchus neglectus Blatchley. Our results also highlighted new biological associations between weevils and Brassicaceae like the CSW with the yellow rocket, Barbarea vulgaris R. Br., native Ceutorhynchus pauxillus Dietz with common pepper grass, Lepidium densiflorum, and native Ceutorhynchus semirufus LeConte with Pennsylvania bittercress, Cardamine pensylvanica Muhl. This study also provides a useful tool to find new biological control agents against Brassicaceae weeds and to monitor the abundance and diversity of this taxon and provide baseline data to assess future impacts of exotic parasitoids of CSW on native weevils.

Sustainable production of biopesticides for common bean root rot control within the biorefinery approach: a Technology Readiness Level 3 experimental proof of concept.

Biopesticides are recognized as an efficient alternative to synthetic pesticides for pest and disease crop management. However, their commercial production processes use grains, generating large amounts of organic waste, even when agriculture waste or byproducts are the feedstock of choice. Frequently, these organic wastes are rich in nutrients that, after adequate treatment, can be used as nitrogen and carbohydrate sources for secondary metabolite production produced by microorganisms during submerged fermentation. In this sense, this study aimed to prove the concept that biopesticides could be produced under a full biorefinery process, using the entire biomass of an underexplored agroindustrial waste-damaged bean-as the main feedstock. A combination of sequential processes, including solid state fermentation, hydrolysis, and submerged fermentation, were designed for the production of two biopesticides (conventional-fungal conidia and second-generation secondary metabolite-cerulenin) from a high potential biological control agent strain Sarocladium oryzae BRM 59907. The combined processes, using damaged common bean grain as the main feedstock, provided biopesticides and organic fertilizer production that successfully controlled common bean root rot disease. This work proved to be possible the biopesticide production using a full biorefinery concept, inside the same productive chain, contributing to a sustainable environment and economy, together with animal and human health safety.

Temperature-dependent Functional Response of the Arboreal Rove Beetle, Oligota flavicornis (Coleoptera: Staphylinidae), a Voracious Predator of Tetranychus urticae (Acarina: Tetranychidae).

The functional responses of Oligota flavicornis (Boisduval & Lacordaire) (Coleoptera: Staphylinidae) preying on the eggs of Tetranychus urticae Koch (Acarina: Tetranychidae) were examined at seven constant temperature settings (12, 15, 18, 22, 25, 30, and 32°C) to elucidate the predator-prey interactions between them. Logistic regression showed that O. flavicornis exhibited type II functional responses to T. urticae eggs at different temperatures. The reciprocal of handling time declined exponentially with warming, and the search rate presented a single hump-shaped relationship with temperature. For the search rate, the lower temperature thresholds were 9.1°C (linear) and 8.7°C (Briere). The optimal temperature and upper temperature threshold were 29.1 and 37.8°C for Logan and 29.7 and 35.8°C for Briere, respectively. The predation threshold window of O. flavicornis reached 27.1°C with a range of 8.7-35.8°C. The predator could consume 244.7-388.4 T. urticae eggs in a day in the optimal temperature range (18-32°C). The voracious predatory behavior of O. flavicornis against T. urticae eggs over a broad temperature range indicates that the predator shows promise as a potential biological control agent and that temperature-dependent predation could be a basis for formulating strategies to control tetranychid mites.

Development and reproduction of a native generalist predator, Coccinella transversalis (Coleoptera: Coccinellidae), on the tomato potato psyllid, Bactericera cockerelli, with a greenhouse assay of biocontrol potential

The tomato potato psyllid (Bactericera cockerelli Šulc (Hemiptera: Triozidae)) can cause significant losses to Solanaceous crop via direct feeding and by transmitting the bacterium Candidatus Liberibacter solanacearum. In the present study, an Australian native ladybird beetle, Coccinella transversalis Fabricius, was examined as a potential biological control agent of B. cockerelli. An age-stage, two sex life table of C. transversalis was constructed, demonstrating that C. transversalis could survive, develop, and reproduce successfully when fed B. cockerelli as a monotypic diet. Predation on B. cockerelli by C. transversalis third and fourth instar larvae and adults fit the Holling 'type II' disc equation. In a glasshouse trial using B. cockerelli-infested tomato plants, C. transversalis larvae reduced the population growth of B. cockerelli larvae by 66% and adults by 59% over one month, reducing loss of leaf chlorophyll and increasing plant biomass relative to controls. The results of the present study were compared with a previous study for the resident ladybird beetle species against B. cockerelli. Whereas C. transversalis suppressed B. cockerelli populations, the impact was less than that of the introduced ladybird, Hippodamia variegata Goeze, which showed higher voracity in previous work. However, B. cockerelli is a suitable prey for C. transversalis and this species should aid in its biological control in agricultural ecosystems in Australia.

Predation potential of the earwig Euborellia annulipes on fruit fly larvae and trophic interactions with the parasitoid Diachasmimorpha longicaudata

AbstractThe earwig Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae), a generalist predator, has been observed in fruits infested with fruit fly larvae, which are frequently parasitized by parasitoid wasps. Neither the capacity of earwigs to predate on fruit flies nor intraguild interactions between earwigs and fruit fly parasitoids have been investigated. Here, we studied in laboratory conditions the predation on the fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) by the earwig E. annulipes, and whether parasitism of fruit fly larvae by the parasitoid wasp Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) influences predation by the earwig. We evaluated the predation capacity, functional response and prey preference of E. annulipes for parasitized and non‐parasitized fruit fly larvae in choice and no‐choice tests. We found that earwigs prey on second‐ and third‐instar larvae and pupae of C. capitata and consumed larger numbers of second‐instar larvae, followed by third‐instar larvae and pupae. Females prey on larger numbers of fruit flies than did males, regardless of the prey developmental stage, but both sexes exhibited a type II functional response. Interestingly, males killed but did not consume fruit fly larvae more than did females. In no‐choice tests, earwig females consumed equal numbers of parasitized and non‐parasitized fruit fly larvae. However, in choice tests, the females avoided feeding on parasitized larvae. Subsequent tests with hexane‐washed parasitized and non‐parasitized larvae showed that putative chemical markings left on fruit flies by parasitoids did not drive the earwig preference towards non‐parasitized larvae. These findings suggest that E. annulipes is a potential biological control agent for C. capitata, and that, because the earwig avoids consuming larvae parasitized by D. longicaudata, a combination of the two natural enemies could have an additive effect on pest mortality.

Characterization of lipopeptide produced by Bacillus altitudinis Q7 and inhibitory effect on Alternaria alternata.

This study identified the antifungal metabolites produced by Bacillus altitudinis Q7 against Alternaria alternata and investigated the antifungal activity and antifungal action. Lipopeptide, the important secondary metabolites were identified by Fourier transform infrared (FTIR) and liquid chromatography-mass spectrometry as lichenysin. The antifungal activity of lipopeptide on A. alternata was determined by microdilution technique, and its minimum inhibitory concentration was 1.2 mg/ml. Stability test showed that lipopeptide had excellent temperature and pH resistance. To investigate whether lichenysin acted on the cell membrane and changed its permeability, the ultra-violet absorption of protein and nucleic acid were measured using a colorimetric method. The antifungal metabolites produced by B. altitudinis Q7 was lichenysin, which showed stable antifungal activity in the extreme environments. Lichenysin could inhibit A. alternata by altering the permeability of cell membrane, leading to the outflow of proteins and nucleic acids from the cytoplasm. This research suggests the lipopeptide from B. altitudinis Q7 is a potential biological control agent against A. alternata.

Assessing the Various Antagonistic Mechanisms of Trichoderma Strains against the Brown Root Rot Pathogen Pyrrhoderma noxium Infecting Heritage Fig Trees

A wide range of phytopathogenic fungi exist causing various plant diseases, which can lead to devastating economic, environmental, and social impacts on a global scale. One such fungus is Pyrrhoderma noxium, causing brown root rot disease in over 200 plant species of a variety of life forms mostly in the tropical and subtropical regions of the globe. The aim of this study was to discover the antagonistic abilities of two Trichoderma strains (#5001 and #5029) found to be closely related to Trichoderma reesei against P. noxium. The mycoparasitic mechanism of these Trichoderma strains against P. noxium involved coiling around the hyphae of the pathogen and producing appressorium like structures. Furthermore, a gene expression study identified an induced expression of the biological control activity associated genes in Trichoderma strains during the interaction with the pathogen. In addition, volatile and diffusible antifungal compounds produced by the Trichoderma strains were also effective in inhibiting the growth of the pathogen. The ability to produce Indole-3-acetic acid (IAA), siderophores and the volatile compounds related to plant growth promotion were also identified as added benefits to the performance of these Trichoderma strains as biological control agents. Overall, these results show promise for the possibility of using the Trichoderma strains as potential biological control agents to protect P. noxium infected trees as well as preventing new infections.

Identification of Bacillus velezensis SBB and Its Antifungal Effects against Verticillium dahliae.

Traditional control methods have drawbacks in controlling Verticillium wilt diseases caused by Verticillium dahliae Kleb.; therefore, an efficient and environmentally friendly strategy for disease control must be identified and the mechanisms determined. In this study, a soil-isolated strain SBB was identified as Bacillus velezensis based on 16S rRNA, gyrA, and gyrB gene sequences. In vitro, strain SBB had excellent inhibitory effects on V. dahliae, with the highest inhibition rate of 70.94%. Moreover, strain SBB inhibited production of the conidia of V. dahliae and suppressed the production of microsclerotia and melanin. Through gas chromatograph–mass spectrometer analysis, nine compounds were detected from the volatile organic compounds produced by SBB, among which 2-nonanol, 2-heptanone, 6-methyl-2-heptanone, and 2-nonanone could completely inhibit V. dahliae growth. Strain SBB produced cellulase, amylase, protease, and siderophore. During inhibitory action on V. dahliae, strain SBB showed upregulated expression of genes encoding non-volatile inhibitory metabolites, including difficidin, bacilysin, and bacillaene, at 1.923-, 1.848-, and 1.448-fold higher, respectively. Thus, our study proved that strain SBB had an efficient antagonistic effect on V. dahliae, suggesting strain SBB can be used as a potential biological control agent against Verticillium wilt.

Role of the predaceous mosquito Toxorhynchites christophi (Diptera: Culicidae) in treehole ecosystems in a Korean forest.

Toxorhynchites mosquitoes have been studied as potential biological mosquito control agents because they consume other mosquito larvae. As a top predator, Toxorhynchites species are also considered keystone predators in phytotelmata. However, limited information is available regarding Toxorhynchites christophi, which is found in northeast Asia. The present study investigated whether Tx. christophi could reduce mosquito populations and increase species diversity by functioning as a mosquito control agent and keystone predator, respectively. During the study, aquatic insects were collected every three weeks (May-October, 2018) from tire habitats, which resemble treehole ecosystems, at the Korean National Arboretum in the central region of the Korean Peninsula. The samples were separated into the surface- and the substrate-groups based on their behavior, and the communities were compared based on the density of Tx. christophi. As a result, the communities with a higher density of the predators showed a higher diversity and evenness, and the communities also had a lower mosquito ratio, dominance, and density of the surface-group. The results of both non-metric multi-dimensional scaling and one-way analysis of similarities also indicated that the communities were affected by the density of Tx. christophi larvae. Similarity percentage analysis results revealed the effects of this predator on the communities could mainly be attributed to reductions in the densities of the three dominant mosquito species (Aedes koreicus, Ae. flavopictus, and Tripteroides bambusa). Thus, Tx. christophi may be valuable as both a biological mosquito control agent and keystone species of treehole ecosystems by reducing dominant mosquito species and improving species diversity.

Could phytoseiid mites impair biological control of the invasive plant, Ailanthus altissima?

Aculus taihangensis is a potential biological control agent of Ailanthus altissima (Miller) Swingle. However, predatory mites found in Europe may affect the action of this eriophyid agent. The aim of the present study was to evaluate the biology of two predatory mites, Euseius stipulatus and Typhlodromus (Typhlodromus) exhilaratus, feeding on A. taihangensis. Rearing stocks were maintained in germination chambers at 25 ± 1 °C, with 12 hours of photophase and relative humidity 70 ± 5%. Of 40 individualized T. (T.) exhilaratus eggs, only 37.5% achieved adulthood, while viability of E. stipulatus was 87.5%. The mean fecundity was 18 eggs/ female. Both predatory mites evaluated in this study feed on A. taihangensis. However, only E. stipulatus seems to be an efficient predator, capable of controlling A. taihangensis.

Identification of entomopathogenic fungus Metarhizium rileyi infested in fall armyworm in the cornfield of Korea, and evaluation of its virulence.

The fall armyworm (FAW) Spodoptera frugiperda is an important invasive pest in Africa and Asia. It is a polyphagous pest with at least 353 recorded host plant species, including corn. Chemical control of this pest is unsuccessful because of a developed resistance and harmful effects on the environment. Entomopathogenic fungi are potential biological control agents for FAW. In this study, the native strain of Metarhizium rileyi (KNU-Ye-1), collected from a cornfield at Yeongcheon, Korea, was identified by morphological and molecular characterization. The susceptibility of the fourth-instar larvae of FAW to the native strain M. rileyi was examined in the laboratory. The results showed that the Korean strain of M. rileyi (KNU-Ye-1) was highly virulent to FAW larvae, causing 89% mortality 7 days posttreatment. Therefore, M. rileyi (KNU-Ye-1) identified in this study is highly valuable for the biological control of FAW in the field.

Epiphytic yeasts as potential antagonists against Fusarium head blight of wheat (Triticum aestivum L.) caused by Fusarium graminearum sensu stricto

Fusarium head blight (FHB), caused by Fusarium graminearum , is a significant disease of wheat in all wheat-growing areas. In this study, we screened a total of 344 yeast epiphytes isolated from cereal and weed plants against F. graminearum in vitro . Twelve potential antagonists were selected and subjected to in planta screening trials. In the in vitro bioassay trials, the highest average percentage inhibition of 64.31% (Isolate MGO2) was observed. The in vivo evaluation of the best 12 isolates showed a reduction in FHB severity and deoxynivalenol (DON) concentration of up to 15.62% (Isolate WL3) and 28.96% (Isolate SCH7), respectively. We observed a positive correlation between Area Under the Disease Progress Curve (AUDPC) and percentage seed infection. The 100-seed weight, however, was negatively correlated to both the AUDPC and the percentage seed infection. The best three yeast antagonists were selected based on AUDPC units, percentage seed infection, and 100-seed weight parameters and were identified as Papiliotrema flavescens (Isolates WL3 and WL6) and Pseudozyma sp. (Isolate MGO1) using 16S rRNA sequence analysis. These three yeast antagonists showed biocontrol efficacy against F . graminearum, and their incorporation in an integrated management programme could provide enhanced FHB control. To the best of our knowledge, this is the first report of yeast epiphytes isolated from Panicum maximum, and Ophiopogon japonicus tested as potential biological control agents against F. graminearum.

Effects of Gamma Irradiation on the Fecundity, Fertility, and Longevity of the Invasive Stink Bug Pest Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae).

The bagrada bug, Bagrada hilaris, is an invasive insect pest in the family Brassicaceae that causes economically important damage to crops. It was originally present in Asia, the Middle East, and Africa, and was reported as invasive in the southwestern part of the US, in Chile, and on a few islands in the Mediterranean Basin. In its native range, B. hilaris is controlled by several egg parasitoid species that are under consideration as potential biological control agents. This research evaluated the impact of gamma irradiation on life history parameters, e.g., the fecundity, fertility, and longevity of B. hilaris, as a critical step towards assessing the feasibility of using the sterile insect technique against this recent invasive pest. Newly emerged adults of a laboratory colony originally collected from the island of Pantelleria (Italy) were gamma-irradiated. Life history parameters were evaluated at nine different doses, ranging from 16 Gy to 140 Gy. The minimal dose to approach full sterility was 100 Gy. Irradiation up to a maximum of 140 Gy apparently did not negatively impact the longevity of the adults. Even if both genders are sensitive to irradiation, the decline in fecundity for irradiated females could be exploited to release irradiated males safely to apply the SIT in combination with classical biological control. The data presented here allow us to consider, for the first time, the irradiation of bagrada adults as a suitable and feasible technique that could contribute to guaranteeing a safe approach to control this important pest species in agro-ecosystems. More research is warranted on the competitive fitness of irradiated males to better understand mating behavior as well as elucidate the possible mechanisms of sperm selection by polyandric B. hilaris females.

Potential of Turkish Beauveria bassiana isolates for the management of the polyphagous planthopper, Orosanga japonica Melichar 1898 (Hemiptera: Ricaniidae)

BackgroundEntomopathogenic fungi are a potential biological control agent for many pests. In this study, 14 native Beauveria bassiana isolates were molecularly identified and assessed for their virulence and mortality against adults of the polyphagous planthopper Orosanga japonica, Melichar (Hemiptera: Ricaniidae) a polyphagous sap-feeding insect, under laboratory conditions.ResultsIsolates obtained from naturally infected adults O. japonica were molecularly identified as B. bassiana by sequencing the internal transcribed spacer and 26S large subunit of ribosomal DNA. In the bioassay, the radial growth and sporulation of isolates significantly differed (P < 0.05). Concentration–time bioassays demonstrated that all isolates had a lethal effect on adult O. japonica at the concentration of 1 × 108 conidia ml–1. The lethal times LT50 and LT90 values for each B. bassiana isolate, which indicate the time required to kill O. japonica, ranged between 2.44–3.19 and 3.78–5.01 days, respectively, at 20 °C, while their values were 1.74–2.76 and 2.76–4.10 days, respectively, at 25 °C depending on the native isolates. The concentration–mortality response showed a statistically significant difference between some isolates B. bassiana tested against adult O. japonica individuals (P < 0.05). With an LC50 value of 2.29 × 106 conidia ml–1, the lowest effective EPF isolate for O. japonica was KA-78-14. The isolates caused 100% adult mortality in O. japonica within five days, while the mortality in the control group was less than 10%.ConclusionsThese findings suggest that some B. bassiana isolates were more virulent on O. japonica and may play an important role in the biocontrol of O. japonica in Turkey.

Parasitic behavior of Pyemotes zhonghuajia (Trombidiformes: Pyemotidae) on fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a destructive, migratory pest that seriously damages corn, sorghum, and other crops. The “insect killer” Pyemotes zhonghuajia (Trombidiformes: Pyemotidae) is an ectoparasitic mite of agricultural and forestry pests in China. To explore the biological control efficiency of P. zhonghuajia on S. frugiperda, we evaluated the parasitic selectivity of P. zhonghuajia on S. frugiperda of different life stages, and distribution of P. zhonghuajia on different body parts of S. frugiperda larvae and pupae, food intake of S. frugiperda larvae affected by P. zhonghuajia density, and field population dynamics of S. frugiperda in relation to the releasing population density of P. zhonghuajia. We found that P. zhonghuajia preferred 4th- to sixth-instar larvae and pupae of S. frugiperda for parasitism, and the ventral part of abdominal segments of fourth-instar larvae and the ventral part of pupal thorax for feeding. Freezing of S. frugiperda 4th instar larvae and pupae had little effect on the distribution of P. zhonghuajia on the surface of these two host stages. The parasitism of P. zhonghuajia regardless of mite population size (i.e., 5, 10, or 20 mites) could significantly decrease the cumulative food intake of fifth-instar larvae of S. frugiperda. Releasing two and three boxes (50,000 mites/box) of P. zhonghuajia significantly suppressed the field population of S. frugiperda on sorghum plants/25 m2 within 7 days. Our results show that P. zhonghuajia may be a potential biological control agent and can be used for biological control of S. frugiperda in the field.  

The diversity of microfungi associated with grasses in the Sporobolus indicus complex in Queensland, Australia.

There are five closely related Sporobolus species, collectively known as weedy Sporobolus grasses (WSG) or the rat's tail grasses. They are fast growing, highly competitive, unpalatable weeds of pastures, roadsides and woodlands. An effective biological control agent would be a welcomed alternative to successive herbicide application and manual removal methods. This study describes the initial exploratory phase of isolating and identifying native Australian microfungi associated with WSG, prior to evaluating their efficacy as inundative biological control agents. Accurate species-level identification of plant-pathogenic microfungi associated with WSG is an essential first step in the evaluation and prioritisation of pathogenicity bioassays. Starting with more than 79 unique fungal morphotypes isolated from diseased Sporobolus grasses in Queensland, Australia, we employed multi-locus phylogenetic analyses to classify these isolates into 54 fungal taxa. These taxa belong to 22 Ascomycete families (12 orders), of which the majority fall within the Pleosporales (>24 taxa in 7 families). In the next phase of the study, the putative species identities of these taxa will allow us to prioritise those which are likely to be pathogenic based on existing literature and their known ecological roles. This study represents the first step in a systematic, high-throughput approach to finding potential plant pathogenic biological control agents.

New records and an annotated checklist of the thick-headed flies from Algeria (Conopidae, Brachycera, Diptera)

BackgroundThe Conopidae are an interesting family of small- to large-sized endoparasitic flies, commonly known as thick-headed flies. These flies have been proposed as potential biological control agents of invasive social wasps (subfamilies: Polistinae and Vespinae, family: Vespidae).ResultsAll known Algerian thick-headed flies (family Conopidae) are listed in the present study. Four subfamilies, nine genera and 23 species were treated. Three of these species are recorded herein from Algeria for the first time, namely Myopa pellucida (Robineau-Desvoidy), M. picta Panzer and Thecophora fulvipes (Robineau-Desvoidy). As far as they are known, Algerian localities and collection dates are provided, which comprise some new locality records. The data for this study were compiled from both available literature and material collected from some Algerian localities.ConclusionThe family Conopidae (thick-headed flies) is hitherto represented in Algeria by four subfamilies, nine genera and 23 species. Three of these species are recorded herein for the first time.

Reduction of Pythium Damping-Off in Soybean by Biocontrol Seed Treatment.

Pythium spp. is one of the major groups of pathogens that cause seedling diseases on soybean, leading to both preemergence and postemergence damping-off and root rot. More than 100 species have been identified within this genus, with Pythium irregulare, P. sylvaticum, P. ultimum var ultimum, and P. torulosum being particularly important for soybean production given their aggressiveness, prevalence, and abundance in production fields. This study investigated the antagonistic activity of potential biological control agents (BCAs) native to the U.S. Midwest against Pythium spp. First, invitro screening identified BCAs that inhibit P. ultimum var. ultimum growth. Scanning electron microscopy demonstrated evidence of mycoparasitism of all potential biocontrol isolates against P. ultimum var. ultimum and P. torulosum, with the formation of appressorium-like structures, short hyphal branches around host hyphae, hook-shaped structures, coiling, and parallel growth of the mycoparasite along the host hyphae. Based on these promising results, selected BCAs were tested under field conditions against six different Pythium spp. Trichoderma afroharzianum 26 used alone and a mix of T. hamatum 16 + T. afroharzianum 19 used as seed treatments protected soybean seedlings from Pythium spp. infection, as BCA-treated plots had on average 15 to 20% greater plant stand and vigor than control plots. Our results also indicate that some of these potential BCAs could be added with a fungicide seed treatment with minimum inhibition occurring, depending on the fungicide active ingredient. This research highlights the need to develop tools incorporating biological control as a facet of soybean seedling disease management programs. The harnessing of native BCAs could be integrated with other management strategies to provide efficient control of seedling diseases.

Selecting aggressiveness to improve biological control agents efficiency.

In agroecosystems, omnivorous predators are recognized as potential biological control agents because of the numerous pest species they prey on. Nonetheless, it could be possible to enhance their efficiency through artificial selection on traits of economical or ecological relevance. Aggressiveness, which defines the readiness of an individual to display agonistic actions toward other individuals, is expected to be related to zoophagy, diet preferences and to a higher attack rate. The study aimed to assess the aggressiveness degree of the damsel bug, Nabis americoferus, and to estimate its heritability. We hypothesized that a high aggressiveness degree can be selected, and that males are more aggressive than females. Using artificial selection, we reared two separate populations, each composed of nine genetically isolated lines characterized by their different aggressiveness degree (aggressive, docile and non-selected). After three generations, we had efficiently selected aggressive behavior. The realized heritability was 0.16 and 0.27 for aggressiveness and docility in the first population. It was 0.25 and 0.23 for the second population. Males were more aggressive than females only for the second population. The potential of these individuals as biological control agents and the ecological consequences of aggressiveness are discussed.

Potential of two omnivorous iolinid mites as predators of the tomato russet mite, Aculops lycopersici

Two iolinid predatory mites were studied in the laboratory as potential biological control agents of the tomato russet mite, Aculops lycopersici (Acari: Eriophyidae). The development, reproduction and predation capacity of Pronematus ubiquitus and Homeopronematus anconai (Acari: Iolinidae) on A. lycopersici were investigated. Developmental time from egg to adult at 25 °C averaged 9.59, 9.31 and 9.52 days for P. ubiquitus on A. lycopersici, A. lycopersici and Typha angustifolia pollen, and pollen only, respectively. H. anconai required 11.18, 10.39 and 11.90 days to complete development on the respective diets. Survival of the immature stages exceeded 83% on all diets for both iolinids. In experimental arenas, both predators caused a substantial reduction of the immature population development of A. lycopersici. The number of tomato russet mite offspring was reduced by 78% and 57% by P. ubiquitus and H. anconai, respectively. The addition of pollen to the arena lowered this population reduction to 35% and 27% for the respective predators. However, supplementing a diet of tomato russet mites with pollen significantly increased the fecundity of both predatory mites from 14–15 to 24–25 eggs over a five-day period. The results suggest that both P. ubiquitus and H. anconai have good potential to suppress A. lycopersici populations and that T. angustifolia pollen can support population establishment of the predators. Overall, P. ubiquitus developed faster on the three diets tested and suppressed A. lycopersici stronger as compared to H. anconai, with or without pollen as a supplementary food source.