Study on the virulence of Metarhizium anisopliae against Spodoptera frugiperda (J. E. Smith, 1797)

This study examined the impact of Metarhizium anisopliae (Hypocreales: Clavicipitaceae) conidia on the eggs, larvae, pupae, and adults of Spodoptera frugiperda. The results showed that eggs, larvae, pupae, and adults exhibited mortality rates that were dependent on the dose. An increased amount of conidia (1.5 × 109 conidia/mL) was found to be toxic to larvae, pupae, and adults after 9 days of treatment, resulting in a 100% mortality rate in eggs, 98% in larvae, 76% in pupae, and 85% in adults. A study using earthworms as bioindicators found that after 3 days of exposure, M. anisopliae conidia did not cause any harmful effects on the earthworms. In contrast, the chemical treatment (positive control) resulted in 100% mortality at a concentration of 40 ppm. Histopathological studies showed that earthworm gut tissues treated with fungal conidia did not show significant differences compared with those of the negative control. The gut tissues of earthworms treated with monocrotophos exhibited significant damage, and notable differences were observed in the chemical treatment. The treatments with 70 and 100 µg/mL solutions of Eudrilus eugeniae epidermal mucus showed no fungal growth. An analysis of the enzymes at a biochemical level revealed a decrease in the levels of acetylcholinesterase, α-carboxylesterase, and β-carboxylesterase in S. frugiperda larvae after exposure to fungal conidia. This study found that M. anisopliae is effective against S. frugiperda, highlighting the potential of this entomopathogenic fungus in controlling this agricultural insect pest.

Possible Biological Control of Ash Dieback Using the Mycoparasite Hymenoscyphus Fraxineus Mitovirus 2

Invasive fungal diseases represent a major threat to forest ecosystems worldwide. As the application of fungicides is often unfeasible and not a sustainable solution, only a few other control options are available, including biological control. In this context, the use of parasitic mycoviruses as biocontrol agents of fungal pathogens has recently gained particular attention. Since the 1990s, the Asian fungus Hymenoscyphus fraxineus has been causing lethal ash dieback across Europe. In the present study, we investigated the biocontrol potential of the mitovirus Hymenoscyphus fraxineus mitovirus 2 (HfMV2) previously identified in Japanese populations of the pathogen. HfMV2 could be successfully introduced via co-culturing into 16 of 105 HfMV2-free isolates. Infection with HfMV2 had contrasting effects on fungal growth in vitro, from cryptic to detrimental or beneficial. Virus-infected H. fraxineus isolates whose growth was reduced by HfMV2 showed overall a lower virulence on ash (Fraxinus excelsior) saplings as compared with their isogenic HfMV2-free lines. The results suggest that mycoviruses exist in the native populations of H. fraxineus in Asia that have the potential for biological control of ash dieback in Europe. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

A Novel Interaction of Nesidiocoris tenuis (Hemiptera: Miridae) as a Biological Control Agent of Bactericera cockerelli (Hemiptera: Triozidae) in Potato

Nesidiocoris tenuis (Hemiptera: Miridae) is a generalist predator commonly used to control the whitefly Bemisia tabaci in Europe. This mirid has been found and established in South Texas, where it was initially observed feeding on nymphs of the psyllid Bactericera cockerelli (Hemiptera: Triozidae) in open tomato fields. B. cockerelli is the vector of the fastidious bacterium "Candidatus Liberibacter solanacearum" that causes diseases in several solanaceous crops, including zebra chip (ZC) disease in potatoes. There is a need to better understand how this predator impacts the control of important crop pests, such as potato psyllids. We assessed the interactions between N. tenuis and B. cockerelli in three different environmental settings. First, we estimated the numeric response of N. tenuis preying on B. cockerelli under laboratory and greenhouse conditions. Second, we evaluated the predator-prey interaction under controlled field cage conditions. Then, we exposed N. tenuis under controlled field release conditions to the natural occurrence of B. cockerelli. Finally, we assessed the compatibility between the use of N. tenuis as a biological control agent in a field study and its impact on ZC disease incidence, severity in potato tubers, and potato yield. Laboratory and greenhouse experiments resulted in diverse types of functional model responses, including exponential and linear mathematical models. Our findings revealed a significant predation effect exerted by N. tenuis, resulting in a reduction of more than fourfold in the number of B. cockerelli nymphs per cage. Specifically, the nymphal population decreased from 21 ± 3.2 in the absence of N. tenuis to 5 ± 1.6 when N. tenuis was present. Furthermore, the combination of N. tenuis with a reduced insecticide program increased potato yields, but only reduced ZC tuber incidence in one of two potato cultivars evaluated, and in one season. Findings from these studies indicate that N. tenuis could be effective as a biological control agent for B. cockerelli in potato production in South Texas. This is the first report of N. tenuis preying on immature stages of any psyllid species.

Bacteriophage Cocktail Comprising Fifi044 and Fifi318 for Biocontrol of Erwinia amylovora

Erwinia amylovora is a plant pathogen that causes fire blight on apples and pears. Bacteriophages, which are viruses that selectively infect specific species of bacteria and are harmless to animal cells, have been considered as biological control agents for the prevention of bacterial pathogens. In this study, we aimed to use bacteriophages that infect E. amylovora as biocontrol agents against fire blight. We isolated bacteriophages Fifi044 and Fifi318 infecting E. amylovora, and characterized their morphology, plaque form, and genetic diversity to use as cocktails for disease control. The stabilities of the two phages were investigated at various temperatures and pH values and under sunlight, and long-term storage experiment was conducted for a year. To evaluate whether the two phages were suitable for use in cocktail form, growth curves of E. amylovora were prepared after treating the bacterial cells with single phages and a phage cocktail. In addition, a disease control test was conducted using immature apples and in vitro cultured apple plantlets to determine the biocontrol effects of the phage cocktail. The two phages were morphologically and genetically different, and highly stable up to 50°C and pH value from 4 to 10. The phages showed synergistic effect when used as a cocktail in the inhibition of host bacterial growth and the disease control. This study demonstrated that the potential of the phage cocktail as a biocontrol agent for commercial use.

Improved Viability of Spray-Dried Pantoea agglomerans for Phage-Carrier Mediated Control of Fire Blight

Fire blight, caused by Erwinia amylovora, is a devastating bacterial disease that threatens apple and pear production. It is mainly controlled by using antibiotics, such as streptomycin. Due to development of E. amylovora resistant strains and the excessive agricultural use of antibiotics, there is an increased awareness of the possibility of antibiotic resistance gene transfer to other microbes. Urgent development of biocontrol agents (BCAs) is needed that can be incorporated into integrated pest management programs as antibiotic alternatives. A novel phage-carrier system (PCS) that combines an antagonistic bacterium, Pantoea agglomerans, with its ability to act as a phage-carrier bacterium for Erwinia phages has been developed. The low viability of P. agglomerans cells following spray-drying (SD) has been a challenge for the industrial-scale production of this PCS. Here, an SD protocol was developed for P. agglomerans by modifying the growth medium and bacterial cell formulation using D(+)-trehalose and maltodextrin. The developed protocol is amenable to the industrial-scale production of the BCA/PCS. The P. agglomerans viability was greater than 90% after SD and had a shelf life at 4 °C of 4 months, and reconstituted cells showed a 3 log reduction in E. amylovora counts with a pear disc assay.

Characterization and evaluation of Bacillus subtilis GYUN-2311 as a biocontrol agent against Colletotrichum spp. on apple and hot pepper in Korea

Crop plants are vulnerable to a variety of diseases, including anthracnose, caused by various species of Colletotrichum fungi that damages major crops, including apples and hot peppers. The use of chemical fungicides for pathogen control may lead to environmental pollution and disease resistance. Therefore, we conducted this research to develop a Bacillus subtilis-based biological control agent (BCA). B. subtilis GYUN-2311 (GYUN-2311), isolated from the rhizosphere soil of an apple orchard, exhibited antagonistic activity against a total of 12 fungal pathogens, including eight Colletotrichum species. The volatile organic compounds (VOCs) and culture filtrate (CF) from GYUN-2311 displayed antifungal activity against all 12 pathogens, with 81% control efficiency against Fusarium oxysporum for VOCs and 81.4% control efficacy against Botryosphaeria dothidea for CF. CF also inhibited germination and appressorium formation in Colletotrichum siamense and C. acutatum. The CF from GYUN-2311 showed antifungal activity against all 12 pathogens in different media, particularly in LB medium. It also exhibited plant growth-promoting (PGP) activity, lytic enzyme activity, siderophore production, and the ability to solubilize insoluble phosphate. In trials on apples and hot peppers, GYUN-2311 effectively controlled disease, with 75 and 70% control efficacies against C. siamense in wounded and unwounded apples, respectively. Similarly, the control efficacy of hot pepper against C. acutatum in wounded inoculation was 72%. Combined application of GYUN-2311 and chemical suppressed hot pepper anthracnose to a larger extent than other treatments, such as chemical control, pyraclostrobin, TK®, GYUN-2311 and cross-spraying of chemical and GYUN-2311 under field conditions. The genome analysis of GYUN-2311 identified a circular chromosome comprising 4,043 predicted protein-coding sequences (CDSs) and 4,096,969 bp. B. subtilis SRCM104005 was the strain with the highest average nucleotide identity (ANI) to GYUN-2311. AntiSMASH analysis identified secondary metabolite biosynthetic genes, such as subtilomycin, bacillaene, fengycin, bacillibactin, pulcherriminic acid, subtilosin A, and bacilysin, whereas BAGEL analysis confirmed the presence of competence (ComX). Six secondary metabolite biosynthetic genes were induced during dual culture in the presence of C. siamense. These findings demonstrate the biological control potential of GYUN-2311 against apple and hot pepper anthracnose.

Colonization and population dynamics of total, viable, and culturable cells of two biological control strains applied to apricot, peach, and grapevine crops

The ecological fitness of the biological control strains Bacillus velezensis A17 and Lactiplantibacillus plantarum PM411 was evaluated in different crops, geographical zones, and growing seasons. Both strains (2 g L-1 of dried formulation) were spray-inoculated on apricot trees, peach trees, and grapevines. Depending on the crop, flowers, fruits, and leaves were picked at several sampling time points. The population dynamics of viable, viable but non-culturable, and dead cells were studied by comparing viability qPCR (v-qPCR), qPCR, and plate counting estimations. A17 showed high survival rates in apricot, peach, and grapevine organs. The A17 viability was confirmed since qPCR and v-qPCR estimations did not significantly differ and were rather constant after field applications. However, higher population levels were estimated by plate counting due to the non-selective characteristics of the medium used. The viability of PM411 was constrained by plant organ, crop, and climate conditions, being higher in apricot than in grapevine. PM411 survival declined after field application, indicating difficulties in its establishment. The PM411 population level was made up of dead, culturable, and viable but non-culturable cells since significant differences between the three methods were observed. In conclusion, A17 and PM411 differ strongly in their survival in grapevine, peach, and apricot.

Bacillus mexicanus sp. nov., a biological control bacterium isolated from the common bean (Phaseolus vulgaris L.) crop in Sinaloa, Mexico

Strain FSQ1T was isolated from the rhizosphere of the common bean (Phaseolus vulgaris L.) crop sampled in a commercial field located in the Gabriel Leyva Solano community, which belongs to the Guasave municipality (state of Sinaloa, Mexico). Based on its full-length 16S rRNA gene sequence, strain FSQ1T was assigned to the genus Bacillus (100 % similarity). This taxonomic affiliation was supported by its morphological and metabolic traits. Strain FSQ1T was a Gram-stain-positive bacterium with the following characteristics: rod-shaped cells, strictly aerobic, spore forming, catalase positive, reduced nitrate to nitrite, hydrolysed starch and casein, grew in the presence of lysozyme and 2 % NaCl, utilized citrate, grew at pH 6.0-8.0, produced acid from glucose, was unable to produce indoles from tryptophan, and presented biological control against Sclerotinia sclerotiorum. The whole-genome phylogenetic results showed that strain FSQ1T formed an individual clade in comparison with highly related Bacillus species. In addition, the maximum values for average nucleotide identity and from Genome-to-Genome Distance Calculator analysis were 91.57 and 44.20 %, respectively, with Bacillus spizizenii TU-B-10T. Analysis of its fatty acid content showed the ability of strain FSQ1T to produce fatty acids that are not present in closely related Bacillus species, such as C18 : 0 and C20 : 0. Thus, these results provide strong evidence that strain FSQ1T represents a novel species of the genus Bacillus, for which the name Bacillus mexicanus sp. nov. is proposed. The type strain is FSQ1T (CM-CNRG TB51T=LBPCV FSQ1T).

Can Entomopathogenic Nematodes and Their Symbiotic Bacteria Suppress Fruit Fly Pests? A Review

Fruit flies (Diptera: Tephritidae) are serious pests that affect fruit production and marketing. Both third instar larvae and pupae are biological stages that persist in the soil until adult emergence. Entomopathogenic nematodes (ENs) are biological control agents that are used to control agricultural pests in greenhouse or field conditions. Several studies have been carried out under laboratory and field conditions showing how ENs can be applied within an area-wide integrated pest management approach to control fruit fly species in orchards and backyard fruit trees. In this review, we analyze how soil physical characteristics and biotic factors affect the performance of these biological control agents. Of the reviewed papers, more than half evaluated the influence of soil texture, humidity, temperature, and other factors on the performance of infective juveniles (IJs). Abiotic factors that significantly influence the performance of IJs are temperature, humidity, and texture. Among the biotic factors that affect IJs are fungi, bacteria, mites, insects, and earthworms. We conclude that ENs have the potential to be applied in the drip area of fruit trees that are infested by fruit flies and contribute to their suppression. This approach, in conjunction with an area-wide pest management approach, may contribute to pest suppression and increase the sustainability of agroecosystems.

Bacillus cabrialesii subsp. cabrialesii subsp. nov. and Bacillus cabrialesii subsp. tritici subsp. nov., plant growth-promoting bacteria and biological control agents isolated from wheat (Triticum turgidum subsp. durum) in the Yaqui Valley, Mexico

Strain TSO2T, a plant growth-promoting rhizobacteria and biological control agent, was isolated from wheat rhizosphere sampled from the Yaqui Valley in Mexico. The strain was identified using a polyphasic approach. Based on its analysis of the full-length 16S rRNA gene, strain TSO2T was assigned to the genus Bacillus , which was supported by morphological and metabolic traits, such as Gram-positive staining, rod shape, spore formation, strictly aerobic metabolism, catalase-positive activity, starch, and casein hydrolysis, reduction of nitrate to nitrite, growth in presence of lysozyme and 2 % NaCl, citrate utilization, growth at pH 6.0, acid production from glucose and indole production from tryptophan. Additionally, strain TSO2T possesses swarming motility, presenting a featureless mat pattern that can cover the whole petri dish. The whole-genome phylogenetic relationship analysis elucidated that strain TSO2T is closely related to Bacillus cabrialesii TE3T. The maximum values for average nucleotide identity (ANI) and in silico DNA–DNA hybridization from the genome-to-genome distance calculator (GGDC) were 97 and 73.4 %, respectively, related to Bacillus cabrialesii TE3T, where both ANI and GGDC values were barely above the species delimitation threshold, but below the subspecies limit. Also, strain TSO2T showed the ability to produce a fatty acid (C18 : 0) that is not present in closely related Bacillus species. These results provide evidence that strain TSO2T is a novel subspecies of the species Bacillus cabrialesii , for which the name Bacillus cabrialesii subsp. tritici subsp. nov. is proposed. The type strain of Bacillus cabrialesii subsp. tritici subsp. nov. is TSO2T (CM-CNRG TB52T=LBPCV TSO2T). The description of this novel subspecies automatically creates the subspecies Bacillus cabrialesii subsp. cabrialesii subsp. nov. for which the type strain is TE3T (CM-CNRG TB54T=CCStamb A1T).

The potential of lactic acid bacteria in mediating the control of plant diseases and plant growth stimulation in crop production - A mini review

The microbial diseases cause significant damage in agriculture, resulting in major yield and quality losses. To control microbiological damage and promote plant growth, a number of chemical control agents such as pesticides, herbicides, and insecticides are available. However, the rising prevalence of chemical control agents has led to unintended consequences for agricultural quality, environmental devastation, and human health. Chemical agents are not naturally broken down by microbes and can be found in the soil and environment long after natural decomposition has occurred. As an alternative to chemical agents, biocontrol agents are employed to manage phytopathogens. Interest in lactic acid bacteria (LAB) research as another class of potentially useful bacteria against phytopathogens has increased in recent years. Due to the high level of biosafety, they possess and the processes they employ to stimulate plant growth, LAB is increasingly being recognized as a viable option. This paper will review the available information on the antagonistic and plant-promoting capabilities of LAB and its mechanisms of action as well as its limitation as BCA. This review aimed at underlining the benefits and inputs from LAB as potential alternatives to chemical usage in sustaining crop productivity.

Synergic effects of some plant-derived essential oils and Iranian isolates of entomopathogenic fungus Metarhizium anisopliae Sorokin to control Acanthoscelides obtectus (Say) (Coleoptera: Chrysomelidae)

Introduction

The bean weevil, Acanthoscelides obtectus, is one of the most important pests of the common bean, Phaseolus vulgaris. The pest attacks P. vulgaris seeds while they are still in the field. However, the damage continues during storage, where it causes the most significant losses.

Methods

The present study was conducted to evaluate the insecticidal activity, and synergic effects of three essential oils (EOs) extracted from fennel (Foeniculum vulgare), tarragon (Artemisia dracunculus), and lavender (Lavandula angustifolia), and three isolates from an entomopathogenic fungus (EPF), Metarhizium anisopliae, including IRAN2273C, IRAN2252C, and IRAN1018C against the adults of A. obtectus. The effects of EOs were also evaluated on mycelial growth and conidiation of the fungal isolates.

Results and Discussion

The results showed that all the EOs and the EPF exhibited insecticidal activity against A. obtectus. According to calculated LC50, L. angustifolia (1.2526 µl/l) and F. vulgare (0.9247 µl/l) EOs caused significantly higher mortality than A. dracunculus (3.1980 µl/l) against A. obtectus. The results of the pathogenicity of M. anisopliae isolates revealed that all isolates had insecticidal activity against A. obtectus. The cumulative mortality of insects varied from 59.12% in IRAN1018C to 80.86% in IRAN2273C. According to the compatibility test results, all EOs were compatible with fungal isolates except for A. dracunculus, which was toxic to the IRAN2252C isolate and showed incompatibility. The mortality of A. obtectus adults differed significantly among combined treatments of EOs and M. anisopliae isolates. According to the calculated synergic ratio, combinations of essential oils and fungal isolates had additive or synergistic effects on the mortality of A. obtectus. Based on the present findings, A. obtectus adults were susceptible to fennel, and lavender EOs, and their mortality was amplified when the EOs were combined with M. anisopliae isolates. These results can be helpful for the integrated management of A. obtectus during storage.

Fusarium diversity associated with the Sorghum-Striga interaction in Ethiopia

Sorghum production is seriously threatened by the root parasitic weeds (RPWs) Striga hermonthica and Striga asiatica in sub-Saharan Africa. Research has shown that Striga control depends on eliminating its seed reserves in soil. Several species of the genus Fusarium (Nectriaceae, Hypocreales), which have been isolated from diseased Striga plants have proven to be highly pathogenic to all developmental stages of these RPWs. In the present study 439 isolates of Fusarium spp. were found associated with soils from Sorghum growing fields, Sorghum rhizosphere, or as endophytes with Sorghum roots and seeds, or as endophytes of Striga stems and seeds. Based on multi-locus phylogenies of combinations of CaM, tef1, rpb1 and rpb2 alignments, and morphological characteristics, 42 species were identified, including three species that are newly described, namely F. extenuatum and F. tangerinum from Sorghum soils, and F. pentaseptatum from seed of Striga hermonthica. Using a previously published AFLP-derived marker that is specific to detect isolates of F. oxysporum f.sp. strigae, an effective soil-borne biocontrol agent against Striga, we also detected the gene in several other Fusarium species. As these isolates were all associated with the Striga/Sorghum pathosystem, the possibility of horizontal gene transfer among these fusaria will be of interest to further investigate in future. Citation: Lombard L, van Doorn R, Groenewald JZ, Tessema T, Kuramae EE, Etolo DW, Raaijmakers JM, Crous PW (2022). Fusarium diversity associated with the Sorghum-Striga interaction in Ethiopia. Fungal Systematics and Evolution 10: 177-215. doi: 10.3114/fuse.2022.10.08.

Inheritance and Biological Characterization of an Orange-nymph Mutant in Orius laevigatus (Hemiptera: Anthocoridae)

A mutation showing a distinct orange color in the nymph stages was found in Orius laevigatus (Fieber) (Hemiptera: Anthocoridae), a key biological control agent in protected crops, used to control small pests, especially thrips. A laboratory strain carrying this body color mutation ambar was established. Genetic analysis determined that the mutation (ambar) was controlled by a single autosomal recessive allele. Some biological and ecological characteristics of this orange strain were compared to a normal population. Longevity, fecundity and fertility were similar in both populations, but immature survival, development rate, body size, starvation tolerance and predation capacity were inferior in the orange strain. The utility of the orange mutant as a visible marker for biological and ecological studies of this important biological control agent is discussed.

Antagonistic Effect of Trichoderma longibrachiatum (TL6 and TL13) on Fusarium solani and Fusarium avenaceum Causing Root Rot on Snow Pea Plants

Snow pea root rot in China is caused by Fusarium solani (FSH) and Fusarium avenaceum (FAH), which affect snow pea production. The chemical control methods used against FSH and FAH are toxic to the environment and resistance may be developed in persistence applications. Therefore, an alternative approach is needed to control these pathogens. This study focuses on Trichoderma longibrachiatum strains (TL6 and TL13), mycoparasitic mechanisms of FSH and FAH, as well as growth-promoting potentials on snow pea seedlings under FSH and FAH stress at the physiological, biochemical, and molecular levels. The average inhibitory rates of TL6 against FSH and FAH were 54.58% and 69.16%, respectively, on day 7. Similarly, TL13 average inhibitory rates against FSH and FAH were 59.06% and 71.27%, respectively, on day 7. The combined TL13 and TL6 with FSH and FAH reduced disease severity by 86.6, 81.6, 57.60, and 60.90%, respectively, in comparison to the controls. The snow pea plants inoculated with FSH and FAH without TL6 and TL13 increased malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents in the leaves by 64.8, 66.0, 64.4 and 65.9%, respectively, compared to the control. However, the combined FSH and FAH with TL6 and TL13 decreased the MDA and H2O2 content by 75.6, 76.8, 70.0, and 76.4%, respectively, in comparison to the controls. In addition, the combined TL6 + FSH and TL6 + FAH increased the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) by 60.5, 64.7, and 60.3%, respectively, and 60.0, 64.9, and 56.6%, respectively, compared to the controls. Again, compared to the controls, the combined TL13 + FSH and TL13 + FAH increased the activity of SOD, POD, and CAT by 69.7, 68.6, and 65.6%, respectively, and 70.10, 69.5, and 65.8%, respectively. Our results suggest that the pretreatment of snow pea seeds with TL6 and TL13 increases snow pea seedling growth, controls FSH and FAH root rot, increases antioxidant enzyme activity, and activates plant defense mechanisms. The TL13 strain had the greatest performance in terms of pathogen inhibition and snow pea growth promotion compared to the TL6 strain.

Effect of Parental Age and Mating Status on Reproductive Performance of Orius laevigatus (Hemiptera: Anthocoridae)

The reproductive potential of biological control agents (BCAs) is crucial for efficient mass-rearing and field performance, and it all begins with mating. Fecundity can be strongly influenced by intrinsic conditions, such as female age and, often neglected, male age and mating status. However, little is known about the impact of parental status at mating on female reproductive outcomes in BCAs. Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is widely used to control thrips in protected crops. We evaluated how many consecutive females a male could successfully mate and the effect on a female's reproductive output. In addition, we studied the effects of male and female age on mating. In the multiple mating experiment, the males showed a high capacity to fertilize females successively, not reducing fecundity until the sixth mated female. In the delayed mating experiment, copulation duration and fecundity increased with male age but decreased with female age. In contrast, fertility followed an opposite pattern, increasing with female age but decreasing with male age. However, fecundity gains outweighed fertility declines in both sexes. Therefore, reproductive capacity is increased when mating newly emerged females with males a few days old. The implications of our results for mass rearing and field performance are discussed.

Fungal endophytes of Brassicaceae: Molecular interactions and crop benefits

Brassicaceae family includes an important group of plants of great scientific interest, e.g., the model plant Arabidopsis thaliana, and of economic interest, such as crops of the genus Brassica (Brassica oleracea, Brassica napus, Brassica rapa, etc.). This group of plants is characterized by the synthesis and accumulation in their tissues of secondary metabolites called glucosinolates (GSLs), sulfur-containing compounds mainly involved in plant defense against pathogens and pests. Brassicaceae plants are among the 30% of plant species that cannot establish optimal associations with mycorrhizal hosts (together with other plant families such as Proteaceae, Chenopodiaceae, and Caryophyllaceae), and GSLs could be involved in this evolutionary process of non-interaction. However, this group of plants can establish beneficial interactions with endophytic fungi, which requires a reduction of defensive responses by the host plant and/or an evasion, tolerance, or suppression of plant defenses by the fungus. Although much remains to be known about the mechanisms involved in the Brassicaceae-endophyte fungal interaction, several cases have been described, in which the fungi need to interfere with the GSL synthesis and hydrolysis in the host plant, or even directly degrade GSLs before they are hydrolyzed to antifungal isothiocyanates. Once the Brassicaceae-endophyte fungus symbiosis is formed, the host plant can obtain important benefits from an agricultural point of view, such as plant growth promotion and increase in yield and quality, increased tolerance to abiotic stresses, and direct and indirect control of plant pests and diseases. This review compiles the studies on the interaction between endophytic fungi and Brassicaceae plants, discussing the mechanisms involved in the success of the symbiosis, together with the benefits obtained by these plants. Due to their unique characteristics, the family Brassicaceae can be seen as a fruitful source of novel beneficial endophytes with applications to crops, as well as to generate new models of study that allow us to better understand the interactions of these amazing fungi with plants.

Isolation of Nine Bacteriophages Shown Effective against Erwinia amylovora in Korea

Erwinia amylovora is a devastating bacterial plant pathogen that infects Rosaceae including apple and pear and causes fire blight. Bacteriophages have been considered as a biological control agent for preventing bacterial infections of plants. In this study, nine bacteriophages (ΦFifi011, ΦFifi044, ΦFifi051, ΦFifi067, ΦFifi106, ΦFifi287, ΦFifi318, ΦFifi450, and ΦFifi451) were isolated from soil and water samples in seven orchards with fire blight in Korea. The genetic diversity of bacteriophage isolates was confirmed through restriction fragment length polymorphism pattern analysis. Host range of the nine phages was tested against 45 E. amylovora strains and 14 E. pyrifoliae strains and nine other bacterial strains. Among the nine phages, ΦFifi044 and ΦFifi451 infected and lysed E. amylovora only. And the remaining seven phages infected both E. amylovora and E. pyrifoliae. The results suggest that the isolated phages were different from each other and effective to control E. amylovora, providing a basis to develop biological agents and utilizing phage cocktails.

Biocontrol Activity of Aspergillus terreus ANU-301 against Two Distinct Plant Diseases, Tomato Fusarium Wilt and Potato Soft Rot

To screen antagonistic fungi against plant pathogens, dual culture assay (DCA) and culture filtrate assay (CFA) were performed with unknown soil-born fungi. Among the different fungi isolated and screened from the soil, fungal isolate ANU-301 successfully inhibited growth of different plant pathogenic fungi, Colletotrichum acutatum, Alternaria alternata, and Fusarium oxysporum, in DCA and CFA. Morphological characteristics and rDNA internal transcribed spacer sequence analysis identified ANU-301 as Aspergillus terreus. Inoculation of tomato plants with Fusarium oxysporum f. sp. lycopersici (FOL) induced severe wilting symptom; however, co-inoculation with ANU-301 significantly enhanced resistance of tomato plants against FOL. In addition, culture filtrate (CF) of ANU-301 not only showed bacterial growth inhibition activity against Dickeya chrysanthemi (Dc), but also demonstrated protective effect in potato tuber against soft rot disease. Gas chromatography-tandem mass spectrometry analysis of CF of ANU-301 identified 2,4-bis(1-methyl-1-phenylethyl)-phenol (MPP) as the most abundant compound. MPP inhibited growth of Dc, but not of FOL, in a dose-dependent manner, and protected potato tuber from the soft rot disease induced by Dc. In conclusion, Aspergillus terreus ANU-301 could be used and further tested as a potential biological control agent.

Impact of biocontrol microbes on soil microbial diversity in ginger (Zingiber officinale Roscoe)

BACKGROUND

Bacteria are the most diverse and abundant group of soil organisms that influence plant growth and health. Bacillus and Trichoderma are commonly used as biological control agents (BCA) that directly or indirectly act on soil bacteria. Therefore, it is essential to understand how the applied microbes impact the indigenous microbial community before exploring their activity in the control of soilborne diseases.

RESULTS

MiSeq sequencing of the 16S rRNA gene was used to decipher the shift of rhizosphere bacterial community in ginger (Zingiber officinale Roscoe) treated with Bacillus subtilus and Trichoderma harzianum at different concentrations. The dominant phyla in treated and nontreated samples were Proteobacteria, Actinobacteria, Acidobacteria and comprised up to 54.7% of the total sequences. There were significant differences between BCA treated and nontreated samples in the bacteria community. BCA treated plants presented higher bacterial diversity than nontreated and higher dosage of BCA had a larger impact on rhizosphere microbiota, but the 'dose-response relationship' varied in different bacterial groups. Potential biomarkers at genus level were found, such as RB41, Pseudomonas, Nitrospira, Candidatus_Udaeobacter.

CONCLUSION

The combined use of Bacillus subtilus and Trichoderma harzianum could alter bacterial community structure and diversity in rhizosphere soil. BCA-microbes interactions as well as soil microbial ecology should be noticed in plant disease management. © 2021 Society of Chemical Industry.

Effectiveness of Augmentative Biological Control of Streptomyces griseorubens UAE2 Depends on 1-Aminocyclopropane-1-Carboxylic Acid Deaminase Activity against Neoscytalidium dimidiatum

To manage stem canker disease on royal poinciana, actinobacterial isolates were used as biological control agents (BCAs) based on their strong in vitro inhibitory effects against Neoscytalidiumdimidiatum. Streptomyces griseorubens UAE2 and Streptomyces wuyuanensis UAE1 had the ability to produce antifungal compounds and cell-wall-degrading enzymes (CWDEs). Only S. griseorubens, however, restored the activity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCD). In vivo apple fruit bioassay showed that lesion development was successfully constrained by either isolates on fruits inoculated with N. dimidiatum. In our greenhouse and container nursery experiments, S. griseorubens showed almost complete suppression of disease symptoms. This was evident when the preventive treatment of S. griseorubens significantly (p < 0.05) reduced the numbers of conidia of N. dimidiatum and defoliated leaves of royal poinciana seedlings to lesser levels than when S. wuyuanensis was applied, but comparable to control treatments (no pathogen). The disease management of stem canker was also associated with significant (p < 0.05) decreases in ACC levels in royal poinciana stems when S. griseorubens was applied compared to the non-ACCD-producing S. wuyuanensis. This study is the first to report the superiority of antagonistic actinobacteria to enhance their effectiveness as BCAs not only for producing antifungal metabolites and CWDEs but also for secreting ACCD.

Performance of Two Trichogrammatid Species from Zambia on Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Simple Summary

Two egg parasitoid species (Trichogramma mwanzai and Trichogrammatoidea lutea) from parasitized eggs of fall armyworm (FAW) Spodoptera frugiperda in Zambia were identified by using a combination of both molecular and morphological characters. We compared the parasitism capabilities of the two species with three native Chinese trichogrammatid species (T. ostriniae, T. leucaniae and T. japonicum) using 0- to 2-day-old FAW eggs. Both parasitoid species accepted eggs of all ages tested and completed their development successfully. Trichogrammatoidea lutea females showed the highest parasitism rate of host eggs among the five tested species. T. mwanzai had the shortest developmental time on all test age eggs. Of the five parasitoid species reared on FAW eggs, T. lutea performed the best overall, while T. japonicum was the worst performing of the parasitoids.

Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a noctuid moth native to the tropical and subtropical Americas that has successfully invaded Africa and Asia, where it is has become a serious threat to food security as a pest of cereals and other crops. Biological control is an environmentally friendly means of combating the pest and contributes to an integrated pest management approach. In our study, two egg parasitoid species (Trichogramma mwanzai and Trichogrammatoidea lutea) found in parasitized fall armyworm eggs in Zambia were identified by using a combination of both molecular and morphological characteristics. To evaluate their potential and efficiency on 0- to 2-day-old fall armyworm eggs, we compared their parasitism capabilities with three Trichogramma species native to China (T. ostriniae, T. leucaniae and T. japonicum) under laboratory conditions. The results showed that both parasitoid species would accept 0-, 1- and 2-day-old fall armyworm eggs, and complete their development successfully. Trichogramma mwanzai and T. lutea preferred parasitizing 0- and 1-day-old eggs over 2-day-old eggs. Trichogrammatoidea lutea females supplied with fall armyworm eggs produced the highest parasitism rate of host eggs among the five tested species, while T. mwanzai had the shortest developmental time on all test age eggs. In general, T. lutea was the best performing of the five species when reared on fall armyworm eggs, while T. japonicum was the worst. There were no significant differences, however, in percent emergence in the five test species when reared on fall armyworm eggs.

Genome Assembly of the Ragweed Leaf Beetle: A Step Forward to Better Predict Rapid Evolution of a Weed Biocontrol Agent to Environmental Novelties

Rapid evolution of weed biological control agents (BCAs) to new biotic and abiotic conditions is poorly understood and so far only little considered both in pre-release and post-release studies, despite potential major negative or positive implications for risks of nontargeted attacks or for colonizing yet unsuitable habitats, respectively. Provision of genetic resources, such as assembled and annotated genomes, is essential to assess potential adaptive processes by identifying underlying genetic mechanisms. Here, we provide the first sequenced genome of a phytophagous insect used as a BCA, that is, the leaf beetle Ophraella communa, a promising BCA of common ragweed, recently and accidentally introduced into Europe. A total 33.98 Gb of raw DNA sequences, representing ∼43-fold coverage, were obtained using the PacBio SMRT-Cell sequencing approach. Among the five different assemblers tested, the SMARTdenovo assembly displaying the best scores was then corrected with Illumina short reads. A final genome of 774 Mb containing 7,003 scaffolds was obtained. The reliability of the final assembly was then assessed by benchmarking universal single-copy orthologous genes (>96.0% of the 1,658 expected insect genes) and by remapping tests of Illumina short reads (average of 98.6 ± 0.7% without filtering). The number of protein-coding genes of 75,642, representing 82% of the published antennal transcriptome, and the phylogenetic analyses based on 825 orthologous genes placing O. communa in the monophyletic group of Chrysomelidae, confirm the relevance of our genome assembly. Overall, the genome provides a valuable resource for studying potential risks and benefits of this BCA facing environmental novelties.

Selection for resistance to pyrethroids in the predator Orius laevigatus

BACKGROUND

Insecticide resistance in the natural enemies of pest species is a very desirable trait. It allows better integration of biological control with the synthetic and natural compounds applied to manage certain pests, especially secondary pest outbreaks. Insecticide resistance in predatory insects has been documented for lady beetles and lacewings, but intriguingly no cases of field-evolved resistance have been noted in any heteropteran predator. In this work, we first explored the variation in susceptibility to pyrethroids in wild and commercial populations of Orius laevigatus (Fieber). Second, we exploited this genetic variation to artificially select a strain of O. laevigatus resistant to pyrethroids.

RESULTS

We found significant variation [median lethal dose (LC₅₀ ) 1.6-77.0 mg L^-1 ] in susceptibility to pyrethroids in wild populations of the heteropteran predator O. laevigatus, with a baseline LC₅₀ value of 14.6 mg L^-1 . We successfully selected a strain of O. laevigatus highly resistant to pyrethroids (LC₅₀ = 1059.9 mg L^-1 ). In addition, such resistance was expressed in every instar, particularly in the last nymphal stages, increasing the resilience of the whole population present in the crop facing pyrethroid application.

CONCLUSION

The level of resistance achieved may be sufficient to allow survival of adults and nymphs of O. laevigatus exposed to the maximum field rate of several pyrethroids and natural pyrethrins, widely used to control a number of pests in organic and integrated pest management crops. Therefore, this strain resistant to pyrethrins and pyrethroids would improve the resilience of biocontrol protocols, which is an urgent requirement for wider adoption of biological control. © 2021 Society of Chemical Industry.

Evolution of growth traits in invasive Pereskia aculeata (Cactaceae): testing the EICA hypothesis using its specialist herbivore, Catorhintha schaffneri (Coreidae)

BACKGROUND

Species introduced into new habitats are fitter than their native populations, as hypothesized by the 'evolution of increased competitive ability' (EICA). Here, Pereskia aculeata Miller was used as a model to test EICA and explore how 'enemy release' may have influenced the invasion success of its 400-year-old introduced populations (genotypes) compared with native populations. Plant growth traits (height and shoot length) of 15 genotypes [four from the introduced range (South Africa) and 11 from the native range (Brazil and Argentina, Venezuela and The Dominican Republic)] were assessed. Damage and impact of a shoot-feeding, sap-sucking specialist Catorhintha schaffneri Brailovsky & Garcia on ten genotypes were also compared.

RESULTS

All but one of the invasive genotypes were significantly taller than native genotypes. Although the invasive genotypes were relatively more damaged by herbivory than some of the native genotypes, the observed differences were not explained completely by their origins. Nonetheless, the findings partially supported the predictions of the EICA hypothesis because invasive genotypes were generally taller than native genotypes, but did not fully support the hypothesis because they were not always more damaged than the native genotypes by C. schaffneri.

CONCLUSION

Invasive genotypes had an advantage in the introduced range as they can climb neighbouring vegetation more quickly than native genotypes, but the damage incurred by the invasive genotypes relative to the native genotypes suggests only that C. schaffneri would be as damaging in South Africa, where it serves as a biocontrol agent, as it is in its native distribution in Brazil. © 2020 Society of Chemical Industry.

Complete Genome Sequence Data of Nonpathogenic Strain Rhizobium vitis VAR03-1, a Biological Control Agent for Grapevine Crown Gall Disease

Crown gall disease in grapevine is caused by pathogenic strains of Rhizobium vitis with a tumor-inducing (Ti) plasmids. A nonpathogenic strain, VAR03-1 of R. vitis, has been isolated from the grapevine root of nursery stock and it was shown to act as a biological control agent to crown gall disease. Its disease-suppressive effect was observed even when it was coinoculated with the pathogen in a 1:1 ratio. Here, we present the complete genome data of R. vitis VAR03-1, assembled by sequencing reads obtained by both PacBio and Illumina technologies with annotation. This genome sequence could contribute to investigations of the molecular basis underlying the biocontrol activity as well as the root-colonization ability of this bacterial strain.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Challenges facing arthropod biological control: identifying traits for genetic improvement of predators in protected crops

Biological control is an efficient pest control method but there are still limitations that are hindering its wider adoption. Genetic improvement of biological control agents (BCAs) can help to overcome these constraints, but the choice of key attributes for better performance that need to be selected is still an open question. Several characteristics have been suggested but the harsh reality is that selective breeding of BCAs has received a lot of attention but resulted in very little progress. Identifying the appropriate traits to be prioritized may be the first step to reverse this situation. In our opinion, the best way is to look at the factors limiting the performance of key BCAs, especially generalist predators (pesticide compatibility, prey-density dependence, non-suitable crops, and extreme environmental conditions), and according to these challenges, to choose the attributes that would allow BCAs to overcome those limitations. The benefits of selection for higher resistance to toxins, whether artificially applied (pesticides) or plant produced (plant defenses); increased fitness when feeding on non-prey food (supplemented or plant-derived); and better adaptation to extreme temperature and humidity are discussed. In conclusion, genetic improvement of BCAs can bring about new opportunities to biocontrol industry and users to enhance biocontrol resilience. © 2020 Society of Chemical Industry.

Assessment of Chrysoperla comanche (Banks) and Chrysoperla externa (Hagen) as Biological Control Agents of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on Tomato (Solanum lycopersicum) under Glasshouse Conditions

We tested the predatory capacity of newly-hatched or newly-molted Chrysoperla comanche (Banks) and Chrysoperla externa (Hagen) larvae after a 24 h fasting period on adults of Frankliniella occidentalis (Pergande) that were feeding on tomato plants (at vegetative and blooming stage) under glasshouse conditions. We also recorded fruit damage by the thrips. Both Chysoperla spp. depredated a similar number of F. occidentalis (thrips) adults regardless of the phenological stage of the plant. Second and third instar larvae of both species consumed significantly more thrips than first instar during plant blooming, however when the plant was at vegetative stage, all larval stages of both species predated a similar number of thrips. A significantly lower fruit damage percentage was recorded at the blooming plant when C. comanche larvae were in the experimental cage, however the presence of second and third instar of both species significantly reduced the fruit damage. No foliar damage was recorded. As far as we know, this is the first assessment of the predatory capacity of C. comanche and C. externa on thrips feeding on tomato under glasshouse conditions.

Fungichromin Production by Streptomyces padanus PMS-702 for Controlling Cucumber Downy Mildew

Streptomyces padanus PMS-702 strain produces a polyene macrolide antibiotic fungichromin and displays antagonistic activities against many phytopathogenic fungi. In the present study, experimental formulations were assessed to improve the production of fungichromin, the efficacy of PMS-702 on the suppression of sporangial germination, and the reduction of cucumber downy mildew caused by Pseudoperonospora cubensis. PMS-702 strain cultured in a soybean meal-glucose (SMG) medium led to low levels of fungichromin accumulation and sporangial germination suppression. Increasing medium compositions and adding plant oils (noticeably coconut oil) in SMG significantly increased fungichromin production from 68 to 1,999.6 μg/ml. Microscopic examination reveals that the resultant suspensions significantly reduced sporangial germination and caused cytoplasmic aggregation. Greenhouse trials reveal that the application of PMS-702 cultural suspensions reduced downy mildew severity considerably. The addition of Tween 80 into the synthetic medium while culturing PMS-702 further increased the suppressive efficacy of downy mildew severity, particularly when applied at 24 h before inoculation or co-applied with inoculum. Fungichromin at 50 μg/ml induced phytotoxicity showing minor necrosis surrounded with light yellowish halos on cucumber leaves. The concentration that leads to 90% inhibition (IC90) of sporangial germination was estimated to be around 10 μg/ml. The results provide a strong possibility of using the S. padanus PMS-702 strain as a biocontrol agent to control other plant pathogens.

TaqMan qPCR for Quantification of Clonostachys rosea Used as a Biological Control Agent Against Fusarium graminearum

Clonostachys rosea is a biological control agent against Fusarium graminearum in small grain cereals and maize. Infections with F. graminearum do not only reduce the yield but, due to the production of mycotoxins, also affect the entire value chain of food and feed. In addition, production of other secondary metabolites such as hydrophobins, also known as gushing inducers, may cause quality challenges for the malting and brewing industry. Sustainable disease control strategies using C. rosea are treatment of infected residues of the previous crop, direct treatment of the actual cereal crop or post-harvest treatment during malting processes. Follow-up of growth and survival of biocontrol organisms during these different stages is of crucial importance. In the current study, we developed a quantitative real-time PCR detection method that amends the currently available culture-dependent techniques by using TaqMan chemistry with a highly specific primer and probe set, targeting the actin gene. We established a sensitive assay that detects the biological control agent down to 100 genome copies per reaction, with PCR efficiencies between 90 and 100%. The specificity of the assay was confirmed against a panel of 30 fungal and 3 bacterial species including 12 members of the Fusarium head blight complex and DNA of barley, maize and wheat. The DNA of C. rosea was detected in Fusarium-infected maize crop residues that were either treated in the laboratory or in the field with C. rosea and followed its DNA throughout the barley malting process to estimate its growth during grain germination. We used a standardized DNA extraction protocol and showed that C. rosea can be quantified in different sample matrices. This method will enable the monitoring of C. rosea during experiments studying the biological control of F. graminearum on cereal crop residues and on cereal grains and will thus contribute to the development of a new disease control strategy.

Potential investment tradeoff between offspring production and functional recovery promoted by larval cannibalism in Coccinella septempunctata (Coleoptera: coccinellidae)

BACKGROUND

Since larval cannibalism is frequently observed in intensive rearing systems, the regeneration of lost legs is common for the beneficial species Coccinella septempunctata (Coccinella: Coccinellidae) to adapt to the competitive environment, but whether functional recovery occurs in the leg-regenerated coccinellids remains unknown. To evaluate the functional recovery of regenerated right foreleg after being damaged, the behaviors of leg-regenerated ladybugs containing predation, attachment, intraspecific competition, prey preference and fecundity were studied in the laboratory.

RESULTS

The prey consumption and searching rate of leg-regenerated ladybugs decreased, and their handling time extended. A significantly reduced attachment coefficient was detected in leg-regenerated coccinellids. Because of the competitive inferiority, leg-regenerated ladybugs were greatly hampered in competition with normal opponents, and this inferiority led to a switch of prey preference from big-sized adults to small-sized first-second instar nymphs of Paratrioza sinica. However, although reduced functional abilities were examined, the leg-regenerated paternity had a higher reproductive output compared to the normal paternity.

CONCLUSION

Leg-regenerated ladybugs caused by cannibalism may make an investment tradeoff between egg fecundity and functional recovery. Thus, larval cannibalism potentially improves the offspring production of the biological control agent in complex environments. © 2018 Society of Chemical Industry.

Optimization of native biocontrol agents, with parasitoids of the invasive pest Drosophila suzukii as an example

The development of biological control methods for exotic invasive pest species has become more challenging during the last decade. Compared to indigenous natural enemies, species from the pest area of origin are often more efficient due to their long coevolutionary history with the pest. The import of these well-adapted exotic species, however, has become restricted under the Nagoya Protocol on Access and Benefit Sharing, reducing the number of available biocontrol candidates. Finding new agents and ways to improve important traits for control agents ("biocontrol traits") is therefore of crucial importance. Here, we demonstrate the potential of a surprisingly under-rated method for improvement of biocontrol: the exploitation of intraspecific variation in biocontrol traits, for example, by selective breeding. We propose a four-step approach to investigate the potential of this method: investigation of the amount of (a) inter- and (b) intraspecific variation for biocontrol traits, (c) determination of the environmental and genetic factors shaping this variation, and (d) exploitation of this variation in breeding programs. We illustrate this approach with a case study on parasitoids of Drosophila suzukii, a highly invasive pest species in Europe and North America. We review all known parasitoids of D. suzukii and find large variation among and within species in their ability to kill this fly. We then consider which genetic and environmental factors shape the interaction between D. suzukii and its parasitoids to explain this variation. Insight into the causes of variation informs us on how and to what extent candidate agents can be improved. Moreover, it aids in predicting the effectiveness of the agent upon release and provides insight into the selective forces that are limiting the adaptation of indigenous species to the new pest. We use this knowledge to give future research directions for the development of selective breeding methods for biocontrol agents.

Environmental fate and behaviour of the biocontrol agent Bacillus amyloliquefaciens CPA-8 after preharvest application to stone fruit

BACKGROUND

Bacillus amyloliquefaciens strain CPA-8 has been described as an effective biocontrol agent to control brown rot in stone fruit for both preharvest and postharvest applications. However, no information about the environmental fate and behaviour of this strain under field conditions is available.

RESULTS

The dispersion of the CPA-8 application was evaluated using water-sensitive papers, and complete coverage was observed on the leaves of treated trees, while <1% of non-treated tree leaves had CPA-8. CPA-8 persisted on the fruit of treated trees during preharvest and postharvest conditions, while a significant decrease on leaves and weeds was observed 21 days after treatment. On non-treated trees, CPA-8 was detected on leaves until 180 days after treatment, and on weeds, the CPA-8 population was dependent on the distance from the treated trees. A high persistence of CPA-8 was detected on inert materials, such as clothes and gloves worn by handlers and plastic harvesting boxes. More than 99% of the samples with a CPA-8 phenotype were confirmed as CPA-8 using polymerase chain reaction (PCR).

CONCLUSION

This work demonstrated a good distribution, persistence and adaptation of the CPA-8 strain to field and postharvest conditions. Monitoring of dispersion and persistence is an excellent tool to determine the time of application and provides valuable information for registering issues. © 2017 Society of Chemical Industry.

Prey Acceptability and Preference of Oenopia conglobata (Coleoptera: Coccinellidae), a Candidate for Biological Control in Urban Green Areas

Oenopia conglobata is one of the most common ladybird species in urban green areas of the Mediterranean region. We have obtained data about its prey acceptability and prey preferences. In a laboratory experiment, we investigated the acceptability of seven aphid and one psyllid species as prey for this coccinellid: the aphids Chaitophorus populeti, Aphis gossypii, Aphis craccivoraMonelliopsis caryae, Eucallipterus tiliae, Aphis nerii (on white poplar, pomegranate, false acacia, black walnut, lime, and oleander, respectively), and the psyllid Acizziajamatonica on Persian silk tree. These species are abundant in urban green areas in the Mediterranean region. In addition, we tested the acceptability of Rhopalosiphum padi on barley, an aphid species easily reared in the laboratory. We also tested preferences of the predator in cafeteria experiments with three aphid species and one aphid and the psyllid. Adults and larvae of the coccinellid accepted all of the preys offered, except A. nerii, with a clear preference for M. caryae. The predator also showed preference for M. caryae when it was offered in a cafeteria experiment with other aphid species or with the psyllid. The aphid R. padi obtained a good acceptability and could be used for rearing O. conglobata in the laboratory.

Assessing effects of the entomopathogenic fungus Metarhizium brunneum on soil microbial communities in Agriotes spp. biological pest control

The release of large quantities of microorganisms to soil for purposes such as pest control or plant growth promotion may affect the indigenous soil microbial communities. In our study, we investigated potential effects of Metarhizium brunneum ART2825 on soil fungi and prokaryota in bulk soil using high-throughput sequencing of ribosomal markers. Different formulations of this strain, and combinations of the fungus with garlic as efficacy-enhancing agent, were tested over 4 months in a pot and a field experiment carried out for biological control of Agriotes spp. in potatoes. A biocontrol effect was observed only in the pot experiment, i.e. the application of FCBK resulted in 77% efficacy. Colony counts combined with genotyping and marker sequence abundance confirmed the successful establishment of the applied strain. Only the formulated applied strain caused small shifts in fungal communities in the pot experiment. Treatment effects were in the same range as the effects caused by barley kernels, the carrier of the FCBK formulation and temporal effects. Garlic treatments and time affected prokaryotic communities. In the field experiment, only spatial differences affected fungal and prokaryotic communities. Our findings suggest that M. brunneum may not adversely affect soil microbial communities.

Cyprinid herpesvirus 3 as a potential biological control agent for carp (Cyprinus carpio) in Australia: susceptibility of non-target species

Carp (Cyprinus carpio L.) is a pest species in Australian waterways, and cyprinid herpesvirus 3 (CyHV-3) is being considered as a potential biological control (biocontrol) agent. An important consideration for any such agent is its target specificity. In this study, the susceptibility to CyHV-3 of a range of non-target species (NTS) was tested. The NTS were as follows: 13 native Australian, and one introduced, fish species; a lamprey species; a crustacean; two native amphibian species (tadpole and mature stages); two native reptilian species; chickens; and laboratory mice. Animals were exposed to 100-1000 times the approximate minimum amount of CyHV-3 required to cause disease in carp by intraperitoneal and/or bath challenge, and then examined clinically each day over the course of 28 days post-challenge. There were no clinical signs, mortalities or histological evidence consistent with a viral infection in a wide taxonomic range of NTS. Furthermore, there was no molecular evidence of infection with CyHV-3, and, in particular, all RT-PCRs for viral mRNA were negative. As a consequence, the results encourage further investigation of CyHV-3 as a potential biocontrol agent that is specific for carp.

Reduced mobility but high survival: thermal tolerance and locomotor response of the specialist herbivore, Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae), to low temperatures

Disentangling the responses of insects to variations in their thermal environment is central to our understanding of the evolution of temperature-dependent performance in these species. Here, we report results of experiments examining the effects of high (upper lethal temperature = ULT) and low (lower lethal temperature = LLT) temperature and exposure time on the survival of larvae and adults of a multivoltine, nocturnal moth species, Pareuchaetes insulata, a biological control agent whose impact on an invasive weed, Chromolaena odorata has been variable in South Africa. The influence of temperature and acclimation on locomotion performance of the moth was also investigated. Temperature and duration of exposure significantly affected survival of both adults and larvae of P. insulata with more extreme temperatures and/or longer durations proving to be more lethal. Third instar larvae and adults are both freeze intolerant and had LT50 of -5.9 and -4.7°C, respectively, after a 2 h exposure. Although cold acclimation was beneficial to the nocturnal larvae, temperatures below 10°C significantly reduce their locomotion activities. The average daily minimum temperatures in the coldest months at three locations in South Africa are over 5°C lower than those of Fort Lauderdale, Florida, USA, where P. insulata was originally collected. Our results suggest that lethal high or low temperatures at short timescales are trivial in explaining the variable performance of P. insulata, but reduced locomotion at sub-lethal temperatures may be an important driver of the population dynamics of the biocontrol agent (especially in winter months) and may consequently explain the low population levels of the moth because of possible reduced feeding by larvae during night-time low temperatures.

Lipopeptides from a novel Bacillus methylotrophicus 39b strain suppress Agrobacterium crown gall tumours on tomato plants

BACKGROUND

This study aims to characterise the antibacterial activity of a novel Bacillus methylotrophicus strain named 39b against tumourigenic Agrobacterium tumefaciens C58 and B6 strains. It also aims to identify the compound that is responsible for its activity and to evaluate its efficiency to control crown gall disease in tomato plants.

RESULTS

B. methylotrophicus strain 39b was found to stop the growth of phytopathogenic A. tumefaciens strains in in vitro experiments. Lipopeptides - surfactins, iturins and fengycins - were detected under various isoforms by mass spectrometry analysis of the methanolic extract. The active principle acting against Agrobacterium strains was isolated from TLC plates and identified by mass spectrometry as surfactin. The strain was effective in reducing the weight and the number of galls induced by A. tumefaciens strains on tomato plants. Total inhibition of gall formation was observed using the antibacterial compounds.

CONCLUSION

B. methylotrophicus strain 39b exhibited antibacterial activity against phytopathogenic A. tumefaciens C58 and B6 both in vitro and in vivo. Lipopeptides are the main compounds that confer the biocontrol ability. This strain has the potential to be developed as a biological control agent for crown gall disease. © 2016 Society of Chemical Industry.

Recent trends in control methods for bacterial wilt diseases caused by Ralstonia solanacearum

Previous studies have described the development of control methods against bacterial wilt diseases caused by Ralstonia solanacearum. This review focused on recent advances in control measures, such as biological, physical, chemical, cultural, and integral measures, as well as biocontrol efficacy and suppression mechanisms. Biological control agents (BCAs) have been dominated by bacteria (90%) and fungi (10%). Avirulent strains of R. solanacearum, Pseudomonas spp., Bacillus spp., and Streptomyces spp. are well-known BCAs. New or uncommon BCAs have also been identified such as Acinetobacter sp., Burkholderia sp., and Paenibacillus sp. Inoculation methods for BCAs affect biocontrol efficacy, such as pouring or drenching soil, dipping of roots, and seed coatings. The amendment of different organic matter, such as plant residue, animal waste, and simple organic compounds, have frequently been reported to suppress bacterial wilt diseases. The combined application of BCAs and their substrates was shown to more effectively suppress bacterial wilt in the tomato. Suppression mechanisms are typically attributed to the antibacterial metabolites produced by BCAs or those present in natural products; however, the number of studies related to host resistance to the pathogen is increasing. Enhanced/modified soil microbial communities are also indirectly involved in disease suppression. New promising types of control measures include biological soil disinfection using substrates that release volatile compounds. This review described recent advances in different control measures. We focused on the importance of integrated pest management (IPM) for bacterial wilt diseases.

Post-introduction evolution in the biological control agent Longitarsus jacobaeae (Coleoptera: Chrysomelidae)

Rapid evolution has rarely been assessed in biological control systems despite the similarity with biological invasions, which are widely used as model systems. We assessed post-introduction climatic adaptation in a population of Longitarsus jacobaeae, a biological control agent of Jacobaea vulgaris, which originated from a low-elevation site in Italy and was introduced in the USA to a high-elevation site (Mt. Hood, Oregon) in the early 1980s. Life-history characteristics of beetle populations from Mt. Hood, from two low-elevation sites in Oregon (Italian origin) and from a high-elevation site from Switzerland were compared in common gardens. The performance of low- and high-elevation populations at a low- and a high-elevation site was evaluated using reciprocal transplants. The results revealed significant changes in aestival diapause and shifts in phenology in the Mt. Hood population, compared with the low-elevation populations. We found increased performance of the Mt. Hood population in its home environment compared with the low-elevation populations that it originated from. The results indicate that the beetles at Mt. Hood have adapted to the cooler conditions by life-history changes that conform to predictions based on theory and the phenology of the cold-adapted Swiss beetles.