Effective Biocontrol Agent Research Articles

Enhancing the Biological Control of Mite Species Infesting Olive Trees through Application of Predatory Mite Agistemus exsertus Gonzalez (Acari: Stigmaeidae) and Eco-Friendly Natural Compounds.

Olive (Olea europaea L.) is a subtropical tree cultivated in arid, dry and temperate regions. Olive orchards in Al-Jouf of Saudi Arabia are the largest worldwide and currently face harmful pest infestation. The present study aimed at evaluating the efficiency of the predatory mite Agistemus exsertus Gonzalez (Acari: Stigmaeidae) and the exogenously applied melatonin (MT), glycine betaine (GB) and 5-aminolevulinic acid (ALA) as eco-friendly approaches for enhancing the biological control of four mite species (Tegolophus hassani, Oxycenus niloticus, Aceria olivi and Tetranychus urticae) infesting olive trees in Al-Jouf under laboratory and field conditions. Field experiment was conducted on 6-year-old Manzanillo olive trees grown in a private orchard farm in Al-Jouf during two seasons, 2020 and 2021. Results revealed that A. exsertus developed successfully from egg to adult. The females of T. hassani, O. niloticus, A. olivi, and T. urticae required 7.36, 8.89, 9.98 and 8.38 days, respectively, to develop from egg to adult at 28°C and 65 ± 5% relative humidity. O. niloticus was the most preferred prey of A. exsertus. The net reproductive rate (R0 ) was 42.1, 38.7, 34.6 and 36.8 females/female/generation, the intrinsic rate of increase (rm ) was 0.27, 0.26, 0.23 and 0.20 females/female/day, and the mean generation time (T) was 16.2, 17.1, 18.6 and 17.2 days when a predator consumed T. hassani, O. niloticus, A. olivi and T. urticae, respectively. The adult female consumed daily about 114 O. niloticus, 105 A. olivi, 95 T. hassani and 15.2 T. urticae individuals, respectively. A. exsertus proved to be an effective biocontrol agent against mites infesting olive trees. In addition, the exogenous application of 1 mM MT, 15 mM GB and 25 mg/L ALA, alone or in combination, caused significant mortality for the four mites. Application of these natural compounds, alone or in combination, also significantly enhanced the growth, relative water content, relative chlorophyll, content of flavonoid and nutrients, antioxidant enzymes activities, stress-related genes expression and fruit yield and quality of the infested olive trees compared to non-treated infested trees. This study is the first that demonstrates the efficiency of these eco-friendly approaches for controlling mites infesting olive trees, and could be used as a replacement for the harmful chemical acaricides.

Bacteriophages PECP14, PECP20, and their endolysins as effective biocontrol agents for Escherichia coli O157:H7 and other foodborne pathogens

Escherichia coli O157:H7 is a notorious foodborne pathogen known to cause severe illnesses such as hemolytic colitis and hemolytic uremic syndrome, with fresh produce consumption being implicated in recent outbreaks. The inappropriate use of antimicrobials to combat pathogens has led to the emergence and rapid dissemination of antimicrobial-resistant microorganisms including pathogenic E. coli, presenting a significant risk to humans. Here, we isolated two E. coli O157:H7 infecting bacteriophages, PECP14 and PECP20, from irrigation water and city sewage, respectively, as alternatives to antimicrobials. Both phages were stable for at least 16 h in a broad range of pH (pH 3–11) and temperature (4–40 °C) conditions and have a double-stranded DNA chromosome. PECP14 and PECP20, classified under the Epseptimavirus and Mosigvirus genera, respectively, exhibit specificity in targeting different host receptors, BtuB protein and lipopolysaccharide. Interestingly, these phages demonstrate the ability to infect not only E. coli O157:H7 but also other foodborne enteric pathogens like Shigella sonnei and S. flexneri. Upon mixing phages with their respective host bacteria, rapid adsorption (at least 68 % adsorption within 10 min) and substantial bacterial lysis were observed. The efficacy of phage treatment was further validated through the reduction of E. coli O157:H7 on radish sprouts. Moreover, purified endolysins, LysPECP14 and LysPECP20, derived from each phage exhibited remarkable bacteriolytic activity against E. coli O157:H7 cells pretreated with EDTA. In particular, the activity of LysPECP20 was also noticeable against Listeria monocytogenes and Bacillus cereus, suggesting its potential for broader antimicrobial applications in food industry. The combined results showed that the phages PECP14, PECP20, and their endolysins could be used for biological control of E. coli O157:H7 in various circumstances, from production, harvesting, and storage stages to processing and distribution steps of agricultural products.

Effect of host genotype on biocontrol of white root rot in Pyrus communis L. rootstocks by Trichoderma harzianum and Bacillus spp.

AbstractA collection of Bacillus and Trichoderma isolates from Iran was investigated for the biological control of pear white root rot caused by Rosellinia necatrix. Among the isolates, B. amyloliquefaciens AP4, B. siamensis AP8 and T. harzianum T20a were selected based on their growth inhibition of R. necatrix in dual cultures, as well as by volatiles, diffusible extracts and culture filtrates. Four pear rootstocks (Pyrodwarf, OHF40, OHF60 and Williams) were assessed for white rot in the greenhouse following soil amendment with the three isolates. For OHF40 rootstock, none of the three isolates significantly reduced disease severity, whereas all three isolates significantly reduced disease severity for OHF69 rootstock. For Pyrodwarf rootstock, only T. harzianum T20a and B. amyloliquefaciens AP4 significantly reduced root rot, but all three isolates significantly reduced leaf fall. For Williams rootstock, all three isolates significantly reduced root rot, but only T. harzianum T20a significantly reduced leaf fall. Thus, the effectiveness of both the Bacillus and Trichoderma isolates was highly dependent upon the pear genotype. The lowest levels of white rot symptoms were observed in the Williams‐T. harzianum T20a interaction resulting in root rot severity of 46.6% and leaf fall of 4.7% at 70 dpi. While the effect of plant genotype on biocontrol activity has been reported frequently for Trichoderma, this is one of the first to report such an effect with a Bacillus biocontrol agent. Both Bacillus and Trichoderma can be effective biocontrol agents of pear white rot, but the plant genotype can have a major impact on their effectiveness.

The Temperature-Dependent Functional Response and Mutual Interference of Cyanopterus ninghais (Hymenoptera: Braconidae) Parasitizing Monochamus alternatus (Coleoptera: Cerambycidae)

Cyanopterus ninghais (Hymenoptera: Braconidae) is a newly discovered parasitoid on the 3rd-5th instar larvae of the Japanese pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae). We investigated the functional response of C. ninghais at three temperatures (20, 25, and 30 °C) and examined mutual interference. Results showed that C. ninghais had a Holling Type II functional response at all temperatures. By increasing the density of the M. alternatus larvae, the number of parasitized larvae increased until a maximum was reached. The parasitoid was most effective (a′/Th) at 30 °C (0.270) and an individual female wasp’s attack rate (a′) was 0.158, the handling time (Th) was 0.587, and the maximum theoretical parasitization rate per day (T/Th) was 11.927. However, the per capita parasitized level and per capita searching efficiency decreased significantly when the parasitoid density ranged from one to five. These findings suggest that intraspecific mutual interference and competition occur when multiple females search for a host in the same area. This study demonstrates that C. ninghais serves as an effective biocontrol agent, displaying strong control capabilities against M. alternatus larvae, with the potential for further development in the context of biological pest management targeting M. alternatus.

Use of Pantoea agglomerans ASB05 as a biocontrol agent to inhibit the growth of Salmonella enterica on intact cantaloupe melons.

To identify biocontrol agents to prevent the growth of Salmonella serotype Enterica on cantaloupe melons during the pre- and postharvest periods. We created a produce-associated bacterial library containing 8736 isolates and screened it using an in-vitro fluorescence inhibition assay to identify bacteria that inhibit the growth of S. Enterica. One isolate, Pantoea agglomerans ASB05, was able to grow, persist, and inhibit the growth of S. Enterica on intact cantaloupe melons under simulated pre- and postharvest conditions. We also demonstrated that the growth inhibition of S. Enterica by P. agglomerans ASB05 was due to the production of a phenazine type antibiotic. Pantoea agglomerans ASB05 is an effective biocontrol agent for the prevention of S. Enterica growth on intact cantaloupe melons in both the pre- and postharvest environments.

Evaluation and Genome Mining of Bacillus stercoris Isolate B.PNR1 as Potential Agent for Fusarium Wilt Control and Growth Promotion of Tomato.

Recently, strategies for controlling Fusarium oxysporum f. sp. lycopersici (Fol), the causal agent of Fusarium wilt of tomato, focus on using effective biocontrol agents. In this study, an analysis of the biocontrol and plant growth promoting (PGP) attributes of 11 isolates of loamy soil Bacillus spp. has been conducted. Among them, the isolates B.PNR1 and B.PNR2 inhibited the mycelial growth of Fol by inducing abnormal fungal cell wall structures and cell wall collapse. Moreover, broad-spectrum activity against four other plant pathogenic fungi, F. oxysporum f. sp. cubense race 1 (Foc), Sclerotium rolfsii, Colletotrichum musae, and C. gloeosporioides were noted for these isolates. These two Bacillus isolates produced indole acetic acid, phosphate solubilization enzymes, and amylolytic and cellulolytic enzymes. In the pot experiment, the culture filtrate from B.PNR1 showed greater inhibition of the fungal pathogens and significantly promoted the growth of tomato plants more than those of the other treatments. Isolate B.PNR1, the best biocontrol and PGP, was identified as Bacillus stercoris by its 16S rRNA gene sequence and whole genome sequencing analysis (WGS). The WGS, through genome mining, confirmed that the B.PNR1 genome contained genes/gene cluster of a nonribosomal peptide synthetase/polyketide synthase, such as fengycin, surfactin, bacillaene, subtilosin A, bacilysin, and bacillibactin, which are involved in antagonistic and PGP activities. Therefore, our finding demonstrates the effectiveness of B. stercoris strain B.PNR1 as an antagonist and for plant growth promotion, highlighting the use of this microorganism as a biocontrol agent against the Fusarium wilt pathogen and PGP abilities in tomatoes.

Exploitation of indigenous fluorescent pseudomonads for the management of wilt of chickpea caused by <i>Fusarium oxysporum</i> f. sp. <i>ciceris</i>

Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris is a devastating soil-borne disease with a significant impact on yields and affecting chickpea production worldwide. Fluorescent pseudomonads are utilized as effective biocontrol agents (BCA) against a variety of phytopathogens and they play a key role in pathogen suppression through various processes. In the present study, twenty indigenous fluorescent pseudomonads were isolated from twenty soil samples collected from different districts of North Eastern Karnataka. The isolates were tested in vitro for their ability to resist the pathogen by using a dual culture approach. Further, morphological and biochemical characters were studied by growing these isolates on King’s B agar medium. All twenty isolates showed inhibition of the test pathogen, with isolate PF-19 showing the highest inhibition of 88.89%. All the isolates developed slimy, irregular colonies with light yellowish green pigmentation, fluorescence under UV light and rod-shaped cells under the microscope, as well as gram negative in reaction. All isolates except PF-2, Pf-9 and PF-10 revealed positive results for KOH, catalase, gelatin liquefaction and starch hydrolysis.

Biocontrol Potential of Trichoderma asperellum Strain 576 against Exserohilum turcicum in Zea mays.

Maize is a crucial cereal crop in China, serving both as a staple food and an essential industrial resource. Northern corn leaf blight (NCLB) is a disease of corn caused by a fungus, Exserohilum turcicum (sexual stage Setosphaeria turcica). This study aimed to assess the biocontrol potential of various Trichoderma strains against Exserohilum turcicum 101 in Jilin, China. Through dual culture tests, the Trichoderma strains were categorized into four groups based on their antagonistic abilities. Eleven Trichoderma strains exhibited strong antagonistic behavior, with comparable or faster growth rates than E. turcicum 101. Microscopic observations confirmed that T. asperellum 576 hyphae effectively encircled E. turcicum 101 hyphae, reinforcing their antagonistic behavior. The production of non-volatile and volatile substances by the Trichoderma strains was evaluated, with T. asperellum 576 showing the highest potency in producing non-volatile and volatile substances, leading to an impressive 80.81% and 65.86% inhibition of E. turcicum 101 growth. Remarkably, co-culture suspensions of T. asperellum 576 + E. turcicum 101 and T. atroviride 393 + E. turcicum 101 exhibited strong antifungal activity. Furthermore, the activities of chitinase, β-1.3-glucanase, and cellulase were evaluated using the 3, 5-dinitrosalicylic acid (DNS) method. T. asperellum 576 + E. turcicum 101 displayed stronger cell wall degradation enzyme activity compared to T. atroviride 393 + E. turcicum 101, with values of 8.34 U/mL, 3.42 U/mL, and 7.75 U/mL, respectively. In greenhouse conditions, the application of a 107 spores/mL conidia suspension of T. asperellum 576 significantly enhanced maize seed germination and plant growth while effectively suppressing E. turcicum 101 infection. Maize seedlings inoculated/treated with both E. turcicum 101 and T. asperellum 576 demonstrated substantial improvements compared to those inoculated solely with E. turcicum 101. The T. asperellum 576 treatment involved a 107 spores/mL conidia suspension applied through a combination of foliar spray and soil drench. These findings highlight T. asperellum 576 as a promising biocontrol candidate against northern leaf blight in maize. Its antagonistic behavior, production of inhibitory compounds, and promotion of plant growth all contribute to its potential as an effective biocontrol agent for disease management.

The Role of Chrysoperla carnea (Steph.) and Beauveria bassina for Controlling Cabbage Aphid, Brevicoryne brassicae L. on Cabbage Plants

Saleh, A.A.A., H. El-Nagar, A.A. Khalifa and M.F.M. Zawrah. 2023. The Role of Chrysoperla carnea (Steph.) and Beauveria bassina for Controlling Cabbage Aphid, Brevicoryne brassicae L. on Cabbage Plants. Arab Journal of Plant Protection, 41(3): 321-326. https://doi.org/10.22268/AJPP-041.3.321326 Field experiments were carried out at Kafr Saqr district, Sharkia governorate during 2019/2020 and 2020/2021 growing seasons to evaluate the predator:prey ratios for the release of C. carnea and evaluation of using Beauveria bassiana suspension against the cabbage aphid, Brevicoryne brassicae. The results obtained showed that the effective control of B. brassicae was achieved ten days after releasing the larvae of the predator C. carnea when the predator:prey ratios were 1:5 and 1:10. Meanwhile, at higher ratios (1:20, 1:25 and 1:50), the cabbage aphid B. brassicae numbers decreased 25 days after predator release. The numbers of B. brassicae decreased by 84.69 and 81.61% at 1:5 and 1:10 predator:prey ratio during the first season, respectively. On the other hand, the aphid numbers were reduced by 81.50 and 70.95% at 5 days after the predator’s release during the second season, for the two predator:prey ratios, respectively. Complete reduction of B. brassicae populations was achieved at 15 days after yhe release of C. carnea larvae with predator ratios of 1:5, 1:10 and 1:15, and numbers of B. brassicae at these ratios depressed completely 20 days after release. The results revealed that the best control of B. brassicae populations under greenhouses conditions was achieved by using the lower predator:prey ratio of 1:5 and 1:10 ten days after releasing larvae of C. carnea. The highest mortality rate in B. brassicae population caused by the fungus B. bassiana was 88.33%, recorded at 7 days after the application of spore concentration 1×107 spores/ml and the LC50 obtained in the field was 1.10×106 spores/ml. It can be concluded from this study that C. Carnea and B. bassiana are effective biocontrol agents in controlling the cabbage aphid B. brassicae in the field. Keywords: B. brassicae, Chrysoperla carnea, Beauveria bassiana, Predator release.

Fungal endophytes as potential biocontrol agent of Panama disease of banana

BackgroundFusarium odoratissimum (Foc TR4) is a devastating fungal pathogen that causes Panama wilt in Cavendish banana, a high value crop that generates significant revenue. The excessive use of synthetic fungicides for disease control poses risks to both human health and the environment. Consequently, there is a pressing need for eco-friendly alternatives to manage this disease. One potential approach is the utilization of biocontrol agents, which have shown promise in disease control. This study aimed to evaluate the biocontrol potential of fungal endophytes isolated from the naturally-resistant cultivar Cardaba banana against Foc TR4. These fungal isolates were subjected to a dual culture assay, characterized based on morpho-cultural characteristics, and confirmed molecularly using the internal transcribed spacer (ITS) region of rDNA.ResultsOf the 15 fungal endophytes isolated from Cardaba; Blakeslea trispora, Pseudopestalotiopsis theae, Xylaria badia, Nigrospora hainanensis, Colletotrichum gloeosporioides, Xylaria feejeensis, Gymnoascus reessii, Fusarium subglutinans, Rigidoporus vinctus, and Macrophomina phaseolina showed potential antagonistic activity against F. odoratissimum. Isolates X. feejeensis (USMJMTBL10), G. reesii (USMJMTBL11), and M. phaseolina (USMJMTBR1) had the highest antagonistic activity of 87.8–96.6% against F. odoratissimum in vitro.ConclusionThis study presents evidence of the potential of Cardaba-associated endophytes isolated and identified in this research, as effective biocontrol agents against F. odoratissimum, the causal agent of Panama disease in Cavendish banana. Our findings suggest that these endophytes hold promise as a biocontrol agent for managing Foc TR4-infected banana plants. Future research will focus on in planta testing, validation in greenhouse and field trials, as well as development of formulations and application protocols to optimize the utilization of these biocontrol agents in an integrated management approach for Foc TR4-infected bananas.

Survey, Incidence and Pathogenicity of Root Rot Disease of Cotton in Different Districts of Haryana Incited by Rhizoctonia spp

Aim: Survey, incidence and pathogenicity of root rot disease of cotton in different districts of Haryana incited by Rhizoctonia spp.
 Design: Survey.
 Place and Duration of Study: Ten major cotton growing districts in Haryana during Kharif 2021 and Kharif 2022.
 Methodology: A roving survey to record cotton root rot incidence was conducted in ten major cotton growing districts of Haryana during the month of June and July for consecutive two Kharif seasons 2021 and 2022. On an average 4 growing region of cotton in each district were visited and percent disease incidence was recorded.
 Results: Among all the surveyed districts of Haryana the maximum mean disease incidence was recorded in Fatehabad (18.75%) followed by Hisar (15.25 %), Sirsa (15%), While the minimum disease incidence was recorded in Nuh and Charkhi dadri 9.25 per cent in both during kharif 2021. Among all the surveyed districts of Haryana the maximum mean disease incidence was recorded in Fatehabad (18.25%) followed by Sirsa (15.25%), Hisar (15.42%), While the minimum disease incidence was recorded Charkhi dadri (9.08%).
 Conclusion: The results of the current study showed that important cotton-growing regions in Haryana have root rot disease incidence. It is clear from the overall study that root rot disease is common in significant mulberry-growing regions in Haryana. As a result, resistant cotton types are urgently needed to address the grower's issue, together with the best management techniques, such as effective biocontrol agents that can significantly reduce the illness. Consequently, research should be conducted to ascertain the incidence of the disease in different places.

Chemical and biological products used in sugarcane and their effect on Trichogramma galloi

AbstractThe parasitoid Trichogramma galloi Zucchi (Hymenoptera: Trichogrammatidae) is an effective biocontrol agent of the sugarcane borer, Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). Its use is often recommended in integrated pest management (IPM) programs in sugarcane. However, the IPM of this crop also involves the use of chemical and biological insecticides, and little is known about the effects of concomitant use of these products together with T. galloi. In this study, we evaluated the effects of the chemical insecticide chlorantraniliprole (Altacor 350 WG) and the biological agents Beauveria bassiana (Bals.‐Criv.) Vuill. (Granada WP), Metarhizium anisopliae (Metchnikoff) Sorokin (Opala WP), and Bacillus thuringiensis Berliner var. kurstaki (Dipel WP) on the parasitism of T. galloi adult females against D. saccharalis eggs under laboratory conditions, in addition to biological parameters of the offspring. Treatments with chlorantraniliprole and B. thuringiensis reduced the parasitism rate of T. galloi females. The biological agents M. anisopliae, B. thuringiensis, and chlorantraniliprole increased offspring mortality by more than 30%. The use of B. bassiana favored adult female parasitism rates and did not cause significant offspring mortality. None of the treatments had significant effects on the emergence, longevity, and sex ratio of the offspring. Our results suggest that an insecticide based on B. bassiana can be used concomitantly with the parasitoid T. galloi in sugarcane IPM programs. Moreover, M. anisopliae, B. thuringiensis, and chlorantraniliprole had significant undesirable effects on T. galloi; therefore, they should be used with caution to avoid potential suppression of the parasitoid effect.

Phenotypic plasticity in an egg parasitoid affects olfactory response to odors from the plant–host complex

Female egg parasitoids must optimize their ability to find a suitable host for reproduction in a limited foraging time. Odorant cues associated with the plant–host complex play an essential role in guiding females toward the host. However, parasitoid response is not always identical within the same genotype, and it could be influenced by the environment. This phenotypic plasticity affects parasitoid behavior and morphology and is directly linked to rearing conditions. Yet, how plasticity influences olfactory responses of egg parasitoids toward plant–host odors is largely unexplored. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is an effective biocontrol agent of the invasive brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). Laboratory no-choice and choice tests showed T. japonicus potential to develop in eggs of non-target Pentatomidae. In Y-tube olfactometer we evaluated the olfactory responses of T. japonicus reared on different hosts toward plant–host derived volatiles associated with H. halys and two other stink bug species. Parasitoids reared on the main host H. halys positively responded only to odors from V. faba–H. halys complex. When reared on alternative hosts, T. japonicus was smaller and did not exhibit attraction to any stimuli, although egg load was only partially affected. Host-induced phenotypic plasticity should be considered when evaluating parasitoids for classical biological control.

Impact of Root Rot Disease of Zanthoxylum armatum on Rhizosphere Soil Microbes and Screening of Antagonistic Bacteria

Zanthoxylum armatum, a significant forest plant in southwestern China, is crucial for preserving soil and water resources. However, the presence of root rot disease has led to plant death, impacting the pepper sector. Effective control measures for this disease are still lacking. Rhizosphere microorganisms play a vital role in plant health by inhibiting plant pathogens and inducing plant resistance. This research aimed to isolate and characterize the pathogen responsible for root rot disease in Z. armatum. Comparative analysis of fungal and bacterial communities in the rhizosphere soil of healthy and diseased plants revealed Fusarium solani as the pathogenic fungus causing root rot disease. Diseased plants had a higher occurrence of Fusarium spp., while disease-free plants had a higher abundance of ecologically beneficial microbial communities that could potentially serve as biocontrol agents. Three bacterial strains (Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus siamensis) were identified as effective biocontrol agents, inhibiting the growth of the pathogenic fungus F. solani both in vivo and in vitro. This study deepens our understanding of the rhizosphere soil microbial community differences between diseased and healthy Z. armatum, providing potential biocontrol bacteria to enhance plant resistance against root rot disease.

Characterization of Salmonella Thompson-specific bacteriophages and their preventive application against Salmonella Thompson biofilm on eggshell as a promising antimicrobial agent in the food industry

Salmonella Thompson is a foodborne pathogen that has attracted attention in Korea since it was identified as the cause of a large-scale domestic food poisoning outbreak in 2018. The present study aims to isolate and characterize bacteriophages specific to Salmonella Thompson and evaluate their efficacy in reducing Salmonella Thompson biofilm on eggshell. In addition, advanced microscopic analysis using field-emission scanning electron microscopy and confocal laser scanning microscopy was conducted to confirm the anti-biofilm activity. The two isolated bacteriophages CAU-STP-1 and CAU-STP-2 showed very high specificity by targeting only Salmonella Thompson. They were determined to be stable at 60–65 °C and pH 4–11. Bacteriophage particles quickly adsorbed to the host cells, with a latent period and burst size of 30–40 min and 19–100 plaque-forming units per cell, respectively. When comparing the two bacteriophages individually, CAU-STP-1 exhibited the highest in vitro inhibition ability, but treatment with both bacteriophages together in a cocktail was significantly more effective than with CAU-STP-1 alone. This bacteriophage cocktail was consequently employed to treat Salmonella Thompson biofilm on eggshell at different storage temperatures. There was a significant reduction in the biofilm on the eggshell with bacteriophage treatment at 10 and 20 °C after 7 days. For example, After 7 days at 10 °C, the biofilm on eggshell was reduced by 0.26, 0.96, and 2.50 log CFU/cm2 for MOI 103, MOI 104, and MOI 105, respectively. On the other hand, at 20 °C, the biofilm on eggshells was reduced by 0.10, 0.24, and 0.33 log CFU/cm2 for MOI 103, MOI 104, and MOI 105, respectively This study thus provides promising information for the potential development of an effective biocontrol agent against Salmonella Thomson within the food industry.

Biocontrol of fungal phytopathogens by Bacillus pumilus.

Plant growth-promoting bacteria are one of the most interesting methods of controlling fungal phytopathogens. These bacteria can participate in biocontrol via a variety of mechanisms including lipopeptide production, hydrolytic enzymes (e.g., chitinase, cellulases, glucanase) production, microbial volatile organic compounds (mVOCs) production, and induced systemic resistance (ISR) triggering. Among the bacterial genera most frequently studied in this aspect are Bacillus spp. including Bacillus pumilus. Due to the range of biocontrol traits, B. pumilus is one of the most interesting members of Bacillus spp. that can be used in the biocontrol of fungal phytopathogens. So far, a number of B. pumilus strains that exhibit biocontrol properties against fungal phytopathogens have been described, e.g., B. pumilus HR10, PTB180, B. pumilus SS-10.7, B. pumilus MCB-7, B. pumilus INR7, B. pumilus SE52, SE34, SE49, B. pumilus RST25, B. pumilus JK-SX001, and B. pumilus KUDC1732. B. pumilus strains are capable of suppressing phytopathogens such as Arthrobotrys conoides, Fusarium solani, Fusarium oxysporum, Sclerotinia sclerotiorum, Rhizoctonia solani, and Fagopyrum esculentum. Importantly, B. pumilus can promote plant growth regardless of whether it alters the native microbiota or not. However, in order to increase its efficacy, research is still needed to clarify the relationship between the native microbiota and B. pumilus. Despite that, it can already be concluded that B. pumilus strains are good candidates to be environmentally friendly and commercially effective biocontrol agents.

Biological control of hemlock woolly adelgid in North America: History, status, and outlook

The hemlock woolly adelgid (HWA, Adelges tsugae, Hemiptera: Adelgidae) is an invasive insect that threatens the ability to maintain eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) as ecologically functional components of eastern North American forests. Since the early 1990 s, a classical biological control program for HWA has been pursued using insect predators from regions of Asia and western North America where the adelgid is native. Early efforts to establish ladybird beetles (Coleoptera: Coccinellidae) resulted in the establishment of Sasajiscymnus tsugae from Japan, but consistently poor field recovery of this species suggests it has not been an effective biocontrol agent in the introduced range. Two additional ladybird beetles, Scymnus ningshanensis Yu & Yao, and S. camptodromus Yu & Liu, were released but did not establish. Subsequent introduction, widespread establishment and spread of Laricobius nigrinus and La. osakensis (Coleoptera: Derodontidae) has provided substantial predation on winter stages of HWA, but has not provided overall regulation of adelgid populations below levels that cause hemlock shoot growth loss and mortality. Recently, efforts have focused on prey-specific genetic lineages of Leucotaraxis argenticollis and Le. piniperda (Diptera: Chamaemyiidae), which co-occur with La. nigrinus in their native range of the Pacific Northwest and show promise for eventual establishment in eastern North America. This review provides a brief introduction on the ecology, evolution, and population dynamics of HWA and its hosts, detailed coverage of the predators that have been (and are being) evaluated as biological control agents, and a discussion of the overall biological program with considerations for its future implementation.

Ectoparasitoid Dinarmus basalis causes greater offspring loss to the winged morph of Callosobruchus maculatus

The pest cowpea weevil Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) exhibits polymorphism with flight and flightless forms that differ in morphology and life-history. Flight forms are generally dispersers with lower fecundity that increase in frequency when population density and intraspecific competition are both high. Callosobruchus maculatus larvae can cause important damage to stored grains and the solitary ectoparasitoid Dinarmus basalis (Rondani) (Hymenoptera: Pteromalidae) is considered to be a good candidate biological control agent. However, whether morphs differ in the likelihood of their offspring surviving attack is unknown. Understanding this has implications for the pest status of the cowpea weevil following biological control. We found that attack by D. basalis lowered the number of emerging offspring produced by both morphs. The ectoparasitoid was most effective at reducing survival of larvae produced by flight morph parents, suggesting that there may be a further cost of dispersal for C. maculatus. Parental morph type did not influence D. basalis behavior or development when foraging, so the biological mechanism resulting in this difference remains unclear. Nevertheless, our study shows that D. basalis affects the offspring of both weevil morphs, as required for an effective biocontrol agent. These results contribute to our understanding of how intraspecific variation, including polymorphism, influences species interactions among biological control agents and their target insect pests.

Biocontrol Efficiency of Rhizospheric Bacillus against the Plant Pathogen Fusarium oxysporum: A Promising Approach for Sustainable Agriculture

Among plant disease management strategies, biological control is a sustainable alternative to the use of chemicals for the control of vascular wilt caused by Fusarium oxysporum. Fusarium wilt is the most devastating disease affecting a wide variety of plants. Bacillus species are the most widely used biological control candidates for the control of these fungal diseases. This review describes the pathogenicity of F. oxysporum, its virulence mechanisms, and host plant–pathogen interactions. The control means deployed by Bacillus species inhibit or kill these phytopathogens. Bacillus spp. produce a wide range of secondary metabolites, including volatile and non-volatile organic compounds. Biocontrol potential is achieved through direct antimicrobial activity, the induction of the host plant’s immune response (Induced Systemic Resistance), and competition for nutrients and space. In addition, parameters governing the selection of effective biocontrol agents and their survival in plant microbial communities are discussed. The influence of the microbiota on the establishment and development of biocontrol agents can assess the potential of these treatments and facilitate the development of effective biopesticides during their field application.

Prioritization of alien plant targets for biological control in South Africa's offshore sub-Antarctic islands

AbstractInvasive alien plants (IAPs) are a significant threat to the biodiversity and ecological functioning of the sub-Antarctic Prince Edward Islands (PEIs); however, weed biological control has not yet been implemented as a management tool. The PEIs have had 23 alien plants recorded, of which several are considered beyond eradication and therefore could benefit from the release of safe and effective biocontrol agents. We used the South African Biological Control Target Selection (BCTS) system to provide a ranked list of the target species in order of priority for further biocontrol research. The highest-scoring species, and therefore those that should be considered first to be targeted, were Sagina procumbens and Cerastium fontanum. No biocontrol agents for IAPs have been released in any climate with as consistent low temperatures as in the PEIs, so the climatic compatibility of agents will be essential prior to any decision to release. However, with very few native species present on the PEIs, the programmes would involve limited host specificity testing, which would improve the feasibility and speed with which new biocontrol agents could be developed. Biocontrol may offer an environmentally safe and sustainable method of reducing the negative impacts of these priority species and thus warrants further investigation.