Candidate For Biological Control Research Articles

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.

Understanding the host finding behavior of a biological weed control candidate specialist as a contribution to pre‐release risk assessments

AbstractPre‐release host range assessments of weed biocontrol agent (BCA) candidates typically rely on no‐choice and choice feeding, oviposition, and development tests. However, these tests may exclude potentially environmentally safe BCA candidates from consideration if they develop on nontarget plant species in no‐choice tests that they would not colonize in the field because of behavioral barriers during host selection. Here, we examined the behavioral responses of Ceutorhynchus rusticus Gyllenhal (Coleoptera: Curculionidae) to olfactory and visual plant cues of nine native North American and two Eurasian confamilial plant species of invasive Eurasian mustard dyer's woad, Isatis tinctoria L. (Brassicaceae). In behavioral bioassays with olfactory, visual, and combined plant cues of one plant species vs. purified air and/or empty arms (control treatments), weevils responded with attraction to all offered I. tinctoria plant cues but showed no preference for most nontarget plant species relative to control treatments. The weevil also responded faster in these bioassays to I. tinctoria cues when compared to most nontarget species. In bioassays with olfactory, visual, or combined cues of nontarget species vs. those of I. tinctoria, C. rusticus preferred I. tinctoria over most nontarget plant species (olfactory cues: eight of 11, visual cues: two of 11, and combined cues: 11 out of 11 nontarget plant species). The results also suggest that C. rusticus mainly uses olfactory or combined olfactory and visual plant cues rather than visual cues alone in the early stages of host finding. Additionally, the findings suggest that during host finding, C. rusticus prefers cues of its Eurasian field host over those of nontarget species, reducing risks of post‐release nontarget attack in the field. Assessing behavioral responses to multimodal cues can advance our understanding of BCA candidates' host discrimination and facilitate the accurate interpretation of conventional no‐choice and choice feeding and development data during pre‐release environmental safety assessments.

Biological traits of the zoophytophagous predatory mirid Nesidiocoris poppiusi (Heteroptera: Miridae), a candidate biocontrol agent in China.

Mirid predators are increasingly used in biological control of multiple greenhouse crops pests. However, due to great morphological similarity and tiny body size, some mirid predators have been largely confused with their allied species. Nesidiocoris tenuis Reuter as a commercial mirid predator was confused largely with Nesidiocoris poppiusi Carvalho in China. To evaluate the biocontrol potential of N. poppiusi, its biological traits and the functional response to Bemisia tabaci Gennadius were studied compared with N. tenuis under laboratory conditions. The results showed that no significant differences of the developmental times from the first instar to adult stages between the 2 mirids fed on Corcyra cephalonica Stainton eggs were observed, while N. poppiusi had better population growth parameters than N. tenuis. Under the condition with prey, both female and male of N. poppiusi lived significantly longer than those of N. tenuis. It could lay 74.0 eggs, which was significantly higher than that of N. tenuis (30.2 eggs). Under the condition without prey, both N. poppiusi and N. tenuis couldn't complete development to adulthood on tomato, tobacco, muskmelon, and cabbage leaves, however, tobacco and tomato were more suitable than the other 2 plants. A type II functional response was observed for both males and females of the 2 predators. Nesidiocoris poppiusi females consumed significantly more B. tabaci pupae than N. tenuis when prey densities were large than 30. Our results indicated that N. poppiusi could be a promising candidate for biological control of B. tabaci.

Risk assessment of the host range of Hydrellia lagarosiphon for the biological control of Lagarosiphon major in Ireland

ABSTRACT Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) is a submerged freshwater plant native to South Africa, and a destructive invader of waterways across Europe, Australasia and the U.S.A. Native range exploration identified a leaf mining ephydrid fly, Hydrellia lagarosiphon, as a promising biological control candidate agent. Host specificity was conducted on H. lagarosiphon, using laboratory no-choice and paired choice tests. A number of non-target native Potamogeton species sustained feeding damage under no-choice and paired choice testing. To prevent rejection of a potentially safe agent, multi-generational population persistence trials were conducted on select native Potamogetonaceae. The non-target species could not sustain a viable H. lagarosiphon population beyond two generations. A risk assessment, incorporating the preference and relative survival, indicated that three non-target species presented extremely low (<1.3%) risk of sustaining damage relative to that of L. major. Potamogeton polygonifolius and P. x lanceolatus present a reproductive risk of 5.61% and 11.5% respectively but could not support a viable population beyond the 2nd generation. These results, coupled with damage efficacy and predicted colonisation, demonstrate the potential H. lagarosiphon has as a biological control agent for L. major in Ireland.

Biological and proteomic analysis of a new isolate of the nematophagous fungus lecanicillium sp

BackgroundIn our continuing search for biologically active natural enemies from North of Africa with special reference to Tunisian fungi, our teamwork screened fungi from different ecological habitats in Tunisia. Our previous study on the comparative effectiveness of filamentous fungi in the biocontrol of Meloidogyne javanica, a taxon (Lecanicillium) showed high potentiality against M. javanica. We undertook the present study to evaluate the ability and understand the mechanism of this fungal parasite as a biological control candidate against the root-knot nematode M. javanica. This study used in vitro bioassays with fungal filtrate cultures, scanning electron microscopy (SEM) observation, and isobaric tag for relative and absolute quantitation (iTRAQ) methodology to characterize the biological and molecular features of this fungus.ResultsThe microscopic and SEM observation revealed that Lecanicillium sp. exhibited exceptional hyperparasitism against M. javanica eggs. The hyphae of this fungi penetrated the eggs, causing destructive damage to the outer eggshell. The exposure to five concentrations of Lecanicillium sp. filtrate cultures showed high inhibition of egg hatching, which increases depending on the exposure time; the best results are recorded at 50%, 75%, and 100% dilutions after seven days of exposure. The SEM observation of nematode-parasitized eggs and juveniles suggests that the production of lytic enzymes degrades the egg cuticle and fungal hyphae penetrate unhatched M.javanica juveniles. Forty-seven unique proteins were identified from the Lecanicillium sp. isolate. These proteins have signalling and stress response functions, bioenergy, metabolism, and protein synthesis and degradation.ConclusionCollectively, Lecanicillium sp. had ovicidal potentiality proved by SEM and proteomic analysis against root-knot nematode’ eggs. This study recommended applying this biological control candidate as a bio-agent on vegetable crops grown in situ.

Insecticidal activity of Bacillus thuringiensis towards Agrotis exclamationis larvae-A widespread and underestimated pest of the Palearctic zone.

acillus thuringiensis is an entomopathogenic bacterium commonly used as a bioinsecticide against numerous invertebrate pests. However, the efficacy of this microbe has not yet been determined towards Agrotis exclamationis-a lepidopteran, polyphagous pest, widespread throughout the Palearctic zone. In this work we have detected very low susceptibility of A. exclamationis to B. thuringiensis commercial strains, used as microbial formulations in pest control. To investigate this matter, the biological activity of six selected (Cry1Aa, Cry1Ca, Cry1Ia, Cry2Ab, Cry9Ea and Vip3Aa), heterogously-expressed Bacillus thuringiensis insecticidal proteins has been assessed towards A. exclamationis. Only Cry9Ea and Vip3Aa caused significant mortality in the tested pest species, with LC50 values of 950 and 140 ng/cm2, respectively. The histopathological effects of Cry9Ea and Vip3Aa on A. exclamationis were determined. On the other hand, Cry1- and Cry2-type toxins, which are the main active molecules of the majority of currently-used B. thuringiensis-based biocontrol agents (including the commercial strains tested in this work), did not cause mortality in target insect, but only different levels of growth inhibition. Moreover, in the case of Cry1Ca and Cry1Ia hormesis has been observed-a phenomenon that may be disadvantageous in implementation of these proteins in pest management. The obtained results broaden the existing knowledge regarding B. thuringiensis insecticidal protein target range and depict variable susceptibility of A. exclamationis to different groups of Cry/Vip toxins. This work indicates Cry9Ea and Vip3Aa as good candidates for efficient biological control of A. exclamationis and possibly other Agrotinae and discusses the potential use of Vip3-type and Cry9-type insecticidal proteins as successful bioinsecticides.

Comparative transcriptome analysis reveals the biocontrol mechanism of Bacillus velezensis E68 against Fusarium graminearum DAOMC 180378, the causal agent of Fusarium head blight.

Fusarium graminearum is the causal agent of Fusarium Head Blight, a serious disease affecting grain crops worldwide. Biological control involves the use of microorganisms to combat plant pathogens such as F. graminearum. Strains of Bacillus velezensis are common biological control candidates for use against F. graminearum and other plant pathogens, as they can secrete antifungal secondary metabolites. Here we study the interaction between B. velezensis E68 and F. graminearum DAOMC 180378 by employing a dual RNA-seq approach to assess the transcriptional changes in both organisms. In dual culture, B. velezensis up-regulated genes related to sporulation and phosphate stress and down-regulated genes related to secondary metabolism, biofilm formation and the tricarboxylic acid cycle. F. graminearum up-regulated genes encoding for killer protein 4-like proteins and genes relating to heavy metal tolerance, and down-regulated genes relating to trichothecene biosynthesis and phenol metabolism. This study provides insight into the molecular mechanisms involved in the interaction between a biocontrol bacterium and a phytopathogenic fungus.

Side effects of Zataria multiflora Boiss (Lamiaceae) essential oil on predation and life table parameters of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae)

The predatory mite, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) is one of the most promising candidates for biological control of some economically important mites and insect pests such as spider mites, whiteflies, and thrips. Western Flower Thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a severe economic pest for many crops in the world. In this study the lethal concentrations of Shirazicum thymus: Zataria multiflora Boiss (Lamiaceae) essential oil was calculated to the adult stage of the WFT. Side effects LC30 and LC50 of the essential oil were assessed on life table parameters and functional response of A. swirskii. Experiments were carried out in growth chambers at 25 ± 1 °C, 60 ± 10% RH, and 16: 8 h (Light: Dark) photoperiod. We utilized the age-stage, two-sex life table method to evaluate the life history features and population growth of A. swirskii on WFT. For assessing the functional response, the first instar of WFT was offered as prey to the adult female of A. swirskii with densities of 2, 4, 8, 16, 32, and 64. The LC50 concentration of the essential oil resulted in lower fecundity (15.05 eggs/female) in comparison with the control (19.8 eggs/female). The application of LC50 and LC30 concentrations also resulted in a significant decrease in net reproductive rate (R0) (8.9, 6.6, and 4.5 eggs per individuals), intrinsic rate of increase (rm) (0.116, 0.093, and 0.077 day -1), finite rate of increase (λ) (1.123, 1.097, and 1.079 day -1), but an increase in mean generation time (T) (18.5, 20.1, and 19.5 days) (for control, LC30, and LC50, applications, respectively). A type II functional response was detected for A. swirskii fed on WFT first instar in all treatments. Adult females of A.swirskii had the highest attack rate (a) (0.11± 0.01 h-1) and shortest handling time (1.61± 0.46h) on control treatment. In conclusion, although Z. multiflora essential oil had potential against F. occidentalis to be applied in integrated pest management programs, the lethal side effects of selected essential oil on the predatory mite, A. swirskii should be considered.

DNA High-Throughput Sequencing for Arthropod Gut Content Analysis to Evaluate Effectiveness and Safety of Biological Control Agents.

The search for effective biological control agents without harmful non-target effects has been constrained by the use of impractical (field direct observation) or imprecise (cage experiments) methods. While advances in the DNA sequencing methods, more specifically the development of high-throughput sequencing (HTS), have been quickly incorporated in biodiversity surveys, they have been slow to be adopted to determine arthropod prey range, predation rate and food web structure, and critical information to evaluate the effectiveness and safety of a biological control agent candidate. The lack of knowledge on how HTS methods could be applied by ecological entomologists constitutes part of the problem, although the lack of expertise and the high cost of the analysis also are important limiting factors. In this review, we describe how the latest HTS methods of metabarcoding and Lazaro, a method to identify prey by mapping unassembled shotgun reads, can serve biological control research, showing both their power and limitations. We explain how they work to determine prey range and also how their data can be used to estimate predation rates and subsequently be translated into food webs of natural enemy and prey populations helping to elucidate their role in the community. We present a brief history of prey detection through molecular gut content analysis and also the attempts to develop a more precise formula to estimate predation rates, a problem that still remains. We focused on arthropods in agricultural ecosystems, but most of what is covered here can be applied to natural systems and non-arthropod biological control candidates as well.

Critical Evaluation of Biocontrol Ability of Bayoud Infected Date Palm Phyllospheric Bacillus spp. Suggests That In Vitro Selection Does Not Guarantee Success in Planta

The vascular wilt of date palm (Phoenix dactylifera L.), also known as Bayoud and caused by Fusarium oxysporum f.sp. albedinis (FOA), is the most destructive disease in North Africa. The disease has resulted in huge economic losses due to declining crop yield and quality. The use of potential biocontrol agents is a sustainable and environmentally friendly strategy compared to synthetic fungicides. The use of date palm-associated microflora for the screening of native antagonistic bacteria with potential applications is the most promising way to control this disease. Thus, the epidemic palm groves (in the valley of M’zab-Ghardaia-Algeria) were chosen for the isolation of rhizospheric bacteria and endophytes from the soil and roots of healthy or infected plants. A total of 8 bacterial isolates (83, 84, 300, 333, 322, 260, 249, and 227) selected from 75 FOA-active strains, showed strong activity against several strains of FOA and other major plant pathogens. Their phylogenetic identification proved they belong to the genus Bacillus (Bacillus sp., B. subtilis, B. atrophaeus, B. halotolerans, B. amyloliquefasiens, and B. paralicheformis). Bacterial cultures and a cell-free culture supernatant tested alone or in co-culture showed FOA inhibitory activity. However, the effect of the co-culture did not show any synergy in both cases. Unlike diffusible compounds, volatile organic compounds did not show a significant antifungal ability. The concept of selecting biocontrol agents in vitro does not always guarantee in vivo performance. In addition to antibiosis, other strategies such as competition and resistance induction are required for biocontrol agent efficacy. To evaluate the biocontrol effect in vivo, germinated seeds of date palm were treated with bacteria, infected with the pathogen, and then incubated for 45 days at room temperature in the dark. The majority of the strains (84, 300, and 333) tested showed moderate fungistatic effects and the protection rate reached an average of 60%. In particular, promising results were obtained with B. paralicheniformis strain 260 which significantly protected palm seeds up to 85%, compared to its in vitro test where a low inhibition rate (27.77%) was recorded. Screening methods should be equipped with multifactorial or plant-mediated control mechanisms. Furthermore, these bacteria have shown other potentialities to improve plant growth and resist stressful conditions. Thus, an effective biocontrol agent must combine several beneficial characteristics to be used successfully in situ. In this respect, Bacillus remains the best candidate for biological control.

Competitive interactions affect larval survival of two root-boring weed biological control candidates of Rumex spp

In weed biocontrol, the release of multiple candidates has been proposed as a way to increase herbivore load and thus impact on the target weed. However, the use of multiple herbivorous species may reduce overall herbivore load due to interspecific interactions. We assessed whether a combined application of two Pyropteron spp. (Lepidoptera: Sesiidae) with root-boring larvae can increase larval infestation rate and impact on two Rumex weeds (Caryophyllales: Polygonaceae). In a laboratory assay (‘behavioural experiment’), interference competition was assessed by comparing the survival of a single larva (no competition), of four conspecific larvae (intraspecific competition) and of two larvae of each species (interspecific competition). In a common garden study (‘infestation and impact experiment’), the outcomes of competitive interactions were assessed on potted plants with single and mixed species applications of the two Pyropteron species using a replacement design. In the behavioural experiment, larval survival was similarly reduced under intra- and interspecific competition compared to no competition, suggesting strong interference competition among larvae independent of the Pyropteron species. In the infestation and impact experiment, mixed application did only scarcely increase herbivore load. Increased herbivore load was found to increase root decay when applied in an inundative approach by placing eggs directly on Rumex plants. However, a joint application of two Pyropteron species did not increase the impact. We propose that detailed behavioural and impact studies be conducted to assess the likely outcome of using multiple candidates in biocontrol programs to minimize associated risks with multiple species introductions.

Predation Capacity of the Banded Thrips Aeolothrips intermedius for the Biological Control of the Onion Thrips Thrips tabaci.

Simple SummaryAeolothrips intermedius is a native predator of Thrips tabaci, one of the most harmful thrips for many open field crops. Our study evaluated the predatory efficiency of A. intermedius against T. tabaci adults. The results showed that A. intermedius can be considered a promising resource for the biological control of onion thrips.The onion thrips, Thrips tabaci, is a main insect pest for many field crops worldwide, with a particular preference for the species of the genus Allium. Aeolothrips intermedius is a banded thrips, whose larvae are considered the primary native predator of T. tabaci. Due of their predatory behaviour, A. intermedius larvae are considered a good candidate for biological control against thrips pests. However, limited information is available on the specific predation rate of A. intermedius against T. tabaci. The aim of our study was to evaluate the predatory efficiency of A. intermedius larvae against T. tabaci adults. Predation assays, performed under laboratory conditions, indicated that A. intermedius larvae begin to prey after an average of about 23 min, and the time taken by an A. intermedius larva to capture and subdue the prey until its death is about 26 min. Furthermore, the maximum number of prey that the A. intermedius larvae are able to kill in 12 h is up to eight adults of T. tabaci/A. intermedius larva.

Assessing the optimal frequency of early parasitoid releases in an apple orchard to control Dysaphis plantaginea: a proof-of-concept study

ABSTRACT Alternatives to pesticides to control the rosy apple aphid, Dysaphis plantaginea, are being developed. Natural enemies usually arrive too late after the first aphid infestation to provide effective control. This study tested the effects of mass release of two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, on the numbers of aphid colonies and aphids per tree. In a trial undertaken in two years in an organic apple orchard, parasitoids were released three times early in the season to match the presence of aphid fundatrix (sensitive stages), on a weekly or bi-weekly frequency. The degree-days necessary for parasitoid emergence in the field after release were calculated. A sufficient level of aphid control by parasitoids was reached during the first month of the survey (March), but for both release treatments the control mostly failed during the second part of the monitoring session (April to late May) compared with the control treatment with neem oil. The relative effects of release frequencies were different between the two years, probably because of interannual differences in aphid population dynamics and initial infestation in orchards. The field survey suggested that parasitoid releases, at either frequency, were promising candidates for biological control of the rosy aphid, although the method still needs further calibration. This case study laid the first empirical basis to help develop future control methods of aphids by parasitoid releases in apple orchards. Releases should be done one to two weeks before first aphid detection to account for long development times of parasitoids at relatively low temperatures.

Mode of action of potential biocontrol agents against Fusarium species and Cochliobolus sativus

ABSTRACT The antagonistic activities of three potential biocontrol agents (BCAs), Clonostachys miodochialis, C. rosea, and Minimedusa polyspora, were tested in vitro against the target fungi Fusarium acuminatum, F. avenaceum, F. equiseti, F. graminearum, and Cochliobolus sativus. In vitro dual-culture assay revealed that the BCAs were able to inhibit the mycelial growth of most of the target fungi, with the most common mode of action being mycoparasitism. After 5 d of incubation, depending on the host-parasite interface, biotrophic mycoparasitism was observed via attachment structures on F. avenaceum, F. equiseti, and C. sativus. Haustoria and appressoria were formed by C. miodochialis and M. polyspora on F. avenaceum and C. sativus, respectively. Clamp-like structures were also produced by both BCAs, depending on the host fungus. Clonostachys rosea formed only contact points on its hosts. Coiling structure was observed with C. rosea and M. polyspora occasionally in pure culture but more abundantly in the dual-culture assay. After an additional 3 to 5 d of incubation, the BCAs started damaging their host cells. Asexual fruiting bodies of the BCAs spread necrotrophically on F. acuminatum and F. graminearum and began destroying their mycelia after the initial 5 d of incubation. Furthermore, mycelial dissolution of F. acuminatum by an excreted substance was observed at a distance before direct contact with C. miodochialis. The diffuse metabolite assay revealed that the highest inhibition of the three BCAs was on C. sativus and their least effectiveness was observed on F. graminearum. Overall, these results provide evidence that C. miodochialis, C. rosea, and M. polyspora are potential candidates for biological control of the tested target fungi. This constitutes the first report that these three BCAs are able to establish an initial biotrophic relationship followed by a necrotrophic lifestyle. In addition, C. miodochialis has not previously been reported as a BCA.

The first record of the genus Plega Navás, 1928 (Neuroptera: Rhachiberothidae: Symphrasinae) as a parasitoid of the sawfly genus Monoctenus Dahlbom, 1835 (Hymenoptera: Symphyta: Diprionidae)

The genus Plega Navás, 1928, belongs to the subfamily Symphrasinae, a group recently transferred from Mantispidae to Rhachiberothidae. This genus is herein reported as parasitoid of the symphytan family Diprionidae for the first time, becoming the first record of association between this neuropteran subfamily and non-aculeate Hymenoptera. This new association was discovered in “Ixcateopan de Cuauhtémoc”, in the Mexican state of Guerrero, where Plega spinosa Ardila et al., 2019 was found associated with immatures of the sawfly Monoctenus cuauhtemoci De Lira, 2021, a pest in forests of Juniperus flaccida Schlechtendal (white cedar). The neuropteran was found to be the most abundant parasitoid of this symphytan, becoming a potential candidate for biological control of phytophagous sawflies in juniper forests, an economically important plant species for the wood industry in the region. Considering the behavior and morphological aspects of the primary larvae and the behavior of the adults of Plega, three possible scenarios in which the primary larvae of P. spinosa board the larvae of Monoctenus to complete its life cycle are outlined. This finding reinforces the hypothesis of a generalist ectoparasitoid lifeway of the larvae of the genus Plega on larvae and pupae of holometabolous insects.

Transcriptomics Reveal Several Novel Viruses from Canegrubs (Coleoptera: Scarabaeidae) in Central Queensland, Australia.

Canegrubs (Coleoptera: Scarabaeidae) are major pests of sugarcane crops in Australia, but despite long-term and intensive research, no commercially viable biological control agents have been identified. We used the RNA-Seq approach to explore the viriomes of three different species of canegrubs from central Queensland, Australia to identify potential candidates for biological control. We identified six novel RNA viruses, characterized their genomes, and inferred their evolutionary relationships with other closely related viruses. These novel viruses showed similarity to other known members from picornaviruses, benyviruses, sobemoviruses, totiviruses, and reoviruses. The abundance of viral reads varied in these libraries; for example, Dermolepida albohirtum picorna-like virus (9696 nt) was built from 83,894 assembled reads while only 1350 reads mapped to Lepidiota negatoria beny-like virus (6371 nt). Future studies are essential to determine their natural incidence in different life stages of the host, biodiversity, geographical distributions, and potential as biological control agents for these important pests of sugarcane.

A modified method for mass production of generalist predatory edaphic mite Gaeolaelaps aculeifer as a candidate for biological control of the saffron corm mite

ABSTRACT Gaeolaelaps aculeifer (Canestrini) (Acari: Laelapidae) is an edaphic predator of several agricultural pests. Development of simple and low-cost innovative mass rearing techniques and the use of this predator to control soil pests have high importance. For the mass production of G. aculeifer, three growth environments were evaluated. Saffron corms and layered potatoes were used to feed mites, and the mixture of “cocopeat + perlite and saffron chaff” was used to maintain more moisture and to prepare the environment for more ventilation and more porosity, increase hiding places, and provide shelter for the predatory mites to lay eggs. In each treatment, 40 male and female adults of G. aculeifer were released. To feed the predators, approximately 500–800 bulb mites were added to each unit, weekly. The results showed a 27-fold increase in G. aculeifer populations within 30 days. After 60 days, the rate of predator population decreased. Saffron is an expensive plant with abundant benefits and diverse uses. The bulb mite Rhizoglyphus robini is a potentially serious pest damaging saffron corms. This method gives saffron growers the choice to improve the biological control of bulb mites in their saffron fields.

Prodiplosis hirsuta Kolesik sp. nov., a new species of gall midge (Diptera: Cecidomyiidae) feeding on shoot tips of Jatropha (Euphorbiaceae) in South America

AbstractA gall midge, Prodiplosis hirsuta Kolesik sp. nov., is described whose larvae feed on shoot tips of Jatropha gossypiifolia and Jatropha clavuligera in Paraguay and Bolivia. Morphology and the mitochondrial COI gene sequence of the new species are given. Field survey and preliminary no‐choice host specificity tests showed that the host plant range of P. hirsuta is confined to J. gossypiifolia and J. clavuligera. The apparent host specificity and the damage potential make P. hirsuta a prospective candidate for biological control of J. gossypiifolia in Australia.

Revisiting the influence of learning in predator functional response, how it can lead to shapes different from type III.

Predator/parasitoid functional response is one of the main tools used to study predation behavior, and in assessing the potential of biological control candidates. It is generally accepted that predator learning in prey searching and manipulation can produce the appearance of a type III functional response. Holling proposed that in the presence of alternative prey, at some point the predator would shift the preferred prey, leading to the appearance of a sigmoid function that characterized that functional response. This is supported by the analogy between enzyme kinetics and functional response that Holling used as the basis for developing this theory. However, after several decades, sigmoidal functional responses appear in the absence of alternative prey in most of the biological taxa studied. Here, we propose modeling the effect of learning on the functional response by using the explicit incorporation of learning curves in the parameters of the Holling functional response, the attack rate (a), and the manipulation time (h). We then study how the variation in the parameters of the learning curves causes variations in the shape of the functional response curve. We found that the functional response product of learning can be either type I, II, or III, depending on what parameters act on the organism, and how much it can learn throughout the length of the study. Therefore, the presence of other types of curves should not be automatically associated with the absence of learning. These results are important from an ecological point of view because when type III functional response is associated with learning, it is generally accepted that it can operate as a stabilizing factor in population dynamics. Our results, to the contrary, suggest that depending on how it acts, it may even be destabilizing by generating the appearance of functional responses close to type I.

Pseudomonas Isolates as Potential Biofungicides of Green Mold (Penicillium Digitatum) on Orange Fruit

ABSTRACT Green mold, caused by Penicillium digitatum, is a serious disease of citrus fruit during postharvest. The focus of this study was to evaluate possible biological alternatives to chemical fungicides for P. digitatum control. Four Pseudomonas isolates (Q110B, Q125B, Q112B, and Q004B) were isolated from rhizospheric soil and evaluated for their antagonistic activity against P. digitatum. The in vitro evaluations of these isolates by dual culture revealed an important zone of inhibition after 3 days of incubation at 25 ± 2°C. The Q004B isolate provided a high zone of inhibition in vitro at 45 mm diameter. Four Pseudomonas isolates tested showed antagonistic activity against P. digitatum on orange fruit after 7 days of inoculation under postharvest conditions. Inhibition percentage of P. digitatum on orange fruit ranged from 22 to 85% for Q004B and Q112B, respectively. Regarding the mechanism of action, the four tested isolates produced volatile compounds in vitro with inhibition percentage ranging from 35% to 79%, respectively for Q004B andQ125B. The Q004B isolate caused a high spore inhibition rate of 46%, while Q110B had no effect on spore germination. The four isolates of Pseudomonas produced siderophores in CAS medium. Additionally, Q125B, Q112B, and Q004B showed a positive chitinolytic activity, whereas Q110B provided negative results to the chitinase assay. These isolates represent potential candidates for biological control of citrus green mold and may be effectively used as a sustainable alternative measure to chemical fungicide control.