Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Mode of action of microbial biological control agents against plant diseases: Relevance beyond efficacy
Köhl, Jürgen ; Kolnaar, Rogier ; Ravensberg, Willem J. - \ 2019
Frontiers in Plant Science 10 (2019). - ISSN 1664-462X
Antagonist - Biological control - Mode of action - Plant diseases - Risk assessment - Screening

Microbial biological control agents (MBCAs) are applied to crops for biological control of plant pathogens where they act via a range of modes of action. Some MBCAs interact with plants by inducing resistance or priming plants without any direct interaction with the targeted pathogen. Other MBCAs act via nutrient competition or other mechanisms modulating the growth conditions for the pathogen. Antagonists acting through hyperparasitism and antibiosis are directly interfering with the pathogen. Such interactions are highly regulated cascades of metabolic events, often combining different modes of action. Compounds involved such as signaling compounds, enzymes and other interfering metabolites are produced in situ at low concentrations during interaction. The potential of microorganisms to produce such a compound in vitro does not necessarily correlate with their in situ antagonism. Understanding the mode of action of MBCAs is essential to achieve optimum disease control. Also understanding the mode of action is important to be able to characterize possible risks for humans or the environment and risks for resistance development against the MBCA. Preferences for certain modes of action for an envisaged application of a MBCA also have impact on the screening methods used to select new microbials. Screening of MBCAs in bioassays on plants or plant tissues has the advantage that MBCAs with multiple modes of action and their combinations potentially can be detected whereas simplified assays on nutrient media strongly bias the selection toward in vitro production of antimicrobial metabolites which may not be responsible for in situ antagonism. Risks assessments for MBCAs are relevant if they contain antimicrobial metabolites at effective concentration in the product. However, in most cases antimicrobial metabolites are produced by antagonists directly on the spot where the targeted organism is harmful. Such ubiquitous metabolites involved in natural, complex, highly regulated interactions between microbial cells and/or plants are not relevant for risk assessments. Currently, risks of microbial metabolites involved in antagonistic modes of action are often assessed similar to assessments of single molecule fungicides. The nature of the mode of action of antagonists requires a rethinking of data requirements for the registration of MBCAs.

Tomato inoculation with a non-pathogenic strain of Fusarium oxysporum enhances pest control by changing the feeding preference of an omnivorous predator
Eschweiler, Julia ; Holstein-Saj, Renata van; Marjolein Kruidhof, H. ; Schouten, Alexander ; Messelink, Gerben J. - \ 2019
Frontiers in Ecology and Evolution 7 (2019)JUN. - ISSN 2296-701X
Biological control - Endophytic fungi - Macrolophus pygmaeus - Multitrophic interactions - Trialeurodes vaporariorum

Mirid predators, a special group of plant-feeding omnivorous predators, have become important biological control agents for pest control in greenhouse cropping systems. Their efficacy and behavior may potentially be affected by microorganisms that induce plant defenses or change plant quality. Here we studied the interaction between a root restricted endophytic non-pathogenic strain of Fusarium oxysporum (Fo162) in tomato plants, the greenhouse whitefly Trialeurodes vaporariorum (Westwood) and the plant-feeding mirid predator Macrolophus pygmaeus (Rambur). In the absence of prey, inoculation of tomato plants with the Fo162 endophyte significantly reduced the reproduction of M. pygmaeus compared to plants without the endophyte. In contrast, the population growth of M. pygmaeus was not affected by the Fo162 endophyte in the presence of whiteflies. Moreover, the combination of the predator and endophyte resulted in lower whitefly densities than the predator alone. Whitefly population development was not different between endophyte-inoculated and untreated plants. Thus, endophyte inoculation of tomato plants seems to shift the feeding preference of this omnivorous predator from plant consumption toward relatively more prey consumption, resulting in enhanced suppression of the herbivore. Moreover, the negative effect of the endophyte on M. pygmaeus reproduction could easily be eliminated by providing decapsulated cysts of Artemia franciscana Kellogg as a supplemental food source. Together, this suggests an overall net positive effect of the Fo162 endophyte on a preventive biological control strategy in tomato using M. pygmaeus. Besides the enhanced whitefly control, endophyte-inoculation of tomato plants both with or without the predator also resulted in a higher yield and a reduced number of fruits with blossom-end rot, a disorder caused by limitations in uptake and transport of calcium to the fruits. This suggests that the Fo162 endophyte is also involved in the acquisition of essential nutrients for the benefit for the plant. Since both the Fo162 endophyte and the predator M. pygmaeus can induce plant defense, further studies need to elucidate the exact mechanisms that occur when both organisms are present. Our findings confirm the importance of studying endophytes and induced plant responses in a multi-trophic context with herbivores and their natural enemies.

Stepwise screening of candidate antagonists for biological control of Blumeria graminis f. sp. tritici
Köhl, Jürgen ; Goossen van de Geijn, Helen ; Groenenboom de Haas, Lia ; Henken, Betty ; Hauschild, Rüdiger ; Hilscher, Ulrike ; Lombaers-van der Plas, Carin ; Bosch, Trudy van den; Wikström, Mariann - \ 2019
Biological Control 136 (2019). - ISSN 1049-9644
Antagonists - Biological control - Blumeria graminis f. sp. tritici - Powdery mildew - Risk assessment - Screening criteria - Tilletiospsis pallescens - Wheat

Antagonists for the biological control of Blumeria graminis f. sp. tritici were selected using a stepwise screening approach. Fungal colonizers of powdery mildew pustules were isolated from leaves of cereals and other plant species. Spore production, cold tolerance, drought tolerance and UV-B resistance as important characteristics for application of biocontrol candidates in the phyllosphere were tested in in vitro assays and preliminary risk assessments were conducted. Amongst 850 tested isolates 58% belonged to various taxonomical groups of Cladosporium. Only 3% belonged to species that have been reported in literature as antagonistic to powdery mildews. The stepwise screening approach allowed to reduce the number of candidate antagonists using screening criteria that can be tested reliably and cost-effectively in in vitro assays and by data mining from initially 1237 isolates down to 143 candidate antagonists belonging to 42 taxonomical groups. The potential of these isolates to reduce conidia production of B. graminis f. sp. tritici. in wheat was assessed in bioassays on potted winter wheat plants under controlled conditions. A set of ten superior isolates was subsequently tested in a series of trials on potted spring wheat plants under open field conditions. Isolates Tilletiopsis pallescens BC0441 and T. pallescens BC0850 significantly reduced the number of powdery mildew pustules per flag leaf by 30 to 62%. Slopes of the regression lines fitted to data on number of powdery mildew pustules during time were significantly reduced by the antagonists indicating that the powdery mildew epidemics were slowed down. Treatments with T. pallescens BC0441 and T. pallescens BC0850 also reduced leaf coverage with powdery mildew pustules in a small-scale field trial in spring wheat.

Is predation of Tuta absoluta by three Neotropical mirid predators affected by tomato lines with different densities in glandular trichomes?
Bueno, Vanda H.P. ; Lins, Juracy C. ; Silva, Diego B. ; Lenteren, Joop C. van - \ 2019
Arthropod-Plant Interactions 13 (2019)1. - ISSN 1872-8855 - p. 41 - 48.
Biological control - Campyloneuropsis infumatus - Engytatus varians - Macrolophus basicornis - Miridae - Solanum lycopersicum - Sticky trichome

Plants with glandular trichomes may provide protection against herbivores by impeding their movement, but may also hinder natural enemies. We investigated walking behavior and predation rates of the mirid predators Campyloneuropsis infumatus, Engytatus varians, and Macrolophus basicornis on two tomato lines with different densities of sticky trichomes. Also, the time spent by each predator species in various activities (immobile, walking, grooming, probing, and feeding) and the searching for and handling time of prey, eggs of Tuta absoluta, were observed. Tomato lines TOM 587 and TOM 687 were used, with TOM 687 having a 179% higher density of glandular trichomes. All three mirid predators easily climbed the sticky stems of both tomato lines and found eggs of T. absoluta on leaflets located on the top of the plants. Predation rates, grooming, probing, and feeding activities and the time spent by the three mirid predators until prey encounter were not influenced by a difference in density of trichomes on the two tomato lines. However, E. varians walked longer on TOM 584, and spent more time grooming than M. basicornis. Macrolophus basicornis walked longer on TOM 687. Our results show that the three mirid predators are apparently specialists of glandular plants, because differences in trichome density do not influence their activities, including their prey finding efficiency.

Adult lifetime predation of Tuta absoluta eggs by three Neotropical mirid predators on tomato
Lenteren, Joop C. van; Bueno, Vanda Helena Paes ; Montes, Flavio Cardoso ; Hemerik, Lia ; Jong, Peter W. de - \ 2018
Bulletin of Insectology 71 (2018)2. - ISSN 1721-8861 - p. 179 - 188.
Biological control - Engytatus varians - Infumatus - Macrolophus basicornis - Miridae - Tomato borer

Tuta absoluta (Meyrick), a key pest of tomato, is quickly spreading over the world. Here we report lifetime predation of T. absoluta eggs by adults of three Neotropical mirid species [Campyloneuropsis infumatus (Carvalho), Engytatus varians (Distant) and Macrolophus basicornis (Stal)]. Prey eggs were offered ad libitum on a tomato leaflet at 24 ± 1 °C, 70 ± 10% RH and 12-h photophase. Daily, the number of eggs consumed by adults was noted. Observations were terminated after all adults had died. Total adult lifetime predation of T. absoluta eggs was 337, 313 and 339 for males, and 845, 668 and 934 for females of C. infumatus, E. varians and M. basicornis, respectively. Mean adult lifespan was 27 days for males and 24 for females of C. infumatus, 17 days for males and 14 for females of E. varians, and 30 days for males and 26 days for females of M. basicornis. Total and daily predation was significantly higher for females than for males, though lifespan was significantly longer for males than for females. The daily predation rates of C. infumatus and M. basicornis were similar, but were significantly lower than that of E. varians. Predation rates tended to decrease significantly with adult age for both sexes of all three species, except for males of M. basicornis, although proportions of explained variance were low (r2 < 0.24). Adult survival and egg predation data will later be combined with data about egg development time and survival, and nymphal development time, survival and egg predation to determine the pest kill rate of the three mirid species. The pest kill rate will then be used to predict which of the mirids might be best for control of T. absoluta on tomato. Eventually, experiments at practical tomato production conditions will show whether our predictions are correct.

Evaluation of pest control efficiencies for different banker plant systems with a simple predator–prey model
Yano, Eizi ; Abe, Junichiro ; Hemerik, Lia - \ 2018
Population Ecology 60 (2018)4. - ISSN 1438-3896 - p. 389 - 396.
Biological control - Initial pest density - Mathematical model - Predator immigration - Transient dynamics

The banker plant system has been introduced for the biological control of various pest species in Japanese greenhouses. With the banker plant system, non-crop plants infested with a host insect (a non-commercial crop pest) are placed in the greenhouse to provide alternative resources for the parasitoids or predators. We want to evaluate the effectiveness for controlling pests on the crop in a quantitative way by immigrating predators from the banker plant. Therefore, we developed a simple model for the interaction of the pest and predator in the crop and included the banker plant only as a source for predators. For three different pest-predator systems we parameterised the model and used these models to predict under what conditions biological control in a banker plant system is successful. We defined successful as keeping the pest below the economic injury level of the crop estimated from damage analysis. Because the crop is mostly grown during a period that lasts less than a year our analysis should not only focus on the equilibrium dynamics. In contrast, it should also focus on the transient dynamics. Our main analytical result, from the equilibrium analysis, is that for successful control the maximum lifetime consumption of immigrating predators should exceed the daily prey growth at half the value of the maximum consumption rate. For practical purpose this translates into the fact that the immigration of predators at a low initial pest density is crucial for successful control.

Comparative effectiveness and injury to tomato plants of three neotropical mirid predators of tuta absoluta (Lepidoptera : Gelechiidae)
Lenteren, Joop C. van; Bueno, V.H.P. ; Calvo, F.J. ; Calixto, Ana M. ; Montes, Flavio C. - \ 2018
Journal of Economic Entomology 111 (2018)3. - ISSN 0022-0493 - p. 1080 - 1086.
Biological control - Miridae - Tomato borer - Zoophytophagy

Tuta absoluta (Meyrick; Lepidoptera: Gelechiidae) is a key pest of tomato and is quickly spreading over the world. We conducted an experiment aimed at evaluating the control capacity and risk for plant damage of three Neotropical mirid species, Campyloneuropsis infumatus (Carvalho; Hemiptera: Miridae), Engytatus varians (Distant; Hemiptera: Miridae) and Macrolophus basicornis (Stal; Hemiptera: Miridae) on T. absoluta infested tomato plants in large cages in an experimental greenhouse. During three successive periods of 9 wk each, we followed population development of the three mirids when exposed to T. absoluta, and of T. absoluta alone in separate cages in the greenhouse. We determined weekly the numbers of T. absoluta eggs and larvae per leaf, the number of mirid predators per leaf, the percentage of damaged leaves and fruits by T. absoluta, and the weight of fruits. Two of the mirid predators, C. infumatus and M. basicornis, successfully established on T. absoluta infested tomato plants and significantly reduced T. absoluta numbers, which ultimately resulted in an increased yield. These two mirid species hardly injured tomato plants or fruits as a result of plant feeding. Surprisingly, the species E. varians, which showed high predation rates in laboratory experiments, did not establish and reduce pest populations in any of the tests.

Performance of immatures of three neotropical miridae at five different temperatures, reared on ephestia kuehniella eggs on tobacco plants
Bueno, Vanda Helena Paes ; Montes, Flavio Cardoso ; Sampaio, Marcus Vinicius ; Calixto, Ana Maria ; Lenteren, Joop C. van - \ 2018
Bulletin of Insectology 71 (2018)1. - ISSN 1721-8861 - p. 77 - 87.
Biological control - Campyloneuropsis infumatus - Engytatus varians - Macrolophus basicornis - Mass production - Thermal constants - Tuta absoluta
Effects of temperature (16, 20, 24, 28 and 32 ± 1 °C), host plant (Nicotiana tabacum L.) and factitious prey (eggs of Ephestia kuehniella Zeller) on immature development of three recently found Neotropical mirids, Campyloneuropsis infumatus (Carvalho), Engytatus varians (Distant) and Macrolophus basicornis (Stal) were studied at RH 70 ± 10% and 12h photophase in climate cabinets. These mirids are being evaluated for biological control of the South American tomato borer Tuta absoluta (Meyrick) and other pests on tomato. Survival of eggs of the three mirid species on tobacco was high (> 80%) at 16-28 °C, but lower (< 80%) at 32 °C. Development times decreased with increasing temperature from 16-28 °C. Nymphal survival was higher (84-96%) at 20, 24 and 28 °C than at 16 and 32 °C (46-83%). The sex ratio of C. infumatus was strongly female biased at all temperatures, whereas it was 1:1 for the other two species. The lower temperature thresholds for egg-adult development of C. infumatus, E. varians and M. basicornis were 9.4, 9.4 and 7.9 °C, and their thermal constants were 384.6, 384.6 and 476.2 DD, respectively. Temperatures between 24 to 28 °C are best for immature performance and for rearing of these mirids species. Eggs of the factitious host E. kuehniella provide adequate food for their mass production. Optimal temperatures for best mirid predator performance are similar to those for the pest T. absoluta, indicating good climate matching.
A pan-European model of landscape potential to support natural pest control services
Rega, Carlo ; Bartual, Agustín M. ; Bocci, Gionata ; Sutter, Louis ; Albrecht, Matthias ; Moonen, Anna Camilla ; Jeanneret, Philippe ; Werf, Wopke van der; Pfister, Sonja C. ; Holland, John M. ; Paracchini, Maria Luisa - \ 2018
Ecological Indicators 90 (2018). - ISSN 1470-160X - p. 653 - 664.
Biological control - Green infrastructure - Landscape complexity - Landscape design - Natural pest control - Semi-natural habitats
Pest control by natural enemies (natural pest control) is an important regulating ecosystem service with significant implications for the sustainability of agro-ecosystems. The presence of semi-natural habitats and landscape heterogeneity are key determinants of the delivery of this service. However, to date, synthetic and consistent indicators at large scales are lacking. We developed a pan-European, spatially-explicit model to map and assess the landscape potential to sustain natural pest control. The model considers landscape composition in terms of semi-natural habitats types, abundance, spatial configuration and distance from the focal field. It combines recent high-resolution geospatial layers with empirical results from extensive field surveys measuring the specific contribution of different semi-natural habitats to support insects flying enemies providing natural pest control. The resulting maps facilitate a comparison of the relative biological control potential of different areas and show that currently a large proportion of high-productive agricultural areas in Europe has low potential. The obtained indicator can inform the formulation of policies and planning strategies aimed at increasing biodiversity and ecosystem services and can be used to assess trade-offs between different services. Potential fields of application include the Common Agricultural Policy and the EU Biodiversity Strategy, in particular the implementation of Green Infrastructure.
Mycokey round table discussions of future directions in research on chemical detection methods, genetics and biodiversity of mycotoxins
Leslie, John F. ; Lattanzio, Veronica ; Audenaert, Kris ; Battilani, Paola ; Cary, Jeffrey ; Chulze, Sofia N. ; Saeger, Sarah De; Gerardino, Annamaria ; Karlovsky, Petr ; Liao, Yu Cai ; Maragos, Chris M. ; Meca, Giuseppe ; Medina, Angel ; Moretti, Antonio ; Munkvold, Gary ; Mulè, Giuseppina ; Njobeh, Patrick ; Pecorelli, Ivan ; Perrone, Giancarlo ; Pietri, Amedeo ; Palazzini, Juan M. ; Proctor, Robert H. ; Rahayu, Endang S. ; Ramírez, Maria L. ; Samson, Robert ; Stroka, Jörg ; Sulyok, Michael ; Sumarah, Mark ; Waalwijk, Cees ; Zhang, Qi ; Zhang, Hao ; Logrieco, Antonio F. - \ 2018
Toxins 10 (2018)3. - ISSN 2072-6651
Antibodies - Biological control - Communication with non-scientists - Metabolomics - Microbiome - Multi-mycotoxin detection protocols - Nominal group discussion technique - Proteomics - Transcriptomics
MycoKey, an EU-funded Horizon 2020 project, includes a series of “Roundtable Discussions” to gather information on trending research areas in the field of mycotoxicology. This paper includes summaries of the Roundtable Discussions on Chemical Detection and Monitoring of mycotoxins and on the role of genetics and biodiversity in mycotoxin production. Discussions were managed by using the nominal group discussion technique, which generates numerous ideas and provides a ranking for those identified as the most important. Four questions were posed for each research area, as well as two questions that were common to both discussions. Test kits, usually antibody based, were one major focus of the discussions at the Chemical Detection and Monitoring roundtable because of their many favorable features, e.g., cost, speed and ease of use. The second area of focus for this roundtable was multi-mycotoxin detection protocols and the challenges still to be met to enable these protocols to become methods of choice for regulated mycotoxins. For the genetic and biodiversity group, both the depth and the breadth of trending research areas were notable. For some areas, e.g., microbiome studies, the suggested research questions were primarily of a descriptive nature. In other areas, multiple experimental approaches, e.g., transcriptomics, proteomics, RNAi and gene deletions, are needed to understand the regulation of toxin production and mechanisms underlying successful biological controls. Answers to the research questions will provide starting points for developing acceptable prevention and remediation processes. Forging a partnership between scientists and appropriately-placed communications experts was recognized by both groups as an essential step to communicating risks, while retaining overall confidence in the safety of the food supply and the integrity of the food production chain.
The status of biological control and recommendations for improving uptake for the future
Barratt, B.I.P. ; Moran, V.C. ; Bigler, F. ; Lenteren, J.C. van - \ 2018
BioControl 63 (2018)1. - ISSN 1386-6141 - p. 155 - 167.
Access and benefit-sharing - Biological control - Communication - Cost-effectiveness - IPM - Research approach - Risk assessment
Classical and augmentative biological control of insect pests and weeds has enjoyed a long history of successes. However, biocontrol practices have not been as universally accepted or optimally utilised as they could be. An International Organisation for Biological Control (IOBC) initiative brought together practitioners and researchers from widely diverse fields to identify the main limitations to biocontrol uptake and to recommend means of mitigation. Limitations to uptake included: risk averse and unwieldy regulatory processes; increasingly bureaucratic barriers to access to biocontrol agents; insufficient engagement and communication with the public, stakeholders, growers and politicians of the considerable economic benefits of biocontrol; and fragmentation of biocontrol sub-disciplines. In this contribution we summarise a range of recommendations for the future that emphasise the need for improved communication of economic, environmental and social successes and benefits of biological control for insect pests, weeds and plant diseases, targeting political, regulatory, grower/land manager and other stakeholder interests. Political initiatives in some countries which augur well for biocontrol in the future are discussed.
Best practices for the use and exchange of invertebrate biological control genetic resources relevant for food and agriculture
Mason, P.G. ; Cock, M.J.W. ; Barratt, B.I.P. ; Klapwijk, J.N. ; Lenteren, J.C. van; Brodeur, J. ; Hoelmer, K.A. ; Heimpel, G.E. - \ 2018
BioControl 63 (2018)1. - ISSN 1386-6141 - p. 149 - 154.
Access and benefit sharing - Best practices - Biological control - Genetic resources - Invertebrate biological control agent
The Nagoya Protocol is a supplementary agreement to the Convention on Biological Diversity that provides a framework for the effective implementation of the fair and equitable sharing of benefits arising out of the utilization of genetic resources, including invertebrate biological control agents. The Protocol came into force on 12 October 2014, and requires signatories and countries acceding to the Protocol to develop a legal framework to ensure access to genetic resources, benefit-sharing and compliance. The biological control community of practice needs to comply with access and benefit sharing regulations arising under the Protocol. The IOBC Global Commission on Biological Control and Access and Benefit Sharing has prepared this best practices guide for the use and exchange of invertebrate biological control genetic resources for the biological control community of practice to demonstrate due diligence in responding to access and benefit sharing requirements, and to reassure the international community that biological control is a very successful and environmentally safe pest management method based on the use of biological diversity. We propose that components of best practice include: collaborations to facilitate information exchange about what invertebrate biological control agents are available and where they may be obtained; knowledge sharing through freely available databases that document successes (and failures); cooperative research to develop capacity in source countries; and transfer of production technology to provide opportunities for small-scale economic activity. We also provide a model concept agreement that can be used for scientific research and non-commercial release into nature where access and benefit sharing regulations exist, and a model policy for provision of invertebrate biological control agents to other parties where access and benefit sharing regulations are not restrictive or do not exist.
Pest management in organic greenhouse horticulture
Messelink, G.J. - \ 2017
Acta Horticulturae 1164 (2017). - ISSN 0567-7572 - p. 361 - 369.
Aubergine - Biological control - Cucumber - Invasive pests - Sweet pepper - Tomato
The management of pests is one of the major challenges in organic greenhouse cropping systems. In this paper, I summarize the currently most problematic and persistent, as well as the newly emerging pest species in organic tomato, sweet pepper, cucumber and aubergine crops in Europe. Furthermore, I discuss 3 new developments in biological pest control with arthropod natural enemies: 1) the integration of augmentative and conservation biological control, 2) the increased use of omnivorous predators as biological control agents and 3) the presence of other factors that affect directly or indirectly the performance of pests and natural enemies, such as endophytes, plant nutrition, disease control and greenhouse climate management. Finally, I suggest some directions for future research.
Exploring opportunities to induce epizootics in greenhouse aphid populations
Dinu, M.M. ; Bloemhard, C.M.J. ; Holstein-Saj, R. Van; Messelink, G.J. - \ 2017
In: 3rd International Symposium on Organic Greenhouse Horticulture International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611603 - p. 371 - 375.
Banker plants - Biological control - Myzus persicae - Pandora neoaphidis - Sitobion avenae
Aphids are a huge problem in organic greenhouse production systems of sweet pepper, eggplant and cucumber in northern Europe. Biological control with arthropod natural enemies is often not effective, resulting in large crop losses yearly. Entomopathogenic fungi of the order Entomophthorales are known for their ability to cause epizootics and reduce host populations dramatically in a short time. These abilities make them potentially more effective biological control agents of pest species than commercially available entomopathogens of the order Hypocreales (e.g., fungi of the genus Beauveria, Metarhizium, Lecanicillium and Isaria). However, a major stumbling block to utilizing these fungi as biological control agents has been the difficulties encountered in growing them in vitro, which is one of the reasons why the biocontrol industry did not develop commercial products based on these fungi. Another approach in utilizing these fungi could be to try inducing epizootics by introducing inoculum of infected aphids into the crop. Here we present our attempts to induce such epizootics with banker plants of wheat with grain aphids infected by the entomophthoralean fungi Pandora neoaphidis. The system of introducing "Pandora bankers" has now been applied by 8 organic greenhouse growers in The Netherlands with various results. The requirements for causing a successful epizootic with this fungus will be discussed.
Predation of Tuta absoluta eggs during the nymphal stages of three neotropical mirid predators on tomato
Lenteren, Joop C. Van; Bueno, V.H.P. ; Smit, Jolein ; Soares, Marianne A. ; Calixto, Ana M. ; Montes, Flavio C. ; Jong, Peter De - \ 2017
Bulletin of Insectology 70 (2017)1. - ISSN 1721-8861 - p. 69 - 74.
Biological control - Campyloneuropsis infumatus - Engytatus varians - Macrolophus basicornis - Miridae - Tomato borer

Tuta absoluta (Meyrick), a key pest of tomato, is quickly spreading over the world. We are evaluating the biology and pest control capacity of three Neotropical mirid species, Campyloneuropsis infumatus (Carvalho), Engytatus varians (Distant) and Macrolophus basicornis (Stal). Here we report about the predation of T. absoluta eggs by all nymphal stages of the three mirid species. A tomato leaflet with ad libitum prey was offered to a newly-emerged 1st instar nymph of a mirid predator and kept at 24 ± 1 °C, 70 ± 10% RH and 12-h photophase. Daily, the developmental stage of the nymph, as well as the number of eggs consumed was noted, and a new leaflet with eggs was added. Observations ended after nymphs had developed into adults and their sex had been determined. The average number of prey eaten by nymphs increased with nymphal age, and the 5th nymphal instar consumed higher numbers of prey than all earlier instars together. Total nymphal predation was 315, 393 and 331 T. absoluta eggs and total nymphal development took 16.9, 16.6 and 17.9 days for C. infumatus, E. varians and M. basicornis, respectively. Female nymphs of M. basicornis consumed significantly more prey than male nymphs. Nymphal survival of the three mirid species was 93%. The adult sex ratios of E. varians and M. basicornis did not deviate from a 1: 1 ratio, whereas the sex ratio of C. infumatus was significantly female biased. Nymphal predation of these three Neotropical mirids was higher than values reported for any other mirid predator, which, together with their earlier published positive characteristics, make them interesting candidates for biological control of T. absoluta.

Occurrence and diversity of fungal pathogens associated with water hyacinth and their potential as biocontrol agents in the Rift Valley of Ethiopia
Gebregiorgis, Firehun ; Struik, P.C. ; Lantinga, E.A. ; Tessema, Taye - \ 2017
International Journal of Pest Management 63 (2017)4. - ISSN 0967-0874 - p. 355 - 363.
Biological control - Eichhornia crassipes - fungal pathogens - multivariate analysis - native bio-agents - pathogenicity - risk assessment - water hyacinth

Water hyacinth poses serious socio-economic and environmental problems in Ethiopia. To integrate fungal pathogens into water hyacinth management, a survey was conducted in the Rift Valley of Ethiopia. Based on morphological characterization and DNA sequencing, 25 fungal species were identified that belong to nine genera. Alternaria tenuissima, A. alternata, Aspergillus niger, Phoma sp., Curvularia trifolii, Mucor fragilis, M. racemosus, A. fumigatus, Fusarium oxysporum, and F. equiseti were the most common fungi detected. However, their occurrence was influenced by water wave action, temperature, season, and altitude. Among the fungal pathogens, A. alternata, A. tenuissima, F. oxysporum, F. equiseti, and Neofisicoccum parvum were highly pathogenic to water hyacinth. Alternaria alternata and A. tenuissima did not cause disease symptoms on ecologically important plant species (e.g. Noug, Tef, and Coffee). Application of the fungal pathogens on water hyacinth plants also showed 11%–67%, 22%–72%, 15%–55%, and 12%–50% reduction in fresh weight, dry weight, plant height, and root length of water hyacinth, respectively. This study suggests that fungal species have the potential to control water hyacinth biologically and provides baseline data for biological control efforts in the future.

New species of Megastylus (Hymenoptera: Ichneumonidae: Orthocentrinae) reared from larvae of Keroplatidae fungus gnats (Diptera) in a Dutch orchid greenhouse
Humala, Andrei E. ; Kruidhof, Marjolein ; Woelke, Joop - \ 2017
Journal of Natural History 51 (2017)1-2. - ISSN 0022-2933 - p. 83 - 95.
Biological control - Lyprauta - orchid root damage - parasitoid - Proceroplatus

A new parasitoid wasp species belonging to the genus Megastylus (Hymenoptera: Ichneumonidae: Orthocentrinae) found in an orchid nursery in The Netherlands is described and illustrated: Megastylus woelkei sp. nov. It was reared from parasitized larvae of fungus gnats (Diptera: Keroplatidae). The biology of this new species and the possibility to use it in biological pest control are briefly discussed.

Controlling powdery mildew (Sphaerotheca mors-uvae) of gooseberry (Ribes uva-crispa) with potassium bicarbonate and risk of phytotoxicity
Wenneker, M. - \ 2016
Acta Horticulturae 1133 (2016). - ISSN 0567-7572 - p. 515 - 520.
Alternative fungicides - Biological control - Efficacy - Phytotoxicity - Small fruits

Powdery mildew (Sphaerotheca mors-uvae) severely infects young shoots, stems and fruits of gooseberry (Ribes uva-crispa). Environmental friendly and biological control measures are being sought throughout the world. Especially in organic currant growing effective control measures are needed, because powdery mildew infections may result in a total loss of the crop. In organic currant growing the number of adequate control methods is very limited. Sulphur as a fungicide against powdery mildew in e.g., gooseberry or table grape growing is not recommendable due to possible bleaching of berries and scorching of tender shoots. Various bicarbonate salts are suggested as a good option to control powdery mildew. In a series of experiments the effect of potassium bicarbonate (formulated and unformulated products) on powdery mildew of gooseberry was evaluated. In the trials different strategies were tested; i.e., preventive and curative strategies. The percent of infected berries, shoots and disease severity were assessed. Very high disease incidences were observed in the untreated control. All potassium bicarbonate treatments significantly reduced the powdery mildew severity in leaves and fruits compared to the untreated controls. The preventive strategies were very successful. However, the number of spray applications was high. Frequently, a severe phytotoxicity caused by potassium bicarbonate was observed. Several experiments were performed with different dosages, timing of sprayings and spray intervals. The potential and limitations of potassium bicarbonate used to control powdery mildew in the field are discussed.

Towards a system of non-chemical flower thrips control in strawberry production
Kruistum, G. van; Belder, E. den - \ 2016
Acta Horticulturae 1117 (2016). - ISSN 0567-7572 - p. 133 - 138.
Ananassa - Biological control - Fragaria × - IPM - Mulching - Orius majusculus - Predatory mites - Thrips major

Different flower thrips species (Thrips major/T. fuscipennis, Frankliniella intonsa) feed on strawberry fruit causing severe production losses. Because of the zero tolerance in The Netherlands for thrips damage the pyrethroid deltamethrin (Decis) is sprayed during blooming. Since 2013 there is a restriction in number of sprays and spraying during blooming is prohibited because of the negative effect on pollinators and natural enemies. A robust integrated pest management system could reduce chemical sprays significantly. Reducing residue levels enhance the positive image of fruit consumption. During the summers of 2012 and 2013 an IPM strategy for control of flower thrips was tested in strawberry field trials ('Elsanta'). Biological control was enhanced by the predatory bug Orius majusculus. In 2012 and 2013 the effect of mulching by white plastic film was also studied. To lure and retain Orius bugs in the crop, dispensers with the attractant methyl salicylate and Alyssum plants were placed in treated plots. From mid-July control of flower thrips by natural enemies was comparable to chemical control with deltamethrin. Good results in reducing thrips larvae in the flowers were also obtained using white plastic mulch. A combination of measures could lead to a robust system of non-chemical flower thrips control in strawberry in the near future.

Predicting the potential establishment of two insect species using the simulation environment INSIM (INsect SIMulation)
Hemerik, Lia ; Nes, Egbert H. van - \ 2016
Entomologia Experimentalis et Applicata 159 (2016)2. - ISSN 0013-8703 - p. 222 - 229.
Podisus maculiventris - Biological control - Degree-day model - Development - Drosophila suzukii - Invasive species - Life history - Mortality - Reproduction - Temperature-dependent

Degree-day models have long been used to predict events in the life cycle of insects and therewith the timing of outbreaks of insect pests and their natural enemies. This approach assumes, however, that the effect of temperature is linear, whereas developmental rates of insects are non-linearly related to temperature. Therefore, we have developed the simulation tool INSIM (INsect SIMulation) that can easily handle non-linear temperature relationships, because the program interpolates between measured growth, mortality, and reproduction parameter values given at two subsequent ambient temperatures. We use the tool for predicting the establishment of two insect species. For the application of the biological control agent Podisus maculiventris (Say) (Hemiptera: Pentatomidae) in The Netherlands, we compare a linear and a non-linear function for the development. The number of adult females increases six-fold in the course of a year for the non-linear case, suggesting that the Dutch climate might be warm enough for this beneficial insect to settle. The implementation of a linear development rate shows approximately the same increase. For the invasive pest Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) in The Netherlands, we assessed that it is probably well-adapted to the current Dutch climate: it is predicted to establish easily in most of the simulated scenarios. However, if it were only to attack blueberries (and not cherries), its invasion success is predicted to be limited, because the reproduction in blueberries is low. The implementation of a linear development rate gives rise to 50% fewer adult females (on cherry) or even 95% fewer (on blueberry) after a year. More data are needed for both systems, specifically on overwintering survival for P. maculiventris and for D. suzukii on lifetime reproduction at various temperatures and in different fruit hosts. From the implementation of the linear rate model we can see that, depending on how well the linear approximation is, the results may differ considerably. We have demonstrated that the INSIM program is a useful tool that can easily be adapted to predict the success and individual variation for different insect species.

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