Fresh root fragments ofRumex crispusandRumex obtusifolius, which initially contain 65-70% moisture, progressively lose moisture when desiccated under conditions matching summer weather in southeast England. The likelihood of shoot emergence and the time it took in glasshouse conditions were both affected by desiccation, withR. crispusthe most affected up to 48 hr andR. obtusifoliusslower to emerge after 48 hr. These effects converged after longer desiccation periods, andR. crispusentirely failed to emerge after 120 hr. The dry weight of emerged shoots was not significantly different between the species until they were desiccated for 96 hr, after whichR. obtusifoliusdry weight was significantly reduced. In outdoor trials, desiccation for 24 or 48 hr had a lesser effect on emergence in either species when fragments were planted at the soil surface or at up to a depth of 10 cm, compared to deeper plantings, but emergence was significantly lower in plantings at 15 or 20 cm. Emergence delays were not significantly different between the species until they were planted at 15 or 20 cm, whenR. obtusifoliuswas slower to emerge thanR. crispus, an effect exacerbated by increasing desiccation. Similar interactions of increasing soil depth and desiccation were found in reductions in dry weight, number of tillers and leaf area, withR. obtusifoliusgenerally, but not exclusively, better able to withstand more extreme trial conditions. Our findings suggest that control of these highly troublesome weeds can be assisted by appropriate agricultural practices, notably exposing cut fragments to drying conditions followed by deep burial.

Cocoa mirids are the most important insect pests of cocoa in West Africa. This study investigated the effect of environmental parameters that are modulated by overhead shade, that is, light intensity and temperature, on nutrient and phenolic concentrations in cocoa and their subsequent effect on mirid feeding. Eight-month-old cocoa seedlings were maintained for 50 days in two growth chambers set to day temperatures of 25 or 30 degrees C. Each chamber had sections with different light intensities (541, 365 and 181 mu mol m(-2)s(-1)photosynthetically active radiation [PAR]). For the field studies at Akim Tafo in Ghana, 8-month-old plants of three cocoa clones were subjected to shaded (PAR = 180 mu mol m(-2)s(-1), between 11:00 a.m. and 12:00 p.m.) and unshaded (PAR = 1,767 mu mol m(-2)s(-1), between 11:00 a.m. and 12:00 p.m.) treatments for 50 days after which nutrient measurements and mirid choice tests were carried out. No significant effect of environment was observed on the phenolic concentration of stems under controlled environment chamber conditions. However, in the field, the phenolic concentration of stems was significantly greater for unshaded compared with shaded plants (p= .04). Under controlled conditions, the leaf nitrogen concentration increased slightly with light intensity (p= .003). The same trend was seen in stems but only at 30 degrees C. In the field, the impact of overhead shade on nitrogen varied between cocoa clones. The concentration of carbohydrates in both leaves and stems in the field was higher under unshaded conditions. When subjected to feeding tests, stems from unshaded cocoa had significantly more mirid feeding lesions (p= .003) after 24 hr exposure to mirids compared to shaded cocoa. Mirid feeding therefore appears not to be deterred by the higher phenolic levels but rather there was a preference for cocoa tissue grown under unshaded conditions. These findings highlight the need to consider the growing environment of cocoa clones when screening for varieties with resistance to mirids.

Docks (Rumex spp.) are a considerable problem in grassland production worldwide. We investigated how different cultural management techniques affected dock populations during grassland renewal: (I) renewal time, (II) companion crop, (III) false seedbed, (IV) taproot cutting (V), plough skimmer and (VI) ploughing depth. Three factorial split-split plot experiments were carried out in Norway in 2007-2008 (three locations), 2008-2009 (one location) and 2009 (one location). After grassland renewal, more dock plants emerged from seeds than from roots. Summer renewal resulted in more dock seed and root plants than spring renewal. Adding a spring barley companion crop to the grassland crop often reduced dock density and biomass. A false seedbed resulted in 71% fewer dock seed plants following summer renewal, but tended to increase the number of dock plants after spring renewal. In some instances, taproot cutting resulted in less dock biomass, but the effect was weak and inconsistent, and if ploughing was shallow (16 cm) or omitted, it instead increased dock root plant emergence. Fewer root plants emerged after deep ploughing (24 cm) compared to shallow ploughing, and a plough skimmer tended to reduce the number further. We conclude that a competitive companion crop can assist in controlling both dock seed and root plants, but it is more important that the renewal time is favourable to the main crop. Taproot cutting in conjunction with ploughing is not an effective way to reduce dock root plants, but ploughing is more effective if it is deep and a skimmer is used.

Mirids (Sahlbergella singularis and Distantiella theobroma) are the most important insect pests affecting cocoa production across West Africa. Understanding the population dynamics of mirids is key to their management; however, the current recommended hand-height assessment method is labour intensive. The objective of the study was to compare recently developed mirid sex pheromone trapping and visual hand-height assessment methods as monitoring tools on cocoa farms and to consider implications for a decision support system. Ten farms from the Eastern and Ashanti regions of Ghana were used for the study. Mirid numbers and damage were assessed fortnightly on twenty trees per farm, using both methods, from January 2012 to April 2013. The mirid population increased rapidly in June, reached a peak in September and began to decline in October. There was a significant linear relationship between numbers of mirids sampled to hand-height and mirid damage. High numbers of male mirids were recorded in pheromone traps between January and April 2012 after which there was a gradual decline. There was a significant inverse relationship between numbers of trapped adult mirids and mirids sampled to hand-height (predominantly nymphs). Higher temperatures and lower relative humidities in the first half of the year were associated with fewer mirids at hand-height, but larger numbers of adult males were caught in pheromone traps. The study showed that relying solely on one method is not sufficient to provide accurate information on mirid population dynamics and a combination of the two methods is necessary.

The green peach aphid, Myzus persicae, is a major insect pest worldwide. The parasitoid Aphidius colemani and more recently, the entomopathogenic fungus Lecanicillium muscarium strain KV01 ( Mycotal (R)), have been considered as potential biological control against M. persicae. However, no studies have been carried out on the interaction between L. muscarium and A. colemani against M. persicae. This study, therefore, was conducted to determine the most effective timing of application of this fungal strain in combination with either naturally occurring or introduced parasitoids to control Myzus persicae in the laboratory and controlled field environments. In the laboratory, mummification, emergence of parasitoid adults from mummified aphids and female sex ratio of the emerging adults, were not affected when the fungus was applied 6 or 7 days after the parasitoids were added, compared with treatment with A. colemani only. Although a 40% reduction in the female sex ratio of emerging parasitoid adults was recorded when fungi applied 3 days after the parasitoids were added, fungal application had no significant effect on longevity and fecundity of the female A. colemani F1 generation that emerged from fungus-treated aphids. In the semi-field experiment, the mean number of aphids per leaf was significantly lower in the treatment involving A. colemani in combination with L. muscarium than those with A. colemani alone. However, aphid reduction in the treatments involving naturally occurring parasitoids alone and those in combination with L. muscarium was not significantly different. This study suggests that it is possible to combine L. muscarium with A. colemani to increase the level of aphid control. A more detailed knowledge of the effects of naturally occurring parasitoids on pest control and their interaction with other biological control agents will help to develop environmentally sound crop management strategies with reduced insecticide applications.

The green peach aphid, Myzus persicae, is a major pest worldwide. An examination of the impact of temperature, relative humidity (RH) and developmental stages of M. persicae on the efficacy of the whitefly mycoinsecticide Mycotal (R), based on Lecanicillium muscarium and the effects of infection on aphid fecundity was evaluated under controlled conditions. Although this fungus can be grown at a broad range of temperatures (15-30 degrees C), the optimum temperature for control of M. persicae ranged between 20 and 30 degrees C. L. muscarium had high efficacy as a microbial control agent against M. persicae between 55% and 90% RH. Total mortality of aphids treated with different spore dosages of L. muscarium varied according to the developmental stage: adults, fourth and third instar nymphs proved more susceptible than first instar nymphs. Although the fungus did not affect the rate of nymph production, the reproductive period of aphids significantly decreased with increasing the spore dosage. Thus, total fecundity of treated aphids was 22.6 +/- 1.1 and 31.6 +/- 2.4 offspring per adult at the medium (644 +/- viable spore/mm(2)) and low (330 +/- 40 viable spore/mm(2)) dosages, compared with 45.7 +/- 4.3 offspring per untreated aphid. The results suggest that L. muscarium has the potential as a biological control agent of M. persicae.

Annual losses of cocoa in Ghana from mirids are significant; therefore, accurate timing of insecticide application is critical to enhance yields. However, cocoa farmers often lack information on the expected mirid population for each season to enable them to optimize pesticide use. This study assessed farmers’ knowledge and perceptions of mirid control and their willingness to use forecasting systems informing them of the expected mirid peaks and the time of pesticide application. A total of 280 farmers were interviewed in the Eastern and Ashanti regions of Ghana with a structured open- and closed-ended questionnaire. Most farmers (87%) considered mirids the most important insect pest on cocoa, with 47% of them attributing 30–40% of annual crop losses to mirid damage. There was a wide variation in the timing of insecticide application as a result of farmers using different sources of information to guide the start of application. The majority of farmers (56%) did not have access to information about the type, frequency and timing of insecticide use. However, respondents who were members of farmer groups had better access to such information. Extension officers were the preferred channel for information transfer to farmers, with 72% of farmers preferring them to other available methods of communication. Almost all the respondents (99%) saw the need for a comprehensive forecasting system to help farmers manage cocoa mirids. The importance of the accurate timing of mirid control based on forecasted information to farmer groups and extension officers is discussed.

One of the aims of the Editorial Board of Weed Research is to help authors with publishing the best weed science. Towards the end of 2014, the Author Guidelines for Weed Research that are hosted online at http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-3180/homepage/ForAuthors.html and are printed in each issue of the journal were revised. Most of the changes were minor, but discussions within the Editorial Board and correspondence with authors indicate that an explanation of journal policies would be helpful and timely. The aim of this editorial is therefore to present the aims of the journal and the expectations the Editorial Board have in regard to papers the journal should be publishing. This should help authors, particularly in assessing the reasons why papers are not accepted for publication. A number of passages in this editorial are taken directly from the Author Guidelines and are given in italics. In 2014, the journal received the highest number of submissions ever, and whilst submission rates in 2015 have dropped back, it is clear that a significant number of papers are rejected without external review. We explore the reasons for this, in terms of journal policies, with the aim of helping potential authors. The Editor-in-Chief (EiC) and the Editorial Board have two critical roles. First, they must uphold the quality and scientific and ethical integrity of this international journal. Secondly, they seek to help authors to communicate the best science. Balancing these roles is not easy, but if successful, it will ensure that the journal will continue to be the leading weed science journal across the globe. In addition to providing comments on submissions to authors, editors will strive to handle papers as quickly as possible, whilst conducting peer review rigorously. The average time to first decision was 67 days for papers submitted in 2014 and the board will be aiming to reduce this time, so authors can progress their scripts quickly. The aim of the journal is to publish the best weed science from around the globe and to be the journal of choice for weed science researchers. This sentence captures exactly our aims of attracting and publishing the best weed science research. So, we seek new work, innovative research and critically we expect papers to be sufficiently robust that the results can be generalised beyond the experimental conditions used. The factors that are taken into account in accepting a manuscript are summarised as follows: originality, relevance, scientific rigour and the clarity of presentation. Aspects of these factors are discussed further below, but it may be useful to outline the four different types of manuscript that Weed Research now publishes. The journal publishes Original Research papers, Reviews, Methods and Insights. We will also publish Priority papers, where the review and editing process has been expedited, to bring important work with time-sensitive results into the public domain. This could apply to any of the four types of paper. Most submissions are Original Research papers and the comments within this editorial are particularly addressed at such manuscripts. However, there are particular requirements for the other three types of paper. We encourage the submission of review papers, but these need to be more than a simple gathering of information on a topic. Review papers should critically evaluate the subject area and identify new conclusions and gaps in knowledge, rather than simply presenting summaries of previous work. Papers may be longer than research articles at the discretion of the editors. To go further, a review should have explicit aims and objectives against which the conclusions can be evaluated. For example, this could be to critically evaluate breakthroughs in a topic area or to identify gaps in research. Methods papers should be prepared as original research articles. These should evaluate new techniques against existing methods, where possible, so that any advantages or disadvantages are clear. A new method may be interesting, but if it is not compared with existing approaches or at least carefully put in to context, its relevance may be too low for Weed Research. Insights papers have been published in the journal for eight years, but they are not straight forward. Whilst many authors think these are short communications, that is with small pieces of research, this is not the aim the Editorial Board has for such articles. These articles were introduced to increase the immediacy impact rating of the journal. Our Guidelines state The journal will accept short Insights articles up to 2500 words in total covering personal views, new methods and breaking news in weed science. These articles may cover scientific opinions, new methods or proof-of-concepts, as well as important and topical pieces of research that require further validation. Key criteria are that the content is of wide interest to weed scientists, is novel and is likely to significantly advance weed science. Thus, short pieces of work may be suitable, but only if it can be demonstrated that the work is of wide interest and likely to lead to significant scientific advances. A small study of limited interest will not succeed. Opinion pieces with good scientific evidence and argument and that elicit reactions amongst reviewers are more likely to be published. We suggest that authors considering reviews or Insights papers contact the Editor-in-Chief with a summary of the paper for comment. ‘Original and innovative research papers relevant to weed biology, ecology and management are sought. There should be sufficient material presented so that the information is of wider interest than just for local conditions’. What does original and innovative mean? Most journals demand ‘novelty’, meaning that the work has not been done before and that is certainly the case with Weed Research. Generally, we expect to see new data with new or extended approaches. But what about old approaches on new species or new situations? This is an area of some subjectivity, but if one can say ‘this confirms someone else's results’ throughout a manuscript, it is unlikely to be novel findings and is likely to be rejected. Further than that, the journal is not looking to catalogue information and certainly does not aim to house all the information on every weed in every situation. As editors, we are looking for work that advances weed science, so using tried and tested approaches is unlikely to bring new insights. Ask the question: Why should this work be of interest to and important for weed scientists in other countries? We often ask that the end of the summary closes with sentences that capture the implications of the reported results (note that speculation is to be avoided) for (a) weed science theory and/or (b) practical weed management. If these can be clearly articulated, the sentences usually express why the paper is important for an international audience and confirm the originality of the work. Authors should aim to convince the editor of the importance of their work in a global context. This is a key area that seems to be a problem in many submissions to the journal. The aims and scope states there should be sufficient material presented so that the information is of wider interest than just for local conditions. Thus, single experiments are unlikely to be acceptable. Research should cover sufficient temporal and spatial variation to be able to make sound generalisations. For example, evaluation of herbicide efficacy should be over more than one year at more than one site or soil type. Editors will evaluate amounts of work on a case by case basis, checking that a design provides a robust test of the hypothesis in question. Appropriate replication is the key, so authors need to consider how temporal and/or spatial variation is addressed. A simple question to ask is ‘Would the same results occur if the work was repeated elsewhere (locally, regionally, nationally or globally), or repeated in a different season or year?’ If a paper cannot safely provide some insight into such considerations, we are unlikely to accept. For most laboratory and glasshouse studies, we expect experiments to be repeated and for there to be clarity (with evidence provided) in how the repeated data are analysed. Of course, there are many exceptions, for example where single experiments are used to generate parameters for modelling studies that form the main focus of a paper. A series of experiments that develop insights into a particular question also may not require replication. Thus, editors will evaluate manuscripts individually. The Editor-in-Chief makes a series of checks on a manuscript to see that it is of sufficient merit for further review. The paper needs to be novel, innovative and with sufficient material to provide evidence of robust results. The EiC cannot be an expert on every subject, so if they are uncertain, the paper will be allocated to a Subject Editor, who will carry out similar evaluations. All papers allocated to Subject Editors are checked using the iThenticate software for plagiarism. At this stage, papers may be returned to authors, most often if the paper is outside the scope of the journal, the manuscript has not been prepared in the journal style, there is insufficient material or the content is such that it does not merit the time and academic commitment provided by reviewers. The policies in regard to novelty and amounts of work in a manuscript are applied to all submissions. The Editorial Board has concerns over repeating particular approaches, which could be viewed as cataloguing. Examples include studies of germination conditions and dormancy, and three further examples are mentioned below and in the Aims and Scope of the journal, to illustrate the point. The journal will only take papers that investigate allelopathy under field-like conditions. The journal will now only take papers on allelopathy that advance the science into the real world. There have been many hundreds of studies and submissions describing the effects of plant extracts on seed germination in Petri dishes. So far as we are aware, not a single practical development in weed management has resulted from all this work, reflecting the fact that interactions in the rhizosphere are complex and bear little if any relation to conditions in Petri dishes. Thus, we expect work submitted to the journal to include studies in soil and also to consider mechanisms. Cases of herbicide resistance should be novel and demonstrate clear conceptual advances in the field of resistance research. Cataloguing cases of resistance in species with a known propensity for resistance evolution with resistance-prone herbicides, whilst important for informing local weed management decisions, is not sufficiently novel for publication. An Insights article published a few years ago (Neve, 2007) closed with a plea for testing new hypotheses, over cataloguing resistance in new species or locations. The journal policy echoes this by looking for new developments and new mechanisms, over simply reporting new cases of resistance. We accept that knowing resistance is developing is important for local weed management, but reporting new cases of existing resistance mechanisms is not usually sufficient for publication. There have been a series of papers in the journal reporting the likely distributions of species based on climate envelopes. These modelling approaches have provided some fascinating insight into potential weed distributions under changing climate conditions (e.g. Kriticos et al., 2011; McConnachie et al., 2011). The models that have been used, such as CLIMEX and MAXENT, could be applied to every weed, where there is sufficient data. However, we are at the stage when such studies are becoming a cataloguing exercise, so we now require that predictions of the effect of climate change on species distributions should go beyond output from simple models. There are other factors that affect occurrence that need to take the science forward. These three areas should be taken as examples of where the Editorial Board deem that the science is moving into a cataloguing stage and that the journal should take care that its papers move the science forward. There are a number of other areas where the board may reject on the grounds of lack of novelty, repetition and lack of scientific interest. As the journal of the European Weed Research Society, it should be understood that the majority of editors and authors have English, the language of the journal, as a second or third language. The board and the EiC are mindful that writing in a second language is difficult and perhaps the greatest challenge to the majority of scientists. However, clarity of the writing is essential. The object of publishing a paper is to communicate accurately the work that has been done, not to obscure the work with complicated expression. The policy of the board and the EiC is guided by the strength of the science within a submission. If the writing is poor, but the science is strong, then editors will try to help authors during the review process. However, if the writing is poor and the science is not very exciting, then papers are unlikely to be sent for external review and will be rejected. There are many editing services available, both free and commercial, that can help with editing. However, we often recommend that authors ask a native English speaker, preferably a weed scientist, to help with editing a paper prior to submission. A further aspect of presentation is the journal style. Each journal has a particular style, including how references are presented. Whilst submitting in the correct style may seem a minor issue, please consider that if the paper is accepted, the EiC could spend hours making final adjustments for style. If you can put the manuscript in the correct style at the outset, using the Word template file provided online with the Author Guidelines and bibliographic software for references, such as EndNote, then the editors are more likely to not make an initial rejection of the paper! The journal has a team of Statistical Consultants who provide support for the Editorial Board. The consultants are truly international, thus having a range of languages and their contact details can be found via the EiC. The Statistical Consultants can advise authors on statistical issues, but cannot analyse their data. The expectations in regard to the use and presentation of statistics in the journal have been published (Onofri et al., 2010). The paper is available as a free download from the journal homepage, and we recommend that it should be consulted by all authors. Please take care to present appropriate measures of error with data in tables and figures, so that readers can apply their own tests of significance. In general, we are unlikely to publish percentage data without the raw data analysed alongside and editors will look for appropriate replication to support general conclusions. The journal is seeking to publish the best weed science research that will become highly cited and maintain the impact of Weed Research. This editorial aims to highlight what editors are looking for in manuscripts, in terms of novelty, amount of work, clarity of writing and presentation, which will satisfy our aims. Published work needs to be new, and there needs to be enough to make at least some safe generalisation of the results. Are the results relevant beyond the experimental conditions? Work that is adding to a catalogue of results is unlikely to succeed. If you are unsure about scope or content, do email the EiC with a summary of the paper for comment. In preparing a paper, get the paper checked and edited by colleagues before submission. Use the correct journal style, so that you do not waste the time of the editors during revision. In return, the board will strive to handle papers quickly and to provide a sound peer review service. If authors require clarification or comment prior to submission, feel free to contact the Editor-in-Chief. Harald Albrecht, TUM, Germany Karen Bailey, Canada Lammert Bastiaans, WUR, The Netherlands Diego Batlla, Universidad de Buenos Aires, Argentina Christian Bohren, Agroscope, Switzerland Graeme Bourdôt, AgResearch, New Zealand David Clements, Trinity Western University, Canada Henri Darmency, INRA, France Adam Davis, USDA-ARS, USA Christophe Délye, INRA, France Rob Freckleton, Sheffield, UK Guillaume Fried, Anses, France Claudio Ghersa, IFEVA UBA-CONICET, Argentina José Gonzalez-Andujar, CSIC, Spain Paul Hatcher, Reading, UK Pietro Iannetta, James Hutton Institute, UK Corné Kempenaar, WUR, The Netherlands Do-Soon Kim, Seoul, Korea Per Kudsk, Aarhus University, Denmark Matt Liebman, Iowa, USA Bert Lotz, WUR, The Netherlands Anna-Camilla Moonen, Scuola Superiore Sant'Anna di Pisa, Italy Paul Neve, Rothamsted Research, UK Stephen Novak, Boise, USA Lisa Rew, Montana, USA Brian Schutte, New Mexico State, Las Cruces, USA Richard Smith, University of New Hampshire, USA Jonathan Storkey, Rothamsted Research, UK Clarence Swanton, Guelph, Canada Francesco Tei, Perugia, Italy Maurizio Vurro, CNR Bari, Italy Paula Westerman, Rostock, Germany Peter Zwerger, JKI, Germany Raúl Macchiavelli (UPRM, Puerto Rico) Martin Mortimer (Liverpool, UK) Andrea Onofri (Perugia, Italy) Hans-Peter Piepho (Hohenheim, Germany)

Phytophagous insects have to contend with a wide variation in food quality brought about by a variety of factors intrinsic and extrinsic to the plant. One of the most important factors is infection by plant pathogenic fungi. Necrotrophic and biotrophic plant pathogenic fungi may have contrasting effects on insect herbivores due to their different infection mechanisms and induction of different resistance pathways, although this has been little studied and there has been no study of their combined effect. We studied the effect of the biotrophic rust fungus U romyces viciae‐fabae ( P ers.) S chroet ( B asidiomycota: U redinales: P ucciniaceae) and the necrotrophic fungus B otrytis cinerea P ers. ( A scomycota: H elotiales: S clerotiniaceae) singly and together on the performance of the aphid A phis fabae S copoli ( H emiptera: A phididae) on V icia faba ( L .) ( F abaceae). Alone, botrytis had an inhibitory effect on individual A . fabae development, survival, and fecundity, whereas rust infection consistently enhanced individual aphids' performance. These effects varied in linear relation to lesion or pustule density. However, whole‐plant infection by either pathogen resulted in a smaller aphid population of smaller aphids than on uninfected plants, indicating a lowering of aphid carrying capacity with infection. When both fungi were applied simultaneously to a leaf they generally cancelled the effect of each other out, resulting in most performance parameters being similar to the controls, although fecundity was reduced. However, sequential plant infection (pathogens applied 5 days apart) led to a 70% decrease in fecundity and 50% reduction in intrinsic rate of increase. The application of rust before botrytis had a greater inhibitory effect on aphids than applying botrytis before rust. Rust infection increased leaf total nitrogen concentration by 30%, whereas infection by botrytis with or without rust led to a 38% decrease. The aphids' responses to the two plant pathogens individually is consistent with the alteration in plant nutrient content by infection and also the induction of different plant defence pathways and the possible cross‐talk between them. This is the first demonstration of the complex effects of the dual infection of a plant by contrasting pathogens on insect herbivores.

Acknowledgements. Chapter 1 Introduction. PART 1 EXPLOITED. Chapter 2 Sargassum and the Sargasso Sea. Chapter 3 Cephalopods. Chapter 4 The Honey Bee. Chapter 5 Sericulture: Silkworms and Mulberries. Chapter 6 Sugar Cane. Chapter 7 Legumes. Chapter 8 The Grapevine. Chapter 9 The Salmon. Chapter 10 Oak. Chapter 11 The Rabbit. PART 2 EXPLOITERS. Chapter 12 Malaria. Chapter 13 Biofouling and the Barnacle. Chapter 14 Bracken. Chapter 15 The Locust. Chapter 16 Plague. Chapter 17 The Red Kite. Chapter 18 Parasitic Plants: Mistletoes. Chapter 19 The Wolf. Index.

Plants can respond to damage by pests with both induced direct defences and indirect defences by the attraction of their natural enemies. Foliar application of several plant-derived chemicals, such as salicylic acid and oxalic acid, can induce these defence mechanisms. The effect of acetylsalicylic acid and oxalic acid on the aphid Myzus persicae Sulzer (Homoptera: Aphididae) and its parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae) was investigated. Experiments were carried out with direct application of acetylsalicylic and oxalic acids on these insects, as well as choice and no-choice tests using foliar application of both chemicals on Brussels sprouts plants, Brassica oleracea var. gemmifera L. (Brassicaceae). Parasitoids were given a choice between treated and untreated plants for oviposition, and the effects of the chemicals on aphid and parasitoid development were determined. Although direct application of both chemicals increased aphid mortality, their foliar application did not induce resistance against aphids. The foliar application of such compounds, even in low concentration as shown in the choice tests, has the potential to induce indirect plant defences against aphids by encouraging aphid parasitisation. Although the direct application of both chemicals reduced parasitoid emergence from their hosts, the foliar application of acetylsalicylic acid and low concentrations of oxalic acid did not have a negative effect on parasitoid emergence ability. However, 10 mm oxalic acid reduced the number of emerged parasitoids in no-choice experiments. This study shows that foliar application of acetylsalicylic and oxalic acids has the potential to encourage aphid parasitisation, but care is needed as high concentrations of oxalic acid can have a negative effect on these beneficial organisms.