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Evidence Project Final Report

EVID4 Evidence Project Final Report (Rev. 06/11) Page 1 of 22

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NoteIn line with the Freedom of Information Act 2000, Defra aims to place the results of its completed research projects in the public domain wherever possible. The Evidence Project Final Report is designed to capture the information on the results and outputs of Defra-funded research in a format that is easily publishable through the Defra websiteAn Evidence Project Final Report must be completed for all projects.

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Project identification

1. Defra Project code PS2142

2. Project title

Review the scope for using natural plant products to reduce reliance on conventional insecticides

3. Contractororganisation(s)

ADAS UK Ltd

54. Total Defra project costs £ 17,360(agreed fixed price)

5. Project: start date................ 1 November 2012

end date................. 31 July 2013


6. It is Defra’s intention to publish this form. Please confirm your agreement to do so......................................................................................YES √ NO (a) When preparing Evidence Project Final Reports contractors should bear in mind that Defra intends that

they be made public. They should be written in a clear and concise manner and represent a full account of the research project which someone not closely associated with the project can follow.Defra recognises that in a small minority of cases there may be information, such as intellectual property or commercially confidential data, used in or generated by the research project, which should not be disclosed. In these cases, such information should be detailed in a separate annex (not to be published) so that the Evidence Project Final Report can be placed in the public domain. Where it is impossible to complete the Final Report without including references to any sensitive or confidential data, the information should be included and section (b) completed. NB: only in exceptional circumstances will Defra expect contractors to give a "No" answer.In all cases, reasons for withholding information must be fully in line with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000.

(b) If you have answered NO, please explain why the Final report should not be released into public domain

Executive Summary7. The executive summary must not exceed 2 sides in total of A4 and should be understandable to the

intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together with any other significant events and options for new work.

This project addressed one of the R&D priorities in Annex 2 of Defra’s Evidence Investment Strategy (2011), to provide evidence that will help to reduce reliance on conventional chemical pesticides by developing alternative strategies. The project investigated potential novel, alternative crop protection strategies in horticulture, for food, amenity and domestic use; specifically for control of three important UK pests with life stages on foliage and in the growing substrate: western flower thrips (WFT), Frankliniella occidentalis, vine weevil (Otiorhynchus sulcatus) and sciarid flies (Bradysia species).

The main objectives were to collect and review scientific data on potential pest management properties of plant natural products, either in planta or extracted, to interpret the results and make suggestions for future development of pest management strategies. In the absence of specific chemical data, information on plant species that affect pest behaviour or growth was also sought.

Search criteria and data table construction were agreed and established at the start of the project and these guided the information collected. The core data set in Excel contains details of plant species and their associated taxonomy, chemical data, insect species and references. The chemical data table includes (where available) CAS Registry numbers and other identifiers such as InChIKeys. The plant species and plant chemistry data are brought together with information on relevant biological activities on a combined entry table in Excel. For the purposes of the report, key data have been further organised into 24 tables on the basis of pest species and type of biological activity. These tables were all extracted from the larger combined entry table in Excel which is provided in the form of supplementary data. Whereas the project focused on three pest species, data on close relatives was also gathered.

In total, 801 data entries were made from more than 120 references, covering approximately 370 plant species and approximately 200 chemicals or extracts affecting insect pest behaviour, growth or mortality.

The findings have identified a number of areas that would benefit from future research, some specific to WFT, vine weevil or sciarid fly and others with more general relevance. Some of these are listed below, others can be found at the end of Section 8.

There are a number of strategies for increasing pest resistance that rely upon utilising in situ plant defence mechanisms including phytochemicals thereby avoiding any requirement for the application of extracts or chemicals. For instance, higher rates of nitrogen fertilization have been shown to favour WFT abundance and vine weevil oviposition and larval development, and also reduce levels of insect


antifeedants such as chlorogenic acid. Controlling nitrogen applications within the optimum range for plant growth is therefore an obvious strategy that also has environmental benefits.

Jasmonates protected plants against WFT and Bradysia; these and other known elicitors of natural plant defence mechanisms should be tested further in an agricultural context.

A finding that feeding on Taxus foliage prior to pyrethroid treatment increased knock-down of adult vine weevils indicates that it may be possible to significantly enhance the potency of approved chemical pesticides with plant extracts or phytochemicals. Relevant to all insect pests, potential plant extract synergists of pyrethrum should be sought from the scientific literature and tested for improvement of pesticidal activity.

With respect to WFT, the concentration of phytochemicals applied can be fundamental to activity as demonstrated by the contrasting activities of certain volatiles (p-anisaldehyde and salicylaldehyde) that were attractive at low concentrations and repellent when undiluted or at high concentrations. There are few known volatiles that affect the behaviour of Bradysia or vine weevil, and for WFT there is room for more potent volatile attractants (to be used in “lure-and-kill” strategies). Observations of plant species that are attractive to pests, e.g. Browallia spp. for WFT, may yield new leads for volatile attractants. Repellents are potentially valuable as extracts or single compound preparations; alternative methods include the use of plant species releasing repellent volatiles grown as companion plants with vulnerable crops or preparations incorporated into growing media.

Vine weevil - damaged roots produce volatile signals that attract natural enemies. A new class of diterpenes (rhizathalenes) with activity against feeding by Bradysia larvae has recently been discovered in Arabidopsis roots. A literature survey of root-located volatiles or semi-volatiles as potential SOS signals (i.e. that attract natural enemies) may yield a number of potential crop protection candidates for the pests reviewed here and others including molluscs and nematodes. The concept is relevant to both soil and foliage-dwelling stages of the pest life cycle and could be extended to chemical signals from aerial plant parts that may attract e.g. WFT predators.

Whereas on their own, the phytochemical actives identified in this report may only provide a partial pest control solution, in combination with other plant products, chemical insecticides, biologicals or devices they may become very effective. For example the reported lure-and-kill strategy using a commercial attractant and Metarhizium anisopliae spores to increase mortality of WFT could be extrapolated to vine weevil adults using attractants based on green plant volatiles and weevil refuge traps.

There are few reports concerning factors affecting larval development and other life-stage parameters e.g. oviposition rates, pupation and adult emergence rates in WFT and this has identified a gap in knowledge and potential area for further research.

Plant materials with pesticidal properties such as isothiocyanate-containing green manures from Brassica spp., garlic extracts and neem products may have potential for control of in particular vine weevil and Bradysia.

There appears to be plenty of scope for identification of new chemical actives in plant species observed to affect pest behaviour, potentially useful as pest control strategies in the form of extract applications, and in resistant crop cultivars, that could provide a basis for breeding targets.

The data presented here covers many different experimental methods and formats, from laboratory, glasshouse and field. Experimental variation due e.g. to source plants, method of extract preparation, application method and chemical concentration, the physiological state of the insects, and spatial scale mean that results obtained from one experimental design and location cannot be relied upon to translate to another. Many of the pest control properties of phytochemicals described in this report have only been derived from laboratory research and now need to be validated in the glasshouse or the field in combination with appropriate delivery methods and devices.

Project Report to Defra8. As a guide this report should be no longer than 20 sides of A4. This report is to provide Defra with details of

the outputs of the research project for internal purposes; to meet the terms of the contract; and to allow Defra


to publish details of the outputs to meet Environmental Information Regulation or Freedom of Information obligations. This short report to Defra does not preclude contractors from also seeking to publish a full, formal scientific report/paper in an appropriate scientific or other journal/publication. Indeed, Defra actively encourages such publications as part of the contract terms. The report to Defra should include: the objectives as set out in the contract; the extent to which the objectives set out in the contract have been met; details of methods used and the results obtained, including statistical analysis (if appropriate); a discussion of the results and their reliability; the main implications of the findings; possible future work; and any action resulting from the research (e.g. IP, Knowledge Exchange).Project objectives

The objectives of the project were to address the need for novel, alternative crop protection strategies in horticulture, for food, amenity and domestic use; specifically for control of three important UK pests with life stages on foliage and in the growing substrate: WFT, vine weevil and sciarid flies. In particular, evidence of plant natural products, either in planta or extracted, that have the potential to reduce reliance on conventional chemical pesticides were to be sought. The proposed project involved the collection and interpretation of data from academic and patent literature from sources including public databases and conference proceedings. Information on commercial products was included.

The specific Objectives were: Objective 1. Define search criteria and construct data tables.Objective 2. Collate data on potential pest management properties of natural products or plant speciesObjective 3. Review data to identify plant species/extracts for potential management of the selected pests Objective 4. Communicate the results to the scientific and industry communities for future development of pest management strategies

The extent to which the objectives have been met

The literature has been surveyed in depth using mainly electronic resources; in addition a number of key older papers and book chapters have been included. In total more than 120 references drawn from literature searches have been used as a data source; most are from peer-reviewed journals, with a few being conference abstracts or short on-line publications with few experimental details. There is some (limited) duplication in data entries due to the inclusion of a couple of excellent reviews (references r16, r27). Details of the data included in the report are provided below under “Details of methods used and the results obtained”.

The data has been reviewed with the objective of identifying plant species and their natural constituents that have the potential to be utilised in pest management. Due to the volume of data, the style of presenting the findings is deliberately concise; however it has been tailored to address the ultimate objective of arriving at a short-list of potential research and/or development areas for future pest control methods based upon plant natural products. These suggestions for further work are given at the end of this section.

Whereas it was planned to contact selected authors in the context of the discussion, given the large number of potential research areas to come out of the report, it would be more relevant to follow up specific projects in the context of future proposals.

Details of methods used and the results obtained

Search criteria and data table construction were agreed and established at the start of the project. The data table construction guided the information collected.

A significant factor in the interpretation of the data collected and presented here concerns the inherent experimental variation due to the chemical treatment, method of preparation and concentration applied, as well as the physiological state of the insects and the experimental system. Spatial scale as a factor means that laboratory-based findings may not translate to the field. Furthermore, the fact that many different terms are used to report behavioural responses may confuse the picture. Key information that could affect data interpretation has therefore been gathered, wherever possible in a standardised format.

For the purposes of the report, key data has been organised into 24 tables, all extracted from the larger


detailed data set which is provided in the form of supplementary data in Excel. The larger data set in Excel consists of five pages entitled “plant species”, “chemical data”, “insect species”, “species_chem” and “references”. The page “species_chem” brings together the plant and chemical data, with other details including biological activity and experimental methods from the source papers. Expressions have been standardised as far as is practical without compromising accuracy or the meaning of the source data.

The review focuses on three types of pest; thrips (mainly WFT, but including other Frankliniella species and other pest thrips species (e.g. Thrips tabaci) where information was provided on other species in the WFT literature source, sciarid flies (Bradysia spp.), and vine weevil species of the genus Otiorhynchus. All those insect pests mentioned in the data set are listed on the Excel page “insect species”. A description of insect pest development stage is given on the “species_chem” page where the information was available.

Chemical data (on the “chemical data” page) include CAS Registry numbers, IUPAC name, InChIKey and SMILES where these were available. A number of entries are not conventional chemical names but rather terms (e.g. “SOS signals” or “volatiles”) or the name of a commercial product, normally taken directly from the source reference. To aid organisation and interpretation, a chemical classification has been adopted that is loosely based upon that used in Dictionary of Natural Products.i In total, 206 chemical names or terms have been collected together on this table, classified into 56 different groups. Toxicological properties of chemicals to e.g. plants or humans have been recorded but a comprehensive search has not been made (therefore the absence of an entry in the data tables does not necessarily indicate lack of toxicity to non-target organisms).

On the “plant species” page, taxonomic details have been added according to the system adopted by Mabberley.ii EPPO codes have not been added but these are available from an open access database iii. Where mentioned, the localisation of phytochemicals to tissue or even cellular level has been included on the “species_chem” page. Although only infrequently described in the papers accessed for this review, localisation of volatiles in foliage and flowers is normally associated with glandular trichomes (e.g. iv). If not specifically mentioned in the source paper, localisation is not mentioned. 377 plant species or cultivars are included in this table.

On the “species_chem” page that brings all the data together, two columns are allocated to plant species (1) Plant species – chemistry and (2) Host/non-host plant species. The former describes the source of chemistry as described in source papers or if the chemical product is obvious (e.g. “Pure Neem Oil”), the latter gives the name of plant species named where a biological effect has been reported (e.g. avoidance, feeding) but no chemistry has specifically been assumed to be involved. Where no plant species is given under either column, the entry usually concerns the testing of a pure chemical.

The “species_chem” page contains 801 entries from more than 120 literature sources. In addition to the plant species and chemistry data, the methods used in making biological activity measurements, e.g. observation of plant avoidance in a glasshouse or olfactometer experiment with a purified phytochemical under laboratory conditions, are necessary for interpretation and have been included where described. Biological activities have been classified into standardised classes with rather general terms, in order to permit the organisation of data into groups consistent with the varying level of detail and experimental methods recorded in the literature. For example, the results of olfactometer experiments are all classified under the activity sub-class “movement” (the activity response then being described as positive, negative or no effect). Some entries concern chemicals that are not directly associated with a biological effect but are rather correlated with plant phenotype (resistant or susceptible) or induced by pest feeding. Information on biological effective concentration is given where possible.

Core data from the “species_chem” page has been extracted and organised into 24 tables according to insect pest and the biological activity (behaviour or growth/development) affected. Each entry on the 24 tables can be matched against the more detailed table “species_chem” in Excel using the unique identifier in the first column “Data ID”. The 24 tables form the basis of the discussion below.

A glossary is provided at the end of the section.

Discussion of the results

For the purpose of interpretation and discussion, the chief findings have been organised into a series of tables describing reports of plant species, phytochemicals or plant extracts that have been been associated with changes in the behaviour, growth or mortality mainly of Otiorhynchus, Bradysia and Frankliniella species. Associations of activities with chemistry have been made either through cause and effect experiments (e.g. apply treatment, observe effect on mortality) or by correlation between e.g. resistant and susceptible plant cultivars. Data has also been included where there is no mention of


chemistry, but rather observations have been made of plant avoidance or plant host status.

The key findings from each table are discussed below. References with the prefix r** are all listed in the attached data table named “References”. Additional references incorporated for the purpose of discussion are hyperlinked to the text and listed in Section 9.

OTIORHYNCHUS

Table 1

OtiorhynchusBehaviour – Movement – Positive

3 references 9 entries 2 host/non-host families represented; Rosaceae (Fragaria and Prunus) and Araliaceae (Hedera) Volatiles of damaged leaves of 4 species were found to be attractive; weevil-damaged (Taxus

baccata and Euonymus fortunei) and mechanically-damaged (Hedera helix and Prunus laurocerasus)

Volatiles of weevil-damaged foliage of Rhododendron catawbiense 'Boursault' and Fragaria x ananassa had no effect on movement (r55), although this rhododendron cultivar was reported to inhibit feeding, oviposition and larval development (Tables 3, 4 and 7, r52), and increased mortality was observed (Table 5, r68).

No negative movements (e.g. deterrent, repellent activities) were reported for Otiorhynchus in the literature reviewed; however since compiling these tables a recent report has come to our attention v that reported repellent activity of synthetic 1-hexenol and (Z)-3-hexenol and attractant activity of (E)-2-hexenol. These green leaf volatiles had all previously been reported to elicit an olfactory response (Table 9).

Table 2

OtiorhynchusBehaviour – Feeding – Promoted

4 references 113 entries 33 host/non-host families represented 1 species (Fragaria x ananassa) was variable in its effect on feeding according to cultivar (relative

preference was unrelated to the presence/absence of leaf hairs) All 5 Liliaceae species promoted feeding in larvae and/or adults All 8 Saxifragaceae species promoted feeding (7 in larvae, 1 in both adults and larvae) 7 out of 8 Polygonaceae species promoted feeding in larvae and/or adults 23 (16 species) out of 33 Rosaceae entries reported promoted feeding in larvae and/or adults.

The remaining 5 species inhibited feeding in larvae.

Table 3

OtiorhynchusBehaviour – Feeding – Inhibited

7 references 88 entries 40 host/non-host families represented Rhododendron essential oil and volatile extracts from leaf scales (lepidote glands) cause feeding

inhibition. Sesquiterpenes are major components. There is some dispute over where the oils are located (possibly not in lepidote glands)

11 out of 13 Compositae species inhibited feeding in larvae All 4 Labiatae species inhibited feeding in larvae All 4 Scropulariaceae species inhibited feeding in larvae In GM strawberry plants expressing cowpea trypsin inhibitor, larval feeding was inversely related

to transgene expression

Table 4


OtiorhynchusBehaviour – Oviposition – Increased

2 references 2 entries, Rubus idaeus (Rosaceae); both entries report that oviposition is positively correlated

with plant nitrogen concentration

Behaviour – Oviposition – Decreased 3 references 11 entries (11 species) in 9 host/non-host families 1 ext/chem entry (azadirachtin) from the neem tree Azadirachta indica Reduced oviposition in Taxus media was attributed to the possible properties of foliage chemistry Of the other species, the chemistry of the hop (H. lupulus) is well-characterised and inhibitory

effects of hops extracts on other pests have been reported e.g. reduced oviposition in the bee pest varroa mite vi and inhibition of feeding and larval development in Colorado beetle vii.

Table 5

OtiorhynchusGrowth/survival – Mortality – Increased

5 references 25 entries 10 host/non-host species in 7 families represented Mortality addressed in reference r52 was relative to feeding on Taxus baccata 3 chemistry species in 2 families represented (Brassica & Taxus) The Taxus entries concern extracts of T. x media and taxoids of T. baccata that were shown to

synergise the adult knock-down effect of pyrethroids when fed first to O. sulcatus The other chemical group reported as increasing mortality is “isothiocyanate”; this diverse group of

chemicals being derived from glucosinolates produced in species mainly of the Brassicaceae. The polarity of 11 synthetic isothiocyanates was shown to correlate significantly with contact toxicity to vine weevil eggs. Rapeseed meal and pure methyl isothiocyanate also increased the mortality of vine weevil larvae when added to soil for 24 hours; rapeseed meal gave 5-100% mortality at a rate of 0.835 - 65.9 g/kg soil.

Table 6

OtiorhynchusGrowth/survival – Adult development – Promoted/inhibited

1 reference 7 entries; for O. ovatus and O. sulcatus Adult development in terms of life cycle times, pre-oviposition, oviposition and survival were

scored after feeding on the same plant species for 9 months. Distinct differences were found between the two pest species. Strawberry was the best host for both pests; Picea abies supported O. ovatus but neither species of Picea were good hosts for O. sulcatus. Taxus was a good host for O. sulcatus but not for O. ovatus.

Table 7

OtiorhynchusGrowth/survival – Larval development – Inhibited

5 references 2 entries (2 plant species) for O. ovatus; these were Rhododendron catawbiense 'Boursault' and

Taxus baccata (already reported as a poor host for O. ovatus. 20 entries (20 species) for O. sulcatus, in 18 host/non-host families. Larval development was inhibited as a result of azadirachtin application and of neem seed cake

(which contains azadirachtin) Inhibition of larval growth by Taxus (r102) was following the feeding of adults on foliage; relative to

feeding on strawberry negative effects were observed on oviposition, larval hatching and development.


Table 8

OtiorhynchusGrowth/survival – Larval development – Promoted/other

Only 4 entries for promotion of larval development O. sulcatus larval development on raspberry was positively correlated with root nitrogen and

magnesium but negatively correlated with root iron concentrations O. ovatus larval development was promoted on Picea glauca (O. ovatus adult development was

supported on Picea abies, see Table 6) Variation in larval development was reported between cultivars of raspberry but not of strawberry

Table 9

OtiorhynchusOther (including olfactory stimulation)

5 references 26 entries of which 22 (2 references) are concerned with olfactory stimulation 1 reference (r65) concerns the stimulatory effect of a number of pure volatiles. In particular, large

EAG (electroantennogram) responses were found among green leaf volatiles including (E)-2-hexenol-1, (Z)-3-hexenol-1, hexanol-1, hexanal, and heptanal. Generally terpenes elicited poor responses and the authors suggest that this may be a reason for the poor host status of conifers for O. sulcatus.

A further paper by the same author (r85) identifies stimulatory green leaf volatiles amongst others collected from the headspace of a preferred O. sulcatus host Euonymus fortunei. The testing of combinations of some of these volatiles in traps in strawberry fields led to the identification of a 1:1 mixture of (Z)-2-pentenol and methyl eugenol as an attractant. Methyl eugenol is a widely distributed plant volatile and C5 alcohols other than (Z)-2-pentenol have been found in strawberry fruits and foliage so these may play a part in attracting O.sulcatus in the field. The authors stress that the attractant volatile composition and trap design both need to be optimised.

Using an olfactometer to detect movement, an O. sulcatus entomopathogenic nematode Heterorhabditis megidis) was shown to be attracted to volatiles released by Thuja occidentalis roots damaged by larval feeding. The effect is described as long-range movement to SOS-signals. More recently the movement of entomopathogenic nematodes has been studied and non-specific (e.g. CO2) and more specific cues identified; for instance β-caryophyllene is reported to act as a similar signal to entomopathogenic nematodes in herbivore-damaged roots of maize viii ix

20-hydroxyecdysone (a phytoecdysteroid) was shown to be induced by O. sulcatus feeding on spinach roots. No direct effect of the chemical was described for O. sulcatus; however our wider data search found reports of larval feeding and development inhibitors and increased larval mortality for Bradysia (Table 11 and 12).

BRADYSIA

Table 10

BradysiaBehaviour – Movement – Negative

3 references, mostly concerning behavioural effects of pure compounds Using a simple olfactometer, 4 volatiles with repellent activity on adults were identified (borneol,

menthol, 1-octen-3-ol and α-terpineol); the other 6 compounds had no effect (r76) The volatiles from Bounce fabric softener drying sheets were shown to repel Bradysia adults using

the same simple olfactometer. Linalool was the main volatile constituent with a number of other compounds identified including benzyl acetate, β-citronellol, and hedione, though these were not directly identified as repellent. Authors suggested lining pots with drying sheets to repel adults. β-citronellol is a known mosquito repellent and linalool is a common component of plant volatiles.

Virus-infection (White clover mosaic virus) of Trifolium repens plants reduced their attraction to Bradysia. Volatiles produced by infected and non-infected plants were distinctly different and β-caryophyllene was only detected in the headspace of virus-infected plants. The repellent activity of individual headspace components has not yet been tested.

Behaviour – Movement – Positive 2 references reported attractive activity to Bradysia, without any specific information about volatile

composition


Observations of visits of adult Bradysia males and pseudocopulatory behaviour to Lepanthes orchid flowers in the wild concluded that the initial long-distant attraction is olfactory

A comparison of different growing media to Bradysia coprophila showed that SB300 containing composted pine bark was more attractive than a growing medium without pine bark. No correlations could be made between attractiveness and GCMS analysis of volatiles. In a previous paper fewer adults were reported to emerge from media containing composted pine bark. x On the basis of these reports the further study of composted pine bark may provide clues to volatiles that might attract Bradysia adults as well as other chemicals that might inhibit their development; for instance the diterpene dehydroabietic acid was reported to be a major constituent of pine bark compost. xi

Table 11

BradysiaBehaviour – Feeding – Inhibited

2 references 20-hydroxyecdysone was shown to inhibit larval feeding in artificial diets, and was inversely

correlated with feeding in methyl jasmonate (MJ)-induced spinach root; MJ is likely to induce multiple defence mechanisms so 20-hydroxyecdysone may not be the only factor in feeding reduction (r91)

In a recent study a new class of semi-volatile diterpenes (rhizathalenes) identified in roots of Arabidopsis thaliana were shown to inhibit larval feeding on artificial diets. Genetic knock-outs for the rhizathalene terpene synthase gene (TPS08) supported higher herbivory, and the localised expression of TPS08 in the root stele suggests that rhizathalenes are released into the peripheral root cell layers. The effective antifeedant concentration in artificial diets was within the range found in plant roots. Taken together this evidence strongly supports an antifeedant role for an in planta product

No reports relating to promotion of feeding, and none relating to oviposition in Bradysia were found.

Table 12

BradysiaGrowth/survival

3 references Azadirachtin was effective in reducing the population of adult Bradysia on sticky traps but less

than treatment with the entomopathogenic nematode Steinernema feltiae (r75) Larval mortality was increased by treatment with 3 botanical products; QRD400 based on an

extract of Chenopodium ambrosioides, garlic bulb juice and Ornazin (neem-based) although the effects were only significant with the Chenopodium extract

Larval mortality was increased on artificial diets containing 20-hydroxyecdysone and larval development was inhibited on MJ-induced spinach plants (r91; see feeding inhibition, Table 11)

Table 13

i http://dnp.chemnetbase.com/intro/DNPIntroduction.pdf ii The Plant Book, 2000, ISBN 0 521 41421 0 iii http://eppt.eppo.org/iv Schmiderer, C., Grassi, P., Novak, J., Weber, M., Franz, C. (2008) Diversity of essential oil glands of clary sage (Salvia sclarea L., Lamiaceae). Plant Biology, 10 (4), pp. 433-440v Karley (2012). Characterising vine weevil aggregation pheromone for use in traps at soft fruit and nursery sites. Final Report HGCA project SF-HNS 127vi Hoffman, G.D., Ahumada, F., Probasco, G., Shantz, L. (2012) The effects of beta acids from hops (Humulus lupulus L.)on mortality of Varroa destructor (Acari: Varroidae). Experimental and Applied Acarology. 58:407-421.vii Gökçe, A., Isaacs, R., Whalon, M.E. (2012) Dose-response relationships for the antifeedant effects of Humulus lupulus extracts against larvae and adults of the Colorado potato beetle. Pest Management Science, 68 (3), pp. 476-481viii Rasmann S, Ko¨llner TG, Degenhardt J, Hiltpold I, Toepfer S, Kuhlmann U, Gershenzon J, Turlings TCJ (2005) Recruitment of entomopathogenic nematodes by insect-damaged maize roots. Nature 434:732–737ix Turlings, T.C.J., Hiltpold, I., Rasmann, S. (2012) The importance of root-produced volatiles as foraging cues for entomopathogenic nematodes. Plant and Soil, 358 (1-2), pp. 51-60


http://eppt.eppo.org/

http://dnp.chemnetbase.com/intro/DNPIntroduction.pdf

BradysiaOther

4 references 20-hydroxyecdysone was induced in spinach roots by Bradysia larval feeding (r91) adding to the

body of evidence for the chemical as part of an induced defence strategy in this plant species Multitrophic interactions in the shape of mycorrhizal association, cardenolide content and

abundance of Bradysia larvae in roots of 13 species of the genus Asclepias were examined; larval density was associated with the extent of mycorrhizal colonization but not with cardenolide concentration.

Bradysia feeding or mechanical wounding 24h before zoospore inoculation increased plant resistance in Pelargonium seedlings to infection by Pythium aphanidermatum

Parboiled rice hulls (PBH) were tested as an amendment to composts and found to have no effect (neither positive nor negative) on Bradysia movement in a choice test. Palmitic acid was identified as a major volatile in dried PBH

FRANKLINIELLA OCCIDENTALIS

In the process of collecting data on F. occidentalis, data on other thrips species was found and is included in tables for reference and comparative purposes.

Table 14

Frankliniella spp.Behaviour – Movement – Positive

15 references 83 entries of which 76 concern the application of extracts or chemicals or identification of active

chemicals, and 7 report plant species that affect behaviour Of the 76 entries concerning reports of active chemicals or extracts, 11 are uncharacterised (i.e.

essential oils, extracts, seed oils or “volatiles”). The remaining 65 entries fall into 6 of the chemical classes adopted in this report (benzenoid, ester, monoterpenoid, phenylpropanoid, pyridine, sesquiterpenoid). F. occidentalis exhibited positive movement to a number of identified chemicals:

o 5 named benzenoids: anisaldehyde (although not specified in reference, probably p-anisaldehyde), benzaldehyde, o-anisaldehyde, p-anisaldehyde and salicylaldehyde

o 5 monoterpenoids: (+)-citronellol, (3S,6S)-tetrahydro- 2,2,6-trimethyl-6-vinyl-2H-pyran-3-ol, 1,8-cineole, geraniol (nerol) and linalool. 1,8-cineole was identified as an attractant in the flower volatiles of meadowsweet (Filipendula ulmaria) and (3S,6S)-tetrahydro- 2,2,6-trimethyl-6-vinyl-2H-pyran-3-ol as an attractant from Verbena x hybrida. Geraniol was significantly active at 1% (r16); however the same study found higher attractant activity in other volatiles (p-anisaldehyde and 3-phenylpropionaldehyde) at lower concentrations

o 2 phenylpropanoids: 3-phenylpropionaldehyde (effective at concentrations as low as 0.001%) and eugenol

o 5 pyridine compounds: ethyl isonicotinate, ethyl nicotinate, methyl 4-pyridyl ketone, methyl isonicotinate and a commercial attractant Lurem-TR containing methyl isonicotinate (Koppert). Lurem-TR was shown to increase WFT mortality in semiochemical-baited traps in combination with the fungal pathogen Metarhizium anisopliae, although the attractant also reduced pathogen conidial viability (r115)

o 1 sesquiterpenoid, i.e. (E-)-β-Farnesene, identified as an attractant in volatiles of flowers and buds of Chrysanthemum “Swingtime” and in other olfactometer experiments

F. occidentalis was attracted to a number of natural chemical mixtureso Essential oils of Eucalyptus and Citrus x aurantium (bitter orange; neroli oil)o Seed oils of canola and mustard and canola pod extract (r118); this was a field study

testing a number of different oils in traps of different colours, and there was no evidence for any specific volatile attractants

o Volatiles of 5 different plant species from 4 different plant families; Chrysanthemum morifolium, Filipendula ulmaria, Verbena x hybrida, Laurus nobilis and Salvia officinalis. Of these, specific chemical attractants have been identified from the first three species. 1,8-cineole has been identified as an attractant in F. ulmaria (see above) and was also identified in the headspace volatiles of L. nobilis and S. officinalis (r108)

In addition to the plant species already mentioned, F. occidentalis was reported to be attracted to the following plant species in greenhouses: Browallia speciosa, Sinningia speciosa and Impatiens wallerana. These species have already been suggested as trap crops in greenhouses and it would be worth analysing their volatiles also.

In the process of collecting this data the following attractant activities for other species of thrips


was noted:o T. major: p-anisaldehydeo T. tabaci: 4 benzenoids (2-phenylethanol, benzaldehyde, p-anisaldehyde and

salicylaldehyde); 2 esters (methyl anthranilate and methyl benzoate); 4 pyridines (ethyl 4-pyridyl ketone, ethyl nicotinate, isopropyl isonicotinate and methyl isonicotinate) and mustard seed oil. This data was mainly from a review (r27).

Table 15

Frankliniella spp.Behaviour – Movement – Negative

13 references 51 entries of which 43 concern the application of extracts or chemicals or identification of active

chemicals, and 8 report plant species that affect behaviour Of the 43 entries concerning reports of active chemicals or extracts, 28 are uncharacterised

(essential oils, extracts or volatiles). The remainder fall into 7 of the chemical classes adopted in this report (benzenoid, ester, isobutylamide, monoterpenoid, phenylpropanoid, pyridine, terpenoid (cyclopropane esters). F. occidentalis exhibited negative movement as a behavioural response to a number of identified chemicals:

o 2 named benzenoids: p-anisaldehyde and salicylaldehyde. Both compounds also had a positive effect on movement (see above) and the divergent activities may be concentration-dependent such that in olfactometer experiments p-anisaldehyde is attractive at 10% dilutions and repellent when undiluted (r16). The negative response to undiluted p-anisaldehyde was in fact reduced flight and therefore greater trap count in a low speed laminar air flow flight chamber (r10); the positive effect noted in a trap experiment was conducted in the field (r25). Salicylaldehyde also had a negative movement effect at low dilutions (undiluted and 1%) compared with a positive effect at higher dilution (0.125%)

o 1 ester: methyl salicylateo 1 isobutylamide: N-isobutyl-(E, E, E, Z)-2,4,10,12-tetradecatetraen-8-ynamide, which was

the repellent chemical identified in leaves of Chrysanthemum morifolium by activity-guided fractionation. The concentration of this compound was correlated with differing degrees of resistance to WFT in 8 cultivars. It would be interesting to determine if the level of the repellent isobutylamide in buds and flowers also correlates with resistance, as WFT are more attracted to these tissues than to leaves.

o 3 monoterpenoids: carvacrol and thymol caused negative movement in larvae, and D-limonene in adult females

o 1 pyridine compound: nicotine caused negative movement in a choice testo Pyrethrum oil, a liquid CO2 extract from Tanacetum cinerariifolium flower heads was

deterrent when either applied to leaf discs or infiltrated into Chrysanthemum leaves at a concentration typically found in T. cinerariifolium

F. occidentalis was deterred by a number of natural chemical mixtureso Essential oils of 7 species, 5 of them in the family Labiatae, plus wintergreen and lemono Extracts of 13 species (a single reference, a screening exercise of Kyrgyzstan plants)o Volatiles of the buds from mixed rose varieties were repellent in an olfactometer assay

In addition to the plant species already mentioned, F. occidentalis was reported to avoid the foliage of 8 species, 3 of these from a single genus Plectranthus in the family Labiatae. Leaves of Plectranthus spp. have subsequently been tested in olfactometer experiments and their volatiles found to be attractive to WFT (r99). A comparison of plant volatiles in different Plectranthus species (of which there are c. 200) and pest movement may yield further chemical targets for WFT control.

From another of the avoided species (Sclerochiton harveyanus), a novel chemical (an iridoid) that increased mortality in WFT larvae was subsequently identified (r1), but had less activity than leaf extracts. A choice test with the purified iridoid was only performed with another thrips species Heliothrips haemorrhoidalis and no effect was shown (r1).

Volatiles collected from rosemary foliage were repellent, however they were also repellent to adults of the WFT predator Orius laevigatus (r99). In a separate olfactometer study no effect of rosemary leaf extracts was found on WFT (r7), perhaps a reflection of the extract preparation method.

Wounded tobacco leaves were deterrent, as was pure nicotine as demonstrated by a choice test in the same study (r42)

In the process of collecting this data it was noted that eugenol and an essential oil from rosemary


foliage were deterrent for Thrips tabaci.

Table 16

Frankliniella spp.Behaviour – Feeding – Promoted

2 references 58 entries 54 entries (all r47) report plant species in 18 different plant families affecting feeding behaviour.

The paper reported a study on uncultivated hosts for thrips in Florida. Of these, the families most represented are Compositae (10 species), Leguminosae (10), Rosaceae (6), Gramineae (5) and Convolvulaceae (3); to a large extent this will reflect the incidence of species in these plant families in the landscape. F. occidentalis was a relatively uncommon thrips species in this study, only being reported on 5 species (Geranium carolinianum, Solidago canadensis, Rubus cuneifolius, Ligustrum sinense and Lonicera japonica) in 5 different families. The other thrips species were all Frankliniella spp.

4 entries report chemistry correlated with promoted feeding (all r5) where feeding damage by WFT larvae was positively correlated with aromatic amino acid concentration in leaf proteins. The authors suggest that as aromatic amino acids are required for cuticle formation, low aromatic amino acid should be a breeding target for resistance to WFT and could be particularly effective used in combination with entomopathogenic fungi.

Table 17

Frankliniella spp.Behaviour – Feeding – Inhibited

14 references 35 entries 4 entries concern non-host plant species (r101). Protein and carbohydrate levels were measured

amongst a range of host (n=23) and non-host (n=4) species for 2 thrips species (F. occidentalis and H. haemorroidalis); whilst overall, sucrose was the most abundant measured sugar in the leaves of host species there were no consistent trends

31 entries concern extracts or chemicals inhibiting feeding, or correlations between plant chemistry and feeding activity. 2 extracts (of Azadirachta indica and Gliricidia sepium) reduced leaf damage. The remainder relate to specific chemicals:

o The presence of a benzoquinone derivative, jacaranone, was found to correlate with reduced leaf silvering damage by WFT susceptible and resistant varieties of Senecio F2 hybrids (r2).

o 2 monoterpenoids, carvacrol and thymol, both at 1% reduced feeding in no-choice bioassays

o 3 phenylpropanoids, kaempferol, chlorogenic acid and feruloylquinic acid were associated with reduced feeding by WFT. Kaempferol concentration was negatively correlated with feeding in Senecio F2 hybrids (r2 as with jacaranone, above). Likewise, chlorogenic acid and feruloylquinic acid inhibited WFT feeding in choice tests and their concentrations in chrysanthemum were negatively correlated with feeding. Unlike the benzoquinone jacaranone (above), all three phenylpropanoids are widely distributed across the plant kingdom and are feasible targets for pest resistance in crop species

o Tannic acid inhibited feeding in artificial diets o The presence of acylsugars was found to correlate with WFT resistance in tomato, and

was shown to be a factor in the resistance of wild varieties Lycopersicon pennellii and L. hirsutum. Acylsugars are the subject of active research as resistance factors in Solanaceae crops xii xiii

o Selenium concentration in Se-hyperaccumulating plant species was correlated with WFT feeding inhibition; whilst an essential trace element Se is also toxic to mammals at higher concentrations

o Pyrrolizidine alkaloids were associated with reduced WFT feeding in Senecio F2 hybrids and Jacoboea spp. in choice tests and by chemical correlation; as these alkaloids are toxic to humans and livestock they have no relevance to pest control in food crops

o Methyl salicylate inhibited feeding at 1% dilutiono The application of jasmonic acid to Chinese cabbage reduced injury due to WFTo Recombinant (non-plant) protease inhibitors in GM potato leaf discs inhibited WFT

feeding


Table 18

Other thrips species Behaviour – Feeding – Inhibited 3 references 15 entries α-tomatine was reported as a feeding deterrent for T. palmi in tomato leaves. Whilst some

steroidal alkaloids are toxic, α-tomatine is well-tolerated in humans, and responsive to N-fertilization xiv

Essential oils of basil, marjoram, mint, rosemary and lavender reduced feeding in T. tabaci, as did the pure aromatics 1,8-cineole, linalool and engenol

Table 19

Frankliniella spp.Behaviour – oviposition – Increased or supported

2 references 37 entries, concerning 26 plant species in 16 different plant families preferred for or supporting

oviposition. One paper (r47) reported a study on uncultivated hosts for thrips species in Florida, the second (r114) a study of WFT in Kenyan bean fields. Of these, the families most represented are Compositae (7 species), Cruciferae (4), Polygonaceae (4), Leguminosae (3), Rosaceae (3); as with the data from the same paper sorted on feeding promotion (see above), to a large extent this will reflect the incidence of species in these plant families in the landscape. However it is notable that preferences for oviposition vs feeding appear to be different across plant families; whilst Compositae is top of the list for both behaviours, e.g. Polygonaceae is more highly represented and Gramineae less so, for oviposition.

Table 20

Frankliniella spp.Behaviour – Oviposition – Decreased

10 references 28 entries 2 entries concern non-host plant species. Nicandra physaloides has been previously reported to

contain an antifeedant steroid in its leaves. xv In tobacco, more oviposition by WFT was found on unwounded vs wounded plants in a greenhouse, suggesting that volatiles were involved in making a choice

26 entries concern extracts or chemicals reported to decrease oviposition in Frankliniella species:o Methyl salicylateo 4 monoterpenoids (1,8-cineole, carvacrol, linalool and thymol) and eugenol

(phenylpropanoid)o Tannic acid (at 1% or 5%)o Pyrethrum oil (0.1%- 1%) in a non-choice test with pollen as food inhibited oviposition,

also when infiltrated into chrysanthemum leaveso Potato cystatin (a protease inhibitor) reduced oviposition in an artificial dieto Jasmonic acid treatment of Arabidopsis or Chinese cabbage induced plant responses that

reduced oviposition 4 essential oils (lavender, marjoram, mint and sage) reduced oviposition by T. tabaci

Table 21

Frankliniella spp.Growth/survival – Mortality – Increased

20 references 77 records of which 76 concern extracts or chemicals that increase mortality and the remaining

record describes a correlation between mortality and chemistry This table includes a number of commercial products with information relating to the active

constituents, and for discussion purposes these are grouped together with other chemicals of the same chemical class as used in this report:

o 18 extracts including a number of commercial products: Bang (extract of Piperaceae spp.)


and 3 products were all produced from mixed species (r6); these and the other botanicals reported in r6 were all much less effective on adult WFT than Monterey Garden Spray which is based on spinosad, a fungal metabolite. Most of the other extracts (all applied at 1%) were prepared from Kyrgyzstan plants in a screening exercise on WFT larvae (r43 – a number of these negatively affected movement, see above); however the increase in mortality was only significant with the extracts of Plantago major and Silene sussamyrica. The remaining two extracts (r1) of Plectranthus zuluensis and Sclerochiton harveyanus were tested following observations of avoidance by WFT in glasshouse plants; extracts of S. harveyanus killed more larvae than the iridoids (sclerochitonosides) subsequently isolated from this plant by bioactivity-guided fractionation

o 7 essential oils: 1 commercial (from Ecotec AG) from “mixed species”, was one of the more effective botanicals tested alongside the extracts above (r6), and essential oils from pennyroyal (main constituent being pulegone) and spearmint (main constituent carvone) were effective as fumigants. An essential oil extract from fennel and a “Labiatae” product increased mortality in a fumigation experiment with cut flowers, but less so than pure 1,8-cineole or safrole (r88). An essential oil prepared from Chenopodium ambrosioides caused contact toxicity. A commercial product from the same species containing sesquiterpenoids and monoterpenoids (QRD400) is marketed for control of thrips and other soft-bodied pests

o In a study with cut roses +/- controlled CO2 atmospheres, essential oil fumigants including Cypress oil and several pure volatiles significantly increased mortality. In the absence of CO2, high mortalities were achieved with e.g. (+)-carvone, but phytotoxicity was seen at similar concentrations. Phytotoxicity was reported to be dependent on plant species and the temperature, duration and concentration of fumigant (r88)

o A number of individual volatiles (alcohols, esters, aldehydes, epoxides and sulphur compounds) significantly increased mortality of WFT on infested chrysanthemum flower buds (r30); in this study only the alcohol, 2-propyn-1-ol, showed any phytotoxicity. 9 different monoterpenoids, 2 volatile phenylpropanoids (anethole and safrole) and a sulphur compound all increased mortality.

o Pyrrolizidine alkaloids and chlorogenic acid in artificial diets increased mortalityo An early study on chrysanthemum (r104) reported that whilst leaf extract fractions had no

effect, mixtures of the fractions increased WFT mortality. Resistance to WFT in vegetative chrysanthemum plants has subsequently been correlated with a number of different leaf chemicals (e.g. chlorogenic acid, r36).

o The acylsugar-based product SucraShield is marketed for control of soft-bodied insect pests, based upon the natural acylsugars found in, for example, Nicotiana gossei xvi

o Increased larval mortality (and longer larval development duration) as induced by methyl jasmonate (MJ) in tomato has been reported recently xvii; a relatively high MJ concentration (2.4 μM ) was required for a significant plant resistance response to WFT cf a number of other herbivores (e.g. 0.03 μM for larvae of Spodoptera litura and Mamestra brassicae)

Table 22

Frankliniella spp.Growth/survival – Larval development – Inhibited

2 references Just 2 entries, one concerning contact toxicity to eggs of Pyrethrum oil (which was also reported to

affect behaviour and mortality), and the other concerning chlorogenic acid in in vitro assays which also affected feeding behaviour and larval mortality

Table 24 includes a reference reporting leaf chemicals correlated with resistance and susceptibility in Capsicum (r31) – resistance/susceptibility being confirmed in terms of larval development and rate of oviposition. Chemicals induced by WFT feeding in R or S phenotopes were also reported. A number of alkanes were associated with susceptibility (both constitutive and induced), whereas tocopherols and a number of unidentified compounds were associated with resistance. A substituted alkane (4,8,12,16-tetramethylheptadecan-4-olide) was induced by feeding in R phenotypes. The authors pointed out the inadequacy of metabolite libraries as a drawback of this type of research

Table 23

Frankliniella spp.Growth/survival – Population – Increased/decreased


8 references 13 entries of which 3 relate to factors that decrease WFT populations and 10 to factors that

increase WFT populations WFT populations were decreased by prior application of jasmonic acid to Arabidopsis and

Chinese cabbage, and on roses by reducing N fertilization to 33% the normal rate All entries reporting an increase in WFT populations relate to N fertilization, or to tissue levels of N

or amino-acids. Plant tissue N levels were correlated with higher populations in chrysanthemum, tomato and peppers. In tomato and peppers, only F. occidentalis (and not F. tritici or F. bispinosa) female adult populations responded to higher N fertilization (r48)

In a 2-year field-study of tomato, WFT populations were also positively correlated with leucine and phenylalanine concentrations in the flowers

Table 24

Frankliniella spp.Other – Olfactory stimulation, phytochemical

23 entries of which 2 concern olfactory response to volatiles using coupled GC-EAG. Specific volatiles from meadowsweet flowers (r108), methyl salicylate and 1,8-cineole gave responses and were also shown to affect movement; methyl salicylate was repellent and 1,8-cineole was attractive (Tables 14 and 15)

The remaining 21 entries relate to chemicals correlated with resistance characteristics and/or induced by feeding:

o WFT resistance in chrysanthemum was correlated with the concentration of a novel isobutylamide, N-isobutyl-(E, E, E, Z)-2,4,10,12-tetradecatetraen-8-ynamide In leaves

o WFT feeding on tobacco seedlings induced volatiles containing a number of identified compounds including nicotine; also shown to have a negative effect on movement (r42, Table 15)

Across the entire dataset, certain chemicals and extracts were mentioned several times, or were active with different pests, sometimes with diverse and even apparently conflicting effects:

Data on a large number of different essential oil extracts were found; most of these were reported to increase mortality or reduce feeding in thrips; only 2 (Eucalyptus and neroli oil) were reported to attract (for WFT, r107). Essential oil from certain Rhododendron cultivars inhibited feeding in O. sulcatus

Some volatiles were reported to have different effects depending on pest species; e.g. eugenol (1%) attracted WFT but repelled T. tabaci

Effects of volatiles can be concentration-dependent; both salicylaldehyde and p-anisaldehyde were reported to attract WFT at lower concentrations and repel at higher concentrations (p-

x Lindquist, R.K., Faber, W.R. and Casey, M.L. (1985) Effect of various soilless root media and insecticides on fungus gnats. HortScience, 20, 358-360xi

V.E. Tarabanko, O.A. Ulyanova, G.S. Kalacheva (2010) Study of dynamics terpene compounds content in composts based on pine bark and their growth-promoting activity. Himija Rastitel’nogo Syr’ja (Chemistry of plant raw material) 1:121-126 http://www.chem.asu.ru/chemwood/volume14/2010_01/1001_121.en.html xii Kim, J., Kang, K., Gonzales-Vigil, E., Shi, F., Daniel Jones, A., Barry, C.S., Last, R.L. (2012) Striking natural diversity in glandular trichome acylsugar composition is shaped by variation at the acyltransferase2 locus in the wild tomato Solanum habrochaites.Plant Physiology, 160 (4), pp. 1854-1870xiii Schilmiller, A.L., Charbonneau, A.L., Last, R.L. (2012) Identification of a BAHD acetyltransferase that produces protective acyl sugars in tomato trichomes.Proceedings of the National Academy of Sciences of the United States of America, 109 (40), pp. 16377-16382xiv Koh, E., Kaffka, S., Mitchell, A.E. (2013)A long-term comparison of the influence of organic and conventional crop management practices on the content of the glycoalkaloid α-tomatine in tomatoes. Journal of the Science of Food and Agriculture, 93 (7), pp. 1537-1542xv Gill, H.K., Smith, R.W., Whiting, D.A. (1986) Biosynthesis of the nicandrenoids: Stages in the oxidative elaboration of the side chain and the fate of the diastereotopic 25-methyl groups of 24-methylenecholesterol. Journal of the Chemical Society, Chemical Communications, (18), pp. 1459-1460xvi Puterka, G.J., Farone, W., Palmer, T., Barrington, A. (2003) Structure-Function Relationships Affecting the Insecticidal and Miticidal Activity of Sugar Esters. Journal of Economic Entomology, 96 (3), pp. 636-644xvii Kawazu, K., Mochizuki, A., Sugeno, W., Seo, S., Mitsuhara, I. (2013) Differences in the susceptibility of five herbivore species and developmental stages to tomato resistance induced by methyl jasmonate treatment. Arthropod-Plant Interactions, 7 (4), pp. 415-422


http://www.chem.asu.ru/chemwood/volume14/2010_01/1001_121.en.html

anisaldehyde is also reported to attract both T. tabaci and T. major, and salicylaldehyde to attract T. tabaci)

Linalool was induced by WFT feeding on tobacco and also attracted WFT, whilst it increased mortality when used as a fumigant. Linalool inhibited feeding of T. tabaci and elicited an olfactory response in O. sulcatus (present in headspace volatiles collected from Euonymus fortunei)

(E, E)-α-farnesene was induced by WFT feeding on tobacco and also elicited an olfactory response in O. sulcatus

Methyl benzoate attracted T. tabaci and also elicited an olfactory response in O. sulcatus β-caryophyllene was induced by feeding of WFT on tobacco; it was also induced in virus-infected

white clover plants, where it was correlated with reduced movement of Bradysia Menthol increased mortality in WFT as a fumigant and repelled Bradysia (and mint oil reduced

feeding and oviposition in T. tabaci) Carvacrol reduced feeding, movement and oviposition in WFT and increased mortality Higher nitrogen favoured positive behavioural responses and growth in WFT and O. sulcatus

Main implications of the findings

Points relating to more than one pest Jasmonic acid and methyl jasmonate treatments protect plants against WFT and Bradysia. Nutritional factors (N, amino-acids, minerals) that can be manipulated by horticultural practise hold

some promise for control of WFT and Otiorhynchus (and possibly for Bradysia, though not reported). Higher rates of N fertilization favour O. sulcatus oviposition and larval development; higher rates of N fertilization also favour WFT abundance. This could be a direct (feeding encouraged by higher N status) or indirect effect (reduced biosynthesis of antifeedant secondary products e.g. chlorogenic acid) in plant tissues

Chemical correlations in planta are best achieved with comparison between genetic knock-outs (e.g. of ecdysteroids) to validate relatedness to function

Chemical concentration is a very important factor, as the same chemical may have contrasting effects depending on dilution

Metabolomics is a very powerful tool for identifying chemical R factors but more comprehensive metabolite libraries are required for identification of chemical factors affecting pest behaviour

In terms of extracts/chemicals that increase mortality, crude extracts often have more potency than fractions (e.g. r1, r104)

Observation of plant avoidance may not necessarily predict deterrent volatiles (r1, r99) Essential oils, when used as fumigants can be phytotoxic; however there may be some

opportunity for practical application with optimisation of concentration, duration and temperature, also in controlled atmospheres (higher CO2)

Otiorhynchus Taxoids were reported to synergise the insecticidal potency of pyrethroids for O. sulcatus. More

recently, in order to replace the commonly used synthetic synergist piperonyl butoxide (PBO), the synergistic effect of plant extracts on pyrethrum have been reported. Whilst not as effective as PBO, dill apiole oil and parsley oil were reported as the most promising candidates, possibly because they contain the same methylenedioxyphenol ring structure.xviii

From this survey, O. sulcatus avoids feeding on certain plant families, e.g. Compositae and Scrophulariaceae. There may be antifeedant or repellent chemical determinants in these families that could be extrapolated to commercially important species

In O. sulcatus, oviposition was lower and mortality higher on hops cf Taxus; hop by-products may be worth testing given the earlier-mentioned reported inhibitory effects of hop extracts on other insect pests (Table 4)

Headspace volatiles of Euonymus fortunei as potential attractants of O. sulcatus have been reported; there are many favoured hosts and/or plant volatiles based upon previous reports that could be tested as attractants

Volatile SOS signals that attract natural enemies such as those produced by O. sulcatus-damaged roots provide another mechanism to protect plants, in conjunction with biocontrols.

Bradysia As reported for rapeseed meal (Table 5), brassicas are potentially useful for control of vine weevil

because of the release of ITCs with biofumigant activity. High ITC varieties of Caliente mustard are available as green manures and may reduce soil pests; effects on O. sulcatus and Bradysia populations both in field and horticultural environments should be tested

Volatile signals and other chemical effectors for Bradysia need more research, e.g. β-


caryophyllene as a potential repellent from virus-infected clover Whilst no direct correlations could be made between volatiles and relative attractiveness of

different kinds of growing media (Table 10), further research into potential chemical factors affecting behaviour and growth or development is warranted based upon these findings and other recent researchxix that reported attraction of sciarid flies to green composts and substrates containing wood fibre, and increased survival of the egg-adult stages when wood fibre formed part of the substrate.

Two interactions (Bradysia feeding induced Pythium-R and virus infection reduced attraction to Bradysia) mentioned here are interesting, suggesting that compromise could be a reasonable tactic in the context of managing pests and disease

As garlic is available in the UK as a “growth-stimulant” and neem may be approved in the future, the negative effects of garlic bulb juice and Ornazin (a neem-based product) on Bradysia larval mortality are of relevance

Phytoecdysteroids are widely distributed across plant taxa and may be partially responsible for negative developmental effects via feeding on flowers or roots

The genetic knock-out experiments possible with Arabidopsis have identified rhizathalenes as part of the defence against root herbivory. Generally, root-located volatiles or semi-volatiles should be good candidates as in planta protectants and a literature survey of potential chemistry would be a good start

Frankliniella occidentalis Volatiles from Browallia speciosa, Sinningia speciosa and Impatiens wallerana, should be

investigated for their volatiles composition and activity in relation to WFT

Possible future work

Points relating to more than one pest Potential plant extract synergists of pyrethrum and other pesticides and biopesticides should be

sought from the phytochemical literature and practically tested for improvement of efficacy against all three insect pests. This approach could also be of benefit in improved control of many other pest species.

Plant species releasing repellent volatiles could be grown as companion plants with vulnerable crops; where brushing of plant foliage is used in mechanised systems (e.g. in culinary potted herb production) it could be used to release volatiles on a regular basis

A literature survey of root-located volatiles or semi-volatiles as potential SOS signals (i.e. that attract natural enemies) may yield a number of potential crop protection candidates for the pests reviewed here and others including molluscs and nematodes. The concept is not only relevant to soil stages of the pest life cycle and could be extended to chemical signals from aerial plant parts that may attract e.g. WFT predators.

Whereas on their own, the phytochemical actives identified in this report may only provide a partial pest control solution, in combination with other plant products, permitted insecticides, biologicals or devices they may become very effective. Examples of this approach have been mentioned (e.g. lure-and-kill using a commercial product based on methyl isonicotinate to attract WFT and Metarhizium anisopliae conidia to increase mortality); this concept could be extended to vine weevil using attractants based on green plant volatiles and weevil refuge traps.

The pesticidal effects of plant chemicals could also be combined with a lure in the form of CO2 in a lure-and-kill strategy (e.g.xx). CO2 can potentially be used to enhance the attractiveness of other plant volatiles as recently reported for Aedes aegypti xxi

In combination with any biologically active phytochemicals identified from this review, there is a need for persistant, slow-release formulations for use in growing media against the ground-dwelling stages of all three insect pests. Good ideas from other disciplines such as the food industry xxii can be extrapolated to crop protection.

On the basis of reported effects on vine weevil oviposition and larval development and WFT abundance, further work is justified on the relationship between N fertiliser use and factors such as plant tissue N and secondary metabolite (e.g. chlorogenic acid) concentrations that may affect pest populations

Elicitors of plant defence mechanisms including the biosynthesis of secondary metabolites with biological activity are potentially important as part of a crop protection strategy. The potential benefits of jasmonates and other currently non-approved elicitors with low toxicities should be investigated further.

Otiorhynchus


Repellents have only recently been reported for O. sulcatus (see comments under Table 1); however the fact that the pest tends to avoid species in certain families such as Compositae may provide a means of filtering species for more detailed research of additional chemical candidates that potentially affect movement

The variability of feeding preference of adult vine weevils for strawberry cultivars independent of the presence/absence of leaf hairs, or N concentration (Table 2), indicates potential for trait identification and breeding for more resistant varieties

Bradysia Effects of ITC-containing green manures and seed meal on O. sulcatus and Bradysia populations

both in field and horticultural environments should be tested as biofumigants Further research into the chemical factors of growing substrates affecting behaviour and

development, based upon information on e.g. the relative attractiveness of “green” composts gained from recent studies

Test garlic extracts and neem products for their effects on larval mortality and other behavioural/developmental parameters

Frankiniella occidentalis Volatiles from WFT- attractant species e.g. Browallia should be collected and tested in pursuit of

new actives for potential use in lure and kill approaches; where possible investigating the effect of individual compounds and taking into account the concentration effect (where the same compound may have opposite effects at different dilutions)

Koschier (r27) has pointed out that essential oil extracts from preferred host plants do not necessarily attract and cites an example of repellency of volatiles from a preferred host (r122); variation in the composition of mixtures due to the source cultivar, growing conditions or extraction method may lead to alteration, masking or imbalance of the constituents. For this reason it is relevant to test single actives in combinations, including essential oil extracts from different plants. Using this strategy, more effective trap crops and repellent plant species and more potent biologically active volatiles may be identified for control of WFT, and also for vine weevil and sciarid flies.

Factors affecting larval development and other life-stage parameters e.g. oviposition rates, pupation and adult emergence rates in WFT are areas requiring more attention – there are few reports

A systemic formulation of foliar-based products for WFT control would be useful; this could be taken up by the plant into the young growth where thrips prefer to feed.

Glossary and abbreviations

Antennal response: Term used where a response was measured using EAG or coupled GC-EAG Biofumigant: Plant species that produces pest-controlling chemicals (e.g. mustards) when grown

as a cover crop and ploughed into soil EAG: Electroantennogram, a laboratory-based technique for measuring electrical impulses in

insect antennae Elepidote: Cultivar without leaf scales, as applied to Rhododendron species Entomopathogenic: Description of an organism (e.g. fungus or nematode) that can parasitise

and/or kill or disable an insect Feeding: Behaviour term used where there is evidence of feeding damage GC-EAG: Gas chromatography – Electroantennogram combined, used to identify individual

chemicals in a mixture that correlate with antennal stimulation GCMS: Gas chromatography/Mass spectrometry Genetic knock-out: An organism in which a gene has been rendered non-functional (in the

context of this report used experimentally to e.g. build evidence for the relationship between a signalling pathway and pest resistance)

Green leaf volatiles: (GLVs) volatiles emitted by most plants, concentrations much increased by wounding and including C6–aldehydes, C6-alcohols, and their acetates

Green manure: Plant species grown as a cover crop and ploughed into soil with release of nutrients

ITC: Isothiocyanate, produced as a degradation product of glucosinolates as found in brassicas Knock-down: Term used to describe adult weevils with no visible movement, as distinct from

dead Lepidote: Cultivar possessing leaf scales, as applied to Rhododendron species MJ: Methyl jasmonate, a plant hormone and elicitor of plant defence mechanisms Movement: Behaviour term used that incorporates repellency, deterrency, attraction or e.g.


counts on choice tests where feeding damage was not measured (negative movement includes e.g. deterrency, repellency, and positive movement includes attraction)

Olfactory stimulation: In the context of this report, the term is used where a response was measured in response to stimulation e.g. by presence of a volatile chemical, using EAG or coupled GC-EAG

Phytoecdysteroid: Chemicals produced in plants that mimic the steroid hormones of insects that are involved in moulting thereby disrupting normal development

Population: Growth/survival term used where sequential pest counts are made e.g. on whole plants, foliage or cut flowers

SOS-signals: In the context of this report, chemical signals produced by plants in response to wounding that attract pest predators or parasitoids

WFT: western flower thrips

Index of Tables

Table No.

Pest Activity class Activity sub-class & response

1 Otiorhynchus Behaviour Movement - positive2 Otiorhynchus Behaviour Feeding - promoted3 Otiorhynchus Behaviour Feeding - inhibited4 Otiorhynchus Behaviour Oviposition – increased/decreased5 Otiorhynchus Growth/survival Mortality - increased6 Otiorhynchus Growth/survival Adult development – promoted/inhibited7 Otiorhynchus Growth/survival Larval development - inhibited8 Otiorhynchus Growth/survival Larval development – promoted/other9 Otiorhynchus Other

10 Bradysia Behaviour Movement – all11 Bradysia Behaviour Feeding – inhibited12 Bradysia Growth/survival13 Bradysia Other14 WFT and other thrips

speciesBehaviour Movement - positive

15 WFT and other thrips species

Behaviour Movement - negative

16 WFT and other Frankliniella species

Behaviour Feeding - promoted

17 WFT and other Frankliniella species

Behaviour Feeding - inhibited


18 Other thrips Behaviour Feeding - inhibited19 WFT and other

Frankliniella speciesBehaviour Oviposition - increased

20 WFT and other thrips species

Behaviour Oviposition - decreased

21 WFT Growth/survival Mortality - increased22 WFT Growth/survival Larval development - inhibited23 WFT and other

Frankliniella speciesGrowth/survival Population – increased/decreased

24 WFT Other

xviii Joffe, T., Gunning, R.V., Allen, G.R., Kristensen, M., Alptekin, S., Field, L.M., Moores, G.D. (2012) Investigating the potential of selected natural compounds to increase the potency of pyrethrum against houseflies Musca domestica (Diptera: Muscidae). Pest Management Science, 68 (2), pp. 178-184xix Chandler (2011). New approaches to microbial control of insect pests in protected crops and their interactions with waste-based growing media. Final report on Horticulture LINK project HL0193xx Schumann, M. , A.Patel , Vidal, S. (2013) Evaluation of an attract and kill strategy for western corn rootworm larvae. Applied Soil Ecology, 64, pp. 178-189xxi Mathew, N., Ayyanar, E., Shanmugavelu, S., Muthuswamy, K. (2013) Mosquito attractant blends to trap host seeking Aedes aegypti. Parasitology Research, 112 (3), pp. 1305-1312xxii Beirão-da-Costa, S., Duarte, C., Bourbon, A.I., Pinheiro, A.C., Januário, M.I.N., Vicente, A.A., Beirão-da-Costa, M.L., Delgadillo, I. (2013) Inulin potential for encapsulation and controlled delivery of Oregano essential oil. Food Hydrocolloids, 33 (2), pp. 199-206


References to published material9. This section should be used to record links (hypertext links where possible) or references to other

published material generated by, or relating to this project.


Documents

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