Minutes of the 16th meeting held at FERA, York, Thursday 27th April, 2006
Collier, Rosemary (Warwick-HRI)
Denholm, Ian (Rothamsted Research, Chair)
Fenton, Brian (SCRI)
Foster, Steve (Rothamsted Research, Secretary)
Hingley, Peter (Certis)
Mattock, Sue (Defra-PSD)
Meredith, Richard (Bayer CropScience)
Parker, Bill (ADAS)
Powell, Vivian (HDC)
Walters, Keith (FERA)
1. Welcome and apologies for absence
David Richardson (Defra-PSD) was welcomed to the meeting.
Apologies for absence were received from:
Bean, Chris (UAP)
McCaffery, Alan (Syngenta)
Solomon, Mike (HRI-East Malling)
Young, John (BASF)
2. Minutes of last meeting
The minutes of the last meeting were agreed.
(IRAG) minutes are also available from the home page.
ID opened by saying that the last (IRAG) meeting had been just before the Resistance Action Groups (RAG)s and Resistance Action Committees (RACs) Open Forum at British Crop Protection Council (BCPC) 2005. The latter had been a very useful session and had created a spirited discussion. A follow-up is likely at BCPC 2007.
3. Feedback from Insecticide Resistance Action Committee (IRAC)
ID gave a brief overview of current (IRAC) activities. He had just attended part of their latest meeting in Edinburgh.
The Michigan State University resistance database (organised by Mark Whalon) had been discussed. It was hoped that it would be made more accessible via the web. There are now 2645 specific cases of insecticide resistance around the world with 542 species of arthropods resistant to at least one compound. 316 different compounds are affected.
A range of bioassay methods are now available to assess resistance. However, they need to be validated between companies to ensure the relevant information is available to allow bioassays to be repeated consistently. There will be a permanent (IRAC) representative on the European Plant Protection Organisation (EPPO) resistance committee. Oliver McDonald is the equivalent representative from PSD.
The (IRAC) poster showing the Modes of Action (MOA) classification is now available. However, it will need to be continually revised as new compounds appear. For example, flonicamid currently sits in the category of compounds where the (MOA) is unknown. However, there is a paper ‘in press’ describing this compound as an A-type potassium channel inhibitor. Also, there are one or two compounds about to reach commercial production that act as ryanodine receptor modulators. (MOAs) are being linked to (BCPC) so they will tie-in with the Pesticide manual. It is becoming a pervasive scheme and there is little dissent on how compounds are grouped. The poster is being translated into a number of European languages and it will be available on the (IRAC) website.
PH re-iterated that articles in the (IRAC) Newsletter were a means of publishing without peer-review. SM said that the French authorities are developing a database for fungicides but there are similar problems of no peer reviewing
4. Regulatory Issues
SM had circulated information prior to the meeting on ‘Resistance warnings and restrictions on labels of insecticide and acaricide products’. This was aimed primarily at companies and not growers. Regulatory issues related mainly to neonicotinoids. Since the last IRAG meeting, Biscaya (thiacloprid) had been approved for use on potatoes against peach-potato aphids (Myzus persicae) with one application to ware and two applications to seed potatoes. This decision had been made in conjunction with Bayer CropScience. It raises a generic issue for PSD when considering expansion of chemistry into new areas. PSD intends to look at this in further approvals and ‘on- and off-label’ use will be carefully restricted. In the future, steps may be taken to reduce exposure as a whole, not only for neonicotinoids but other groups of chemistry. Another issue, also relating to thiacloprid, is that it has gone through a re-registration process looking at resistance, and off-label usage is a potential loop-hole. PSD will keep a close eye on each application for approval and ensure a coherent approach. Any approval notices will consider potential resistance risks.
A discussion took place on registration labels. Thiacloprid has many off-label uses. PSD are grateful to VP for her consultation with growers and the agreed approach that has been reached. This looks at how many applications are justified in light of the length of the growing season.
ID said that this approach raises the long-standing question of how growers know of the (MOAs) at their disposal in terms of being able to alternate products.
SM replied that this information is at the back of the Guidelines document. Companies should also say which group a product belongs to on the label. At present the system is reliant on the growers and the companies themselves.
ID asked where Appendix 2 was available. DR replied that it is on the PSD website. ID asked if PSD foresaw the usage of code numbers based on the (MOA) scheme. SM said that these could be incorporated into the Guidelines and be updated as new actives become approved. It would therefore be a ‘working document’. It will also contain information on restrictions, e.g. flonicamid is due to be added in the next publication due soon.
DR pointed out that relatively recently we have had different resistance issues in the herbicide and fungicide areas and PSD has sought advice on the type of approach that should be taken for resistance management. This will be in the form of ‘restrictions on applications’. However, it is not easy to maintain a level of uniformity across the board. Re-registration can re-visit older compounds to see if the guidance should remain as it is.
RM said that it is good to restrict the number of applications to force alternation but there are some scenarios where only one chemistry is available for a crop, e.g. imidacloprid on hops. SM replied by saying that PSD will work on a case-by-case basis.
RM said that conversations with brassica advisors have produced anecdotal evidence that they are not concerned about incidental applications to M. persicae when targeting Brevicoryne brassicae. A focus on M. persicae in guidelines may be hampering control of B. brassicae. PH pointed out that brassicas are a long-term crop where up to four treatments may be used. This is also the case for seed potatoes. In a long-term crop such as Brussels sprouts, on which the aphids can arrive in spring and be present until October, selection can be high. DR pointed out that in deliberating over the number of applications on crops such as Brussels sprouts he had discussed the issue with the chairman of the Brassicas Grower Associations (BGA). DR said that all EU member states should be adopting precautionary messages for restricting resistance. However, this is undermined if foreign growers are allowed more applications, and he was pushing (EPPO) to consider how to harmonise resistance management strategies at EU level. PH reiterated that different chemistry remains the key and options have improved recently. ID responded by saying it is difficult to manage resistance on crops that receive lots of applications, particularly when different pests are being targeted at different times. RM said that on a winter crop, treatments may also need to be made against over-wintering pests.
ID pointed out that neonicotinoids have allowed us to focus on ‘risk issues’. We now have a very useful opportunity to update matters and ensure that the ‘alternation’ message comes across in any guidance as we generally tend to have compounds available reflecting three to four different (MOAs). VP said that one good avenue would be a news article or Factsheet aimed at growers and industry. RC said that a Defra project on brassicas (see later) aims to produce such guidelines. SM said that the guidelines for M. persicae on potatoes should be updated in light of new compounds (flonicamid and thiacloprid) that have become available. Subsequently BP agreed to consider the existing texts with a view to updating them. RC said that guidelines should be crop-specific. RM said that there is a ‘grey area’ for anti-feedants.
ID pointed out that the (MOA) of pymetrozine is still unknown but it was justified to place it in a different category to flonicamid. DR replied by saying that pymetrozine is used on a small number of crops and has been available for a reasonable period of time but, as use on a broader range of M. persicae host crops is likely to increase, we need to think about the number of applications that are appropriate. PH said that this compound is widely available as off-label applications. RM said that pymetrozine is essential in some crops such as hops as an alternative to imidacloprid.
BF said that we must encourage alternations to neonicotinoids as applications are becoming biased towards them.
VP said that reference numbering is very important and it would be useful to have restrictions relating to ambient temperature. ID followed by saying these should be on the label. RM pointed out that sometimes there may be ‘tailing-off’ temperature effects; information that will be difficult to communicate to growers on a label.
DR pointed out that the discussion that took place highlights the problems that PSD have as a regulator. From PSD’s perspective it is a balance between allowing a number of applications to permit effective pest management versus the need to restrict applications to endeavour to achieve effective resistance management. This is very difficult as each submission relates to a single active and not the whole group it belongs to. PSD is taking the initiative at present but would welcome (IRAG) and other (RAGs) and (RACs) taking the initiative first? ID said that the challenge for compounds from any particular group that come ‘in sequence’ will be not to penalise any late additions to the ‘application toolbox’. A group like (IRAG) must anticipate resistance risks but the relevant information needed to do this lies within PSD.
PH said that some fungicides have insecticidal effects and KW suggested the writing of a discussion paper.
Action: send comments on the latest draft of the Guidance Document to SM by the end of June 2006.
Action: BP to update guidelines on resistance management of Myzus persicae in potatoes.
5. Update on Research
5.a. DEFRA/HDC funded project on aphid pests of lettuce and brassicas (RC)
RC updated the meeting with her project testing various active ingredients (including pirimicarb, pymetrozine, new AIs and bio-pesticides) against several aphid species (M. persicae, Nasonovia ribisnigri and B. brassicae). This is aimed at addressing the shortage of actives and ultimately developing Resistance Management Strategies on these crops. In year 1 (2004), she looked at the efficacy of a range of insecticides against the target pests in caged plots. In year 2 (2005), she looked at the timing of treatments, selected from year 1. The growth of each crop was divided into two periods, ensuring that the middle period coincided with the ‘aphid crash’. Insecticide applications were made before and after this time in various permutations in 96 plots.
The bio-pesticide did not work against either M. persicae or B. brassicae. Very low numbers of N. ribisnigri made data interpretation difficult. Imidacloprid (Gaucho) seed treatments (followed by sprays after the ‘crash’) gave the best control of all three aphid pests.
The third year of the project is aimed at putting together control strategies to be disseminated as guidelines and through training days. DR asked if the guidelines were scheduled for this year. RC replied that they would be produced by the end of 2006.
BP pointed out that the ‘aphid crash’ last year was particularly early (in June).
5.b. SA-Link project on stewardship of neonicotinoids (SF and ID)
SF gave a short presentation on progress for this project, which aims to address risks of M. persicae developing resistance to neonicotinoids. It has three main components:
Assessing the response of imidacloprid-susceptible and –resistant clones of M. persicae to several neonicotinoids in bioassays.
(i) Topical bioassays with dinotefuran have shown a consistent pattern of response in comparison with several other neonicotinoid compounds tested although its potency is lower. The causes of variation in response to neonicotinoids remain unknown.
(ii) Screening aphids collected from field and UK glasshouse populations by staff from ADAS and Brooms Barn for their response to imidacloprid.
In addition to bioassays applying 10 ppm imidacloprid, samples collected since April 2005 have also been tested with a second, lower dose of 2 ppm imidacloprid that is close to the ED99 of the imidacloprid-susceptible standard clone. This has allowed the detection of aphids carrying lower RFs than the low-level resistant standard clone, 926B (RF~10 fold). In contrast to the UK M. persicae samples collected in 2004, some of the 2005 samples have contained mobile aphids in the bioassays applying 10 ppm imidacloprid. EC50 values have been calculated from full-dose range bioassays for two clones produced from two samples showing the highest proportions of mobile aphids. These are statistically the same as the laboratory standard clone with the highest level of imidacloprid resistance (926B). There is therefore still no evidence of the evolution of greater resistance that will cause control failures for neonicotinoids applied at doses aimed at aphid control.
(iii) Several field-simulator experiments have examined how commercial seed treatments with imidacloprid in oilseed rape (OSR) and cabbage affect various components of fitness of two standard clones of M. persicae showing susceptibility and low-level resistance to neonicotinoids. These have provided a contrast, with the brassica treatment targeted against aphids and the (OSR) treatment aimed at Coleopteran pests. The experiments challenged aphids with plant/insecticide combinations that are currently present in the field. Measurements of feeding behaviour and fecundity were made up to six days after adult apterae were inoculated onto seed-treated and untreated plants using small clip cages (attached at various periods of the plants’ development). The data show treated (OSR) appears to have little impact on M. persicae, irrespective of neonicotinoid resistance phenotype. In contrast, treated cabbage has a major impact, but doesn’t discriminate to any great extent between the two standard clones. A follow up experiment looking at aphid success after several weeks is planned for (OSR).
5.c. SEERAD project on factors affecting M. persicae clones in Scotland (BF)
BF gave a presentation of the progress on a project looking at the diversity of M. persicae primarily in Scotland. The work has revealed huge diversity in sexual populations, i.e. France, but limited clone variability in Scotland, which is asexual. Two predominant Modified Acetylcholinesterase (MACE) clones, seen in 2001 on potato and oilseed rape, appear to have been superceded by two new (MACE) clones which may be better adapted to survival in this region. It would be very interesting to see if these forms also predominate in England.
5.d. Relevant projects at FERA(KW)
KW gave a summary of research on integrated pest management at FERA. Publication of work on quarantine whiteflies and thrips has been completed. One paper on thrips is in press and one on whiteflies is at the draft stage.
A new project looking at novel approaches for controlling Thrips palmi began in September 2005. This is looking at different aspects/modules of the IPM system. The project began with a literature review of useful data which has now been completed and accepted for publication.
There is also a new project looking at alternatives to controlling quarantine pests with methyl bromide; a chemical under pressure of withdrawal. However, alternatives carry resistance issues, as a lot are based on phosphine which is used in many areas.
ID made the group aware of work which has shown the two most serious cases of neonicotinoid resistance. This is metabolic-based in whiteflies (Bemisia tabaci) being conferred by over-expression of P450. In contrast in brown planthoppers (Nilaparvata lugens), resistance appears to arise from both detoxification and target-site modification. Furthermore, the point mutation does not affect binding of acetylcholine as the receptor is fully functional. It also looks as if we have the first case of neonicotinoid resistance in the UK in the whitefly, Trialeurodes vaporarium. A sample received after a control failure with imidacloprid has shown similar resistance to a sample collected from a resistant population in Holland.
6. Proposal for a joint meeting of RAGs and RACs (ID)
Following the success of the Open Forum discussion at (BCPC) 2005, Phil Russell has contacted ID asking if there could be a similar discussion for the (RAGs) and (RACs) at (BCPC) 2007. (IRAC) are keen for this to take place. The (IRAG) members also thought this would be a good idea.
7. Discussion led by RC on resistance management on brassica crops (including Specific Off Label Approvals (SOLAs))
RC precipitated the discussion through a presentation on the intricacies of brassica pest control. There are a wide range of brassica crops, including oilseed rape, and their pests are diverse. Stan Finch has listed 49 species which have changed in importance over time. The main players in order of importance are:
Cabbage root fly (controlled with chlopyrifos, carbosulfan and spinosad (a (SOLA) on Chinese cabbage at present)
Cabbage aphid (controlled by a wide range of compounds: (OPs), dimethoate and chlorpyrifos, carbamates, pyrethroids, imidacloprid, nicotine, pymetrozine and thiacloprid)
Peach-potato aphid (controlled with the same compounds as cabbage aphid; a pest mainly since 1996)
Diamond-back moth (controlled with OPs, pyrethroids, diflubenzuron, Dovetail, Bt, nicotine and spinosad; no evidence of resistance in the UK)/small white butterfly
Other lepidopteran pests (controlled with the same compounds as diamond-back moth)
Pollen beetle (controlled with alpha cypermethrin and Dovetail; no evidence of resistance in the UK although there is resistance to pyrethroids in regions of mainland Europe)
Flea beetle/other beetles (controlled with pyrethroids and carbosulfan)
Some species in this complex are regular pests. However, others are more sporadic.
A discussion now took place on the average number of applications for various brassica crops. RC pointed out that this is dependent on the life of the crop with Brussel sprouts receiving more applications. Although pyrethroids are approved for control of a range of brassica pests, there is evidence that their use can exacerbate problems with certain pests e.g. aphids and cabbage root fly, probably by killing beneficial insects - so they should be used with care.
BP said that growers can take a pest ‘threshold approach’ but this requires monitoring of the crop. Essentially, they need to ‘hold their nerve’ and not apply pyrethroids unnecessarily early in the growing season. BF said that there was migration of peach-potato aphids from potatoes to brassicas. He also raised the issue of glasshouses potentially being sources of pests. PH replied by saying that they were generally very clean environments and glasshouse growers were aware of the problems with transporting aphids on plant material.
Pests that are limited by host availability could change in frequency with the increasing acreage of oilseed rape and the more general growth of this crop around the UK.
KW said that there are good historical records of pests and crops.
ID stressed that (IRAG) should be advocating lower use of pyrethroids.
RM asked whether insecticide mixtures were a better anti-resistance strategy than alternations.
RC said that guidelines should be put together for the use of compounds against brassica pests.
BP said that field experiments have shown that the sequence of insecticide usage is extremely important for controlling M. persicae with early pyrethroid usage causing control problems later on. DR questioned whether pyrethroids are being used by growers for aphid control. BP replied that growers were likely to apply more sprays against aphids in comparison with caterpillars. The basic message to get across is “be careful when choosing whether to apply pyrethroids”. PH reiterated that part of the problem was that pyrethroids are cheap to buy. RC said that a joint (IRAG/HDC) publication formed part of one of her projects.
PH said another issue was resistance in pollen beetles although there is no evidence of this in the UK. SF said that bioassays done in 2004 showed no resistance to lambda-cyhalothrin in this species. DR said that spray doses were lower in Europe. An interesting project would be to assess how different spray strategies, using different doses, affect resistance selection and management in pollen beetles and other pests.
8. (IRAG) outputs
The M. persicae Guidelines on the (IRAG) website need updating. Something more specific to potatoes and brassicas is also needed.
Resistance 2007 will be held at Rothamsted Research (16-18th April) in 2007. Themes include:
- The current status of resistance to pesticides
- Resistance mechanisms
- Population biology and modelling
- Applications of genomics
- Risk assessment and management
- Transgenic crops
It is hoped that the meeting will include a workshop on resistance diagnostics and management sponsored by (IRAC) and European Network for the Durable Exploitation of Crop Protection Strategies (ENDURE).
People can register their interest in attending by visiting the website: www.rothamsted.ac.uk/Research/Resistance2007.html
9. EU Network of Excellence in Crop Protection (ID)
ID said that the EU had called for proposals, aimed at integrating work around Europe in a particular area, about 18 months ago. A project, named (ENDURE) and headed by French National Institute for Agricultural Research (INRA) in France, was submitted and the reviewers had given it a good score. More recently, it has been confirmed that (ENDURE) will be funded but that the EU require cuts to the original budget. A meeting will be held in Paris shortly to discuss how these cuts can be accommodated.
RM informed the group that Bayer CropScience is looking to re-register deltamethrin. This will include pear-sucker control. ID said that French researchers have documented resistance in this species to (OPs) and pyrethroids and that some growers apply end-of-season clean-up sprays. DR said that PSD’s response will be for Bayer to prove that the situation hasn’t changed and that the product is still performing.
Action: (IRAG)-UK members to decide on who will be invited to attend the next (IRAG) meeting to discuss resistance issues.
11. Date/venue of next meeting
The 17th meeting of (IRAG)-UK will take place on Tuesday 31st October 2006 at Defra-PSD in York. It will be hosted by SM and DR.
Post-Meeting Note on insecticide use on Brussels sprouts (indicating the frequency of applications as recorded by Pesticides Usage Survey Group (PUSG), as well as purpose of use).
From the 2003 (PUSG) survey:
Brussels area grown = 4,216 ha
Percentage of crop treated with insecticides = 98.7%
Area treated with insecticides = 41,128 spray ha
Average number of times treated (where treated) = 6.1
Average proportion of full label rate = 85%
Percentage of crop treated with pyrethroids = 97.7%
Area treated with pyrethroids = 16,015 spray ha
Average number of times treated (where treated) = 3.9
Average proportion of full label rate = 77%
All pyrethroids (including pyrethroid/carbamate co-formulations) Percentage of crop treated with pyrethroids/carbamates = 97.7% Area treated with pyrethroids/carbamates = 17,652 spray ha Average number of times treated (where treated) = 4.3 Average proportion of full label rate = 86%
For the pyrethroids, breakdown of use is as follows
Reasons for using pyrethroids (including those formulated with pirimicarb)
Percent of area treated
diamond back moth
cabbage stem flea beetle
peach potato aphid
aphids/cabbage root fly