Minutes of the 15th meeting held at BASF, Woolpit, Suffolk, Thursday 13th October 2005
Collier, Rosemary (Warwick-HRI) - RC
Denholm, Ian (Rothamsted, Chair) - ID
Foster, Steve (Rothamsted, Secretary) - SF
Grosjean, Otto (BASF) - OG
Hingley, Peter (Certis) - PH
McCaffery, Alan (Syngenta) - AMcC
Mattock, Sue (PSD) - SM
Parker, Bill (ADAS) - BP
Powell, Vivian (HDC) - VP
Walters, Keith (FERA) - KW
1. Welcome and apologies for absence
Jude Bennison (ADAS) - JB, Kevin Gorman (Rothamsted Research) - KG and John Young (BASF) - JY were welcomed to the meeting. JB had accepted an invitation to provide an overview of resistance in glasshouse pests. JY will be taking over from OG on the Steering Group.
Apologies for absence were received from:
Bean, Chris (UAP)
Fenton, Brian (SCRI)
Macnicoll, Alan (FERA)
Meredith, Richard (Bayer CropScience)
Solomon, Mike (East Malling Research)
2. Minutes of last meeting
The minutes of the last meeting were agreed.
(IRAG) minutes are available on:
Insecticide Resistance Action Group Home Page
3. Feedback from Insecticides Resistance Action Committee (IRAC)
AMcC gave a brief overview of current IRAC activities. The IRAC website has recently been accessed from over 80 countries with an average of 30 specific visits per day. Greater than 30% of visits are to look at the Modes of Action (MOA) classification, 16% are on insecticide resistance and 60% come via Google where it rates as number one for the search phrase ‘Resistance Management’. It is now a very functional website and has a new look. A free Newsletter is sent out through e-connection around 4 to 6 times a year with approximately 500 recipients on the distribution list. The Newsletter has included comments on European Crop Protection (ECP) and the lack of a diversity of additives for use on minor crops such as oilseed rape (against pollen beetles) and the development of apparent resistance to neonicotinoids in the brown plant-hopper on rice in IND.
There has been a major revision of the MOA Classification (updated in September 2005). This has been reformatted for easier use and is completely aligned with the Pesticide Manual. The search facility can be used to rapidly cross-reference chemical classes, active ingredients and modes of action. A poster has also been produced showing the MOA classification. This includes chemical structures and names. 3000 copies are being printed.
IRAC will be involved in the forthcoming Open Forum workshop due to be held at British Crop Protection Council (BCPC) in Glasgow on November 2nd.
At present the subscriptions to IRAC are small so it cannot fund research. At some point it is hoped to introduce a bursary system and IRAC has proposed supporting and manning a Resistance Workshop that will be based at Rothamsted Research.
Different countries are taking up MOA labelling so there needs to be a very good reason for changing something on the website as alterations to labels will be expensive. Realistically, information needs to be ‘General Guidance’. ID said there should be a standard methodology for resistance analysis. This would harmonise methods so that users can employ common and comparable bioassay methods. Nigel Arms (IRAC) is in charge of collating different methodologies for standardisation.
4. Regulatory Issues
SM informed everyone that there has been a special meeting of the Weed Action Group (WAG).
Peter Glendinning has concerns that there are not the same levels of hop aphid control as in the past. ID reminded the meeting that Ralf Nauen has found no actual resistance to imidacloprid in hop aphids in DEU. He has concluded that reduced efficacy was a result of a major switch by Growers to a new hop variety, Magnum, which presented greater challenges to the product and its application due to its much larger leaf size (relative to previous varieties). Bayer CropScience has found evidence of resistance in this pest in mainland Europe. PH pointed out that there has been a long run of imidacloprid use on hops (approximately 10 years) and evidence of resistance remains anecdotal. ID said that Rothamsted have gained susceptible baselines so all we now need are samples from ‘problem areas’ to assess the current situation.
5. Update on Research
5.1. Defra/HDC funded project on aphid pests of lettuce and brassicas (RC)
RC brought everyone up-to-date with her project testing various active ingredients (including pirimicarb, pymetrozine, new AIs and bio-pesticides) against several aphid species (Myzus persicae, Nasonovia ribisnigri and Brevicoryne brassicae). This is aimed at addressing the shortage of actives and ultimately developing Resistance Management Strategies on these crops. The project has produced a lot of data which will be analysed fully in the near future.
5.2. Link project on stewardship of neonicotinoids (ID and SF)
ID described progress on this project which aims to address risks of M. persicae developing resistance to neonicotinoids. It has three main components:
(i) Assessing the response of imidacloprid-susceptible and resistant clones of M. persicae to several neonicotinoids in bioassays. This work is now complete and has shown a consistent pattern of response across the compounds tested. At this stage the causes of variation in response to neonicotinoids are 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 (with an RF approximately 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. These include two recently-collected samples with 50% mobility; the highest to date. However, the mobile aphids in these did not produce any viable offspring. Other aphids from these samples (from subsequent generations) will be assessed.
(iii) Several field-simulator experiments have examined how commercial seed treatments with imidacloprid in oilseed rape 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 oilseed rape treatment aimed at Coleopteran pests. The experiments challenged aphids with plant/insecticide combinations that are currently present in the field. Measurements of survival, feeding behaviour and fecundity have been taken 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 are currently being analysed.
On the subject of resistance to neonicotinoids, Rothamsted is involved in collaborative research on whiteflies (Bemisia tabaci). Resistance in this species is conferred by increased activity of mono-oxygenase enzymes which break up the insecticide molecules. Sexual crosses using Q biotypes are exploring co-segregation of resistance with a particular DNA marker that may lead to a rapid resistance diagnostic. Q biotypes have supplanted the B biotypes in some Mediterranean regions and there are now major concerns that they may also become established in the USA and CHN. They are often found on Poinsettia. Exports of this crop appear to be facilitating whitefly movement around the world.
There is an emerging problem with controlling the brown plant-hopper in IND and other regions of Asia. Resistance to imidacloprid appears to be conferred by mutations in the target site protein (the nicotinic receptor) as well as enhanced detoxification. Over the last few months work at Rothamsted has looked at the binding of several neonicotinoids to susceptible and resistant forms of the protein expressed using oocytes. This has disclosed large differences that are fairly broad-spectrum to the neonicotinoids.
In the absence of Brian Fenton Scottish Crop Research Institute (SCRI), ID gave a short summary of progress on a project looking at the diversity of M. persicae primarily in the SCT (based on a meeting that had been held in June 2005). The work has revealed limited clone variability. Two predominant 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 ENG.
6. Emergency SOLAs for controlling resistant M. persicae on winter oilseed rape
Should IRAG be involved in stimulating emergency Specific Off-Label Approvals (SOLAs)? If there is a resistant pest situation in the field with no approved insecticide available for control then someone needs to provide the stimulus for action. IRAG should be involved on a consultative "What are the right products needed as (SOLAs)" type approach. For example, we are currently in a situation where there is no effective insecticide approved and available for use in rape should resistant M. persicae need controlling in the crop, although by next autumn there will be foliar applications of thiacloprid (Biscaya) for control of pollen beetles. This compound has also been recommended for use on potatoes.
If IRAG is to be of value to the industry and continue to develop itself then should it act in a proactive capacity as it does in terms of advice on how to approach a problem? IRAG can identify ‘gaps to growers’ and develop a ‘wish list’ of problems that may be looming. VP proposed a gap analysis based on the potential for resistance to develop. This could include looking at whether a product(s) is already in effective use on the continent. The deadline for the Review Programme is 2008 when we will have a better idea of the diversity of compounds remaining at our disposal.
VP pointed out that essential uses will become more difficult to achieve and for minor uses we will end up with a situation where new products are not in the pipeline. OG said that from a practical standpoint there first needs to be a control problem. The Resistance Matrix that has been put together by BP should address this issue to some extent.
7. Liability of IRAG for advice on Resistance Management
A discussion took place on the legal implications of advice given by IRAG. If this expands there may be the need to take a more formal approach and have liability insurance. However, this may not be an issue as IRAG has been giving advice for a relatively long period of time without any problems. BP pointed out that most information going to growers is interpreted mainly by people that are relaying the advice (i.e. consultants). We can list the different MOAs that are available but advocating any one product may create difficulties. RC suggested that any Guidelines should contain some sort of Disclaimer saying that the information should be used at a user’s risk. Possibly IRAG should stick to guidance in a general sense that needs interpretation by advisors or growers.
8. Discussion led by JB on resistance in glasshouses
JB described the current situation of insecticide resistance in several glasshouse pests including aphids, whiteflies, thrips, spider mites and leaf miners.
M. persicae is a major pest under glass. Aphis gossypii is a major pest of hardy nursery stock (in glasshouses and polythene tunnels) and appears to be totally resistant to pirimicarb. Pymetrozine (Chess) is working well as part of IPM programmes which can also include nicotine (aimed primarily at aphid control). Thiacloprid (Calypso) is also being used but is not as compatible with IPM aimed at controlling both aphid species. Imidacloprid is used more against aphids and whiteflies. When control problems persist, another product, Eradicote, can be used as a contact pesticide against whiteflies and spider mites. It works well when it has good coverage. PH pointed out that product was usually more expensive and will also kill beneficial parasitoids but has a short persistence.
There have been very few reports of problems with Macrosiphum euphorbiae. This is controlled well by pymetrozine. Aulocorthum solani remains fully susceptible to insecticides and is also controlled well by the parasitoid, Aphidius ervi.
SM asked if growers were mixing products. JB replied that this is limited and depends on the pests present.
There are increasing problems with controlling the whitefly, Trialeurodes vaporariorum which appears to be resistant to many insecticides. JB said that growers were not getting good control with imidacloprid against this pest and that pymetrozine does not work well against whiteflies. KG informed the meeting that there is now evidence for resistance to imidacloprid in T. vaporariorum in the UK. He has analysed 28 populations from the UK and some from Europe and other parts of the world. No resistance was seen until recently but in 2004 two populations (one UK and one NLD) showed reduced mortality at high concentrations of imidacloprid. It is unclear if the UK sample reflects UK-based selection or immigration from NLD. No samples have been looked at in 2005 so the current extent of the problem is unknown apart from continued reports of control failures. The mechanism(s) involved and the cross-resistance profiles have not been looked at and deserve some attention. JB said that she is aware of whitefly populations that appear to be poorly controlled by pymetrozine and spiromesifen (Oberon). KG has a sample of one in culture and will be assessing it for resistance. PH was confident that some control problems were related to poor application of insecticides.
Buprofezin resistance has remained stable over the last few years in laboratory and some field populations of T. vaporariorum. This suggests that there has been little immigration of susceptible forms and there are limited fitness costs associated with buprofezin resistance in this species. PH said that in NLD efficacy appears to have returned, as there is anecdotal evidence of neonicotinoid resistant B. tabaci being effectively controlled by buprofezin. There is likely to be an increased use of pesticides on Poinsettia as growers are particularly nervous about getting whiteflies on this crop. ID said that when this happens they are quite likely to be Q biotypes. KG said that there is no evidence of resistance to abamectin in B or Q biotypes; T. vaporariorum has not been tested with this compound. PH asked if there is good activity of spinosad against whiteflies; subsequent literature searches have disclosed that there is, however, resistance known in B. tabaci at least.
Western Flower thrips (WFT) have a history of developing resistance so biological control is an important component of resistance management strategies. JB remarked that this pest is becoming an increasing issue on strawberries. When pyrethroids are used they select for this species out of the thrips present. PH suggested that oxamyl may soon receive registrations to include use against WFT in Strawberries. There is resistance in WFT to spinosad in AUS (work done by Grant Herron) so it is probably only a matter of time before it spreads to other areas, research is urgently needed for UK populations. Resistance to spinosad is also known to exist in some Lepidoptera (Resistance Factors over > 100).
ID said that Grant Herron has also shown resistance to fipronil (Vi-Nil) in Western Flower thrips (WFT). JB said that IPM in the long term is the answer for protecting strawberries. She was not aware of any resistance in Thrips tabaci. RC pointed out that the pyrethroids have not worked well against this T. tabaci over the past two years. SM said that there are data showing that this pest is difficult to target. RC said that there are control problems in leeks, salad onions and white cabbage and it would be informative to get samples from these crops tested with pyrethroids. VP said that leek growers are keen to find out when thrips feed so that treatments can be directed towards best control. So far, this has only been done for WFT (as part of a PhD study).
PH highlighted the issue of adding anti-feedants to thrips sprays to alter their behaviour, however, these would have to be registered as pesticides. Control using nematodes works well on ground-dwelling phases. KW pointed out that exposure to a short period of light leads to increased thrips movement. JB responded by saying that there are conflicting data on this subject.
Abamectin (Dynamec), fenbutatin oxide (Torq) and spiromesifen work well against spider mites. Bifenthrin (Talstar) is becoming less reliable. These pests can be very difficult to control, particularly in warmer conditions during the summer.
There are documented cases of resistance in leaf miners to abamectin and pyrethroids and suspected problems with imidacloprid and thiacloprid.
JB said that there is no standard ‘Guidelines Leaflet’ for growers and they get their advice from consultants. ID asked how complicated it would be to devise control strategies. SM replied by saying that there is scope for general good practice recommendations. Factsheets and a dedicated seminar (in consultation with IRAG-UK) could be the first steps. VP said there are a lot of lessons that soft fruit growers could learn from growers of protected crops. ID said that it will be an interesting challenge to get all this advice into an IPM context.
Action JB to pass on contact details for the PhD study to VP.
Action: JB to enquire on how to proceed with getting advice across to growers.
9. IRAG outputs
The M. persicae Guidelines have been updated. However, we still need to distil key pieces of information for ease of interpretation. This is an opportune time as new approvals and chemistries are on the way. RC said that a Factsheet will be produced as part of her Defra-funded project. She also said that there is an argument for doing something more crop-specific. VP said that it needs to be something that leads growers to alternate chemistries. What form it takes needs to be decided by IRAG-UK. RC said that an issue that arises regularly is which mixtures and doses of insecticides, fungicides and herbicides should be used. SM said that there is less scope for reducing the doses of insecticides.
SF gave a brief description of the Resistance Management sessions (for insecticides, herbicides and fungicides) at the forthcoming BCPC in Glasgow. This will include an Open Forum on the work of the Resistance Action Committees (RACs) and Resistance Action Groups (RAGs).
A meeting on pest resistance is planned to be held at Rothamsted in 2007 (Resistance 2007). It is hoped that this will include a workshop on resistance diagnostics and management.
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 16th meeting of IRAG-UK is scheduled to take place on Thursday 27th April 2006 at FERA(York) and will be hosted by Keith Walters.