Insecticide Resistance Action Group
Minutes of the IRAG meeting on resistance management for pollen beetle in 2008 (Held at PSD, York),Wednesday, 7th November, 2007
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Brain, Peter (Bayer Crop Science) (PB) Denholm, Ian (Rothamsted Research) (ID) Foster, Steve (Rothamsted Research) (SF) Foster, Vicky (HGCA) (VF) Hingley, Peter (Certis) (PH) Howarth, Julie (Defra-PSD) (JH) McCaffery, Alan (Syngenta) (AM) Mattock, Sue (Defra-PSD) (SM) Oakley, Jon (ADAS) (JO) Richardson, David (Defra-PSD) (Chair) (DR) Slater, Russell (Syngenta) (RS) Storer, Rob (BASF) (ROS) Walters, Keith (FERA) (KW) |
1. Introduction and objectives (DR)
The purpose of the meeting was to review recent work on pollen beetle resistance in the UK, and to formulate a resistance management strategy for the UK in advance of the 2008 season. This follows on from a recent European and Mediterranean Plant Protection Organisation (EPPO)-sponsored meeting in
2. Overview of EPPO Workshop in Berlin (DR/ID/AM/RS/KW)
Full details of discussions and outputs can be found on EPPO website. Some of the key discussion points were:
- Pyrethroid resistance is widespread and has caused extensive crop losses in some countries. Brought about by overuse of/reliance on this group of active substances.
- More research is needed on pollen beetle biology, particularly issues like overwintering sites.
- Great variation in threshold levels (and also what part of the plant is assessed) between different countries. There are issues over the confidence of using such thresholds. In addition the costs/time in monitoring compared with cheapness of pyrethroids leads to much prophylactic use regardless of need.
- Great variation in recommended rates of the same products between countries.
- There is a need for alternative modes of action and there are unlikely to be any for the UK in 2008.
Key outcomes were:
- Use appropriate justified dose and products within a chemical class that have the highest effectiveness.
- Alternate Modes of Action (MOA), and a minimum of 2 fully effective MOA are required.
- Pyrethroids must be considered as having the same MOA for resistance management regardless of differences in activity demonstrated by individual actives within the group.
- Organophosphates (OPs) and neonicotinoids form a very important part of strategy.
- MOA should be included on product labels.
- Promote other (biological/cultural) control methods.
3. Pesticide usage patterns (KW)
Survey started in 1981 across major oilseed rape ( OSR) growing regions (70-80 commercial unsprayed fields each year). Overall conclusion when comparing spraying with population levels is that there is evidence of unnecessary spraying (particularly during flowering), and this is not related to threshold levels.
Highest populations of adult beetles usually occur during early flowering but, particularly in recent years, also significant populations at the green-yellow bud stage. There seems to be a trend for adults to come into the crops earlier because of warmer climate. It is at this point that most damage is caused.
In recent years reliance increasingly on only one mode of action (pyrethroid), although results of 2006 survey still being drafted and this may include ‘Biscaya’ use (approved on OSR in mid 2005). But there will always be the issue of price between ‘Biscaya’ and the pyrethroids. It may also be one of convenience, with insecticides being added to tank mixes at the same time as fungicide treatments (which are increasingly more intensively used).
In ‘90s alpha-cypermethrin dominated, but now overtaken by other actives (cypermethrin, lambda-cyhalothrin, more recently deltamethrin, zetacypermethrin, taufluvalinate). Currently several applications of each pyrethroid would be permitted (unlike ‘Biscaya’ with only 1 application), but this is likely to change during the Annex I and re-registration process. However, there are a large number of pyrethroid active substances. Possible in future that other neonicotinoids will also be registered on OSR.
Total area sprayed is 75-90% of the area grown, with an average of 1.6 sprays per crop. It was noted that there should be no need for a grower to spray more than two applications of any product.
There was a general discussion on the lack of confidence on the current UK threshold levels – 15/plant, or 5/plant for ‘backward’ winter crops (suffered through bird-related damage) – based on work done in the ‘80s. There is also an additional threshold of 2/plant for hybrids promoted by industry but no real evidence to substantiate this has been found. UK growers are aware these thresholds are significantly above other European countries. Analysis of the data suggest growers are spraying at population levels of around 2 per plant. One of the other issues is that monitoring probably takes place around the edges of the crop which is easier than going into the middle. However, adults tend to congregate at edges (and gates) and so the levels assessed may significantly overestimate actual numbers. Survey data indicate even in areas of low risk there is significant spraying. However, the survey data does indicate that there is a degree of room for manoeuvre in restricting use as part of a management strategy, but still having enough applications to treat the actual (not perceived) risk.
4. Industry/Insecticide Resistance Action Committee ( IRAC) perspective (AM/RS) and UK monitoring data (RS, JO, DR)
A review of the current situation was presented, along with the proposed IRAC decision tree for pollen beetle resistance management. This will become available from their website shortly. Key points:
- Pyrethroid resistance mechanism is metabolic based on P450 mono-oxygenase. There is cross resistance to actives within the group, but no cross resistance to other chemical groups (e.g. OPs, neonicotinoids, spinosad).
- An overview of survey results was presented. In France and Germany the susceptible populations tended to be in the southern areas of the country which are not major OSR growing areas.
- Netherlands – small area of OSR grown (c4000 ha)
- Map of UK samples discussed – 15-20% samples (68 populations) had MR or R (both resulting in control failure). Based largely in South East/East Anglia regions.
- IRAC Decision tree split into pre- and flowering options (noting that OPs not available during flowering because of bee toxicity). Based around alternation of pyrethroids, OPs and neonicotinoids. Exact detail will depend on what is available in each country.
- Noted that France only uses pyrethroids (does not permit neonicotinoids and OPs due to ongoing concerns over bee effects). Therefore any UK strategy will have to face the fact that resistant beetles (which can migrate long distances), are likely to be dispersed in UK from nearby countries.
ACTION: RS to check on UK locations and update map
ACTION: HGCA will put link to IRAC decision tree on their website.
5. Proposed UK RM strategy for 2008 (All)
Based on the information provided, a UK management strategy for 2008 was discussed and drafted. In drafting this it took account of –
- Need to alternate modes of action.
- Thresholds – much discussion but agreed that at present we must stick to the current ones until data are available to amend.
- Resistance management needed to be realistic and one that the growers could readily understand.
- Pyrethroid use (and therefore incidental exposure) on other crops needed consideration. (For example C. napi appears to now be a UK pest requiring treatment, seed weevil on the other hand is no longer a pest, there also needs to be consideration of the use of aphicides).
The agreed strategy is as attached. It was also identified that there should be some introductory comments to the strategy so that growers could understand how the strategy was developed. This would be based on information on how resistance has developed elsewhere in Europe, some of the survey data (including the UK) to give a clear message on the potential threat of resistance development. Also some of the other factors on, e.g., monitoring – potential misleading information if only looking at field margins. These comments will be developed and included in a newsletter to growers - discussed further under 7.)
ACTION – KW will look at the survey data which does differentiate between the edge and middle of fields. If relevant this can be added to Factsheet.
6. Strategy for dissemination (All)
ACTION - Series of HGCA Roadshows are planned where JO and DR will provide presentations on background to problem and proposed UK strategy.
ACTION - JO will produce background information for the management strategy, and also produce an article for farming press.
ACTION: HGCA to produce news article and Factsheet for growers, farming press. This will include the IRAG, HGCA and PSD logos (Action – DR to check use of PSD logo OK).
ACTION: Distributors need to know ASAP for the coming season. Factsheet needs to go out after the IRAG meeting next week. ID will write to Agricultural Industries Confederation (AIC) after the IRAG meeting (contact is David Caffall – action PH to provide details).
7. UK Monitoring in 2008
Future monitoring in Europe is unlikely now due to the established pyrethroid resistance problem. All agreed however that there should be more monitoring in UK next year distributed appropriately across the country. This will be discussed at next IRAC meeting in December. KW noted that The Food and Environment Research Agency( FERA) could do this on behalf of companies as part of their survey work. There was a discussion over whether 4 screening diagnostic concentrations were still needed, this will be discussed at the December meeting. Syngenta could supply technical lambda cyhalothrin to anyone who wanted to make up their own testing kits.
8. Research gaps/needs (ALL)
HGCA have an ongoing research project looking again at threshold values. JO noted that there was no point developing (or introducing) a more sensitive monitoring system at this point because, until the threshold levels are revised, it would simply encourage more spraying. It was noted that the Austrians have a headland threshold, which presumably has the advantage that growers do not have to go into the crop (but also takes account of adult distribution within the crop).
A key issue to be resolved is the ‘plasticity’ of the new hybrid and dwarf varieties i.e. their ability to compensate for pollen beetle damage in the way that older varieties could. HGCA is funding work looking at plant physiology and actual damage caused by beetles using simulation studies. It should also take account of the increasing use of triazoles which can have PGR properties and affect plant growth (shorten the crop). During the EPPO meeting the Danes presented information on a model they have looking at spring OSR compensation.
There is a LINK proposal to look at pest monitoring and development of trap crops as an alternative control measure.
More research is needed on pest biology, but this would be expensive to fund (for example, this is a very mobile pest which is not easily suited to small plot work).
9. AOB
- Agreed there needed to be a ‘watching brief’ on horticultural crops with a view to raising the awareness of the potential for resistance issues to develop, and the need for careful management of pest problems on crops. Excessive pyrethroid use on these crops might undermine strategies to manage resistance on OSR. This would be raised at the next IRAG meeting to inform relevant horticultural members.
- Agreed that another meeting next year would be worthwhile. Proposed date Wednesday 24th September 2008, venue to be confirmed.
[POST MEETING NOTE – IRAG strategy was refined slightly following post-meeting comments, and drafted into the HGCA pollen beetle factsheet along with some background notes]