1 Introduction
2 Methods
2.1 General
2.2 Stage 1
2.3 Stage 2
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The pesticide is a potential challenge for water company compliance with the DWD without the adoption of enhanced treatment technologies.
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The pesticide will potentially not be reapproved under EU pesticide approval Regulation 1107/2009 (EC 2009) and there is reason to suspect that replacements might cause water quality problems.
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The efficacy of the pesticide is threatened by the emergence of resistance which means that alternatives might be needed in the future.
2.4 Stage 3
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H n : There is no consensus in responses to the Likert item.
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H a : There is a consensus in responses to the Likert item.
3 Results
3.1 Stage 1 and 2 Findings
3.1.1 Basic Agronomic Features
Winter wheat | Winter OSR |
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Stale seedbed | Stale seedbed |
Delay drilling to allow a stale seedbed followed by application of a non-selective herbicide, typically glyphosate, to kill any weeds which have germinated before drilling. | NB: This is not widely used because OSR is drilled earlier than wheat. |
Pre-emergence treatment | Pre-emergence treatment |
Apply residual herbicides at the pre-emergence stage. Stack (apply) a range of actives based upon a flufenacet base (10/10). Other residual herbicides for inclusion in the stack include: | |
• Metazachlor (7/10) | |
• Metazachlor + quinmerac (3/10) | |
• Metazachlor + quinmerac + dimethanimid – p (2/10) | |
• Diflufenican (10/10) | |
• Pendimethalin (10/10) | |
• Triallate (5/10) | |
• Prosulfocarb (6/10) | |
• CTU (2/10) | |
• Flurtamone (1/10) | |
Post-emergence treatment | Post-emergence treatment |
Atlantis (mesosulfuron-methyl + iodosulfuron-methyl) is the dominant product (10/10). | Propyzamide AND/OR Carbetamide (10/10) |
Tepraloxydim and cycloxydim can be used as support (1/10) |
3.1.2 The Combinable Crop Rotation
3.1.3 The Impact of Regulation on Pesticide Use Patterns
3.2 Stage 3 Results
3.2.1 Introduction
3.2.2 Hypotheses (Likert Scale) Based Upon Multiple Likert Items
Hypothesis | Number of Likert items to test hypothesis | Likert items supporting hypotheses | |
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A | There are no direct substitutes for currently used herbicides. | 4 | 100 % |
B | Cultural control is a complement to not substitute for pesticide active substances | 5 | 100 % |
C | Herbicide losses in wheat will lead to increased dependence on currently available pre-emergence herbicides | 8 | 100 % |
D | Effective resistance management requires as many modes of action as possible | 5 | 100 % |
E | The order of preference for adaptation to the loss of a pesticide active substance is: substitute pesticides, alternative pesticide in rotation, cultural control, crop architecture, rotational control | 8 | 100 % |
F | The development of new active substances takes time (at least 5 years), and is not triggered in response to the potential loss of a currently approved active substance. The loss of active substances does not create an incentive for new pesticide active substances to come to market | 3 | 100 % |
3.2.3 Active Substances Specific Findings
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Propyzamide and carbetamide: Propyzamide, and to an extent carbetamide, are crucial to blackgrass management in a combinable crop rotation on heavy soil. Without these active substances it would be difficult to grow OSR or any other autumn break crop, so rotational change based upon increased spring cropping might occur. It is uncertain whether carbetamide could substitute directly for propyzamide.
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Metaldehyde: Cultural control options cannot eliminate the need for slug pellets. Substitutes for metaldehyde are available. If metaldehyde were restricted for any reason, increased use of these substitutes could prevent rotational change. However, agronomist comments express concern regarding the relative cost, efficacy, availability, proven track record and environmental impact of these possible substitutes.
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Mesosulfuron-methyl (‘Atlantis’): Reduced efficacy of post-emergence blackgrass control in wheat will reduce wheat yields and increase the use of pre-emergence herbicides. Cultural control options are inadequate to cover for reduced efficacy; if control was too difficult, a change to the rotation might be considered.
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Clopyralid: Clopyralid is the only herbicide available for the control of sow thistles. Cultural control is largely ineffective. If clopyralid were unavailable where sow thistles are a particular problem, OSR yields would decrease and reduced OSR planting might occur.
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Pendimethalin and chlortoluron: Blackgrass control depends upon many active substances and different modes of action to increase total efficacy and reduce resistance risk. The loss of one active substance would have impacts on how others were used.
3.2.4 Likert Items on General Themes
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When one active substance is lost (for whatever reason) other active substance(s) will be used to manage the weed, pest or disease issue.
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In the absence of effective pesticide control, weed and pest pressures will increase over time.
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The agronomic impact of losing an active substance depends on which active substances remain available.
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No new herbicides for blackgrass are likely to be available in the next 5 years.
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A change to the rotation is the intervention of last resort.
3.2.5 Tests for Acquiescence Bias and Internal Consistency
4 Discussion
4.1 Agronomic Adaptation Options and Preferences
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Agronomists who need to explain the practical ramifications of the loss of any active substance.
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Regulators who need to understand the ramifications of any decision to restrict active substance availability.
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Water suppliers who need to anticipate which active substances to expect in ‘raw’ water in the future.
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1st Preference: Use a direct substitute. A direct substitute is a pesticide active substance with an equally established agronomic track record that can be applied at the same stage in the rotation with equally efficacy at an equivalent cost. Likert scale Hypothesis A indicates that direct substitutes are very rare. Metaldehyde for slug control illustrates the rarity of direct substitutes: methiocarb and ferric phosphate were identified as possible alternatives and at least one was rated as similarly efficacious. However, neither substance can be considered as a direct substitute because agronomists identify strong reservations regarding the relative cost, relative efficacy, environmental impact (methiocarb), availability of supply and lack of proven track record (ferric phosphate).
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2nd Preference: Use a close substitute. A close substitute is an active substance that could potentially replace a currently used active substance at similar timing but differs to some degree in terms of one or more factors from efficacy, cost, proven track record and environmental impact.Likert scale Hypothesis D establishes the need for multiple modes of action to manage resistance, and Table 1 illustrates the need for a range of active substances, to be used in some circumstances, to maximise the level of control achieved. Therefore, a distinction is needed between close substitutes and those active substances already used as part of a programme of control alongside the active substance in question. For example, flufenacet and diflufenican (Table 1) are complements rather than substitutes, because blackgrass control is most effective when these residual herbicides are used in combination (Shah et al. 2012; Hull and Moss 2012). Thus, in reality, close substitutes are also rare.
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3rd Preference: A substitute at a different timing in the rotation. Similar to a close substitute but applied at a different timing. A prominent example of this is given by Likert scale Hypothesis C, where in the absence of direct or close substitutes, agronomists have begun to adapt to the decreased efficacy of the post-emergence herbicide mesosulfuron-methyl (‘Atlantis’) by combining more pre-emergence herbicides.The 1st, 2nd and 3rd adaptation options all relate to replacing one active substance with another. However, the feasibility of these options is constrained by the availability of active substance chemistry. Likert scale Hypothesis F, agronomist comments and information from the literature (Shah et al. 2012) identify a shortage of new active substances coming to market, decreased availability of active substances as a result of European pesticide legislation and the perception that WFD Article 7 may potentially further-restrict active substance availability. Therefore, before restricting any active substance a regulator must consider whether sufficient (and appropriate) alternatives are available to provide equivalent control, at an equivalent cost with lower environmental and DWD compliance risks. Similar considerations must be made by any water company implementing a catchment management strategy based upon promotion of active substance substitution.Several agronomists in the survey expected the loss of active substances to be particularly acute for horticulture, because it is dependent on specific off-label approvals (SOLAs) of active substances originally developed for other crop types, and it is costly (relative to the returns achievable), to register an active substance for minor use.
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4th Preference: Use cultural control. Cultural control is the use of cultivation practices without a fundamental change to the rotation, to improve control and preventatively manage disease, weed or pest problems. Cultural control options are increasingly becoming part of an integrated control strategy (Hull and Moss 2012; Neale 2012). Examples include compaction of seed beds to reduce slug risk, the use of rotational ploughing to bury weed seeds and stale seed beds with glyphosate to reduce weed levels prior to crop drilling (Table 1). However, Likert Hypothesis B concludes that these actions should be a complement to, and not a substitute for pesticide use. This may be explained by poor efficacy and reliability in comparison to pesticides, as (Moss 2010) observes ‘Nonchemical control methods have mean efficacy levels equivalent to a very poor [pesticide] product, but often at a premium price’.
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5th Preference: Change crop architecture. This intervention avoids the need for a change to the rotation by changing the approach to the management of one or more crops in the rotation. Current UK research is investigating whether precision spraying techniques can be applied to manage blackgrass using a non-selective herbicide such as glyphosate between wide rows of OSR, thereby restricting propyzamide and carbetamide use solely to the cultivated area (Ballinghall 2013). At present the agronomist community is uncertain whether this type of intervention will reduce water quality problems caused by certain active substances. Reasons for this uncertainty are threefold: research to develop selective spraying techniques is ongoing; work to establish the optimal row width for OSR is yet to be completed; whether only applying propyzamide and carbetamide to the cultivated area will reduce movement to water is has not been investigated. If selective spraying techniques are perfected and made commercially available, it is possible that they could be transferable to other crops.
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6th Preference: Change cropping/rotation. Although this intervention was identified as a last resort, it may occur if the other options fail, if the cost of a cropping change is less than adopting one of the other options (1–5), or if the expected benefit from changing the rotation outweighs the short term cost. There are three possible types of cropping change: a different crop grown in the same growing season, a spring crop introduced into the rotation in place of an autumn sown crop and the introduction of an occasional fallow into the rotation. Moss and Hull (2012) confirm agronomist comments that the potential for spring cropping is limited by the suitability of land, relative economics, the difficulty of establishing subsequent crops and the availability of active substances to manage weeds emerging in spring.The adaptation options framework assumes all factors other than active substance availability will remain constant. However, exogenous factors have the potential to disrupt relative preferences for the adaptation options. Examples of such factors include global commodity prices, changes to elements of European policy (e.g. CAP reform, GMO policy, drinking water standards for pesticide active substances and incentive payments for energy crops) and technical developments making certain crops easier to produce.
4.2 Using the Current Strategy to Anticipate Adaptation
4.3 Constraints to Adaptation
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The availability (or not) and cost of direct substitutes, close substitutes, or substances for use elsewhere in the rotation.
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The availability, efficacy, time and cost of cultural control options.
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The need to manage the risk of resistance.
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The need to avoid short term risk in the current crop.
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Reluctance to use unproven solutions in place of proven solutions.
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The risks and cost of spring cropping.
4.4 Messages for Catchment Management
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Restrictions on active substances will have knock-on effects for the use of other active substances and in many cases on agricultural productivity. How adaptation occurs and the scale of the impact will depend on the context of active substance availability at the time of any restriction and whether adaptation preferences 1, 2 and 3 (Fig. 1) are available.
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In the majority of cases, the active substances being used are those which are most effective and the agricultural benefits of application outweigh purchase and application costs.
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Catchment management based upon product substitution is unlikely to engage pesticide users if it is voluntary, and it would impose costs on agriculture, if it were statutory.
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Cultural control options are an increasingly important element of a control programme, but are unlikely to replace active substance use (Likert scale Hypothesis B).
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The use of the adaptation option preference framework (Fig. 1) coupled with a knowledge of the agricultural drivers for pesticide use to tackle a particular problem in a particular rotation (e.g. Table 1), can provide a foundation for regulators and water companies to anticipate the possible impacts of action to address any water quality issue for pesticides.
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Both farmers and water companies need to take a long term, whole rotation perspective on the cost of inaction, compared to the cost of action (Moss and Hull 2012). Where costs must be incurred, evidence of a long term benefit must be available.