AGROCHEMICALS
Trial numbers, zones, extrapolation
Once a draft GAP exists, the focus shifts to how many trials are required and where they must be conducted. EPPO standards distinguish between‘ major’ and‘ minor’ uses.
Major uses, which cover widely grown crops or critical pests in a country, usually require at least ten independent GEP trials conducted over two seasons and distributed across the relevant EPPO climatic zones. Minor uses can be supported with six trials. The number of required trials increases with the number of crops and pests in the GAP, meaning broad efficacy claims can lead to sizeable programmes.
It should be noted that EPPO climatic zones apply only to outdoor uses. For products intended exclusively for use on protected crops such as in glasshouses and polytunnels, climatic zoning is not relevant because growing conditions are controlled. These uses follow the specific EPPO standards for protected crops, and trial numbers are generally lower than for field uses.
To help keep trial numbers proportionate, EPPO allows for extrapolation across similar crops and target pests where justified, with detailed lists of allowable extrapolations available. Data may sometimes be extrapolated, for example, from apples to pears, or from wheat to barley when the target organism and application conditions are similar.
Extrapolation rules are carefully defined, and when used appropriately they can significantly reduce trial numbers without compromising data quality. When using them it can often be good practice to confirm with the regulatory authorities that they will be accepted.
Minimum effective dose & crop safety
Another central requirement under the regulations is the justification of the minimum effective dose.
Regulatory authorities expect the proposed label dose to be the lowest rate that consistently provides effective control under practical conditions. This is important for environmental protection, resistance management and the economics of crop production.
To demonstrate the minimum effective dose, trials typically include a number of lower rates as well as the target label rate. Comparing performance across these treatments allows applicants to show that the proposed application rate is well supported and that lower rates do not deliver satisfactory control.
In some cases, different rates may be needed for different pests or crops. These rates, timings and use restrictions are then captured in the final GAP table, which reflects what has been proven in the field.
Since efficacy is measured as the balance of positive and negative effects, crop safety is also a key component of the efficacy assessment. EPPO standards describe how such effects should be measured and interpreted. All efficacy trials must monitor visible symptoms of crop damage or growth inhibition(‘ phytotoxicity’), while dedicated crop selectivity trials assess the safety of the product on the full range of crops covered by the product label, including measurement of any delayed impacts on yield or crop quality.
Crop safety can be influenced by many factors including variety, growth stage and environmental stress, and a product that is generally safe but occasionally causes unacceptable damage may require use restrictions or amended GAP wording.
The BAD
When the trial programme is complete, data are assembled into the Biological Assessment Dossier( BAD). This explains how the trials were conducted, summarises results for efficacy and crop safety, and ultimately seeks to justify the
proposed uses and application rates. This document becomes the basis for the efficacy section of the final registration dossier. A clear, wellconstructed BAD greatly facilitates a more efficient regulatory evaluation.
The consequences of a weak efficacy data package can be significant. Insufficient data can lead to label claims being rejected, crop uses being refused by regulators, and product registrations being delayed. On the other hand, a strong efficacy package provides clear evidence of agronomic benefit, supports farmer confidence, and ensures the environmental exposure associated with the product is justified.
In an increasingly demanding regulatory environment, efficacy is not simply another dossier section but a central pillar of a successful product registration. Designing efficacy programmes that fulfil all requirements set out under Regulation 284 / 2013, following EPPO guidance and using recognised GEP organisations to conduct trials is therefore essential for securing timely access to EU crop protection markets. ●
J j
Dr Barry Brogan
SENIOR REGULATORY EFFICACY CONSULTANT
ENVIRESEARCH LTD. barry. brogan @ enviresearch. com www. enviresearch. com
18 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981