# Pesticide efficacy testing: interpreting trials for farm product decisions URL: https://leafwrit.com/ie/pesticide-product-testing/ Reviewed: 2026-10-29 **Pesticide efficacy testing asks whether a treatment works in a defined crop and situation.** Examine experimental conditions, treatment application, assessment and reporting in the trial evidence. For a farm purchase, check how closely the evidence matches the proposed use. Start with [EPPO’s explanation of efficacy evaluation](https://www.eppo.int/ACTIVITIES/ppp_activities), then request the complete technical account behind a supplier’s claim. Use the [DAFM product resources](https://www.pcs.agriculture.gov.ie/products/) to resolve Irish product identity and status as a separate enquiry. A trial result does not authorise the product for use in Ireland. ## Write the claim before examining the graph Write down the marketed formulation or experimental treatment, the target organism, the crop, variety and growth stage, and the purpose. Say whether the claim is insect control, lower disease severity, weed suppression or a plant-growth response. Ask what the supplier means by better performance: less visible injury, fewer pests, more marketable output, a longer effect or a particular quality characteristic. Save the claim together with the report that supports it. Keep comparisons specific. A result for one formulation does not describe every product with the same active substance, so ask whether the tested product, adjuvant and application method match what you plan to buy. ## Read the protocol and treatment list together Use general efficacy standards alongside the standards for the particular crop and pest. General standards are freely accessible; access to specific standards requires a subscription. Ask for the trial objective, design, crop and target, location, application record and assessment dates. Work out which differences between treatments were intended and which operations were the same across the whole trial. Ask the report author which protocol and edition were used, and if the trial departed from it, ask why and keep that note beside the result. Ask what happened in the untreated comparison. Was there enough pest or disease pressure for the trial to show anything? If pressure was very low in every treatment, a lack of damage proves little. Also ask which routine husbandry and non-target treatments the untreated plots received. ## Identify the reference treatment Compare treatment performance against an appropriate reference product across trials. Ask why that reference was chosen and whether it fits the use you have in mind. A reference treatment and an untreated comparison answer different questions, so look for both. For mixtures or programmes, get the full sequence and check whether adding the product was the only difference from the reference programme. Ask how plots were allocated, whether treatments were replicated and how the design dealt with differences in slope, soil, starting infestation or crop density. Ask the trial author which observations come from independent plots and which are repeat samples from one plot: several photographs of one plot are not several experiments. A commercial demonstration can show the work involved and how the crop looks, but ask what was measured and what was only a visual impression. Note who organised and paid for it, and keep the date, crop position and treatment behind each photograph, with the original caption. Ask the trial author to separate incidence, severity, pest numbers, survival, fresh damage and marketable output, and to say what a percentage is a percentage of: leaves, plants, shoots, fruit or quadrats. For a disease trial, ask whether the figure counts infected plants or the extent of damage on them. For weeds, ask whether they counted survivors, weight or seed production. For insects, ask which species and which stage. Ask which analysis was used and why it suits the design, and which differences it supports. For a percentage-control claim, get the underlying counts and the comparator behind the percentage. Then compare the size of the effect with what the crop needs commercially: a small difference may not pay. ## Assess crop safety alongside target control Assess direct efficacy alongside phytotoxicity, yield and quality. Target suppression alone does not describe the complete crop response. Look for notes on yellowing, scorch, distortion or stunting, and when they were made and whether the crop recovered. For a buyer with quality requirements, ask for marketable grade or processing results, and compare total yield and marketable yield separately. ## Compare environments with the intended field Choose trial locations representing the agricultural, plant-health and environmental conditions of the proposed use. This makes climate, crop husbandry and target pressure material to interpretation. Check whether the trial was in a field, glasshouse, tunnel, container or laboratory, and tell your adviser which of these matches your holding. For an overseas trial, note the location and season and do not present it as Irish field performance. Ask the specialist what supports carrying the result over to your farm and what still needs evidence. Treat trial application details as part of the result: formulation, dose, water volume, equipment, timing, any partner product or adjuvant, and the crop stage at application. For a programme, get the full sequence and intervals, and note any weather problem or interrupted pass. These explain the trial; they are not a recipe for your own spraying, so confirm the Irish authorised use through the product documentation. ## Consider quality after processing Assess effects on harvested quality, including taint and processing. The relevance depends on the crop and its destination. A grain, fruit or vegetable trial can therefore need an endpoint beyond visual target control. Ask whether the evidence covers what your buyer actually requires, and whether it was measured on harvested, stored or processed material. For a claim about flavour or appearance, keep the laboratory method and sample details. ## Describe selectivity without conflating it with suppression Include phytotoxicity and effects on succeeding or adjacent crops in the evaluation. Those are separate questions from the treatment’s intended action on a target. Give your adviser the planned crop sequence, any sensitive neighbouring crops and how you intend to apply. Ask which part of the evidence answers each concern. Ask the supplier to list the benefits, the adverse observations and the inconsistent results, and read them next to the authors’ full conclusions. ## Ask about material kept for propagation Assess effects on plants or plant parts retained for propagation or reproduction. The information needed depends on the treated crop. Restrictions on propagation uses can be necessary to avoid adverse effects. A result for harvested food therefore leaves a separate question about material intended to produce another generation. Tell the trial author whether your use is food, planting material or another reproductive use, and ask which observations cover it. For a nursery treatment, do not judge by how the current crop looks alone. ## Describe carry-over and neighbouring-crop questions separately Assess succeeding crops separately from adjacent crops. For succeeding crops, consider residues or metabolites in soil. For neighbouring crops, consider movement such as volatilisation. These are technical assessment pathways rather than interchangeable descriptions of damage. When you write to a specialist, describe the treated area, neighbouring vegetation, crop sequence and what was done when, plus the product, how it was applied and the pattern of any injury. Ask what evidence covers persistence, movement or exposure. For a laboratory assay, keep the test organism, endpoint and exposure conditions, and ask what field evidence links the lab result to the practical benefit. In a crop-safety comparison, ask whether good pest control could be hiding a loss of growth or yield. ## Next step Request the complete trial protocol and results, then check the separate [Irish product status](/ie/pesticide-register-ireland/).