# Spraying herbicide in hot weather: prevent injury and report incidents URL: https://leafwrit.com/uk/herbicide-crop-damage/ Reviewed: 2026-10-29 **Chemical spray drift** occurs when spray reaches an area beyond the intended target. Wind at nozzle height, atmospheric stability, nozzle and pressure choice, vehicle speed, boom height, maintenance and equipment settings all affect drift. Map the target and neighbouring water, crops, homes and wildlife features before selecting the drift precautions. ## Spray drift control and the actual off-target movement To assess herbicide spray drift, identify the application method and conditions. Pesticide drift is the broader term for off-target movement of any pesticide spray. Droplet characteristics, wind, nozzle choice and application height influence that movement. ## Check weather at nozzle height Wind velocity at nozzle height at the treatment location is what counts, not the forecast or the sheltered yard where the sprayer was filled. Atmospheric stability matters alongside wind velocity. ## Check nozzle settings and boom movement Nozzle and pressure choice affect spray quality and drift. Use the coarsest appropriate spray quality. On a boom sprayer, reduce the operating pressure and forward speed, and keep dose, volume and spray quality within the label recommendations. Air-inclusion nozzles draw air into the liquid stream and produce air-containing droplets. Keep the boom low enough to limit drift while maintaining an even pattern at the correct target height. Account for the spray angle and fitted nozzle spacing when setting the height. HARDI mounted sprayers have optional sensor-based boom-control functions. Assess vehicle speed alongside operating pressure when checking drift. Poor maintenance and incorrect settings increase drift risk. ## Plan the boundary and operator route Environmental protection conditions sit alongside the crop, application and timing conditions on the label. Buffer zones are covered in the [LERAP guide](/uk/lerap-spray-records/). For use in Great Britain, [Article 55(2)](https://www.legislation.gov.uk/eur/2009/1107/article/55/data.html) includes compliance with the authorised conditions specified on the labelling within proper use. Consider leaving untreated the boom section nearest a sensitive boundary. Notify nearby occupiers before spraying as good practice. | Subject | Useful working information | | --- | --- | | Target | Identified treatment area and boundary | | Surroundings | Relevant water, neighbouring land and sensitive activity | | Weather | Forecast source and observations at the site | | Equipment | Machine, fitted tips and relevant settings | | Decision | Proceed, change the plan or stop, with the reason | | Completion | Actual area treated and any interruption | **Yaw** is forward and backward boom-wing movement; **roll** is upward and downward movement. Neither is wanted: both contribute to application inaccuracy. ## Spraying herbicide in hot weather **Spraying herbicide in hot weather raises drift risk: hot, dry conditions shrink droplets through evaporation.** The label sets the environmental protection, timing and application requirements for the product. Check the weather forecast before work, then conditions at the treatment site. Met Office Weather DataHub offers site-specific deterministic and probabilistic forecasts. Trees, buildings and other local features influence wind speed and direction. A sheltered anemometer reading can misrepresent conditions around the nozzles. Wind at nozzle height, humidity, atmospheric stability and sensitive downwind features all matter before spraying. Stop or revise the operation when drift precautions cannot be met. Little or no wind under a clear sky in the morning or evening, when air layers do not mix, can leave drift hanging over the treated area. Low winds on warm sunny afternoons with low humidity also need assessment. ## Hot-weather checks also apply to insecticide enquiries Spraying insecticide in hot weather carries the same drift risk, and the product's own environmental conditions apply. ## Herbicide damage and herbicide injury: diagnose the symptoms **Weedkiller injury has different symptom patterns: contact injury, hormonal damage and systemic effects.** A distorted leaf does not identify the product responsible. Hormonal weedkillers, such as those containing clopyralid and triclopyr, damage broad-leaved plants and leave grasses unharmed; roses, tomatoes, potatoes and vines are particularly sensitive. Investigate **misapplication, spray drift and contaminated materials** as possible exposure routes. Contact products damage the plant parts struck by droplets. Hormonal injury can narrow or cup leaves, twist stalks and produce adventitious roots, swollen stems or abnormal fruit. Systemic injury can produce yellowing, collapse, pale tufted growth and delayed deformation. Residual products can affect roots beneath treated surfaces, with visible injury delayed for weeks. ## Herbicide damage on corn, peppers and tomato plants: pesticides that kill plants The same method serves herbicide injury in corn (maize), herbicide damage on peppers, damage to tomato plants and sunflower or canola damage: describe the symptom pattern first (contact, hormonal or systemic), then trace the exposure routes of misapplication, spray drift and contaminated materials. A substance named in the enquiry, such as atrazine damage on corn, dicamba damage to corn or trees, aminopyralid damage, imazapyr damage, clethodim damage on canola or Grazon damage, is only a hypothesis until the spray record, the label and the neighbour's records show what was applied. Pesticides kill plants for three reasons: wrong product for the crop, right product in the wrong place (drift) and contaminated materials; the diagnosis and the incident report below separate them. ## Suspected 2,4-D damage or dicamba injury to tomatoes For suspected 2,4-D damage or dicamba injury to tomatoes, report the incident promptly. Report when, where and how exposure happened, plus the product and registration details where known. The label of a named dicamba herbicide is in the [HSE register guide](/uk/hse-gb-pesticides-approval-register/). ## Glyphosate (Roundup) damage, Roundup overspray damage and the exposure history For suspected glyphosate injury on tomatoes the exposure routes are the same: misapplication, drift and contaminated materials. ## Suspected incidents and insurance **Report a suspected pesticide incident promptly; delay can prevent an effective investigation.** Include **when, where and how exposure occurred**, its duration, extreme weather, and the manufacturer, product, active ingredients and registration number where known. ### Insurance NFU Mutual offers optional agricultural-contractor cover for **damage to another person's crops from spray drift**. ## Dicamba tree damage: what the symptoms look like Dicamba is a hormone-type herbicide that is readily absorbed by roots and foliage and moves through the whole plant, so a tree can be hurt by spray drift and also by an application made over its root zone. Symptoms typically appear first on newly developing tissues, and on broadleaf trees they usually show as upward cupping of the leaves. On a London plane it can damage or kill vertical sections of bark. Conifers show twisting or distortion of needles, needle death from the base outwards, or club-shaped swellings on new growth. The type and severity of damage varies with species, stage of growth, the amount applied and watering after application, and dicamba can persist in the soil for most of the growing season or into the next. Photograph the symptoms and note the date, the weather and what was sprayed nearby, then report the incident as described below. ## Next step See the [nozzle chart](/uk/sprayer-nozzle-chart/) and [product conditions](/uk/hse-gb-pesticides-approval-register/). To report an incident, use [HSE's reporting route](https://www.hse.gov.uk/pesticides/enforcement/reporting-incidents.htm).