Judicious use of agricultural chemicals on dairy farms

Estimated reading time: 5 minutes

During the latter part of 2023, the Dairy Standard Agency (DSA) hosted a webinar on the correct use of agricultural chemicals on dairy farms. The discussion took place against the background of the new Global Harmonised System for the Classification and Labelling of Chemicals (GHS system). The presenter was Dr Gerhard Verdoorn, a well-known expert on pesticide exposure and chemical disaster management in South Africa.

Lees dit in Afrikaans.

Safe storage of agricultural chemicals

Photo of Gerhard Verdoorn
Dr Gerhard Verdoorn, operations and stewardship manager at CropLife South Africa, and director of the Griffon Poison Information Centre.

Chemical and pesticide storage is an important aspect of any farming management system. Having visited many farms in South Africa and other countries, Dr Verdoorn is all too aware of the general poor management and storage practices relating to agricultural chemicals on farms. Accidents on farms involving chemicals do happen, he emphasised, and can lead to major disasters.

Pesticide stores on the farm should be clearly marked with a DANGER sign and should always be housed in a stand-alone building or be completely separated by firewalls from other sections of stores. “The simple reason for this complete separation is that hazardous agricultural chemicals should never be stored near any animal feeds, equipment or fertilisers that can become contaminated by it.

“I don’t see a problem with ectoparasiticides being kept in the same store as pesticides, but only if it is separated from it and clearly marked to avoid any confusion when having to use these substances. Endectocides and veterinary medicines must, however, be stored in a completely separate store.”

Importance of labels

The importance of pesticide and stock remedy labels is hugely underrated, said Dr Verdoorn. The Fertilizers, Farm Feeds, Seeds and Remedies Act, 1947 (Act 36 of 1947) and the Medicines and Related Substances Act, 1965 (Act 101 of 1965) determine that the user of pesticides, stock remedies and veterinary medicine must use these products strictly according to label instructions.

“People must read the label instructions because the company who registered that particular product put in a lot of work relating to, among others, trials designed to make sure that it is compatible and doing what is needed without posing any unnecessary risk to people, animals and the environment.”

Hazards and risk prevention

The safe handling, measuring, mixing and application of agricultural chemicals and stock remedies on dairy farms are crucial. Producers must read the label instructions before taking these steps and make sure they have the required equipment ready.

The following information must be confirmed through checking and communicating with staff:

  • Is the product registered for its intended use (animals, pests, crops or weeds)?
  • What warnings or precautions should be noted?
  • Are the required buffers, adjuvants and clean water at hand?
  • What is the mixing sequence of the chemical to be used?
  • What is the dosage rate per hectare or animal?
  • How much product must be decanted into the spray tank and/or onto the animal?
  • Is my personal protective equipment (PPE) suitable for protection against the specific product?
  • Staff must be made aware that no smoking, eating or drinking may take place during the application of this chemical.
  • To use ablutions, one must first remove all PPE, wash the hands and face, and then use the toilet.
  • Spray operations must be planned to include adequate breaks where staff can remove PPE, wash their hands and faces, and then eat, drink or smoke.
  • Take safety precautions into consideration when spraying in an area where there could be children, bees, poultry, pets, wildlife, livestock and spectators.
  • Perform applications when the skies are sunny without rain for at least six hours. Apply only after dew evaporated, in not-too-windy conditions and amid adequate temperatures between 10 to 30°C, with no temperature inversion when cool air is trapped at the ground under a layer of warm air.

Specific safety precautions specific to a dairy farm entail:

  • Dairy cows should never be present in paddocks or camps where pesticides are being applied.
  • Strict adherence to PHLs (preharvest intervals) is very important for cow health and dairy product food safety compliance.
  • Never use unregistered agricultural chemicals, stock remedies and veterinary medicines.
  • Never make your own home-made ectoparasiticides.

Post-handling safety principles for agricultural chemicals

“As the person applying pesticides, it is your job to ensure decontamination after having worked with such products,” says Dr Verdoorn. “Once you have taken your PPE clothing off, wash your hands and arms properly for at least two minutes, including your neck and face, and then take a cool shower. The PPE clothing must be cleaned and left at work when you go home.”



Triple rinsing of pesticide packaging removes 99,7% of all the agricultural chemicals in a container, which can thereafter be recycled. “There is no reason why these empty containers must remain on the farm, or for contaminated containers to end up in the hands of someone who may want to use it for food or water.”

He concluded that one should never leave a spray mixture in a sprayer overnight, but should dispense of all of the spray mixture before rinsing the sprayer three times with clean water. “These chemicals can be aggressive and abrasive and damage the spray can, or worse, get mixed up with other sprays.

“Left-over containers must be sealed with their screw taps, while polypropylene (PP) bags can be closed by taping it with duct tape. Label each container or bag. Return all pesticides to the store, complete all spray and stock records, and lock the store. Remember to self-decontaminate your body and PPE clothing.” – By Carin Venter, Plaas Media

For more information, contact Dr Gerhard Verdoorn on 082 446 8946 or gerhard@croplife.co.za, or the DSA on 012 665 4250 or info@dairystandard.co.za.

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