As the spraying season picks up, I always have plenty of discussions with farmers about cleaning out sprayers, and which order to spray crops in order to minimise downtime. It is crucial to remember that crop growth can be affected by tank residues from a previous spray, even when you cannot see visual in the field.

Damaged wheat ears from residues of a hormone herbicide in the spray tank – farmer sprayed a late sown crop of barley, and did not wash out before spraying a more advanced crop of wheat.

The procedure starts with planning spraying to minimise the number of washes required. In general, fungicides and insecticides are fairly safe (be cautious with epoxiconazole products on Canola or peas, or residues of unapproved pesticides on vegetable crops).

ALS herbicide damage in peas. Not uncommon to see the yield halved.

It is worth investing in some good quality Tank Cleaner when using ALS and hormone herbicides. Otherwise Chlorine Bleach or Ammonia (NEVER MIX THE TWO TOGETHER!) can be effective. Simple rule: always read the label on the spray can and follow the instructions.

Herbicides require a much more rigorous approach, which starts immediately after spraying:

  1. Drain the tank immediately, and wash any residues off the sprayer and the booms in the field preferably to avoid water contamination through drains around the farm buildings.
    NOTE: if residues are left to stick to the tank and filters overnight, it is not uncommon to wash the tank next day, then to see the damage only after a few more tank fills when the deposits have slowly solubilised again.
  2. Don’t forget to clean the wheels on a trailed or self propelled sprayer, clean the tank lid, and to pay particular attention to the induction bowl – always a favourite place for neat deposits of chemical to linger.
  3. Wash all interior surfaces with 10% of the volume of the tank for most non-ALS herbicides. If you are using ALS (sulfonylurea herbicides), you need will need to fill the tank, and use a much high recommended rate of a Tank Cleaner.
  4. Take out all of the nozzles and filters and clean them separately in a bucket with an approved Tank Cleaner. Lower quality formulations of Atrazine and Chlorothalonil are particularly prone to blocking filters from my experience.
  5. If you have been using ALS herbicides or synthetic hormones, circulate and agitate for 10-15 minutes before draining and flushing the pump, filters and booms. TAKE CARE TO DRAIN OUT EACH BOOM SECTION – ideally fit valves or screw in caps to allow water to be drained completely.
  6. Re-fit the nozzles and use a further 10% water volume to rinse out, especially if going into a broadleaved crop after using herbicides such as DERBY or ARIANE in cereals.

Remember that some herbicides are particularly adept as tank cleaners – EC formulations of pyrethroids for example can often remove other oil-based herbicides such as 2,4-D Esters and Fluroxypyr. Clean out well before using these types of insecticides in Broadleaved Crops.

Glyphosate and Group A herbicides (fop’s and dim’s e.g. FUSILADE and AGIL) are surprisingly easy to clean provided the above steps are followed with a single tank, nozzle and filter rinse, and are far less active at low doses than LANCELOT for example.

Some useful links:


Hormone containing herbicides: ARIANE, BUCTRIL, 2,4-D



Fall Armyworm reminder:

  • We can safely say this pest is endemic across the country now.
  • Scout crops thoroughly from 3 leaf stage. Remember attacks can be patchy across the field.
  • Spray immediately when pest is found. Evening is best.
  • Keep monitoring and spray again with a different mode of action insecticide 10-14 days later.
  • Key is to keep the pest out by intervening early.



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