Getting the most from your insecticide dollar

Most insecticides are aimed at the insect. If you don’t hit them, they don’t die.

Costs not only include the chemical – there’s the application equipment and labour. It’s quite a significant dollar number when you add up what you spend to get higher yields of unblemished produce to market.

Pest insects cost you. Decreasing pest damage to increase yield is the aim. If the value of your increased harvest is greater than the spend, you have a worthwhile return on your insect control dollar.

If your mission is to get better yield for less expense, you’d better ensure you’re getting the best possible result from your insecticidal dollar by hitting the insects.

Application technique is critical. You can choose to spray, mist, ULV, fog, or dust. To say: “We’ve always sprayed” is a bad reason to discard thinking about the alternatives. Spraying is application of big droplets, misting and ULV are smaller droplets so you use less liquid – and fogging uses less again. And now there are drones.

You may have trusty spray equipment that does the job for you, but maybe misting/ULV/ drones will also reach the pests using less liquid and save you money as well as application time. Cold fogging, which fires out water-based pesticide just might be better again.

Adjustable nozzles on a boom is normal. Adding air-blast increases efficiency. There are now cold fogging machines of various sizes (check out for cold foggers and for drones).

Two critically important criteria are: the pesticide must reach the pest, and tank size (frequency of refilling). Contacting the pest often depends on the type of pest. Aphids, thrips, caterpillars, various bugs and leafhoppers are always on the plant and are mostly reachable.

Systemic pesticides move around the sap-stream but you need to consider the withholding period. Residual insecticides stay where they are put – but plants grow new leaves in a couple of days and the sap-suckers move to the new, juicy growth – so you may need to re-spray.

There is a quick and foolproof way to find out if your application technique is up to the mark. Do your own bioassay using a rudimentary scientific method. It will take you maybe an hour to test-treat 2–3 small patches in a crop.

Live insects are essential. If you use PyBo Natural Pyrethrum Insecticidal Concentrate, diluted at 1 ml/L, any pests you contact will be dead in about 5–10 minutes (large caterpillars or bugs may take longer but you will recognise from their twitching that they at least were contacted).

·      Using your current equipment and technique, apply the solution to say 3–5 trees at the end of a row (both sides)

·      Check the result within 10 minutes. Dead or dying insects were contacted; anything living were missed

·      Change something physical; nozzle angles, droplet size, air blast, speed?

·      Go to another row and do the same process; apply and check

·      If you’re not satisfied, change something else and repeat on another section

·      When you are getting over 90% affected – that’s the way you do it from then on – for any insecticide.

Commercial growers can obtain a free 1L sample of PyBo by Googling ‘pybo trial’ and test the results for themselves using the above techniques.

You can also use this process to compare the effectiveness/efficiency of different pieces of equipment.

A bioassay gives a real-world result; it involves you, your equipment, your plants against your insects. If one application technique provides better results than the others – that’s the way to go from then on.

The PyBo is not obligatory; it is suggested because it kills – in a few minutes, every arthropod it contacts – and there is no residual problem because there is only a one-day withholding period.

If you now recognise that insect control is an investment toward high-yielding crops you might as well tweak your application and reassess your equipment to get the best return.

Written by Ion Staunton an entomologist and the owner of Pestech Australia. Email:

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