How good are you at killing insects?

Aug. 22, 2023 | 5 Min read
Are you getting the best out of your spray equipment? You get better at doing things only if you want to improve, and that usually means trying new things and tweaking your methods,

Are you getting the best out of your spray equipment?

You get better at doing things only if you want to improve, and that usually means trying new things and tweaking your methods, Ion Staunton* writes.

Leaves and insects tend to have a waterproof waxiness, so even actually measuring the results with and without a smidgen of wetting agent is worth the effort. Because then you’ll know.

Getting droplets to the target is a no-brainer; you need to ensure the liquids get to where they will do their job, not too much, not too little, just right. No waste. Nothing missed.

Aphids sit right out in the open on the growing tips; thrips are also mostly on the new growth but can be hiding further inside the flowers (it just may be why they call them western flower thrips), Rutherglen bugs can be, and usually are, anywhere from the top down into the leaf-litter below, caterpillars are well down in the foliage (away from birds) during the day but higher up and more exposed once the sun has gone down and the birds have gone ‘home’.

The usual adult bugs and leafhoppers come and go because they can fly, but their nymphs wander around anywhere there are tender shoots, stems and leaves.

Then there is the problem job of hitting those that are always on the underside of leaves: whitefly and olive lace bug, for example.

When bunch fruit is getting bigger, such as cherries, tomatoes, and grapes (I know, not a tree crop), earwigs can leave their normal hiding places in the soil or rough bark and hide in the bunch for full-time feeding, saving commuting.

Then there are the fly-in beetle invaders such as Monoleptas and scarabs (black, brown and Christmas beetles) that usually turn up a week or so after good spring rain to eat any foliage, your crop or the nearby native trees.

You can tinker a bit with droplet size, angles of different nozzles (if you have a sprayer with nozzles) and application rates of litres per tree (mature vs young trees).

There may be times when you want to combine insect killing, fungicide, and foliar fertilising any two or all three! It will save you time and fuel (and is permitted on the label); why not?

To begin this test, let’s think about droplet size. You can choose to vary the size for different application purposes.

Really small droplets say aerosol size, may not actually land on your tree. They are so tiny they float up to a leaf, but they don’t have the weight or momentum that would get them to ‘crash’ into a surface; there is a ‘buffer’ layer of air molecules surrounding such tiny drops that actually prevent such a crash, so they keep floating until they evaporate.

The next size up can be described as a mist. These droplets also float but float mostly downwards because of their weight. On the way down, they can meander in the air currents around and under leaves and stems, sometimes impacting the surface or the insect sitting on that surface.

Orchard spraying equipment with an air blasting capability can force a crash-landing of mist droplets because of the speed, which slows them further away from the emitting source, allowing droplets to get around but still impact most surfaces. There are a variety of droplet sizes during any application, but if you choose to apply mostly mist-sized droplets, you will use less liquid/tree to get a kill than if you use bigger, almost spray-sized droplets. Money saved and probably more contact with more insects.

Here’s how you can really find out what setting is just right for your trees and your particular pests. Yellow spray papers are an indicator (which you can use for confirmation), but actually seeing whether you reach and kill your insects is a simple matter of treating a couple of infested trees at a time to see if all pests died or just most of them. Here’s how.

Add Py-Bo to your tank at the rate of 1 litre per thousand litres of water. Why choose Py-BO for the test? Apart from the disclosed fact that I make and sell it via your ag agents, it kills every insect you hit within minutes, so there’s no waiting for the result. You’ll know.

Find a patch of trees where pests are busy and need to be eliminated. Say the last two trees in a row. Choose whatever setting you’ve been using or think you should be using, apply to both sides of those two trees and stop, get off and go check to see what’s happened to the pests.

The stages of death are excitation, convulsion, paralysis, and death. Think of how Louie the Fly reacts to a spray with Mortein; if flies are resting on the light cord or curtain, they immediately take off and fly erratically around (excitement), and then they crash into the window and fall to the ledge or sill and start buzzing in one spot (convulsion) until they just lay there with slow leg movements (paralysis) which eventually subside (death).

Small insects like aphids, thrips, whiteflies and small bug nymphs could be dead by the time you get off to go look for them. Some will be twitching or moving very slowly. Caterpillars may have bailed out from the leaves and be hanging by their silk abseiling thread.

Unless you have put a tarpaulin under the tree, you won’t find any, say leafhoppers; they will have been excited and hopped/flew hurriedly out of there. You can, however, check the ground and notice larger bugs/beetles/caterpillars twitching in the excitement/paralysis stages. You can pick some up and put them in your cap or a paper bag to see that they finally die.

Judgment time. If they’re all dead or affected, your application is perfect (or overdone). If there are some unaffected, you’ll know the application needs to improve. Simple.

Finding unaffected pests obviously means they weren’t contacted. Are they under the leaves? Are they down in the lower sections? How come they didn’t get a dose? Time to make appropriate adjustments.

It is usually a matter of droplet size, angle or velocity into the tree. By doing both sides of each test tree, some droplets should get right through to the other side or not (which could be the problem).

But hey! What if there are no pests left? All dead or dying? Just maybe you are using too much spray/tree. You can’t kill them any deader than dead, so in this case, make adjustments to deliver less, maybe by reducing droplet size.

So whether your bioassay resulted in under-kill or over-kill, make appropriate adjustments and go do another couple of trees to confirm. And even a third set.

Because once you get it right, that’s cost/efficiency you’ll have forever.

*Ion Staunton is an entomologist and manufactures Py-Bo Natural Pyrethrum Insecticidal Concentrate. Contact Pestech.com.au or 0407 30 88 67.

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