In the September Rural Business magazine, there was an important announcement: 
“…the fact is, without pesticides, 78 per cent of fruit, 54 per cent of vegetables and 32 per cent of cereals currently produced for consumption would not exist”. 
 
That translates to… you’d pick about 80 per cent less fruit if you didn’t use pesticides. 
 
The choice of pesticide and the timing of the application is up to you, the grower, so, this month’s Know your pest column is an effort to help you ‘marry’ the pesticide choice to the pest.  
 
As this issue of Tree Crop lands in your mailbox, you are already checking for pests every few days. Aren’t you? (Remember, a week is a quarter to a half the lifetime of mites, aphids and thrips). And it’s not always 50:50 male/female ratio either.  
 
Aphids produce mostly female progeny and save time by doing it without pausing for sex (parthenogenesis). It really is a population explosion.  
 
Let’s generalise about the main insect control methods; beneficials, systemics, residual contact and instant kill/no-residual contact. 
 
I decided to include the use of beneficial insects; you can consider them as living pesticides. They cost you money, you have to ‘apply’ them and they control pests. 
 
If you are going to use beneficials, you should already be talking with your supplier.  
 
The beneficials have to have something to eat or they won’t survive.  
 
If you’ve left it until the crop has too high a pest population, they may suggest you first use an instant kill, non-residual application to get the numbers right down and then release the beneficials when the pest numbers rise a bit.  
 
Beneficials suppliers know their stuff. Usually the balance of beneficials/pests is maintained right up until and beyond harvest, but keep inspecting to ensure control is being maintained (a new swarm may arrive).  
 
You might choose to do a last-minute instant kill/no residual application when harvest is about to begin so there are no signs of pests to bug-ger up your presentation to buyers. 
 
“Systemic” is the group name for insecticides that circulate through the sap stream.  
 
They can be applied to the leaves for absorption or to the soil for absorption by the roots. The label will have the directions.  
 
When trees are deciduous and without leaves, there’ll be no absorption through non-existent leaves and next to nothing through the roots until the tree decides to wake up for spring.  
 
The label directions will specify which crops, how many times a season it can be used and what is the withholding period (meaning the minimum time to elapse between application and harvest).  
 
The insecticidally effective period is a little less than the withholding period because that’s the safety buffer in case pickers decide to eat fruit while harvesting. 
 
Systemics are of many chemical groups which gives you some alternatives to avoid insect resistance by not using the same group all the time.  
 
Any pest sucking sap or eating leaves will be affected. Insects that get inside the plant such as leaf miners, moth or beetle borers are really living dangerously… but not for long.  
 
This systemic group is particularly useful against pests that live on the undersides of leaves, sometimes causing leaf curl, making them even harder to contact with spray droplets from the next two groups. 
 
Residual contact pesticides, when applied to your crop will kill every pest hit and once dried, the residue on the leaf/stem/young fruit surface will kill pests that fly in over the next few weeks to either stand on the toxic surface or eat a leaf/bud with that coating.  
 
The effective life of these residues is usually noted on the label. Of course, the plant keeps growing, putting out new shoots and leaves which have no residual coating.  
 
New insects flying into your crop have little interest in old growth; their focus is on the new, juicy and tender tucker, so most will survive. 
 
Some residual contact pesticides are for use in the soil.  
 
They are meant to penetrate below the soil surface and the target pests are often beetle larvae eating roots, earwigs, millipedes, centipedes, army worms, lucerne flea, etc.  
 
White louse scale and other scales can overwinter on the lower bark of fruit trees and a direct application to that area will kill the ones you hit and those still heading down to that area once they arrive. 
 
Residual insecticidal powders and granules are useful products to spread around. They wash down into the soil during rain and application may be quicker and more economical than loading up your spray tank many times. 
 
In general, residual contact insecticides, once applied, do not move, are not absorbed into the plant tissue and degrade over time. Labels give this information. 
 
Lastly, the instant kill, non-residual insecticides.  
 
They kill every pest you hit; they break down in a couple of hours of UV light and have a 1-day withholding period.  
 
If you apply last thing in the day/early evening, the insects you couldn’t hit because they were deep in a flower or a curled leaf, are likely to be flushed out by the agitating action response and therefore killed by contact during the night.  
 
This instant kill group works against all arthropods on “Fruit and vegetable crops, cut flowers and ornamental plants” (says the label).  
 
It is becoming the “go-to” answer to regaining control should a new pest swarm arrive or the pest population is building and it is getting too close to harvest to use other options.  
 
It’s the product to have on hand in your shed in case Monoleptas arrive late one afternoon to eat most of your flower buds. (Maybe that’s where some of the 78 per cent of fruit saved comes from). Anyway, there’s no time to duck into town for supplies. 
 
*Ion Staunton is the entomologist at Pestech Australia, manufacturer of Py-Bo Natural Pyrethrum Insecticidal Concentrate.  
Contact: ion@pestech.com.au