Plants grow. Insects see them as desirable food. Then they become pests.

Egg to adult can be as short as a couple of weeks and females can produce dozens to a few hundred progeny. You don’t need to be mathematical to know that in a couple of short generations you have a pest population problem.

Pests differ in what they eat, where they eat and when they eat.

Let’s categorise the pests of tree crops: first, those that live outside – on the surface:

- The sap suckers: aphids, leafhoppers, various bugs, scale insects and mealy bugs

- The sap-lappers: thrips which abrade the tissue and lap up the juice

- The leaf and bud-eating caterpillars

- The leaf and bud eating beetles

- …and others.

Then there are the ones that eat inside the plant tissue:

- Fruit fly

- Nut borers

- Codling moths

- Leaf miners

- Gall wasps

- Stem weevils

- …and others.

And finally, the ones that live in the soil, attacking the roots. Many beetle larvae eat the roots of pasture grasses or the plants between your tree rows; the larvae may not do much damage to your crop but if they turn into Monolepta beetles they become significant when overnight, they swarm in to eat the flowers of avocado, mango and macadamia crops.

These are your basic pest control options:

1. You can do nothing, hoping the native parasitic and predatory insects and birds do their job; or:

2. You can buy in beneficials from Biological Services or Bugs for Bugs

3. You can apply a systemic pesticide from Bayer, Corteva, Syngenta, or

4. You can use a contact spray… all regular advertisers in this magazine.

If you integrate any two of these above options, that becomes integrated pest management (IPM). Each option on its own has validity but, thoughtful choice of combining two or more over the season is more likely to deliver perfect produce at harvest. Timing is of the essence; that’s your call.

Pome and stone fruit:

But… if you are growing pome and stone fruit, the fruit fly, codling moths and other pests that live inside the plant tissue are generally not controlled by beneficials and certainly not by contact sprays.

Systemics are your answer here. Yep, it sometimes happens that new pests arrive too close to harvest… depending on the withholding period of the systemic you use… and an instant kill contact application may be considered worthwhile in that instance.

Another “for instance”:

Earwigs love bunches of fruit. Cherries, grapes (I know, not a tree crop) and other ripening fruit can entice earwigs from the soil or the rougher bark up to the fruit, especially at night.

If the hiding space between fruits is good enough, they may stay there eating away. Custard apples and other tropical fruits are often attacked by bugs, leafhoppers, and those giant fruit moths and so, this close to harvest, you need to break out the Py-Bo you’ve been keeping on hand just for such an occasion.

It’ll cost you more to need Py-Bo and not have it – than to have it and not need it… and even five-year-old batch retention samples still work fine!

Summary:

Use of beneficials, systemic insecticides and contact insecticides are your three basic options for controlling pest insects and mites. There are times when you will use all three during a season… perfectly integrated pest management for perfect fruit!

*Ion Staunton is an entomologist at Pestech.com.au – manufacturers of Py-Bo Natural Pyrethrum Insecticidal Concentrate. Contact: 1800 12345 7.

Typical pest control scenario:

This issue of Australian TreeCropmagazine gets to you in late October/November and features pome and stone fruit crops. By then, flowers will be gone, and leaves will be newish, which means pest species will be threatening. Of the four choices listed above, you may decide to:

1. Let loose some beneficials. If they prosper and keep the pests at bay, you may not need to apply systemics
2. But, if the pests overwhelm them and it looks like your harvest will be threatened, you can regain control with Py-Bo. (It will of course take out all the beneficials it contacts as well as the pests, so timing is important)
3. A variation on 2, above: very early in the season, aphids appear in their thousands even before the petals have turned to mulch on the ground. This is when the swarm
pests arrive from grasslands (Rutherglen bugs) or from other nearby vegetation – think thrips
4. As the numbers maybe too many for beneficials to reduce before there’s damage to fruit-set, etc., get control using, say Py-Bo. It will rescue the situation and then you can bring in the beneficials because there is no residue to deter their establishment. (Mind you, they won’t have much to eat for a few days unless the swarming continues). This is a regular strategy recommended by our bug merchants
5. Apply a systemic. (You can’t get it into the sap stream until there are leaves)! You can then add beneficials; they are not affected by systemics already coursing through the sap stream. Check the label as recommendations for continuing protection from follow-up applications vary
6. Regularly and often, monitor your crop and use contact sprays only when pests threaten your yield and quality