Ion Staunton*

Congratulations! If you’ve chosen to grow a citrus crop, you’ve picked a tree crop with probably the most pests wanting to share in the fun.

I haven’t done exhaustive research; it’s too close to Christmas to bog myself down in that issue... but you probably agree with the vibe.

Let’s first cover pests eating from the outside.

Aphids, thrips, bugs, scales, weevils, a few moth and butterfly caterpillars and budworms, mealybugs, mites, some jassids and leafhoppers... and bloody grasshoppers that will eat anything green.

Then there’s those that prefer the inside of the citrus plant for at least part of their life cycle... where they inflict most of their damage: fruit fly, leaf miners, branch borers and gall wasps.

Fruitfly.

Let me know if I’ve missed any.

First, let’s generalise on the aphids: black citrus aphids and other aphids of different colours are mostly interested on the growing tips.

Bronze orange bug.

They don’t want to try too hard, so they stick their beaks into thin tissue.

The sapstream pressure almost force-feeds them and they exude droplets of sweetness (nicknamed honeydew) which attracts ants for a cheap feed and the sooty mould fungus is highly unattractive and price reducing.

Thrips often arrive in a swarm, often from native vegetation and they like the same buds and shoots... particularly the whiteness of flowers.

Aphids and thrips can go through a few moulting nymphal stages from egg to adult in a couple of weeks... many generations a year. I reckon they triggered the term ‘population explosion’.

With a wider food preference, the spiny citrus bug and the bronze orange bugs that also don’t mind mandarins or lemons along with various leafhoppers, poke holes in stems, fruit and older leaves to suck out the sap and maybe make a contribution of virus pathogens.

There are also leaf-eating weevils that leave signature scalloped teethmarks around the edges of leaves.

Are you tired of all this doom and gloom yet?

Grasshopper and a spiny citrus bug.

And we still haven’t gotten to all the scales insects, where there’s white wax, white louse, soft brown, pink wax, Californian red and circular black.

At least I haven’t bored you with their Latin names! Mealy bugs are like a mobile wax scale.

Last to mention in this list of external pest are the mites and the grasshoppers, along with a few caterpillars.

The inside caterpillars come just below if you can brace yourself.

Many of these exposed pests can be controlled by various contact sprays, applied to hit them while they are feeding.

Some hide during the daylight hours so a late arvo application gives immediate results, killing on through the night before UV light degrades them within a couple of hours after dawn.

Insecticides that have systemic action will give great results too; if any insect has its snout in the tissue it will imbibe and die. Note: the label is the law; not every systemic can be used on citrus, you may be limited to 2-3 applications per season and as stated, observe the withholding period.

Thrip.

The scales are not as easily controlled by contact sprays because of their waxy coating, which repels water-based insecticides, however the systemics, beneficials (and/or judicious pruning) are good options.

What about the hidden pests? Queensland Fruit Fly, leaf miners and gall wasps that eat inside the tissue. Again, the systemics have their place because anything eating tissue that conducts sap (with its systemic additive) will die.

Sure, there are many mandated QFF programs that need to be observed to reduce/eliminate the spread... but you’ll know about those in your locality.

Then there are the mites.

Many varieties; their names don’t matter a bit to the pesticide you use. Hit ’em, wet ’em... they die.

Control overview

Beneficial insects and mites do a good job if they get on-site early in the season.

They need pests to feed upon or they won’t become established in numbers.

If your crop is under real threat you can use a contact spray to eliminate all the insects you hit (sadly, including the beneficials).

This means all the nymphal and adult stages of aphids, thrips and bugs are killed immediately.

Natural pyrethrum contact spray residues are degraded in a few hours of UV light so that any eggs that were not affected by the spray will hatch.

Introducing a new batch of beneficials into this lower pest population will mean they will have tucker yet not be at all affected by the degraded contact spray.

*Ion Staunton is the entomologist at Pestech Australia, manufacturer of Py-Bo Natural Pyrethrum Insecticidal Concentrate. Contact: ion@pestech.com.au