For your next crop inspection, winkle the wax out of your ears and you hardly need to look.
Hold tight - we’re checking permissions before loading more content
You can hear caterpillars chewing, they don’t have lips to close, and their mouthparts are grinding machines.
They have two big mandibles, a couple of lesser teeth called maxillae, a flap top and bottom and for good measure, some palps to wave about and taste what they are about to bite and to help stuff in the food.
Your crop is quickly devalued if you let hatching caterpillars go unnoticed for more than a couple of days so, a couple of close together sprays will cost you money, but you’ll get fruit to more than compensate.
Caterpillars breathe through spiracles which they can open or close.
They’re like ‘portholes’, down both sides.
They have a pair of short front legs on each of the first three segments behind the head and up to five pairs of stumpy pro-legs bringing up the rear.
Loopers are a variant caterpillar in the way they crawl; standing on their hindmost legs, they reach up and as far forward as they can with their head and front legs, get a grip and then bring their backside forward making their body arch (like a loop).
Everywhere caterpillars travel they leave a fine filament of silk (think silkworms).
If you disturb or spray them, they abseil down on this silk thread.
Moth caterpillars use their silken skills to build a cocoon around themselves.
The butterfly pupae form a chrysalis capsule usually hanging free like metallic baubles.
The pupal stage is usually short during the warm weather and, as the days shorten and cool, both moths and butterfly pupae can extend their ‘hibernation’, overwintering until spring warms things up and it all begins again.
Adult moths and butterflies fly somewhat erratically.
When they land, butterflies open and close their wings vertically above their body. Moths hold their wings like a pitched roof over their abdomen. You may have heard the name Lepidoptera; in Latin that means scale wings.
Butterflies have a club on the end of their filament antennae; moths may have a long filament-style antenna without a club, but others have feather-like, more complex shapes… but still no club.
Adults of both generally don’t live for long, particularly those that don’t eat.
You might know of fruit piercing moths which can poke holes into ripening custard apples and feed big-time.
Many butterflies have a coiled-up tube for mouthparts to unroll and suck nectar from deep inside a flower.
Codling moths
When finished its destruction of the inside of an apple, the fully-fed pinkish larva, now about 15mm long with a dark brown head leaves the fruits and heads to the trunk of the tree, attaching itself to the bark while spinning its cocoon.
By the time you’ve picked the last of your fruit, next year’s pest problem is waiting in residence in (almost) plain sight (if you go looking).
The Codling Moth cocoon survives the winter and when the spring days lengthen and warm, the first of three generations p.a. of moths emerge, mate and the females (about 10mm long and with brown-grey banded forewings with a fringe, held along the body) choose to lay single flat eggs on new fruit just after petal fall or on a nearby leaf.
Once hatched, the tiny white caterpillar with a black head moves to the developing fruit and bores down inside, usually adjacent to the stalk.
They moult about five times as they outgrow their cuticle before leaving the fruit 2-4 weeks later and head off to pupate in the cocoon stage on the bark.
The second generation of the codling moth is a little faster, getting through in about 5-6 weeks and the third generation (which includes the overwintering cocoon) is often more than six months.
By-the-way, you may well find cocoons in crevices in and around your packing shed.
The ‘good thing’ is that the moths do not fly far. Your population of codling moths are essentially yours alone, mostly confined to your orchard (unless you have a next-door apple grower with only a wire fence a bit over a metre high as a ‘boundary’.
Oriental fruit moths mostly attack stone fruits during summer.
Eggs are laid on the undersides of leaves and young stems, the hatching caterpillars bore into the young tips which wilt and die causing multiple shoots.
Fruit is often attacked later in the season as the caterpillar enters adjacent to the stem and bores down to the stone.
Yellow peach moth also attacks custard apples, mangos, pawpaw, even citrus.
Like the Oriental moth, above, they become more damaging as summer arrives. This yellow-orange moth is about 15mm long with some black spots on the wings and body, it lays its eggs directly on the fruit and, on hatching, the caterpillar bores inside, grows to about 25mm over the 3 weeks then emerges to weave its cocoon. Egg to adult is about 6 weeks in summer.
The macadamia flower caterpillar reduces nut set dramatically.
It doesn’t take long or many young caterpillars to completely destroy a macadamia flower raceme… and move onto other racemes.
Fruit Piercing moths at work on a mango
Half millimetre white eggs are laid usually at the bud stage between the buds or hiding places in the bracts.
The caterpillar stage lasts about 2-3 weeks, pupation is usually off the tree and the cycle takes about a month.
When macadamias are not flowering, the small grey moths lay eggs on native grevilleas.
It would seem macadamia nut borers were programmed to make growers lives even more difficult as they attack trees that the flower caterpillar didn’t entirely denude of flowers.
The brownish, 20mm approx. moth lays its scale-like eggs singly on the nut husks.
A couple of days later, while the nutshell is still soft, it tunnels into the kernel.
Feeding continues for about 1-2 weeks.
Damaged nuts prematurely fall and those that don’t, have to be sorted from the saleable nuts.
Egg to adult is about 5-6 weeks. Again, these pests can breed on many exotic trees such as poinciana, golden rain tree, tamarinds and lychees. The good(ish) news is the moth is a reluctant flyer so spread is lessened.
Control
Contact insecticide applications only kills the pests which are hit, but it stops them immediately; residual insecticides also kill by contact but because the plant is growing fast during spring-early summer and caterpillars move on to the new growth; the residues are left behind.
Systemic insecticides continue to provide kill because the pesticide is in the sap stream being consumed by the insect eating new growth… even inside the stems or nuts.
Withholding periods are less of an issue at fruit set time which is well before harvest and human consumption.
Beneficials as always, have their place in controlling many of the caterpillar pests
Ion Staunton is the owner ofpestech.com.au, manufacturer of PyBo Natural Pyrethrum Insecticidal Concentrate. Talk to a human 1800 12345 7; or visit your local ag supplier.
14°C