I vaguely remember my professor back in the day saying there were more species of Coleoptera (beetles) than any other insect Order, so, before I went to print with this article, I thought I’d check my go-to reference book which is The Insects of Australia –CSIRO 1970, Ion Staunton* writes.

It has over a thousand pages, weighs over 2.5kg and comes only in dark blue with gold lettering on the spine. It’s been 52 years of careful handling of this entomological treasure and today I dug out numbers to quote you: in 1970, worldwide there were 278,000+ species of Coleoptera (19,219 in Australia).

The next biggest Order numbers (sticking to Oz) were 11,221 for Lepidoptera (moths/butterflies), 8834 for Hymenoptera (wasps/ants), 6256 for Diptera (flies/mozzies) and 3661 in Hemiptera (bugs/aphids/scales, etc).

But, when it comes to damaging crops, Hemiptera probably wins. They have piercing and sucking mouthparts to poke a hole into the plant tissue and they hardly need to suck because they pick the newest tissue, and the sugary juices just flow into them. Most have shortish life cycles of a couple of weeks to a month or so and highish reproduction rates… like females producing up to 200 or more offspring.

From this point we’ll only be referring to the proper bugs of the Sub-Order Heteroptera that attack tree crops; those with the forewings of two textures: the leathery half closest to the body and membranous for the outer half; the hindwing is all membrane and both wings are folded flat over the abdomen when not flying. Most have longish, 4–5 jointed antennae. The nymphs hatching from the eggs usually go through five moults (the period between moults is called an instar) and they walk to new tissue to feed but, once wings and their reproductive organs are developed at adulthood, they can and do fly to another tree or another crop. Each of the four listed below is a native Aussie.

Depending on where you grow and the tree crop(s) you grow the ‘Most Not Wanted’ are:

Fruit-spotting bug, Amblypelta nitida. It is a pest of avocados, guavas, macadamia nuts, pecan nuts, lychees, mangoes and many exotic tropical and subtropical tree crops mostly in coastal Queensland but also on the Atherton Tablelands. Its main focus is to damage fruit by spotting it. A few singular eggs are laid each day and can total over 150 in a female’s lifespan (they take about a week to hatch). The first instar is green/black and is ant-like. Later instars are orange with dark spots, and they become adults about 7–9 weeks later. It’s the adults that “overwinter” (when there is a winter to speak of).

Banana-spotting bug, Amblypelta lutescens lutescens. (No, it doesn’t stutter… that’s its name). It is the same genus as the fruit-spotting bug, above, but being a different species, it has slightly different appearance being a lighter red as an adult and the scent glands on the abdomen are ringed with white. They don’t restrict attack to bananas as their common name might suggest; the crops listed above for the fruit-spotting bug are also attacked. One difference is they don’t stick to fruit but will also damage other tissue, particularly the growing tips and stems. Egg laying and life cycle times are very similar.

Bronze orange stink bug, Musgraveia sulciventris. Eggs laid in 12–14 batches of 2mm green spheres on the undersides of leaves hatch in about a week. Nymph colours vary: green, orange with dark spots, green and bronze. Last instar nymphs show developing wing buds. There’s usually only one generation a year and, as the second instar usually over-winters, it means new adults don’t appear until late spring/early summer. The stink? Beware! your eyes are precious; adults and last instar nymphs can squirt their caustic potion sideways about half a metre. Adults are about 25mm and bronze with green ‘piping’ on the edges and the middle of the thorax.

Spined citrus bug, Biprorulus bibax. Rafts of up to 50 eggs with white frilled top are laid on twigs, the underside of leaves or fruit and hatch into first instar nymphs which stay clustered around the empty egg cases. They change colours through black with yellow, orange and green markings, move onto fruit and begin feeding. Egg–adult takes 6–8 weeks and there can be four generations a year. Adults live for a bit over a year and usually are the overwintering stage. They are a dull green with a black spine on each shoulder… and yes, they also make offensive smells if you get close. They attack all citrus, preferring lemons over mandarins then oranges but that’s a bit subjective; if they are attacking your half-grown fruit and causing fruit drop, that’s what really matters.

Control

Birds, wasps and predatory bugs are your main biological support team.

Systemic insecticides do their job because all these bugs are sap-suckers and systemics run through the sapstream. Check the withholding period for your crop.

Instant knockdown contact sprays do the job with only a 1-day withholding and, if your bug numbers are starting to cost you money, two sprays about two weeks apart are recommended because eggs are not always affected and after a week all the eggs should have hatched and the second spray kills the nymphs well before they get to become egg-laying adults.

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