By Ion Staunton, entomologist, Pestech Australia

It’s mid-July as I type this. In Queensland, the Granite Belt has had a few snow flurries, the prediction this morning for the Atherton Tablelands temperatures goes from single figures and may get to 20C. The Southern States are colder, and bugs are overwintering as best they can.

As a tree crop grower, you’ll be pleased you don’t need to do much about insects in July but when you’re reading this in Aug/Sept, the ceasefire is over and the war begins again. 

Of course, on the coastal fringe, from the Tropic of Capricorn northwards, bug warfare hardly stops … just sometimes it has a bit less action.

There are a couple of bugs which thrive in these areas – the Fruit Spotting bug and the Banana Spotting bug.

They are cousins; the first is Amblypelta nitida and the Banana version is Amblypelta lutescens lutescens (it stutters) and it also troubles growers further south – and not just banana growers.

They both like the tropical fruits you’ve planted in their backyard … a welcome change from the native scrub plants such as umbrella tree, corky passion vine, white cedar, rough leafed fig, rubber vine, etc.

The Fruit Spotting Bug is the one shown in the drawings and their green is a bit darker than the green in the Banana Spotting Bug.

The adults have wings, are about 15mm long and when you approach your trees, they tend to fly off, or go around the other side of a branch or leaves or fruit.

The five nymphal stages can’t fly (no wings) so they often just bail out, tumbling through the branches to the ground.

These nymphs are mostly orange, have long legs and at first glance you may think you’re seeing ants… although less likely during the final two nymphal stages which have more body proportion and are growing wing buds.

Females lay their eggs singly on flowers, fruit or foliage – and just a few each day – accumulating as many as 150 in her lifetime. Eggs hatch in about a week.

Generally, females don’t fly far and the result is a hot spot in your orchard rather than even distribution … unless you get slack in checking.

There are 3-4 generations a year: one in spring, one or two in summer and one in autumn. Adults of the autumn generation survive the winter and begin a new generation when temperatures increase.

Damage

Adults and nymphs feed by piercing and sucking, sticking their long mouthparts deep into plant tissue.

This often causes sunken black spots due to tissue damage, and maybe introduced enzymes. Damage occurs mainly from September through March - April.

Small fruits, which have just set, are usually shed, while slightly larger fruit may be retained but you’ll see the 'dimple' where the damage has occurred.

Injured fruit remaining on the tree are usually unmarketable due to the large lesions that develop around the feeding site.

The bugs are more prevalent in coastal orchards, particularly those close to rainforest or scrub.

Orchards that are more openly situated generally have a lower incidence of bugs.

Considerable fruit damage can result from the feeding of a relatively small number of bugs.

Damage can be confused with Queensland fruit fly damage, but bug damage is more common on the uppermost part of the fruit.

Fruit fly damage can be usually determined by cutting through the entry spot and searching for the curved white 3mm long eggs, or for the white-cream maggots of the fruit fly.

No grubs inside a bug-stabbed fruit.        

Control

If it is shaping up to be a great crop, you won’t want to risk it. You probably have a contract or a buyer you don’t want to disappoint, so the pressure is on.

If there are beneficial predators eating pests and things aren’t serious, that’s OK. But if the risk is increasing and it will cost you less to treat than you will lose if you don’t … your decision is simple.

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

Systemic insecticides will do their job because all these bugs are sap-suckers and systemic insecticides circulate throughout the sap stream. Check the label for the withholding period for your crop.

Instant knockdown contact sprays also do the job with only a one-day withholding.

If your bug numbers are starting to cost you money, two sprays about two weeks apart is recommended because eggs are not always affected, and after a week all the eggs should have hatched and emerged, and the second spray kills the nymphs well before they get to become egg-laying adults.

Because bees work office hours; well, starting a bit before nine and gone before dark means your trees are free of bees between sunset and sunrise.

So, use your PyBo instant kill spray just after sunset, and the bees will stay away until about morning teatime next day by which time the natural pyrethrum which remains on the surface will be degraded so as not to affect foraging bees.

Pestech Australia Pty Ltd is the manufacturer of Py-Bo Natural Pyrethrum Insecticidal. Phone: 1800 20 30 20