In the vast and diverse insect world, each insect serves a purpose.

A scoping study of beneficial insects for the Riverina Plains Farming Systems Group found 91 different beneficial species in the sampled 10 paddocks of wheat, triticale, canola and lucerne pasture.

Sampling in March, July and November 2006, Dr Joanne Holloway of NSW Department of Primary Industries found that of the 91 beneficials, 47 were wasp species - not the sort that chase you out of the garden shed.

They deserve tag "beneficial" by being either predatory or parasitic on other species, particularly pests.

"The highest numbers of wasps were found in lucerne pastures, probably as a response to aphid swarms," Dr Holloway, a research entomologist based at Wagga Wagga Agricultural Institute said.

"In all paddocks spiders, which use a range of hunting techniques to predate on pests, were among those groups with the highest numbers.

"As with most other beneficial species, spider numbers were highest in November.

"Canola crops recorded the highest number of spiders."

Seven species of beetles, adults and/or their larvae, were found.

Other beneficial species found included predatory bugs, flies, lacewings, earwigs, mantids and mites.

"Whilst the cotton industry had great incentive to lead the field in developing Integrated Pest Management (IPM), everyone can learn a lot about how to reduce insecticide use, save on input costs, increase the health and safety of those who apply and use insecticides and not jeopardise crops, pastures or stock," Dr Holloway said.

"In considering which are beneficial, or reflecting on whether we always recognise the pests before they do any real damage, the new science of IPM asks us to think more sustainably in considering the impacts of decisions."

• Pesticides may be an option but have other alternatives been considered?
• Is there data available on the efficacy of the product you are considering and any residual effects on other insect species?
• If you know what the pest is and understand its life-cycle, has a biological control ever been released?
• Is it present now?

Dr Holloway said using insect sprays as "insurance" was not Integrated Pest Management when pests were not present, or were not what they were thought to be.

Unnecessary sprays become timeconsuming and costly for the operator.

Choosing to follow-up on a repeat spray without understanding the insect’s life cycle is often defeating and frustrating, and can assist in building resistance to insecticides.

Dr Holloway said growers should always adhere to stock withholding periods on paddocks where insecticides were to be used.

The Grains Research Development Corporation funded the scoping study.

Contact your local district agronomist or DPI entomologist if you are unsure whether an insect is a pest or a beneficial and send in a sample.