To a large degree, many crop and pasture insect pests have a wide range of other insects and sometimes other natural enemies like fungi, that attack them.
Sometimes these are at such a level that pesticide control is not necessary.
In other cases where pest levels are not being adequately controlled by natural enemies, it is possible to choose pesticides that are less harmful to their natural enemies.
Ecologist Dr Francisco Sanchez-Bayo, Sydney Institute of Agriculture, Sydney University, in a recent national radio interview, stressed that using insecticides only as a last resort was necessary.
Using them routinely, was not necessary and contributed to a worrying world decline of insect populations, many if not most of them useful species, including beneficial ones that attack common pest species.
Two approaches to less pesticide use include not treating with pesticides unless absolutely necessary, and if pesticides are required, choose ones that are known to be less harmful to beneficial insects that help kill pest species.
Reducing pesticide use requires careful monitoring of crop pest numbers, as well as numbers of beneficial pests that are known to attach to them.
Research is yet to define what pest threshold number for various crops threatens to dramatically affect crop yield or quality.
However, grower notes from bodies such as GRDC or NSW DPI, based on best available research, commonly do indicate likely pest threshold as well as beneficial levels to warrant insecticide use.
For some pests, there commonly are different levels throughout a crop.
For example, aphids can be bad on crop edges but much less well into the crop or pasture.
Also assessing insect predator numbers can help determine their likely effect on pests.
An example of predators keeping pest numbers down are red legged earth mites and blue oat mite (BOM).
In 13 years on our current property for example we, like many farmers, have only treated sparingly. In our case, part of one paddock was treated once in this period, for BOM.
We can find BOM most years across pastures and within crops, but mainly only at well below threshold levels.
Research company, Cesar Australia, details French Anystis mites, Snout mites and other predatory mites are effective natural enemies of BOM.
Perhaps these and other insects keep populations of BOM at low levels most of the time.
In the latest GRDC canola publication, integrated strategies can help minimise pests attacking the crop.
For example, the publication notes diamond back moth control is helped via green bridge management (early fallow weed control), and natural predators.
Entomopathogenic fungus can reduce pest numbers by 90 per cent.
Parasitic wasps (at least five different species), green and brown lacewings, spiders and other predatory bugs also reduce numbers.
Various species of aphids can severely damage many crops and pastures including canola lucerne and clover.
Aphid control in lucerne, for example, can commonly be controlled by a combination of strategies.
Varieties have been developed with good resistance to some of these, especially spotted alpha and blue green aphids.
Establish strong stands via sound grazing management and good soil fertility.
A number of predators and fungi also help control lucerne aphids.
GRDC's recently updated 'Beneficial Insects, The Back Pocket Guide' is a good starting point for the identification of several important insects.
Species detailed include wasps, various flies, bugs, beetles (including ladybirds), lacewigs, hoverfly, and spiders.
'Impact of insecticides on beneficial insects in Australian grain crops' is a valuable publication detailing pesticides for protecting beneficial insects.
Dr Sanchez-Bayo was a lot more radical than most of us would consider, but makes good logic.
His idea's included leaving shelterbelts or refuges to maintain natural enemy populations and to dilute resistant pests.
The cotton industry has for example promoted this as part of pest management for years.
In many districts, there are large expanses of pastures, including native, which are largely untouched by insecticides.
They are probably good refuges for predatory insects and fungi.
Next week: Sunflowers, a summer crop option with many credits.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or call 0428 752 149.
Love agricultural news? Sign up for The Land's daily newsletter.