Not all bad: Promoting beneficial insects
While many growers think of insects as pests that can cause havoc in crops, the majority of insect species are benign or beneficial. Integrated management, rather than relying on insecticides, can promote the growth of these species to help control pest insects. Beneficial insects also have other advantages in cropping such as nutrient cycling and pollination.
Dr Paul Umina from cesar and The University of Melbourne says that a number of beneficial insects are active at present in south-eastern Australia.
“Red velvet mites and other predatory mites will be increasing in number after the initial surge of pest numbers we had with this season’s break, and terrestrial flatworms have been spotted, which might be impacting on slug numbers,” he said. “Red velvet mites are recognisable by their bright red colour and velvety appearance.”
Some beneficial organisms are bred and applied or released in the field to counter upsurges in pest populations. But there are also many naturally occurring beneficial species that help keep pest populations under control.
There are many beneficial insects in southern cropping systems, which can help control a range of crop pests (see Table 1).
Table 1: Examples of common beneficial insects and crop pests they can help control.
|Beneficial Insect||Crop Pest|
|Predatory mites||Earthmires, Lucerne flea|
|Carabit beetles||Slugs, earwigs|
|Parasitic wasps||Aphids, Heliothis, Diamondback moth|
|Lacewings||Aphids, thrips, mites|
|Ladybird beetles||Aphids, Diamondback moth|
"It is important to understand the difference between pest and beneficial insects so good species can be encouraged and predate on the pests, rather than using insecticides, which indiscriminately kill both the pest and the beneficial insects,” Dr Umina said.
Dr Umina recommends growers inspect their crops and look for beneficial insects and mites. The GRDC has produced several guides to assist identify some of the most common beneficial insects, including predatory beetles, bugs, lacewings, wasps, flies, mites and spiders (see ‘Useful Resources’).
Promoting beneficial insects
Beneficial insects are generally more susceptible to insecticides than pests, so Dr Umina recommends monitoring both pest and beneficial insect populations before making a decision to spray. Beneficial insects may help keep pest numbers below a threshold where spraying is required.
“It is important to realise there is often a lag time between the growth of pest populations and increases in abundance of their natural enemies. If pest populations are growing relatively slowly and monitoring detects beneficial insect activity, it is often advisable to hold off spraying and allow the beneficial insects an opportunity to suppress pest populations, he said.
If chemicals are needed, growers should consider using insecticides that are specific to the pest and less harmful to non-target species, including beneficials.
Another strategy that encourages beneficials is native vegetation shelterbelts or refuges. A GRDC funded project “Pest Suppressive Landscapes” has found that native vegetation is more likely to support beneficial insects, while weeds are a key habitat for pests. Generally, native vegetation remnants in the landscape mean that crop paddocks are in a better position to suppress pests throughout the season by encouraging beneficial insects.
Controlling weedy plants, particularly over summer, will help reduce pest insect habitats and provide some control of pests.
Dr Paul Umina
03 9349 4723
- GRDC Insect ID: The Ute Guide, available at Google Play or the App Store.
- cesar insect gallery.
- Identification information on the red velvet mite can be found in the current edition of PestFacts south-eastern.
To report pest or beneficial species, contact PestFacts:
- South-eastern: 03 9349 4723, email@example.com or twitter @PestFactscesar
- South Australia: 08 8303 9536, firstname.lastname@example.org or twitter @PestFactsSARDI
GRDC Project Code DAQ00201, CES00054, CSE00051, CSE00059