Red velvet mites, which can prey on pest mites, have been spotted in the Victorian Mallee. Photo: A. Weeks (cesar)
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.
||Earthmires, Lucerne flea
||Aphids, Heliothis, Diamondback moth
||Aphids, thrips, mites
||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.
New GRDC pest project
A new GRDC project is developing new knowledge to improve the timing of pest management decisions in grain crops. Grain crops are home to a diversity of invertebrate pest species, but each year only a few species will reach high enough densities to cause significant damage and yield loss.
The diversity of beneficial species can suppress pest population growth, stopping pest outbreaks. Growers and consultants need to know what factors increase outbreak risk, when to monitor for pests, when to intervene with insecticides, and how to conserve important beneficials in-field during the season, and in the landscape across the year.
This project will generate new knowledge about the life cycle and biology of a range of pest and beneficial species across southern and western regions, which will enable pathways for better spray decision-making and the proactive management of pests.
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.
Pest Suppressive Landscapes
The GRDC and CSIRO have investigated the types of landscapes that are best suited to controlling crop pests. The project found:
- Both pests and beneficials can be found in a range of habitats in grain cropping landscapes throughout the year.
- Pastures play a key role in providing habitat for pest populations.
- Pests were more commonly found on exotic weeds than on native plants.
- Native vegetation remnants in good condition (i.e. containing few weeds with an intact understory) may reduce the number of pests and support beneficials.
- Management of weeds in pasture fields may be crucial for achieving pest suppression in nearby grain crops.
- Highly weedy native vegetation patches may also be a source of pests – growers should take stock of where these are in relation to high-risk crops.
- Growers who are thinking about re-vegetation can choose ‘low-risk’ native plants that don’t harbour pests but do support adult and immature beneficials.
- For more information see the pest suppressive landscapes fact sheet.
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:
GRDC Project Code
DAQ00201, CES00054, CSE00051, CSE00059