The impact of beneficial arthropods can be maximised by conserving or encouraging naturally-occurring populations and encouraging population increases, or by supplementing the natural enemy complex by releasing mass-reared beneficials into the cropping system.
Conservation and promotion of beneficial arthropods
Crop management considerations to preserve and promote beneficial activity include:
- Regular monitoring for pests and beneficials
- Awareness of thresholds for specific pests
- Tolerance of early season damage (if the crop has time to compensate)
- Are there ‘hotspots’ that can be treated rather than the entire field?
- Can novel approaches be used (e.g. biological formulations such as NPV or Bt, or attractants such as Magnet®)
- Awareness of insecticide choices
- Seed treatments are generally more selective than foliar sprays foliar sprays
- Know your pesticide: selective insecticides are generally considered to be ‘softer’ on natural enemies, but still may be highly toxic to certain arthropod groups
- Consider longer term economic benefit (e.g. a more expensive spray now may save money over the season by reducing the risk of secondary outbreaks)
Whole-of farm considerations include:
- Farm hygiene – control weeds and volunteer crop plants to minimise pest carry-over
- Farmscaping to provide habitat for beneficials within the farming system
- Insectary crops (provide a source of nectar and enhance beneficial activity)
- Preserving native/remnant vegetation as a good habitat for beneficials (see pest-suppressive landscapes)
- Windbreaks can also offer habitat for beneficial arthropods
- Prevent pesticide drift into areas where beneficials may be residing
Supplementing beneficial arthropod populations
Augmentative biocontrol is most common in glasshouses and intensive horticulture, but has potential for use in some broadacre cropping .
Innoculative releases occurs early in a pest infestation. Low numbers are released, often into areas where the species is not already present, with the expectation they will establish and suppress pest populations. Examples of inoculative releases in broadacre agriculture include:
- Trichopoda giacomellii, a fly parasitoid that attacks green vegetable bug (GVB) has been released in summer pulse growing regions to suppress GVB numbers.
- Trichogramma pretiosum, a wasp parasitoid (attacking helicoverpa, armyworm, and diamondback moth eggs), has been released widely across eastern Australia and is now well established.
Innundative releases involve high numbers of beneficials with the aim of quickly reducing pest populations (knockdown). Innundative releases have a much implementation cost (in both insects and labour). Ensure the crop is free of potentially harmful residues before releasing beneficials.
For more information on beneficials available for purchase in Australia or New Zealand, visit goodbugs.org.au
Considerations when utilising beneficials
The degree of effectiveness of beneficials will vary between crops and regions. Consider the following in determining whether beneficial releases have a place in your insect pest management strategy.
- Are effective beneficial arthropods for the major pests of your crop present in your region? Are they present at susceptible crop stages?
- If so, but they are not contributing to pest control, what might be causing this? Are there any management changes you can make to support or increase populations?
- Are your current insecticide choices impacting adversely on beneficial populations?
- Is an area-wide approach to managing some pests an option?