The Theory

Mass released beneficial insects can make a significant impact of crop pests but so too can local natural enemies if the environment is suitable providing food and shelter. They are capable of controlling a pest before we realise and at other times are clearly observed by growers and consultants.

Even if not fully controlling a pest, natural enemy activity may delay a pest infestation. This can significantly reduce damage and can give the grower and consultant more time to make spray decisions. For instance, delaying lacebug buildup gives time for fruit to set and be less susceptible.

Having good natural enemy activity also provides a breather if you cant get onto the crop straight away due to weather conditions or access to equipment etc.

In brief, increased plant diversity and a reduction in disturbances will promote a higher level of beneficial activity.

Plant diversity can be increased in various ways (reduced mowing, planting insectary strips) but must be done in such a way as to not introduce hosts for key pests.

Disturbances may be drought, flood, mowing, grading or pesticide use. Disturbances can create fluctuation food and shelter sources for "non-economic" insects and natural eneimes. Reduced light penetration can also result in lower insect numbers.

These interactions can be summarised as follows:

  • More light produces more growth and plant diversity
  • More growth results in more insects and insect diversity
  • The more insects, the more predatous arthropods and parasitoids and more insectivorous birds.
  • The more flowering plants, the more support for adult stages of beneficial insects like lacewings, hover flies, lady beetles and parasitoids as well as pollinators.
  • The more natural enemies the greater their contribution to suppressing crop pests and the more resistant the crop is to pest incursions.

What does this mean for macadamias?

It is common practice in macadamias to mow frequently to keep the farm clean and tidy and growers are also concerned about rats. Unfortuneately this is not so good for beneficial insects.

But fortuneately, in macadamias there are typically very few plants growing in the inter-row that support pests of the trees.

This provides an opportunity to encourage beneficial insects in the inter row. Practices to try:

  • Allow grasses to get to pollen producing stage when possible.
  • Reduce mowing when possible to reduce boom bust cycle for beneficial insects
  • Do alternate row mowing to further reduce boom bust cycle
  • Leave a "mohawk" strip down the centre of the inter row during harvest if rows are wide enough.
  • Disturb centre of inter row to allow weeds and other grasses to emerge
  • Plant pollen and nectar producing plants in inter row. Every 4th row for instance.
  • Consider doing same in adjacent headlands and non-crop areas.
  • Plant native shrubs along boundaries to attract insectivorous birds

See: Literature Review - BioResources Inter-Row Project


Inter-row management to aid beneficial arthropods and improve soil health

This spider has entangled this banana spotting bug nymph in its web

Assassin bug nymph attacking a weevil (this weevil is not Sigastus)


Likewise this fruit spotting bug adult, caught between trees


Weedy strip provides flower and pollen hosting a wide variety of insects and pollinators

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