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:
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:
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