Agronomists using biologicals in the battle against pests

Beneficial insects can greatly assist in pest management if used in combination with chemical control by reducing pest populations and providing an additional benefit over chemical applications alone. Increasing the biodiversity of beneficial insects in crops can assist in reduced pest populations and minimise pest flare up during the season.

Wasps are released in a variety of horticultural crops including cucurbits, capsicums and eggplant, normally as a preventative, early in the season from March and continued until mid-October on a bi-weekly schedule depending on weather and target pest behaviour. Releases are made into new crops with good canopy cover to protect the wasps from chemical contact and the elements to try to establish a population within the crop. We also use the prevailing wind direction to help the wasps migrate across blocks more quickly.

The two main beneficial wasps we release are the Eretmocerous hayati for Silver leaf white fly (SLWF) and Aphidus colemani for aphid parasitism respectively.

BGA AgriServices Paula Mizzi in field releasing wasp
Paula Mizzi releasing wasps in Rockmelon crop.

A. Colemani deposits an egg inside the aphid, as the egg hatches the larva feeds on the aphid leaving behind a mummified shell. E. Hayati are smaller in comparison to the A. Colemani and also deposit their eggs into the SLWF nymph. A 40X hand lens is needed to see parasitised SLWF nymphs.

Generally, we still see beneficial activity weeks and even months after one release on farm which gives us a good indication of the versatility and survival of the wasps.

Parasitised Aphids on Leaf
Parasitised aphids from A. Colemani.

As we develop this program we would like to quantify the level of parasitism in crops with leaf collections and count the number of parasitised nymphs to further understand the ability of beneficials to breed and establish a resident population in crops. This will also help us understand the survival rates of beneficials in conjunction with applied chemical controls. Where possible we use selective, less disruptive chemistry to preserve our beneficial population in the field. The introduction of biologicals into the crop production system as an integrated pest management strategy will reduce the reliance on insecticides and aid in preserving current chemistry for longer.

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