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There have been a number of enquires received over the last few weeks of small grubs being found in large numbers within crops. We have examined many of these samples and identified these as hoverfly larvae. The good news is that hoverflies are not a crop pest; rather an important beneficial insect. Hoverflies attack a range of soft-bodied insects and are a particularly voracious predator of aphids. Hoverfly larvae are often mistaken for pest caterpillars such as diamondback moth. This spring, hoverfly numbers have been very high across large parts of south-eastern Australia.

Hoverfly adults are 4-10 mm long and have dark-coloured flattened bodies with black and yellow markings. As the name suggests they ‘hover’ over objects and look similar to bees and wasps. Adults feed on aphid honeydew and pollen, and can also be a useful pollinator. Eggs are laid on the vegetation, in close proximity to pests. Larvae are maggot-like, legless grubs with no eyes and vary in colour from cream to green or brown. Many have white stripes on their dorsal side, and they can be up 10 mm long. Larvae move on the vegetation searching for prey. They grip and pierce their prey with their mouth hooks and suck out the body contents.

Click here for images of hoverflies. For further information on beneficial insects likely to be encountered in broadacre crops and pastures, view the GRDC Back Pocket Guide – Beneficial Insects.

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