Beneficial invertebrates

Several groups of beneficial invertebrates are prevalent during spring and can play a key role in pest control when low to moderate numbers of pests, such as aphids and lepidopteran larvae, are present. It is important to consider numbers of beneficials before deciding on a control strategy. Recent reports indicate high levels of beneficial invertebrate activity in many areas, however pest populations (particularly aphids) have also built up very rapidly this season. Under these circumstances it is important to monitor crops carefully and regularly to ascertain whether additional control measures are required to prevent yield loss. Beneficial invertebrates likely to be encountered now include:

• Hoverflies (Family: Syrphidae) – larvae prey on aphids by spearing them with their mouth hooks and sucking out the body contents. They are grub or maggot-like, up to 10 mm long, blind, legless and transparent cream to green or brown in colour. It is important not to confuse hoverfly larvae with larvae of the diamondback moth (Plutella xylostella), a significant pest of canola and other brassicaceous crops. Adults feed on pollen and honeydew, grow up to 10 mm long and have a flattened body with black and yellow markings. Adults can hover and fly swiftly, and may be confused with bees or wasps. Click here for images of hoverflies.

• Parasitic wasps (Order Hymenoptera) - adults vary in size (1-120mm long), and colour ranging from brightly coloured orange to completely shiny black. They have two sets of wings that are clear or dark coloured. Female wasps often lay their eggs into host larvae or eggs. The developing wasp larva feeds inside the host. Aphid ‘mummies’ (buff to bronze coloured, bloated/enlarged aphids) indicate the activity of aphid parasitoid wasps that are small, usually dark in colour and difficult to detect. Females lay their eggs into the bodies of live aphids and the developing larva feeds inside, eventually killing the aphid. The adult wasp then emerges through an exit hole in the body. Click here for images of aphid parasitoids.

• Ladybird beetles (Family: Coccinellidae) – both adults and larvae consume prey including aphids, leafhoppers, thrips, moth eggs and small larvae. Adults are round or oval in shape, shiny and typically have patterns of black on a red, orange or yellow body. Larvae are generally elongated and mostly grey or black with orange markings and black legs. Click here for images of the common spotted ladybird.

• Lacewings (Order: Neuroptera) – adults are 6-15 mm in length, have long antennae and wings with numerous veins giving them a lacy appearance. Their wings are held over the abdomen in an inverted ‘V’ shape. Larvae vary in shape and size depending on species, but all have a tapered body and prominent, sickle-shaped mouthparts. Brown lacewings (Family: Hemerobidae) are predatory as both larvae and adults, whereas only the larvae of green lacewings (Family: Chrysopidae) are active predators. Click here for images of brown lacewings and click here for images of green lacewings.