Beneficial allies for your crops: Ladybird beetles

Beneficial insects are important for sustainable farming as they help with pollination and controlling pests. As spring arrives, we're already seeing parasitoid wasps, lacewings, ladybird beetles, and other predators.

By managing these helpful insects, growers may be able to use fewer pesticides, leading to healthier crops.

Adult ladybird beetles are one of the most easily recognisable natural enemies in cropping systems, but larval ladybird beetles look very different to adult ladybird beetles. They vary in colour, but are typically black, grey, or brown, lacking the wings, spots and the vibrant red colour of adults. Instead, their appearance includes an elongated, segmented body covered in tiny spines. Learn more about ladybird beetle larvae in TheBeatsheet Queensland's ladybird larvae identification guide.

Both adults and larvae are voracious predators and can have a considerable impact on pest populations, particularly aphids. Ladybird beetles will consume more aphids as temperatures increase in spring and summer and as their populations increase.

Watch the following videos by TheBeatsheet Queensland to see how ladybird larvae and adults feed on aphids:

• Minute two-spotted ladybird larva eating a cotton aphid
• Minute two-spotted ladybird adult eating a cotton aphid

In laboratory studies, adult common spotted ladybird beetles (Harmonia conformis) attack more green peach aphids (Myzus persicae) and are quicker to consume each aphid as temperatures increase from 10 °C to 32 °C. Their optimum temperature is 32 °C, where they can consume over 200 aphids a day.

Ladybird beetles are also smart and can move around the canola field to identify aphid patches. Adult females will often identify clusters of aphids in the canola crop, consume some, but then lay their eggs right next to those left behind. This is strategic so that when the eggs hatch, the immatures have a nearby food source. Ladybird beetles are generalists and consume many types of prey. They often learn from their experiences in the field to focus their search on the most densely populated prey.

We can't yet say how many ladybird beetles you need in your canola field to achieve good levels of pest control, but it's a good thing to see adults moving and searching for aphid patches, eggs laid near aphid clusters, and immatures crawling around on the crop.

Adult ladybird beetle (photo by R.Hamdorf)

Larvae ladybird beetle (Coccinella repanda)