Portuguese Millipedes in the Yass Valley

Over the last couple of weeks there have been numerous sightings of Portuguese Millipedes (Ommatoiulus moreleti) in the Yass Valley, with some people saying that they’ve never seen so many of the pests.

Black Portuguese millipedes can be identified by their smooth, cylindrical body, which is made up of 50 segments when fully developed. Adults are 30-45 mm long, dark grey to black in colour and have two pairs of legs on most body segments. Juveniles are light brown with a darker stripe along each side of their body.

It is likely that our recent mild temperatures and humidity have caused them to grow in number and become conspicuous. There is also the view that the rise is numbers is due to increased stubble retention, which provides millipedes with a favourable habitat.

Despite fears, Portuguese Millipedes rarely cause crop damage, as they generally feed on organic matter such as leaf litter, decaying wood and fungi. There are many instances where high numbers of millipedes are present in a paddock but no crop damage occurs. Portuguese millipedes occasionally attack living plants by chewing the leaves and stems. In canola, they remove irregular sections from the leaves, and can kill whole plants if damage is severe. Damage to cereals can also occur when the stems of young plants are chewed. There have been suggestions that millipedes feed on crop plants to access moisture when moisture is limited.

Removal of trash is an effective management strategy. Burning stubble in paddocks known to harbor millipedes has been shown to give satisfactory control. Natural predators such as spiders, beetles and scorpions are known to feed on millipedes.

Homeowners should be aware that Portuguese Millipedes are attracted to lights, so turn off external lights that are close to buildings and minimise the escape of light from buildings through use of curtains, blinds and weather-strips on doors. Effective door seals will prevent the entry of these unwanted pests.

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• Rural Roundup