Millipedes

Millipedes can be numerous in soils with a high organic matter content but they generally have little impact on plants.

Spotted snake millipede

Spotted snake millipede

Quick facts

Common name Millipedes
Scientific names Blaniulus, Cylindroiulus and Brachydesmus species
Plants affected Mainly strawberry fruits and potato tubers
Main cause Many-legged elongate millipedes
Timing Present all year round but mainly seen summer-autumn

What are millipedes?

Millipedes belong to a group of animals that are known as myriapods. They have elongate segmented bodies with each segment having two pairs of legs. Centipedes, which are soil-dwelling predatory animals, are also myriapods but they have only one pair of legs per body segment. Centipedes are also much more active and run for cover when disturbed, whereas millipedes often stay motionless.

Symptoms

There are more than 50 species of millipede in the UK, although some are introduced species that are confined to glasshouses. They vary considerably in size and appearance. Some, like Brachydesmus and Polydesmus species, have flat bodies and might be confused with centipedes. Most other millipedes have long cylindrical bodies. Millipedes can be up to 40mm long and can be black, greyish brown or creamy white. The species most frequently found feeding on plants is the spotted snake millipede, Blaniulus guttulatus. This has a slender, creamy white cylindical body, up to 20mm long, with a row of reddish dots along the sides of the body. When disturbed, they lie of their side in a coiled fashion.

Millipedes feed mainly on decaying plant material and the associated fungal growth. They will sometimes damage seedlings and other soft growth, such as strawberry fruits. Millipedes, especially the spotted snake millipede, are sometimes found feeding inside bulbs, potato tubers and on other root vegetables. In this situation, they are enlarging damage initiated by slugs or some other pest or disease. The relatively weak mouthparts of a millipede will make little impression on healthy undamaged bulbs, roots or tubers.

Control

Non-chemical control

As millipedes rarely cause serious damage, it is not necessary to control them.

Where damage is occurring on potato tubers, steps taken to reduce the slug problem is the best answer. Strawberry fruits are more likely to be damaged when the fruits are resting on the soil. Placing straw or hay around the plants lifts the fruit trusses up and makes them less vulnerable. Keep seedlings watered so they grow quickly through this critical stage in plant growth.

Millipedes have many natural enemies including birds (particularly starlings), frogs, toads, hedgehogs and ground beetles.

Chemical control

None of the pesticides available for garden use is recommended for use against millipedes.

Biology

Millipedes deposit their eggs during spring and summer in the soil, either singly or in small batches. These hatch into small versions of the adult animal. It can take several years before they reach the adult stage. During that time they will have shed their outer skins 7-15 times and will have increased their length by adding additional segments to their bodies. During the day, millipedes are hidden in the soil or under logs and stones. At night, they roam around on the soil surface and sometimes climb high up on plants.


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