OCTOBER 2013 BLACK PORTUGUESE MILLIPEDES & SLATERS FACT SHEET SOUTHERN REGION MILLIPEDES AND SLATERS IN NO-TILL SYSTEMS The black Portuguese millipede is emerging as a sporadic but damaging pest of broadacre agriculture, particularly canola, while high populations of slaters have damaged some crops in recent years. PHOTOS: © NICK MONAGHAN, LIFEUNSEEN.COM Black Portuguese millipedes (left) and slaters (right) generally feed on organic matter, however their populations and the incidence of crop attack has increased in recent years. BLACK PORTUGUESE MILLIPEDES KEY POINTS In the past five to 10 years, damage caused to some broadacre crops by black Portuguese millipedes (Ommatoiulus moreleti) has Black Portuguese millipede damage to emerging canola been increasing. plants has increased in recent seasons. The increase has been linked to stubble retention, no-till farming Rises in populations have been linked to increased uptake practices and improvements in soil organic matter, which have of no-till and stubble retention. provided a more favourable habitat for millipedes to survive and Reducing paddock stubble loads over summer will generally reproduce. Recent wet summers have contributed to a population reduce millipede numbers. build-up in some parts of southern Australia while planting of more vulnerable crops has led to increased damage. Slaters can cause extensive crop damage to emerging seedlings. The species The Australiodillo bifrons slater species has the ability to The black Portuguese millipede is native to Europe and has been swarm over a soil surface. accidentally introduced to other countries, including Australia, where Finding black Portuguese millipedes and slaters in a crop it is now common in South Australia, New South Wales, Victoria, does not necessarily mean damage will occur. Tasmania and Western Australia. Management options are limited after crop emergence so The smooth, cylindrical body of the black Portuguese millipede prevention is a key part of control. distinguishes it from other native species, which often have rougher and more uneven bodies. They are part of the same family as Level 1, Tourism House | 40 Blackall Street, Barton ACT 2600 | PO Box 5367, Kingston ACT 2604 | T +61 2 6166 4500 | F +61 2 6166 4599 | E [email protected] | W www.grdc.com.au several native Australian millipedes and layer) is soft and easily damaged when AUTHORITY 2003 AGRICULTURE PHOTO: © WA centipedes called myriapods, meaning first formed. Black Portuguese millipedes ‘many-legged’. Measuring 30 to 45 usually mature after two years when they millimetres, adult millipede bodies consist are in the tenth or eleventh stage of growth. of up to 50 segments with each segment having two pairs of legs. When disturbed, Habitat The smooth, cylindrical body of the they either curl up in a tight spiral or thrash black Portuguese millipede distinguishes to escape. Millipedes feed on leaf litter, damp and decaying wood, fungus and vegetable it from other native species, which often have rougher and more uneven bodies. Native millipedes are widespread in low matter like tender roots, mosses, pollen or numbers but black Portuguese millipedes green leaves on the ground. They can play a are found in large numbers and are quite role breaking down organic matter in the soil. mobile for their size, especially after In the southern region, damage has been opening autumn rains. They can move As a result, they occur in greater numbers reported in the medium and high rainfall several hundred metres in a year. in undisturbed leaf litter and organic mulch zones including near Wagga Wagga and and in areas where winter weeds, such They are transported between properties Henty in New South Wales; the Mid North, as sour sobs and salvation jane, form a and to new regions in plant material, Yorke Peninsula and Kangaroo Island in mostly continuous ground cover. Millipedes infested soil and farm machinery. South Australia; and the Western Districts are not numerous in cultivated areas or and Wimmera areas of Victoria. In many bare ground. Life cycle cases, damage has been worst in areas Black Portuguese millipedes start mating in Crop damage with high volumes of retained stubble or March and April and lay most of their eggs in where plant matter from the previous year April and May. Mature females lay about 200 Since black Portuguese millipedes generally was present. yellowish-white eggs the size of a pinhead in feed on organic matter, crop feeding a small hole they make in the soil. damage is relatively rare and unusual. The presence of black Portuguese millipedes does not always result in Black Portuguese millipedes occasionally An immobile, legless stage hatches from damage. There have been many instances each egg and develops into the first active attack living plants by chewing the leaves where no damage has occurred despite stage of the life cycle after about one week. and stems. It has been suggested that large millipede populations. Millipedes are This first stage has only three pairs of legs. millipedes feed on crop plants when they mostly active and feed at night, which is are seeking moisture but this has not been Millipedes grow through a series of moults. confirmed. the best time to check if they are causing At each moult, the millipede adds more damage to canola plants. legs and body segments until it is mature. Most reported millipede damage has During the first year of life, millipedes are occurred in emerging canola crops on Management quite small and easily overlooked. After black organic soils with heavy stubble Control options for millipedes are limited the first year, juveniles have reached loads, although damage has also been the seventh, eighth or ninth stage of observed on lighter soils. but there are some measures that will curb populations. development and will be about 1.5 In canola, millipedes remove irregular centimetres long. After this, they only moult sections from the leaves and can kill whole in spring and summer. Chemical plants if damage is severe. Damage to During moulting, millipedes are vulnerable cereals can also occur where the stems of There are no insecticides registered to because the new cuticle (outside skin young plants are chewed. control millipedes in broadacre agriculture. PHOTO: KYM PERRY, SARDI PHOTO: KYM PERRY, IMAGE: © WA AGRICULTURE AUTHORITY 2003 & PIRSA AGRICULTURE IMAGE: © WA 200-300 eggs are laid in a chamber in the soil After two years, An immobile, legless stage millipedes are at the hatches from each egg tenth and eleventh stage of growth and are ready to reproduce Eggs are laid in autumn The first active 1.5 life size stage has only three pairs of legs. It can be found about a month after the eggs were laid The light brown juveniles moult from six to eight times during the first year All meaurements shown in millimetres The life cycle of the black Portuguese millipede. Seedling damage from millipedes. page 2 Cultural PHOTO: A WEEKS, PHOTO: A WEEKS, Reducing the amount of trash and stubble over summer and early autumn is likely to be the most effective way to reduce cesar cesar millipede numbers. Other factors to consider in management of crops and rotations include: 3 PHOTOS: ©NICK MONAGHAN, LIFEUNSEEN.COM Canola sown into paddocks with high organic matter have a greater risk of Typical swarming behaviour of pest millipede damage. slater species Australiodillo bifrons moving across a wheat paddock. Burning stubbles may reduce millipede populations. Early sowing of high-vigour varieties at a higher seeding rate will help Most slaters are detritivores, meaning compensate for seedling losses from they feed on decaying vegetation and pest damage. associated fungi, as well as on dead animal matter such as insects. They can eat Biological living plants, such as seedlings and root vegetables, but only rarely. There are very few natural predators of millipedes because their bodies contain Slaters need damp conditions and will die rows of glands that secrete a pungent if exposed to open and dry situations. They yellowish fluid when they are agitated. tend to be active at night when the risk of This fluid makes millipedes distasteful to dehydration is low. predators, such as birds. Female slaters keep their eggs in a pouch until the young hatch. Hatchlings then leave A parasitic native nematode, Rhabditis the parent and are completely independent. necromena, attacks and kills millipedes Slaters grow through a series of moults by reproducing in the millipede’s gut. in which the outer rigid skeleton is shed, However the use of nematodes is unlikely allowing growth to the next larger stage and to be economically viable for broadacre finally to adult stage. When moulting, slaters crop release. shed in two stages – the top half of their Some spiders and beetles will eat body first followed by the remaining half two millipedes but these predators will not days later. During moulting, the slater is very significantly reduce large populations. vulnerable and must find shelter. There are a number of slater species in Australia including (from top) Flood SLATERS Species bug slater (A. bifrons); Common slater Native and introduced slaters have There are a number of slater species in (Porcellio scaber) and the Pill bug slater become an increasing pest of broadacre Australia including: (Armadillidium vulgare). When moulting, slaters shed in two stages – the top crops and pastures but this has not always Common slater half of their body first followed by the been the case. The common slater, Porcellio scaber, remaining half two days later (above). The move to minimum or no-tillage and is widespread in Australia, originally stubble retention is likely to have created introduced from Europe. The species can a more habitable landscape in cropping grow up to 20 millimetres in length and is paddocks for slaters. usually pale grey however brown, yellow or colour with darker irregular spots and a dark orange hues have been observed.