OCTOBER 2013 BLACK PORTUGUESE & SLATERS FACT SHEET

SOUTHERN REGION MILLIPEDES AND SLATERS IN NO-TILL SYSTEMS The black Portuguese 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 ( 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 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 , , , does not necessarily mean damage will occur. and . –– 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 PHOTO: © WA AGRICULTURE AUTHORITY 2003 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, , 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 IMAGE: © WA AGRICULTURE AUTHORITY 2003 & PIRSA 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 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 , 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 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. brown stripe down the middle of its back. It Stubble provides a cool, moist habitat while is a low-land swampy soil species adapted –– Pill bug crumbly clay soil surfaces and cracking to marshy environments. Areas worst- clays aid their survival. Armadillidium vulgare is a European species, introduced to Australia, which affected in the past by A. bifrons are prone to flooding. Identification gets its name from its ability to roll into a ball when disturbed. It can grow up to Slaters are also known as woodlice, 18 millimetres and is dark brown to black Slaters as pests sowbugs and pill bugs. They are in colour. There is presently very little known about crustaceans related to crabs, lobsters and the biology of slaters and their potential to –– Flood bugs prawns but are adapted to living on land. become a widespread agricultural pests Populations of Australiodillo bifrons, also in Australia. They have a hard skeleton on the outside called ‘flood bugs’, have increased in parts of their bodies, seven pairs of jointed legs, of New South Wales. A. bifrons is about Slaters can cause significant feeding and two pairs of antennae. They perform an 7-8 millimetres long and 4mm wide with an damage, particularly on canola, leading to important recycling role in the environment. oval-shaped and flattened body, light brown seedling mortality and stunted plant growth. page 3 Slaters have been observed crawling up Damage wheat and oat seedlings and feeding from USEFUL RESOURCES the tips of young plants. Research suggests It is uncommon for slaters to attack broadacre crops but issues with slaters some crops, such as chickpeas, are not have increased considerably in the past five MILLIPEDES: susceptible to feeding damage but this is years. In south-eastern Australia, slaters Emerging issues with diseases, still to be proven. have caused damage to wheat, oats, weeds and pests In some situations, crops or parts of canola, lentils and pastures. Ground Cover Supplement Jan-Feb paddocks may need to be re-sown. Often 2013, page 12 Slater feeding on plants results in an symptoms resemble feeding damage uneven rasping-type damage that can www.grdc.com.au/GCS102 caused by lucerne flea. appear similar to slug and snail damage. In particularly, the flood bug has potential They can chew the tops of emerging SARDI Portuguese Millipedes to cause rapid damage to crops due to its cotyledons or leaves of crop seedlings, Fact Sheet ability to swarm. A consistent mass of slaters leaving only the seedling stumps. www.sardi.sa.gov.au (search millipedes) moves along the soil surface, climbing trees The presence of slaters, even in high DAFWA Garden Note: Black or moving into logs or posts. Swarms can numbers, in a paddock does not always Portuguese millipedes contain more than 100,000 individuals – mean crop damage will occur because www.agric.wa.gov.au (search millipedes) sometimes up to one million – and include all slaters generally feed on decaying organic life stages, from juveniles to adults. matter. Feeding on emerging crop SLATERS: The size of swarms varies and is likely seedlings is relatively rare. It is not known DAFWA Garden Note: Slaters and to be influenced by the time of day, weather what makes slaters suddenly prefer to eat their control seedlings rather than organic matter. conditions and surrounding vegetation. www.agric.wa.gov.au/OBJTWR/ Thousands of seedlings can be eaten In south-eastern Australia, damage has imported_assets/content/pw/ins/hp/ in a very short time when swarms are been reported in the medium and high gn2004_15.pdf large enough. rainfall zones including South Australia’s Mid North and Yorke Peninsula, Victoria’s Wimmera and Western Districts, and central MORE INFORMATION New South Wales. In many cases – but not Sign up for pest news ... all – damage has been reported where there Dr Paul Umina was an accumulation of stubble or other The latest invertebrate pest-related cesar and the University of Melbourne plant matter or cracked soils. issues and solutions in the GRDC 03 9349 4723 [email protected] Southern Region are available by Management subscribing to the free PestFacts Kym Perry services. The information services Management options are limited after crop South Australian Research and provide subscribers with pest emergence so prevention is a key part Development Institute reports and field observations on of control. 08 8303 9370 the appearance and distribution [email protected] Chemical of invertebrate pests across Svetlana Micic south-eastern Australia. This There are no insecticides registered Department for Agriculture and Food WA to control slaters. Slaters are relatively information, along with advice and 08 9892 8591 unaffected by most foliar applications of recommendations, is emailed to nearly [email protected] 2000 individuals, organisations and synthetic pyrethroids and organophosphates businesses working with broadacre to control other crop-establishment pests, even when applied at very high rates. crops and pastures. Subscribe in SA GRDC PROJECT CODE by contacting Kym Perry, 08 8303 Cultural 9370 or [email protected] and CSE00054 in Victoria and NSW by contacting Managing stubble is likely to be the Paul Umina 03 9349 4723 or email most effective strategy to reduce slater [email protected] numbers. Some growers have had success Acknowledgements: Paul Umina; managing slaters ahead of canola rotations Kym Perry; Svetlana Micic; Nick Monaghan; through burning crop residues. DAFWA

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