Clearly, there is still much to be learnt about the relationship between millipedes and stubble management practices
Where have they been reported?
A damaging outbreak of millipedes has been reported in Victoria’s North East attacking emerging canola.
In many canola–cereal rotations where stubble is mostly retained, millipede (and slater) numbers have been on the increase over the years.
Crop damage has often been tolerable. However in a counter-intuitive twist, burning the stubble in one paddock this year seems to have exacerbated the damage, possibly because the surviving millipedes have fewer food options so focus their feeding on emerging seedlings. Similar observations were made last year in the same area with slaters.
In other areas, there have been relatively few reports of millipedes. They have been observed in a canola paddock near Temora in the Central West Slopes & Plains district of NSW, but are not believed to be causing any signifcant feeding damage.
About the black Portugese millipede
Rises in black Portuguese millipede (Ommatoiulus moreletii) populations are likely due to increased uptake of no-till practices and stubble retention.
The presence of millipedes in crops does not necessarily mean damage will occur. Millipedes have a two-year lifecycle, suggesting that the current generation began in autumn 2014 after an early break.
Adult females lay eggs into the soil during autumn or early winter. When juveniles hatch from eggs they are immobile and legless. Feeding damage is relatively rare because millipedes predominantly feed on organic matter such as leaf litter, decaying wood and fungi.
Researcher, Josh Douglas, has had difficulty inducing millipedes to feed on certain seedlings under glasshouse conditions.
For detailed information on this pest, including their occurrence, lifecycle, behaviour, damage symptoms and management strategies, go to the new PestNote on black Portuguese millipedes.
Reduction of paddock stubble during summer may reduce numbers.
Monitoring of canola paddocks with high numbers of millipedes is recommended.
Be sure to distinguish millipede damage from that of other pests, such as slugs.
If millipedes are found within paddocks, a night time visit will help determine if they are feeding on crop plants – as millipedes are mainly active and feed at night. During the day, it is best to search under rocks, stubble residue, wood, or to dig up the soil with a spade. Refuge traps such as carpet squares, tiles or pot plant bases can be used to detect millipedes.
There are currently no insecticides registered against black Portuguese millipedes in broad-acre crops. Field reports suggest fipronil seed treatment may be helpful (assuming the pest loads are not too heavy), but it is not registered against this pest.
Source of field reports of black Portuguese millipedes
Josh Douglas – Researcher, The University of Melbourne
Alan Edis – Agronomist, Landmark (NSW Central West Slopes & Plains)
Paul Lavis – Agronomist, IK Caldwell (North East Victoria)