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Black Portuguese millipedes damaging canola

Control options for the black Portuguese millipede are limited post sowing.

 

Crop stubble and residues provide the black Portuguese millipede (Ommatoiulus moreletii) with the two-fold comfort of a cool, moist habitat and an abundant source of food. While they are primarily decomposers of decaying organic matter, the black Portuguese millipede has been known to turn its attention to establishing crops, especially canola.

Widescale damage has been observed in canola seedlings grown in some stubble retained paddocks this winter. Areas of seedlings have been taken out at the ground level, eliminating the prospect of plants recovering and prompting re-sowing.

While some areas of south-eastern Australia have received enough rain to allow young canola plants to get up and away, others are suffering from moisture stress, and delayed development has heightened their susceptibility to attack by millipedes (and other establishment pests). As these plants mature, they will fortunately become less susceptible to attack by millipedes.

Prospects for control of millipedes are limited post-sowing. We have undertaken laboratory-based microcosm trials with Bayer CropScience looking at methiocarb baits, which are registered in a number of crops to control slugs and snails. Although preliminary, these trials showed methiocarb has efficacy against the black Portuguese millipede.

There are no foliar insecticides registered against the black Portuguese millipede in broadacre crops, and field reports indicate they are often unaffected by sprays of both synthetic pyrethroids and organophosphates applied to control other crop establishment pests. Additionally, using broad-spectrum insecticides will have negative consequences on beneficial invertebrates that play a role in controlling crop pests. One of the control challenges is their behaviour – these millipedes tend to shelter under stubble, rocks and clods of soil, avoiding contact with insecticide sprays.

If you have identified millipede problem paddocks, take note of these areas for planning of next year’s crops. Seed treatment choice will influence the degree of feeding damage. We have conducted research trials that show fipronil-based seed dressings can help protect canola seedlings (read about pre-sowing controls here). We are currently conducting further trials on seed treatment effects on millipede mortality and plant damage with funding by the GRDC. These results will be available for growers by next year.

Black Portuguese millipede (Source: cesar).

 

Field observations

David Cook – Grower (Northern Country, VIC)

Tim Polner – AGRIvision (Wimmera, VIC)

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