The grey field, or reticulated, slug is a major
pest of Australian grain crops and pastures.
It is 35 to 50 millimetres long and ranges
from light grey to fawn in colour with
dark-brown mottling. Under favourable
conditions, this species will breed any
time, with a pair able to produce up to
1000 eggs a year.
PHOTO: Michael Nash
The University of Melbourne’s Dr Michael Nash says slug trials in the past year have shown baiting is still the best option for chemical control and grain growers should not skimp on bait rates.
“One clear result of recent trial work was that ingestion of active toxicants works better than spray applications, so future control research will focus on baits and other novel actives delivered by ingestion,” he says. “Baiting at crop establishment is still the best emergency control option.”
Dr Nash says growers must closely monitor crops after rain when conditions are moist and favourable for slugs, particularly in areas affected by the pests in the past.
Speaking at the recent GRDC Adviser Updates series in the southern region, Dr Nash says baiting success depends on the chances a slug will encounter individual baits, which is influenced by slug activity, attractiveness of the bait and the number of baits.
He says small baits with active ingredients incorporated into the bait may last longer in wet conditions, which is when baits are most effective because of slug activity.
“The industry standard bait, containing metaldehyde, does break down more quickly under wet conditions, with initial trials indicating effective bait life is between two and three weeks,” Dr Nash says. “Trials supported previous research that recommends the application of baits immediately after sowing to protect emerging seedlings.”
Dr Nash says research continues on bait efficacy, but burning and cultivation are needed to keep populations in check. Rolling after sowing to consolidate the seedbed provides successful control, and use of shallow discs reduces grey field slug populations by 40 to 50 per cent.
Next: Cropping network targets regional production issues
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