Slugs, slaters and lucerne flea

It is not surprising that slugs, slaters and lucerne flea continue to cause significant problems with crops at emergence. For slugs, bait timing, rate and evenness of spread is everything!

Slugs

Referring to the southern regions of the Western and Central districts of Victoria, slug expert, Dr Michael Nash (SARDI), has emphasised that baiting in all canola and cereal crops is strongly recommended. This year he has observed significant activity of both grey field slug (Deroceras reticulatum) and black-keeled slug (Milax gagates) in cereals as well as canola; he believes that these large populations are a carry-over from excellent breeding conditions last spring. Recent rain has brought all adult slugs into full activity. High Rainfall Zone IPM consultant, Neil Hives, stresses that timing and rate are the two most important aspects of baiting for slugs. This is even more important considering that the next generation of juvenile slugs are already present in many paddocks, in some cases well before canola crops were sown.

It is critical that baiting provides a uniform coverage and that an adequate dose of active ingredient is provided. Recent trials have demonstrated that an even distribution of at least 25 bait pellets/m2 gives an 80% chance of a slug encountering a pellet in the first night after spreading. Characteristics of the available bait products vary greatly so to assist Michael has developed a slug bait comparison table.

Large populations of the black-keeled slug have been devastating a newly established fescue-sub clover pasture in the Holbrook area, in the Riverina district of NSW. Most plants in large areas of the paddock have been destroyed and re-sowing will be necessary. All available management options will be deployed, including tillage (to a fine tilth), rolling and baiting at plant emergence to ensure both maximum slug exposure to the bait pellets and that the active ingredient is at a rate necessary to avoid sub-lethal doses. Slugs have also been reported to have caused serious damage to numerous canola crops in the Northern County district of Victoria. Refer to PestFacts Issue No. 1 for further information on slugs.

Slaters

An additional incidence of slaters causing extensive damage to canola occurred near Barooga, in the southern Riverina district of NSW. The 200 ha crop of cotyledon canola was largely lost to slater feeding. Imidacloprid seed dressing appeared to offer little protection. The paddock had optimal soil moisture and was burnt just prior to seeding. Greatest plant survival occurred along the wheel furrows, where the soil had been compressed. An adjacent canola crop, which was sown into cereal stubble and baited for slugs, had no evidence of slater damage. Refer to PestFacts Issue No. 1 for further information on slaters.

Lucerne flea

Lucerne flea (Sminthurus viridis) damage has been reported from various regions across southern NSW and Victoria. Specifically, reports of widespread incidence include those from near Cootamundra (clover based pastures), and near Lockhart both in the South West Slopes district of NSW, in the North East district of Victoria (in lucerne, where second generation fleas are abundant) and in the Victorian Wimmera. In many cases the feeding has been significant, but the pastures/crops appear to be outgrowing the damage. If spraying is warranted, do not use synthetic pyrethroids. As lucerne fleas are mostly distributed patchily within crops, spot spraying is often all that is required. Refer to PestFacts Issue No. 2 for further information on lucerne flea.

 

* Sources of field reports

Phil Bowden - Agronomist (NSW South West Slopes)

Ben Cordes – Agronomist, Tylers Hardware & Rural Supplies (Victorian Wimmera)

Josh Douglas – Researcher, The University of Melbourne

Michael Nash – Researcher, SARDI (Adelaide)

Roger Garnsey – Agronomist, Roger Garnsey Agronomy (NSW Southern Tablelands)

Paul Lavis – Agronomist, IK Caldell (NSW Riverina)

Rik Maatman – Agronomist, Landmark (Victorian Wimmera)

Warwick Nightingale – Agronomist, Delta Ag (NSW Riverina)

Damien Tanner – Agronomist, JSA Independent (Victorian Wimmera)