- Life of a Slug
- Research and Impact
- New Control Strategies
If monitoring reveals slug presence and damage, identification confirmed damage by slugs, and action thresholds are established by the grower (which indicate that slug control is required), a control method can be employed. Unfortunately, there is no general agreement regarding the relationship between slug counts (and monitoring technique) and expected damage, as of yet. Control methods are evaluated on effectiveness and relative risk. Bait, pellets and liquids have been typically used in the past for chemical control of D. reticulatum and other slugs. Baits can contain active ingredients such as: metaldehyde, methiocarb, iron phosphate, or chelated iron. Pellets or granules are typically broadcasted on the soil, on seedlings, over established crop, or drilled in the furrow (and closed) with the seed.
Under favorable conditions, slugs can significantly damage a seedling crop in just 1 or 2 days. As the crop emerges (or in the case of cereals, as the seed swells with moisture soon after planting), slugs begin significant feeding. Therefore, application timing, the amount of bait used, bait density (number of pellets per square foot), and bait quality are crucial for successful treatment.
The more effective commercially available baits are made from cereal bran or flour and formulated into pellets much smaller than the pencil-eraser-size pellets of the past. These so-called minipellets, or shorts, are smaller and provide for more pellets per unit area than the larger baits did. For instance, Metarex brand slug bait pellets are a uniform 2.5 mm long. Use bait in which the pellets are uniform in size, have a high bulk density, and are relatively dust free. Broadcasting these pellets results in a very dense and uniform pellet distribution per unit area treated. This is significant because slugs tend to encounter these pellets at a greater frequency than the larger, older style type. Research in the PNW indicates that a pellet density approaching five-six/sq ft is optimum. This density can be achieved by applying a per-acre rate of just 5 lb of a 2.5 mm bait, or about 8-10 lb of the mini-pellet bait. Doubling or tripling the bait density does not necessarily increase control proportionally. Generally, it is recommended to reapply bait every 10 to 14 days if slug pressure persists, plant damage continues, all bait has been consumed, or the bait has broken down (due to weather). Be sure that the label on the bait product applied will allow for reapplication if needed within this time frame.