Prevention—minimizing conditions that attract slugs—is integral to an IPM program. Prevention includes taking steps to ensure that slug populations cannot increase to unacceptable levels and become a threat to your crop, IPM programs work to manage crops, garden plants and landscapes—creating an unfavorable environment for slugs to colonize, grow, and reproduce.
Prevention measures should include early scouting for slugs before trying to establish a new crop. For example, scout for slugs in previous crop to help determine future populations. If you find that slug populations are moderate to high (what slug numbers are high to you?), practices such as lightly cultivating to expose slugs and reducing favorable habitat (e.g., weeds), removing residue that supports slug habitat, and avoiding high-risk crop rotations may reduce slug populations.
Cultural practices should be implemented to help reduce slug establishment, egg-laying, and survival. For example, tillage can crush and bury slugs, expose them to predators, disrupt a slug’s movement through the field, alter the environment, reduce hiding places, and will remove volunteer weeds that slugs like. Rotating crops, selecting slug-resistant varieties, and creating a habitat (e.g., installing beetle banks) that encourages natural enemies of slugs such as predatory beetles, amphibians, are a few tools and practices that a grower might consider.
Effects of Tiles and Straw Residue on Slug Populations
(Gavin et al. 2006; USDA-ARS Corvallis)
Tiles installed in field. Better drained soils that have been tiled have higher gray field slug populations than poorer drained fields; cultivation of land reduced population slug densities. Gavin et al 2006.
Straw residue level. Five times more slug egg clutches (yellow bars) were found in high residue fields (line on figure) (3.75T/A) compared to low residue fields (1T/A). Slugs survival is greater when the cover in field is moist. Kamm and Gavin, past slug researchers in Oregon, found slugs can survive on residue alone as young volunteer sprouts beneath the straw offer suitable food. Gavin et al. 2006.