Silvery slime trails on poinsettia bracts, translucent to white eggs clusters on the root ball, and slugs hiding beneath a poinsettia container and around the drainage holes. | W. Garrett Owen, OSU
In greenhouse environments with plants grown at ground level, paired with moist and humid environmental conditions, slugs can become a common pest. This can be a particularly common and challenging occurrence in poinsettia production, especially when such growing conditions “combined with the dense canopy of poinsettias, create an ideal habitat for slugs to thrive.”
With the poinsettia market high for holiday festivities, slugs can become most prevalent in the fall and winter months, due to “cooler temperatures and higher humidity levels” favoring their presence. So, what’s the best way to manage this slimy pest? W. Garrett Owen of The Ohio State University tackles the topic in a recent e-Gro Alert.
The Identification of Slug Activity and Damage in Greenhouses
As stated by Owen, slugs “are soft-bodied, slimy mollusks that are most active at night or during periods of high humidity. They hide during the day in dark, moist areas such as under containers, benches, or debris on the greenhouse floor.” Signs and symptoms of them include:
- Defoliation (the removal/loss of leaves)
- Irregular holes in plant tissue
- Silvery slime trails
- Translucent eggs
Damage from slugs, paired with slime trails, can significantly reduce the aesthetic appeal of poinsettias, thereby reducing their market value or making them entirely unsellable, creating a loss for the grower.
Integrated Pest Management (IPM) Strategies for Slugs
There are both cultural, chemical, and physical control practices that growers can implement, modifying a greenhouse environment “to make it less favorable for slugs.”
Cultural Control Practices
- Benching: Elevating plants off the ground through benching systems (either through temporary methods or investing in permanent equipment) improves air circulation to improve moisture levels and lowers the risk of slug infestation.
- Gravel: Using gravel as a ground cover for ground-level grown plants can act as a deterrent for slugs.
- Irrigation: As excess moisture and humidity are favorable to slugs, and because they primarily come out at night, adjust irrigation schedules so that excess water on plants and surfaces dry out earlier in the day.
- Sanitation: Remove plant leaves and debris to eliminate excess hiding spots for slugs.
- Substrate choice: Choosing a “well-draining soilless substrate” can make the greenhouse environment less appealing to slugs.
Chemical Control Practices
- Baits: Slug baits “are formulated with active ingredients that attract slugs, which then ingest the bait and die.”
- Molluscicides: Molluscicides are chemical products, applied as granules or liquids, that are “specifically designed to kill slugs.”
Physical Control Practices
- Hand-picking: Inspect plants and containers around drainage areas and remove any discovered slugs.
- Trap: As slugs are not the most mobile creatures, the placement of flat objects near attractive plants can be used to block and/or trap slugs
For more information and additional methods regarding slug infestation prevention and management, please read the full e-Gro (Electronic Grower Resources Online) alert “Slime Trails and Leaf Damage: Effective Strategies for Managing Slugs in Poinsettia Production.” Additional and current e-Gro alert pieces from Volume 13 (2024) can be found online.
