Description of the Pest
Slugs have no shell, are slimy and have bodies that are flexible in shape. They move by gliding along on a muscular "foot." This muscle constantly secretes mucus, which later dries to form the silvery slime trail that signals the presence of these pests. Slugs can be found on the plant at night and in the early morning, and under the plastic or other mulch during the day. They are sensitive to dryness, and will seek out moisture, making the humid environment under the mulch of strawberries attractive to them.
The garden slug is larger than the gray garden slug. It measures about 1 to 1.5 inch in length and is gray to dark brown. Living for about one year, the garden slug is sexually mature in about 3 weeks. This slug is sensitive to cold and many will not survive a cold winter.
The gray garden slug is mottled gray and about 0.5 to 0.75 inch (12–19 mm) long. It takes from 3 to 4 months for the gray garden slug to reach maturity. This slug is less sensitive to cold than the garden slug and is better able to survive mild winters in high numbers.
Peak egg-laying for both slugs occurs from late September through early November. Most eggs deposited before late October hatch during fall; those deposited in November hatch from late February through spring.
Damage
Slugs feed on ripe fruit and produce rough holes that render the fruit unmarketable. These holes may be invaded by secondary pests such as sowbugs, earwigs, and small beetles. Slugs also feed on the leaves of strawberries, and the effects of the rasping feeding are ragged holes in the leaves.
Management
Cleaning up debris in fields to make them less hospitable to slugs can help prevent large numbers of slugs from developing. If damaging numbers of slugs are present, baits can be applied.
Cultural Control
The elimination of hiding places such as rocks, weeds, logs and boards will assist in reducing the numbers of slugs, because of the removal of habitat. Furthermore, growers can seek to plant away from areas with lots of debris, such as leaves and ground covers.
Organically Acceptable Methods
Use cultural controls and Sluggo bait on organically certified strawberries.
Treatment Decisions
Apply baits during fall and spring when slugs are most mobile on the ground surface in search of food and mates. Adverse weather conditions keep the slugs, especially the juveniles, inactive and they do not consume enough bait. The efficacy of metaldehyde baits may also be reduced by cool, wet weather because slugs produce less mucus during these periods.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | METALDEHYDE | |||
| (Deadline M-PS) | 10–25 lb | 12 | 0 | |
| COMMENTS: Use higher rate for heavy infestation. This bait has minimal impact on other organisms in the field. Avoid contacting the fruit with bait. | ||||
| B. | IRON PHOSPHATE# | |||
| (Sluggo G) | 20–44 lb | 0 | 0 | |
| COMMENTS: Apply using standard fertilizer granular spreader. If ground is dry, wet it before applying bait. Reapply as bait is consumed or at least every 2 weeks. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| 1 | Rotate insecticides with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers for insecticides and miticides (un=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |
| # | Acceptable for use on organically grown produce. |