How to Manage Pests
UC Pest Management Guidelines
Brown garden snail: Helix aspersa
Gray garden slug: Agriolimax reticulatus
In this Guideline:
Both snails and
similar in structure and biology, except slugs lack the snail's external spiral
shell. Snails and slugs 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. They are most active during the night
and early morning when it is damp. In southern California, particularly along
the coast, young snails and slugs are active throughout the year.
Adult brown garden snails lay about 80 spherical, pearly white eggs a
month in shallow depressions in the topsoil. They may lay eggs up to six times
Slugs and snails are of major concern on perennial artichokes
especially in winter. The juveniles and adults feed on all parts of the
In heavily infested fields, slug feeding on foliage causes shot holes on the
leaf lamina. Slugs are particularly injurious to the buds when they scrape off soft tissues from the artichoke bracts.
This injury later turns black and the quality and marketability of the affected
produce is greatly reduced. Mollusks do not pose any threat to annual
artichokes throughout California.
Controlling weeds and applying bait are important practices in
keeping snail and slug populations under control.
Cutting-back artichokes annually helps reduce the slug population.
Regions where the artichokes are cut shallower or not cut at all usually
sustain higher infestations of both slugs and snails. Keeping weeds under
control reduces the plant cover under which the slugs and snail take refuge during
the day. Similarly, artichokes planted in heavier soils are more prone to slug
and snail damage than in lighter soils. Frequent cultivation and tillage
generally keep the infestation under control by killing the slugs and exposing
their eggs to natural predators like ground beetles and birds. However, slugs
staying very close to the base of the plants or under the crown remain
unaffected by this operation and in due course their populations rebound.
that have yearly problems with these pests,start baiting immediately after the
annual cutback of the perennial artichokes in May and June by broadcasting the
bait on the ground around the base of the plant. Avoid applying the bait
directly to plant foliage or as a heap on the ground near the base of the
plant. Continue baiting at 2-3 week intervals through November preferably after
irrigating the field. In the past, control with baits has been only
marginal in part because slug and snails have always been dealt with on a crisis
basis. Research indicates that peak egg-laying in 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. Therefore, slugs are best controlled during October when they are more
mobile on the ground surface in search of food and mate.
Several new formulations of metaldehyde bait have been
introduced in recent years. Granular baits and micro-pellets have given better
control, as the individual particles remain intact in the rain and irrigation
water. Also, when the sand-based granular formulations are used during the
production phase of artichokes, individual granules can get lodged in the
flower buds and become a health hazard to the consumers. Slug control with
metaldehyde is dependent on many factors, including weather. Metaldehyde
rapidly breaks down in irrigation and rainwater. Adverse weather conditions
such as the rain and wind keep the slugs, especially the juveniles, inactive
and either they do not consume enough bait or they are able to recover from the
|When choosing a pesticide, consider
information relative to environmental impact.
||(Deadline) 4% bait
||(Durham) 7.5% G
||8 – 15 lb
||(Metarex) 4% bait
||5.5 -15 lb
||(Orcal) 3.25% bait
||15 – 20 lb
||COMMENTS: Use higher rate for heavy
infestation. This bait has minimal impact on other organisms in the field.
Avoid contamination of buds by spreading the bait on the ground; tolerance has not yet been established.
||COMMENTS: Can be applied to a field
approaching bud harvest without concern of contamination because this product
is exempt from tolerance. 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. Check
with your organic certifier to determine if this product is acceptable for use on organically certified produce.
UC IPM Pest Management Guidelines: Artichoke
UC ANR Publication 3434
M. A. Bari, Artichoke Research Foundation, Salinas
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Arthropods:
W. E. Chaney, UC Cooperative Extension, Monterey County
W. L. Schrader, UC Cooperative Extension, San Diego County
L. Handel and T. K. Shannon, Kleen Globe, Inc., Castroville, CA
Top of page