Bean slug

The bean slug (Sarasinula plebeia) is a terrestrial pulmonate gastropod belonging to the family Veronicellidae, often referred to as a leatherleaf slug. Unlike many common garden slugs, this species lacks a shell, possesses a smooth, leathery body capable of significant contraction, and has become a highly invasive and destructive pest in tropical and subtropical agricultural systems worldwide.

This pest is highly polyphagous, meaning it feeds on a vast array of plant hosts. It causes significant economic damage to vegetable crops such as beans, tomatoes, cabbage, lettuce, and peppers, while also attacking various ornamental plants and young tree seedlings. Under humid conditions, high populations of this slug can destroy up to 50–80% of emerging seedlings within a very short period.

The biology of the species is defined by its strong adaptation to humid environments. As a simultaneous hermaphrodite, Sarasinula plebeia exhibits high reproductive efficiency under favorable thermal conditions. The life cycle, encompassing egg-laying in the soil and reaching maturity, is relatively fast, allowing for multiple generations per year and rapid population growth.

Feeding damage is characterized by the consumption of leaf tissue, often leading to severe skeletonization or total defoliation of the crop. The slugs leave behind mucus trails, which facilitate the spread of secondary pathogens and fungal diseases on the damaged plant tissues. Activity is nocturnal, making it difficult to monitor populations without nocturnal inspections.

Integrated pest management (IPM) is essential for effective control. Key strategies include:

• Mechanical soil cultivation to destroy egg clusters.
• Removal of plant debris and weeds that provide daytime shelters.
• Improving field drainage to reduce humidity.
• Application of molluscicides containing metaldehyde or iron phosphate as bait granules during peak activity.