Tadpole shrimp

The tadpole shrimp (Lepidurus) belongs to the order Notostraca. While often studied as a living fossil, it is also recognized as an agricultural pest in specific environments, particularly in water-managed fields like rice paddies where they can cause significant economic losses.

These crustaceans typically inhabit temporary freshwater pools. In an agricultural context, they thrive in flooded irrigation systems where organic matter is abundant. Their opportunistic nature allows them to exploit these environments as soon as water becomes available.

The life cycle is remarkably adapted to harsh conditions. The eggs (cysts) can remain dormant in dry soil for many years, resisting extreme temperatures and desiccation. Upon flooding, hatching occurs rapidly, and the population increases exponentially, often reaching high densities within a few weeks of water introduction.

The damage to crops is primarily caused by their benthic foraging behavior. As they scrape the bottom of the paddy, they uproot young seedlings and cut roots, leading to plant death or poor establishment. Furthermore, their activity causes water turbidity, which blocks sunlight and hinders the initial photosynthetic growth of the crop.

Management strategies focus on breaking the reproductive cycle of the pest. Effective control involves:

• Careful water management and timely drainage of fields to kill larvae.
• Preparation of seedbeds to ensure rapid germination before the shrimps reach maturity.
• Chemical control using targeted pesticides during the early stages of paddy flooding.