Short communicationTropisternus lateralis (Say) (Coleoptera: Hydrophilidae) as a potential stand reducer in water-seeded rice under a continuous flood

- Greenhouse experiments show Tropisternus lateralis uproot seedlings.
- Higher densities of T. lateralis resulted in increased floating seedlings and lower stands.
- Foraging activity by T. lateralis may be a possible cause of uprooting.
- Mating activity may also be a cause of uprooted seedlings.

Water-seeded rice under a continuous flood is susceptible to stand reduction by aquatic invertebrates. Field observations in water-seeded rice with reduced stand revealed the possibility that Tropisternus lateralis may be responsible for dramatically reducing rice stands. Greenhouse experiments were performed with aerated, covered bins that were water-seeded and infested with varying densities of T. lateralis. Uprooted seedlings (floaters) were counted and removed, and stands were recorded. Results showed significantly increased numbers of floaters in bins with higher densities of T. lateralis. Stands were also significantly reduced in the higher density bins. The results of these experiments strongly suggest that T. lateralis is responsible for dislodging rice seedlings in a water-seeded regime with a continuous flood. Foraging activity appeared to be associated with this damage. Observations also suggest female T. lateralis may be more likely to dislodge seedlings than males because of their egg laying activities.