Eleocharis dulcis (Burm.f) as a promising trap plant for the biocontrol of rice white stem borer, Scirpophaga innotata (Walker)

Abstract

The rice white stem borer, Scirpophaga innotata Walker (Family: Crambidae) is a major lepidopteran pest of rice from seedling to ear setting stage. Due to their hidden life style, no satisfactory means of control other than systemic pesticide application, habitat management, and egg parasitism have been prescribed yet. It is observed that S. innotata use a plant, the Chinese water chestnut (Eleocharis dulcis (Burm. F.)) (Family: Cyperaceae) for oviposition. We investigated why and how S. innotata is benefited by using E. dulcis for oviposition to prescribe it as a trap plant for managing the pest. We surveyed moths and egg clutches, and studied functional traits of eggs, egg hatching, and egg parasitism in eggs deposited on rice and the chestnut for three years in Kaipad rice fields of peninsular India. We observed 20 times more egg clutches on the chestnut than on rice. The egg density in clutches and hatching rate were high in eggs deposited on the chestnut. Egg parasitism was meager and restricted only to the eggs deposited on rice. However, no larvae hatched on the chestnut in the lab survived. The results suggest that E. dulcis could be a dead-end trap plant for biological control of S. innotata. We do not rule out the probability of the moth using E. dulcis for oviposition, escaping from egg parasitoids, and most importantly for rapid spread of neonates to rice. We recommend using E. dulcis as a trap plant to trap the eggs and removing them to manage this pest in rice fields.