First Report of the Plague Caterpillar Tiracola plagiata (Walker) (Noctuidae) as a Pest of Crops in Kerala, India with New Host Plant Records

Abstract

The plague caterpillar, Tiracola plagiata (Walker) (Lepidoptera: Noctuidae), distributed throughout Asia and Oceania, is a highly polyphagous pest of fruits, vegetables, plantation crops and spices. According to Watabiki & Yoshimatsu (2021), 15 species in 14 plant families are hosts of T. plagiata. Robinson et al. (2003) have recorded T. plagiata on 52 plant genera belonging to 28 families. These include economically important crop plants such as banana, black pepper, cardamom, cocoa, dolichos bean, mulberry, rubber and tobacco. In India, T. plagiata is known as a pest of mulberry in Tamil Nadu (Sakthivel et al. 2015) and dolichos bean in Meghalaya (Firake et al. 2014). An outbreak of T. plagiata was observed in MayOctober, 2021 in Kerala in Kannur, Ernakulam, Kottayam, Pathanamthitta and Trivandrum districts (Table 1, Map 1). Field visits were carried out and host plants and the nature of damage were recorded. Field collected larvae were reared in the laboratory and adults (Fig. 3) were obtained. Identity of the pest was confirmed based on Watabiki & Yoshimatsu (2021). Voucher specimens of T. plagiata are deposited in the ICAR-National Bureau of Agricultural Insect Resources, Bengaluru (Accession numbers NIM/NBAIR/LEP(1-6)/71021). Field visits revealed that the caterpillars multiplied in all the five localities in large numbers on Mucuna bracteata DC. ex Kurz. (Fabaceae) (Fig. 1), a cover crop in rubber plantations, and then spread to the neighbouring crop fields. The caterpillars (Fig. 2) were observed feeding voraciously on banana, chillies, cowpea, elephant foot yam, okra, ginger, tapioca and several other economically important plants. A list of plants, on which larval feeding was observed, is given in Table 2. At Vithura, Pandalam Thekkekkara and Alakode, the population of caterpillars was so high that they even invaded homes in large numbers. At Pandalam Thekkekkara, people living near the rubber plantation had to vacate their houses temporarily as the caterpillars invaded living rooms and kitchen, besides large numbers of them ending up dead in drinking water wells. Larvae were found to totally skeletonize the leaves of tapioca (Fig. 4). They fed on the leaves and fruits of chilli (Fig. 5), okra (Fig. 6) and flowers and flower buds of rose and jasmine. Death of larvae, probably due to a Nuclear Polyhedrosis Virus (NPV) (Fig. 7), was observed at Alakode, Poothrikka and Vithura. Large scale predation by the common crow (Corvus splendens Vieillot), rufous tree pie (Dendrocitta vagabunda