A Review of the Pest Status and Natural Enemy Complex of Banana Skipper Erionota Torus Evans in South India and Its Management
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20042-- J Poorani Indian Journal of Entomology Review Article (2020) DoI No.: A REVIEW OF THE PEST STATUS AND NATURAL ENEMY COMPLEX OF BANANA SKIPPER ERIONOTA TORUS EVANS IN SOUTH INDIA AND ITS MANAGEMENT J POORANI*, B PADMANABAN, SHARANABASAPPA DESHMUKH1, R. THANIGAIRAJ AND GAVAS RAGESH2 ICAR-National Research Centre for Banana, Thogamalai Road, Thayanur Post, Tiruchirappalli 620102, Tamil Nadu 1Department of Agricultural Entomology, College of Agriculture, University of Agricultural and Horticultural Sciences, Shivamogga 577225, Karnataka 2Banana Research Station, Kerala Agricultural University, Kannara, Thrissur 680652 *Email: [email protected] (corresponding author) ABSTRACT Huge outbreaks of the banana skipper, Erionota torus Evans (Lepidoptera: Hesperiidae), considered as a minor pest of bananas and plantains in the northeast India, were witnessed in South India during 2012- 16. Its present status as a pest of bananas in South India is briefly reviewed here with information on its natural enemies, seasonal incidence and varietal preference. Natural enemies of E. torus from South India were surveyed during 2015-18 due to the lack of information on its bioagents in Indian conditions and totally 14 parasitoids were observed on various stages of E. torus including five on eggs, seven on larvae and two on pupae. Most of the parasitoids observed in South India are known to parasitize E. torus in other parts of South and South East Asia, except Acropimpla sp. nr. nigroscutis (Hymenoptera: Ichneumonidae), which is reported here as a larval parasitoid of E. torus for the first time in the world. Egg parasitism by Ooencyrtus pallidipes (Ashmead) and early larval parasitism by Elasmus brevicornis Gahan and heavy bird predation on older larvae were identified as major regulatory factors of E. torus in South India. At present, E. torus is mostly confined to parts of Western Ghats with cooler weather than the plains and its population is lower absent in the plains of South India where outbreaks were reported earlier, possibly due to the influence of natural enemies and adverse abiotic factors. Other management options available for the pest are briefly discussed. Key words: Erionota torus, Hesperiidae, banana, parasitoids, Acropimpla sp., Oencyrtus pallidipes, Elasmus brevicornis, predators, birds, management, Western Ghats Banana (Musa spp.) has a special significance in Erionota torus, originally described from Sikkim, South Indian culture as the leaves are widely used as is indigenous to north India (Western Himalaya) and disposable plates for serving food and whole plants found in Nepal, northeast India to southern China and with bunches are used as symbols of auspiciousness in Peninsular Malaysia (Cock, 2015). Erionota torus is religious and cultural functions besides the known use more restricted in its geographic spread than E. thrax, of fruits for dessert and cooking purposes. Two species but now it has been widely introduced in different of skippers of the genus Erionota Mabille (Lepidoptera: countries including Taiwan, Japan, Mauritius, and Hesperiidae) are known to feed on the leaves of bananas the Philippines (Cock, 2015; GBIF, 2018) and Sri and plantains in different parts of Southeast and South Lanka (Gunawardana et al., 2015), besides India. In Asia. Cock (2015) critically reviewed the literature India, E. torus is known to be distributed in Arunachal pertaining to the taxonomy, distribution, food plants, Pradesh (Jayashankar et al., 2018), Assam, Meghalaya, early stages, natural enemiesPreview and biological control of Chhattisgarh, Madhya Pradesh, West Bengal, Manipur, Erionota spp. including E. thrax (L.), E. torus Evans Mizoram, Tripura, Kerala, Karnataka, Maharashtra, and E. acroleuca (Wood-Mason and de Niceville) (=E. Tamil Nadu and Andhra Pradesh (Chitra et al., 2016; hiraca (Moore)), a pest of palms. Of these, E. thrax (L.) Raju et al., 2019; unpublished data). Ghorpade and is more widely distributed in South and South East Asia Kunte (2010) included E. torus in their list of butterflies and reported in published literature as banana skipper. In of the Palani Hills of Southern Western Ghats, but it had India, Erionota thrax is distributed in the northeastern not been known to be a pest of banana in peninsular region (West Bengal, Meghalaya, Mizoram) (Kunte India until recently. Sporadic outbreaks of E. torus in 2019), where it coexists with its close relative, E. torus. Palghat, Peechi, Nilambur, and some northern districts 2 Indian Journal of Entomology Review Article 2020 of Kerala state, South India, were first reported in 2013, gave characters to separate the adults from E. thrax which spread to the entire state within a year (Soumya et based on appearance and male genitalia. In view of al., 2013; Sivakumar et al., 2014). Soon after, outbreaks their external similarity, E. torus and E. thrax are were witnessed in 2013-14 in the neighbouring states of not easy to identify without examination of the male Tamil Nadu and Karnataka (south and coastal districts), genitalia and females can be reliably identified only by which are major banana growing belts. It was first the genitalia (Cock, 2015). The immature stages and reported from Andhra Pradesh in 2015 (Kamala Jayanthi adults of E. torus (Fig. 1) and E. thrax are externally et al., 2015) and later in 2018 (Reddy and Hemadri, very similar and males of E. torus can usually but not 2018). It is also present in the Western Ghats section always be distinguished from those of E. thrax by the of Maharashtra (Kunte 2019). more rounded distal margin of the forewing in E. torus (Fig. 2b) compared to the straighter margin and apically In South India, outbreaks of E. torus were initially more pointed forewing of E. thrax (Fig. 2a). When wrongly attributed to E. thrax and reported as such by E. torus was introduced in Mauritius, it was initially some workers (Soumya et al., 2013; Padmanaban, 2014; misidentified asE. thrax as the latter was better known Sivakumar et al., 2014), but later the pest was correctly as banana skipper. Unsurprisingly, in South India too, identified as E. torus. The skipper larvae caused direct outbreaks of E. torus were initially attributed to E. thrax damage by feeding on leaf lamina and reduced the total (Soumya et al., 2013; Padmanaban, 2014; Sivakumar et photosynthetic area of leaves and the banana leaf industry al., 2014), but later corrected as that of E. torus. was badly affected due to these outbreaks (Sivakumar et al., 2014).Studies on economic losses due to E. torus The genitalia of E. torus are illustrated by Evans are lacking in India and elsewhere probably because (1949), Inoué and Kawazoé (1970), and Raju et al. ‘economic entomologists have hitherto treated both E. (2019). The present study identified all the specimens thrax and E. torus as a single species wherever they occur collected from the states of Karnataka, Kerala and together’ (Cock, 2015). Economic impact of E. thrax on Tamil Nadu during 2015-18 as E. torus based on the banana yield was worked out by Waterhouse et al. (1998) characters of female and male genitalia and DNA who extrapolated from several studies on defoliation barcodes. Sympatric occurrence of both E. torus and and fruit loss indicating that more than 16% defoliation E. thrax was observed only in Meghalaya, northeastern will cause loss of yield, and 50% defoliation will cause region, during surveys in 2018, with E. torus being the 28% yield loss. Infestation by E. thrax was found to lead more predominant species. The male (Fig. 3a-d) and to both a serious delay in fruit maturation and reduced female genitalia (Fig. 3e) of representative samples weight of banana bunches (Waterhouse et al., 1998). of E. torus from South India and that of E. thrax from Meghalaya (Fig.3 f-i) are illustrated here. As the name In the aftermath of the recent outbreaks of E. torus E. thrax continues to be used by some authors for the on banana in south India, attempts have been made by species from peninsular India even after the pest has many researchers to formulate management strategies been correctly identified asE. torus (e.g., Irulandi et al., for the pest. Surprisingly, many of these were based 2018), it is advisable to follow Cock’s (2015) precaution on use of insecticides and though biological control “to ensure that voucher specimens are preserved and has been identified as the major management strategy documented for all observations on Erionota spp.”. for E. torus and effective parasitoids have been known (Cock, 2015), systematic attempts have not been Host plants and varietal preference made to document the parasitoids of E. torus in Indian The common name of E. torus is Rounded palm- conditions. This study made intensive efforts to survey redeye and that of E. thrax thrax (the subspecies found and document the natural enemies of E. torus from in India) is Acute palm-redeye (Kunte, 2019), both Southern Indian states Previewduring 2015-18. The natural of which are misnomers as the pests do not feed on enemies of E. torus collected and documented in our palms. Cock (2015) recommended that use of these surveys are reported here with a brief review of the common names for all Erionota spp. should be totally present status of the pest in South India, its seasonal discontinued as they are inappropriate and likely to incidence, varietal preference and management cause confusion in view of the well documented damage strategies in Indian conditions. caused on banana. In the present study, surveys came across E. torus damage on several popular banana Taxonomy cultivars (Musa spp., Musaceae) and bird of paradise Evans (1941) described E. torus from Sikkim and (Strelitzia reginae Banks, Strelitziaceae). 20042-- J Poorani A review of the pest status and natural enemy complex of banana skipper Erionota torus Evans in South India and its management 3 J Poorani et al. Fig. Fig1. Erionota. 1.