First Report of Elephant Beetles in the GenusXylotrupesHope (Coleoptera: Scarabaeidae) Attacking Guava (original) (raw)

Abstract

Guava, Psidium guajava (L.) (Myrtaceae), is the fourth most intensely cultivated tree fruit on the Indian subcontinent (Chandy 2002). Guava is exceptionally hardy, and even on marginal lands it bears marketable fruit with high vitamin C content and maintains for its producers an attractive income versus investment profile (Singh 2010). In India, guava is cultivated on about 205,000 hectares which yield about 2,500 metric tons per annum (Anonymous 2011). The subtropical climatic conditions of the northeastern Indian state of Meghalaya generate a single, relatively well defined guava fruiting and harvest cycle. During April and May, guava produces its flowers and then fruits in September to October. A large number of insect pests have been reported to occur on guava, but only a few of those reported are known to constitute a significant impediment to the successful cultivation of this crop (Shylesha et al. 2000; Firake et al. 2013). Recently, adult specimens of the elephant beetle genus Xylotrupes Hope were found feeding on the flesh of guava fruits in Meghalaya (Fig. 1), causing considerable losses in yield (35–45%). Furthermore, the often minimal damage inflicted by these beetles on the mature fruits can predispose the fruits to secondary attack by other insects (Fig. 2) and pathogens, all of which can augment market losses. On occasion, up to 98% of fruit can be damaged by Xylotrupes. Three male specimens of Xylotrupes from Meghalaya were sequenced at the 5′ region of the COI gene (NCBI Accession No: KF494189) and these sequences were found by Jen-Pan Huang, University of Michigan (personal communication) to nest within an unpublished, large series of specimens sequenced at the same region of COI gene. The latter series was assembled from diverse localities across Southeast Asia and had been previously identified as Xylotrupes siamensis Minck by criteria in Rowland (2003, 2011). According to the latter evidence, the identity of the Xylotrupes beetles found attacking guava in Meghalaya is here assigned as X. siamensis. Xylotrupes siamensis is reddish brown to black in color and 30–40 mm in body length. The males bear cephalic and pronotal horns, and the females are smaller and do not bear horns (Endrödi 1985; Waite and Elder 2000). The genus Xylotrupes is one of the most widespread genera of large beetles in the world. Its natural distribution extends over nearly a third of the earth’s circumference from the high valleys of Himalayan Pakistan east and south into India, Southeast Asia, China, the Malay Archipelago, Australasia into Melanesia as far as Vanuatu in the South Pacific (CAB International 2002; Rowland 2003, 2011, in Foreword in Hwang 2011). Xylotrupes beetles are known to be polyphagous, feeding on bark, fruits, panicles, and inflorescences of a large number of host plants viz., Acacia mearnsii De Wild (Fabaceae), Toona australis Kuntz (Meliaceae), pineapple, longan, lychee (Waite and Elder 2000), bamboo, coconut, cashewnut, cinnamon, African oil palm, rubber, banana, plantain, sugarcane, potato (CAB International 2002), passion fruit (Shylesha and Rao 2004), maize, sword bean (Shylesha et al. 2006), okra (Nair et al. 2001), poinciana, gulmohar, cacao, and som (Eswarareddy and Rajan 2011). To our knowledge, infestation or management of Xylotrupes beetles on guava has not been previously reported. For this reason, we have initiated studies based upon quantifiable variables associated with feeding by X. siamensis on guava fruit in the orchards of our experimental farm in Meghalaya, so that feasible