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J. Nat. Hist. Mus. Vol. 25, 2010, 333-338 FORTUITOUS BIOLOGICAL CONTROL OF PARTHENIUM HYSTEROPHORUS BY ZYGOGRAMMA BICOLORATA IN NEPAL B. B. Shrestha1, A. Poudel1, J. KC1, D. Karki2, R. D. Gautam3 and P. K. Jha1 Parthenium hysterophorus L (Fam: Asteraceae, common name: parthenium, hereafter referred as Parthenium), a native of central America, is one of the most problematic alien invasive weed in tropical and subtropical world (Evans, 1997, Bhowmik et al.., 2007). Strong allelopathic potential (Kanchan and Jayachandra 1981, Singh et al.., 2002, Maharjan et al.., 2007), prolifi c seed production (Pandey and Dubey 1988) and phenotypic plasticity in growth form (Annapurna and Singh 2003, Pandey et al.., 2003) enable this species to invade a wide range of habitats in areas where natural ecosystems are disturbed to varying scales by anthropogenic activi- ties. Invasion of this species has replaced native species, impoverished the native biodiversity (Grice 2006, Timisina et al.,. 2011), increased health hazards to animals and human (McFadyen 1995, Evans 1997, Bhowmik et al.., 2007), and reduced agricultural productivity, fodder supply to livestock, and degrade quality of milk and meat (Ayele, 2007, Wegari, 2008, Karki, 2009). Parthenium is partly responsible for allergic eczematous dermatitis, allergic rhinitis, fever and asthma in urban populations of human (McFadyen, 1995, Bhowmik et al.. 2007). Parthenium might have entered Nepal early in 1950s from India. Herbarium specimens of this plant were collected from Trishuli valley of Nuwakot district, a small city north to Kathmandu, in 1967 (Tiwari et al. ,2005). However, rapid expansion of this weed in urban areas has been noticed during 1990s. Now it has invaded most of the urban areas and roadside vegetations including agriculture lands and community forest of tropical and sub tropical regions through- out Nepal (Joshi, 2005, Tiwari et al.., 2005, Timsina 2007, Shrestha, 2008, Karki, 2009). It is already a dominant weed in major urban areas such as Kathmandu, Hetauda (Figure 1A), Narayangargh, Butwal, Dang, etc. People of Hetaunda have faced the problems of increased labor in agriculture, bitter taste in milk, loss of pasture land, and severe allergy in animals and humans (Karki, 2009). 334 J. Nat. Hist. Mus. Vol. 25, 2010 Figure 1. Invasion by Parthenium hysterophorus in Hetaunda. A) A Grazing Land Infested by P. hysterophorus, B) A Healthy Plant without Defoliation, C) The Plant after Defoliation. Biological Control of Parthenium Ecological impact and economic loss due to rapid expansion of Parthenium has become a regional environmental issue of tropical world. Australia, Ethiopia and India have been most affected by this weed, and these countries have developed national strategic plans to eradicate this weed from infested areas and protect remaining areas from its invasion (Evans 1997, Bhowmik et al.., 2007). Among several components of integrated management, biological control has been considered as the most important approach, due to its cost effectiveness, environmental safety and sustainability, to control Parthenium (Evans 1997). Attempts have been made in screening natural enemies such as insects and fungal pathogens from the na- tive range of Parthenium for their potential use in invaded areas as biocontrol agents. Out of nine species of insects and one rust fungus introduced to Australia (Queensland) from central America (Mexico) as potential biocontrol agents of this weed, six species of insects and one rust fungus were known to be established successfully in the fi eld conditions (Dhileepan ,2001). Among them Zygogramma bicolorata (Dhileepan et al.. ,2000) and Epiblema strenu- ana (Dhileepan and McFadyen, 2001) have been most effective in suppressing Parthenium. Following the Australian experiences, Z. bicolorata was introduced to India (Bangalore) from Mexico during 1983-1984 (Jayanth, 1987, Gautam 2008). Zygogramma bicolorata in Nepal There is no offi cial record of deliberate introduction of Zygogramma bicolorata Pallister (Co- leoptera: Chrysomelidae) to Nepal. However in August 2009, we encountered this beetle and observed defoliation of Parthenium in Hetaunda (Makawanpur district, central Nepal) (Figure 1C, 2). Identifi cation of the beetle was confi rmed by one of the authors (RDG). We did not observe such kind of defoliation in the same area during our survey in 2008. Absence of defolia- tion in previous years was also confi rmed by the local people who were quite happy to notice suppression of Parthenium by the beetle in 2009. Though the beetle was found throughout the Shrestha et al. : Fortuitous biological control of ................335 city in August 2009, defoliation was virtually absent on northern part while there was complete defoliation of Parthenium inside Hetaunda Industrial Estate lying on the southern part of the city. In September 2009, additional defoliation was observed at Lamsure Danda which was a large grassland used by local people for cattle grazing. Similar defoliation, but less extensive in area and level of defoliation, was also observed in Bharatpur (Chitwan district), Gaindakot (Nawalparasi district), Butwal and Bhairahawa (Rupandehi district). In Bharatpur, defoliation was observed near newly constructed central bus terminal and along the highway, but the beetle was encountered in other parts of the city too. In Gaindakot, there was defoliation along the highway. In Butwal, the defoliation was common in eastern and northern part of the city. In Bhairahawa, we observed mild defoliation near the bus park, and the stadium. In August 2009, we carried out a detailed survey in Kathmandu valley (covering three cities Kathmandu, Patan and Bhaktapur) to prepare distribution map of Parthenium and observe possible defoliation by the beetle. Though Parthenium was the dominant weed in grassland, fallowland and roadside vegetation of the Kathmandu valley, we did not observe defoliation neither encountered any beetle feeding on this weed. Figure 2. Stages in life Cycle of Zygogramma Bicolorata. Our observation showed that Zygogramma bicolorata has already been established in some parts of southern Nepal, and an interesting phenomenon of ‘fortuitous biological control’ of Parthenium is operating. Due to open border, ecosystem corridors, direct road connection, 336 J. Nat. Hist. Mus. Vol. 25, 2010 and free vehicular movement between Nepal and India, it is almost sure that the beetle en- tered Nepal from India in the same way as Parthenium did. In fact, the temperature regime of northern India which borders Nepal is considered favorable for Z. bicolorata (Jayanth and Ganga-Visalakshy 1994). Since visible defoliation of Parthenium in Hetaunda area was not observed in 2008, where there was extensive defoliation in 2009, the beetle might have entered Nepal recently between 2004 and 2006. This estimation of probable date of entry of the beetle to Nepal has been based on experiences from India and Australia. In India, the beetle was released in Bangalore in 1984 and the defoliation in fi eld was noticed after four years in 1988 (Jayanth and Visalakshy, 1994). In Australia, defoliation in fi eld was noticed in 1990, after ten years since it was released in 1980 (Dhileepan et al.., 2000). Such a long duration between release of Z. bicolorata and the subsequent defoliation in Parthenium appears to be an artifact. Since the beetle was released at a place which was far from human settlements, it could be possible that there was defoliation long before it was known to the scientifi c community (Steve W Adkins, University of Queensland, Australia, personal communication on December 10, 2009). Zygogramma bicolorata has been emerging as a real hope for the biological control of Parthe- nium weed (Bhowmik et al.., 2007). Both larvae and adults feed voraciously on leaves of Parthenium. Generally this is considered as monophagous beetle feeding only on Parthenium weed. It moves from one individual plant to another only after complete defoliation. In Butwal, we observed larva and adults of Z. bicolorata feeding on leaves of another invasive species Xanthium strumarium. Similar report of feeding on leaves of X. strumarium in fi eld condition was also reported in India by Gupta et al.., (2004). There are also reports that Z. bicolorata feeds on leaves of sunfl ower, but the damage to this plant in fi eld is insignifi cant (Evans 1997). Ganga-Visalakshy et al.., (2008) confi rmed that sunfl ower is not a host of Z. bicolorata, and that feeding observed on sunfl ower is due to the nibbling of leaves by newly emerged hungry adults. Once fl ight muscle is fully developed, the beetle fl ies away. Except sunfl ower, there is no report of damage to any of the crop species by Z. bicolorata in India. Therefore it may be safe to introduce Z. bicolorata in new areas as biocontrol agent of Parthenium weed. Conclusions Though Zygogramma bicolorata has already been established in southern part of Nepal, it has not reached to all areas where Parthenium weed has infested. The beetle may expand its area by natural dispersal, but the time duration for natural dispersal to the valleys like Kathmandu will take unnecessarily longer period. It would be better to prepare distribution map of this beetle in Nepal as soon as possible and introduce it as biocontrol agent of Parthenium weed in new areas after ecological assessment. Acknowledgements The cost of fi eld visit by BBS, AP, JKC and DK was covered from a research grant awarded to BBS by Nepal Academy of Science and Technology (NAST), Lalitpur, Nepal. We are thankful to Prem Budha, Central Department of Zoology, Tribhuvan University, Kathmandu, for micro- photography of young larva of the beetle. Shrestha et al. : Fortuitous biological control of ................337 References Annapurna, C. and J.S. Singh, ,2003. Variation in Parthenium hysterophorus L. in response to soil quality: implication for invasiveness. Weed Research 43:190-198. Ayele, S., 2007. Impact of parthenium (Parthenium hysterophorus L.) on the Range Ecosystem Dynamics of the Jijiga Rangeland, Ethiopia [Ph D dissertation]. Department of Animal Sciences, School of Graduate Studies, Haramaya University, Ethiopia.

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